Sowing carnivorous plant seeds.

Kamil Pasek, 1999


I. Conditions for sowing

Containers

Humidity

Temperature

Planting medium

Location and light

Repotting and acclimatization

Sowing times

Germination and lifespan of seeds

Artificial stimulation of seed germination using gibberellic acid

Pests, algae and diseases

Stratification

Specific tips and tricks

Aldrovanda vesiculosa

Byblis (Byblis gigantea, B. aquatica, B. filifolia, B. liniflora, B. rorida)

Cephalotus (Cephalotus folicularis)

Darlingtonia (Darlingtonia californica)

Dionaea (Dionaea muscipula)

Drosera

Drosophyllum (Drosophyllum lusitanicum)

Genlisea

Heliamphora

Ibicella and Proboscidea

Nepenthes

Pinguicula

Polypompholyx (Utricularia)

Roridula

Sarracenia

Utricularia

II. Specifics for sowing seed of individual genera


Introduction

Sowing seeds is one of the basic techniques used to reproduce most carnivorous plants. The information available on this subject in Czech and foreign literature is insufficient, older growing procedures have become outdated and most growers have limited practical experience. I was inspired to write this article based on my experiences and on the ideas of other experimenters. We were anxious when small portions of expensive seeds from foreign countries were sown under uncertain experimental conditions. Yet, in spite of a high risk of loss, we had successful germination.

It has been ten years since I started growing CP, in which time I have sown hundreds of seeds of many species and varieties from various parts of the world. However, I have not always been successful, often making mistakes, so it is yet another thing to write an article on this topic. Even the best instruction is imperfect. Try your own methods, conduct new experiments, and report the results. Only this method allows for progress in growing cp. I would be very grateful for any comments or suggestions since in the future I would like to supplement new information to the information presented here.

My great thanks to the unstoppable experimenter Mr.Jan Flsek (CZ), who extensively participated in the writing of this article, and also to Mr.Vt ejka (CZ) and Mr.Vlastik Rybka (CZ) for their critical comments. I also thank Mr. Marek Svtek (CZ), Douglas Darnowski (USA) and Chris Teichreb (CAN) for their helps in making an English translation of this text.

Let even your last seed germinate.


I. Conditions for sowing

Containers

CP seeds should be sown in transparent, closed and easily cleaned pots. You can also use other containers such as glasses (e.g. canning jars), saucers, or plastic boxes. All pots must be cleaned very carefully in order to obtain successful results. Seeds can also be sown in regular plastic pots if you can maintain high humidity, for example, in an aquarium covered with a lid (see "Location and Light" below).

Humidity

Seeds should be sown on the surface of the moist planting medium and maintained in a humid environment (RH, relative humidity, from 60 to 100%). Seeds should be gently pressed into the growing medium, covered lightly with soil or left uncovered. Carnivorous plants germinate with bright light. The soil should be kept moist at all times (bottom watering is best), using only boiled or distilled water. After the seed starts germinating, slowly harden the young seedlings by successive increases in ventilation. Allow the humidity to decrease to approximately 60 - 80%.

Temperature

Most CP germinate within a temperature range of 17 C - 35 C. Indirect or filtered sunlight is best. Temperatures over 40 C are harmful to seeds and especially to young seedlings. Seeds of some species require special treatments such as stratification; a cold or heat treatment required before germination can occur. This procedure removes germination inhibitors, without which germination takes too long or does not occur at all.

Many species have shown a requirement for temperature fluctuations between day and night for successful germination.

At the present time gibberellic acid (GA3) has proven to be a good stimulator of germination. This substance removes cold and heat dormancy and allows uniform germination even for species which are difficult to germinate, such as Byblis gigantea, Genlisea, Heliamphora, Nepenthes, Sarracenia, and others. Seeds must be soaked in the solution for 24 hours and then sown according to the specific condition required by each species.

Planting medium

It seems the best medium for sowing CP seed is pure peat moss, often mixed with a little silica sand or washed river sand, and perlite. Sometimes one can use cut living sphagnum moss, especially for very sensitive species such as Darlingtonia, Heliamphora, and Nepenthes. We crock our pots, placing 1 cm or so of material (silica sand being best) on the bottom of the pot. Top quality peat moss is almost sterile (there are no traces of microorganisms such as bacteria or fungal spores), and it will not start to mold.

Location and light

Seeds can be sown in transparent containers (glasses or plastic saucers), in pots located in an aquarium, or directly on the window or greenhouse parapet where the pots are placed in a tray of water. Southeast or southwest exposure is the best for indoors. All seeds require bright light after sowing, but it must be indirect to prevent excessive heating.

Light is one of the most crucial factors for growing CP, especially subsequent cultivation of the young seedlings. You can successfully grow CP using artificial light (fluorescent tubes, incandescent bulbs, etc.) using a daylength of 10-16 hours per day with the lights held 10-20 cm above the plants. Cool-white fluorescent tubes are sufficient, but the best for growing are those tubes whose spectral balance more closely approximates that of the sun with the red and blue parts necessary for healthy plant growth predominating.

Repotting and acclimatization

Seedlings must be transplanted if they are too closely spaced or if they have 3-5 true leaves. This usually occurs 1-9 months after sowing. Immediately after transplanting high humidity must be provided for better acclimatization of the young plants. As soon as the young plants have grown larger, they can be hardened off with slight increases in aeration. Later reduction of humidity to 60-80% is very important to prevent fungal attack due to high humidity.

Sowing times

The best time to sow seeds of CP is in early spring (February- April), but seeds can be sown at any time. The seedlings are very sensitive to a lack of light, thus the requirement for artificial light in the winter.

Germination and lifespan of seeds

CP seeds maintain their viability for a long time, even over ten years in the case of Drosera, given appropriate conditions. However, it is important to maintain suitable conditions for seed storage. Seeds should be placed in plastic or paper bags and kept in the refrigerator at 0 - 4C. Seeds should not be stored in absolutely dry conditions as relative humidity levels above zero help promote seed viability. Seeds of European butterworts (Pinguicula) can be stored in sterile water.

The shortest germination times were observed for the Nepenthes and for European Pinguicula species. Patience is required. Some CP may germinate only one to three years after sowing, for example Drosera, Nepenthes, and Sarracenia. Germination can be stimulated by using gibberellic acid or other procedures to break dormancy.

Some CP species germinate sporadically whereas common species may all germinate within several days. Others do not germinate for a long time, e.g. months or even years, which can be very unpleasant. Determining methods for germination often requires many experiments, repetitions, and patience to answer. Nevertheless there are some tips and tricks for stimulating germination, which will be noted below in the sections dealing with individual species. Tips include stratification, change of temperature, and stimulation using gibberellic acid. We can recommend at least one method for successful germination of most types of seeds.

Artificial stimulation of seed germination using gibberellic acid

Gibberellins were discovered approximately fifty years ago. They are a group of related substances forming a class of plant hormones. Today approximately 90 molecules based on the basic gibberelline structure are known. These hormones are weak, stabile organic acids which fit into the terpenes. Intensive research continues with many aspects of the effects of gibberellins remaining poorly understood.

Seeds of many plant species require exposure to low or high temperature within a certain period before they will germinate. This process is called thermal stratification. Alternatively, the hormone gibberelline can be used to break such dormancy. Apparently, there are some factors that inhibit germination, causing dormancy, such as abscissic acid (ABA). It is likely that the proportion of gibberellins to germination inhibitors, such as ABA and auxin, also determines how long dormancy lasts. Germination inhibitors are removed via cold stratification or by increasing the concentration of gibberellin. Abscissic acid may be removed by soaking the seeds in water for a period of time. Seeds of European species butterworts (Pinguicula) will germinate within several days if sown directly in water. The storage of these seeds in water and in a cold environment allows seed viability to be prolonged for as long as several years due to ABA removal. It also appears that uniform germination of the seeds of Drosera arcturi is enhanced when the seeds lie on damp or water saturated media and are subjected to temperature changes. The artificial use of gibberellins to break dormancy is useful if there are mostly inhibitory substances in the seeds, especially those such as auxins. Gibberellins may also compensate for poor lighting, increasing germination rates.

To stimulate germination of CP seeds, a 1-0.1% solution of gibberellic acid (GA3) has proved to be effective. To prepare the desired solution we place 1g of GA3 in 1 litre of sterile distilled water. Clean seed should be soaked in this solution for 24 hours, soaking seeds enclosed in a hard coat for longer, at most three days. Keep the seeds at room temperature with occasional careful shaking. The seeds may then be sown. The prepared GA3 solution may be stored in the refrigerator (-10-0C) and reused.

Seed germination rates of poorly germinating species, such as those from the genera Byblis, Drosophyllum, Drosera, Genlisea, Heliamphora, Nepenthes, Sarracenia, may be greatly increased via the use of GA3. The application of GA3 leads to uniform germination in a shorter time, breaking the dormancy exhibited by many seeds.

Pests, algae and diseases

When your plant is affected by fungus, simply remove and destroy the source of the infection. Sometime it may be useful to lower humidity. If the infestation continues to spread or appeared too late, it may be necessary to spray the affected plants with a systemic fungicide or to dust the affected parts with a fungicide. Use of clean seeds and pots, sterile or boiled water, and top quality planting medium significantly decreases the risk of any contamination. Some seeds are already contaminated with microorganisms. They should be washed wash in water with a fungicide or a weak solution of potassium permanganate (KMnO4), which has a pinkish colour. Of course, it is best if you do not use any chemicals.

Various larvae (appearing as small worms or caterpillars) may take a fancy to the planting medium. This is a sign that a poor quality media was used, usually living sphagnum moss. In that case, long term insecticide may be necessary.

If algae or moss have appeared in your pots, the cause again is probably use of low-grade or contaminated medium. Algae often overwhelm small seedlings and may even prevent the germination of seeds. This problem cannot be solved by using chemicals. Sometimes humidity may be decreased, but an optimal solution does not exist. I have noticed in books on cultivating cacti some information indicating that charcoal inhibits the growth of algae. Alternatively, sources suggested the use of a 1% solution of Chinosol. Unfortunately I have not tried either of these possibilities when attempting to control algal growth.

Complete elimination of the spores of fungus, moss, and other pests may be assured by steam sterilization, e.g. in the Pippin's pot (a pressure cooker). Growing medium is placed into the microtene bags or glass jars and sterilized for 20-30 minutes. This procedure eliminates both desirable and undesirable soil microflora and is used only rarely.

Stratification

The biological clock plays a role in various plant processes, which includes those involving seeds. Some seeds of CP require a signal to break inhibition of germination. Once suitable conditions occur, germination can start.

Stratification is a cold or heat treatment required by some seeds for a period of time to break dormancy. Cold stratification is used to germinate species from temperate climates where temperatures of 0C or lower experience part of the year. These genera include those from Europe, North America and New Zealand such as Darlingtonia, Dionaea, Drosera, Pinguicula, and Sarracenia.

Seed are sown on the surface of moist planting medium, the "wet method," in prepared pots. These pots are then placed in a warm area (around 20C) for 1-3 days. Then the pots are placed in the refrigerator (0-5C) for 6-8 weeks. It is necessary to control the spread of molds, which we do by dusting the seed with a fungicide. After this time we remove the pots from the refrigerator, put them in a bright place, and then treat them like other seeds that do not require stratification. The so-called "dry method" gives the worse results. This is when dry seeds are put in paper bags and stored in a cool area at 0-5C for 6-8 weeks.

The other way to obtain good results is to use variable low temperature (0-15C) in early spring (April - May). Prepared seeds are sown outdoors, e.g. in the garden or on a terrace, for 6-8 weeks to simulate their natural growing conditions. The seeds are then placed in a common growing area.

The best results are received when we use both "wet" stratification and gibberellic acid. Whatever method used, it is very important to control the occurrence of mold on a regular basis, treating the seed with a fungicide.

Stratification may be induced by lowering the temperature below 0C. This can be done for the following species: Darlingtonia californica; Dionaea muscipula; Drosera anglica, D. arcturi, D. burmannii, D. intermedia, D. linearis, D. filiformis ssp.tracyi, D. filiformis ssp. filiformis, D. rotundifolia, D. stenopetala; Pinguicula alpina, P. balcanica, P. brevifolia, P. corsica, P. dertosensis, P. grandiflora, P. leptoceras, P. nevadensis, P. ramosa, P. vallisneriifolia, P. variegata, P. villosa, P. vulgaris; Sarracenia flava, S. minor (from northern areas), S. purpurea ssp. purpurea, S. purpurea ssp. purpurea var. heterophylla, S. purpurea ssp. venosa (?), S. rubra ssp. (from northern areas), all (?) hybrids of S. purpurea and S. flava; and Utricularia (from northern areas).

It is interesting to note that a part of the fresh seed crop of species of Drosera, Pinguicula, and Sarracenia sown immediately after being harvested will germinate within the same year. However, seed from the same crop stored until next year requires stratification before being capable of germination.

Heat stratification is used to germinate species from frequently burned areas, pyrophytic plants, or species from an area where some season is very hot. During this unfavorable season the plants survive in the form of dormant bulbs or roots. Similarly, seeds of these species are adapted to these temperatures. The natural trigger of germination consists of undergoing the hot season followed by a subsequent decline in temperature. This form of stratification is applicable especially for the endemic Australian species of the genus Drosera, Byblis gigantea, and South African caulescent sundews (Drosera).

Until now, procedures for enhancing germination based on burning straw on the surface of the wet planting medium on which the seeds have been sprinkled or the pouring of boiling water over the seeds of Byblis gigantea have not been very effective. On the other hand the application of the hormone gibberellin may be recommended and allows very good results in many species requiring heat stratification.

Seeds of the Australian tuberous sundews (Drosera) and Byblis gigantea may germinate if they are sown on the planting medium mixed with cold ash. The presence of some substances in the ash likely stimulates the germination of these seeds.

There are two interesting methods publishing by an Australian grower, Allen Lowrie. These methods are applicable for most of the Australian and South African species of Drosera. The first method consists of sowing seeds on the moist planting medium and then placing the pots in a smoking chamber or near the smoke from an outdoor frying grate, fireplace, or barbeque for an hour. The second method is based on using so-called "smoke water" that is probably ash or smoke leachate which an Australian firm offers for sale. Seeds are soaked in this solution for 24 hours and then are sown. I do not have detailed information about any of the ingredients of this solution.

The Czech grower Mr.Jan Flisek had an interesting experience. He put seeds into a paper bag and attached them to the warm central heating of his apartment for several weeks or months to allow heat stratification. His results have been very encouraging. Seeds of the tuberous and pygmy sundews germinate uniformly while seeds of these species sown without stratification germinate at low frequency.

Specific tips and tricks

You should pay attention to the ecological requirements of each species. Try to look for as much information as possible about the natural environment of a given species in its natural growing medium, if it prefers a sunny or shady area, etc. This can help you to understand what the optimal growing conditions are. These details are usually the most important information. Do not underestimate their importance!

Sometime plants germinate without any problems only to die later on. You have made some mistake! This year I sowed seeds of the rare P. crystallina from southern Turkey, the natural locality of which I had visited in person. I sowed the seed according to the best of my knowledge and personal observations, but the seedlings died after they had germinated. It turned out that I had significantly underrated the importance of the pH of the mixture. In the end a mixture with pH 8-9 was found to be more appropriate. This simple mistake resulted in the loss of these rare plants. This example shows that we must respect the ecological requirements of the plants.

Top quality peat moss for seed sowing

I have been using highland peat moss for seed-sowing medium for several years. It is of very good quality and can be bought without concern about pests or diseases. Also sold on the Czech market are Lithuanian or German peat moss, but unfortunately these are often contaminated with moss and algal spores. The acceptability of these for seed sowing must be tested. Unsuitable is the peat consists of a high amount of plant and tree remains, with a higher content of nutrients. Do not use any mixed peat substrates for sowing since these are mixtures with limestone and/or fertilizers. The best medium for sowing seed is pure fibrous peat moss.

Silica sand

This pellucid sand used for glass-making, with 0.3-0.8 mm diameter grains, may be obtained from a waterworks, where it is utilised as a filling for water filters, and in petshops, where it is sold for use in aquaria. If you cannot obtain it, you can use fine-grained river sand for similar results. River sand should be sterilized before use.

Fungicides

When seeds are afflicted with fungus, I apply Fundazol (Benlate), Euparen, and Topsin. Recently I tried Sandofan and Dithane with good results. I have always used the concentration recommended by the manufacturer.

Foreign suppliers

There are several major firms in the world specializing in seeds of CP. The price for one portion (2-100 seeds) is from $1 to $3 (US). Seed quality varies considerably, and I must say that the rarer a species is, the worse the germination will be. Germination depends on the length of storage, dormancy, the site of the collection of the matured seed, and the reliability of the supplier. Rare species (Cephalotus, Heliamphora) which contain a small number of seeds per portion (1-4), germinate poorly. Combines with cultivation difficulties, these plants are often unrewarding and it is not worth the trouble to order expensive seed.

Czech CP Literature

Only two books about growing CP have been published in the Czech Republic:

Studnika Miloslav (1984): Carnivorous plants, Academia Praha (150 p.)

This book contains complete information about the ecology, distribution, and cultivation of most genera of CP. Although this book has not been published during the past 13 years, it contains much practical information and is suitable for all novice cp growers. I recommend this book for everyone. Unfortunately this book can only be obtained in second hand bookstores. If you find it, buy a copy, whatever the cost!

Jeek Zdenek (1997): Carnivorous plants, CZS Kvt (70 p.)

The author of this recently published hardcover book specializes in cultivation of orchids and Tillandsia. While it provides basic information about growing CP, the author makes many fundamental mistakes, especially with regards to growing procedures. Therefore, this book can only by recommended for beginners as a source of very basic information. This book should be available for sale at 49-K (US$ 2). For growing procedures you should consult an experienced grower or other literature.

Specialized Czech CP literature is also occasionally published:

ADLA - Revue of the carnivorous plants: This specialist journal gives actual information from the world of CPs. It consists of translations of the most important journals and other literature from around the world. It is acceptable for a person who wants to keep up to date and to read some interesting news about CP. This magazine continues with publication of the excellent magazine, Pel-Mel (numbers 1-4), which had been discontinued.

Specialist articles: In the past few years, several very interesting and well written articles about growing CP have been published in the Czech journal iva.

II. Specifics for sowing seed of individual genera

Aldrovanda vesiculosa

Since the plants are rare, and the seeds even more so, experience in sowing these seeds is limited. Nevertheless I have obtained quantities of these seeds recently from various of European localities.

It seems that germination is rather poor with seeds requiring a long period of dormancy. Utilization of gibberellin appears to be a useful procedure for breaking dormancy. Based on my experience, the fresh seed sown after harvest starts to germinate in sporadically after two months. Seeds stored in the refrigerator within a temperature range of 2-5C for 2-3 years start to germinate spontaneously, even in the refrigerator (!!!). A white protuberance with a black tip (0.5-1mm) sprouting on the top of the seed characterizes germination. Such seeds can be stored in the refrigerator for several months. When they can be placed in sufficient light where the temperature is approximately 25C, germination will quickly be completed. The young seedlings remain about 0.5 cm long for two months.

Many of the seeds (60-80%) are internally contaminated, leading to the death of this large portion of the seed lot.

Byblis (Byblis gigantea, B. aquatica, B. filifolia, B. liniflora, B. rorida)

Byblis liniflora germinates at room temperature (15-25C) in two or more weeks. Seeds are sown (5-10) in the early spring (February-April) on the surface of the standard seed sowing medium (peat moss: sand at 2:1), in plastic pots (e.g. 8x8 cm). Seed germinates within several day or weeks. B. liniflora is an annual, usually dying during winter. Occasionally, the plants survive the winter and continue growing in spring. Since the plants grow as annuals, they must flower the same year that they germinate in order to produce sufficient seed for the next year. After Byblis liniflora matures, it should not be repotted because it has a sensitive root system, which will not regrow if damaged. Only the young plantlets (1-2cm) may be transplanted, very carefully before their roots establish themselves securely in the planting medium. That way the roots will not be destroyed during transplanting. When transplanting, remove a ball of soil with the roots.

Byblis aquatica germinates at a temperature more than (27-35C) and requires high relative humidity.

Seeds of Byblis gigantea require heat stratification (see previous chapter), though good germination has been obtained using gibberellic acid. When using gibberellin, seeds are soaked in the gibberellic acid solution for 24 hours and then spread on the surface of the planting medium (peat moss: sand at 2: 1). B. gigantea starts to germinate within several weeks with maximum temperatures of 15-25C.

Cephalotus (Cephalotus folicularis)

Seeds of Cephalotus are sown on the surface of the mixture (peat moss: sand at 3: 1) or living sphagnum moss (eventually mixed with perlite). Fluctuations in temperature are required for seed germination. Seed usually germinates within several months, with up to five months mentioned in the literature. The young seedlings are very sensitive and often die. They can be transplanted one year after sowing. Unfortunately, due to the rarity of the seeds, there is little practical sowing information available.

Darlingtonia (Darlingtonia californica)

Seeds of D. californica require cold stratification (see above). The seeds germinate in one to two weeks, but germination can be prolonged, up to several months. The mixture of peat moss and sand (3:1) or living sphagnum moss is used for sowing. Darlingtonia plants are intolerant of temperatures above 30C. Sown seed need a stratification period with maximum temperatures of 17-25C. Outdoor conditions are generally more acceptable for sowing. As soon as the young seedlings are developed to the stage where they have 2-5 true leaves, they can be transplanted. Seedling plants do not transplant very easily. Do not transplant in winter! Best results are obtained by transplanting the seedlings in the spring before active growth resumes.

I made an interesting observation when I sowed seed of Darlingtonia from higher elevations, about 1900 m. In spite of a high percent germination (70%- 80%) after sowing at 20-25C, all seedlings died early during development. Other seeds from some "greenhouse" sources germinated without any problem and are growing well now. The origin of seeds appears to be very important: use an appropriate sowing technique. In this case, seeds from areas having low temperatures should be sown at lower temperatures.

Dionaea (Dionaea muscipula)

Seeds of D. muscipula require cold stratification and a common planting medium (peat moss: sand at 2:1). Seeds germinate at temperatures of 15-25C and 100% relative humidity within several weeks. Germination is rather prolonged. The young seedlings are transplanted once they have at least 3 true leaves.

Germination of fresh seeds sown immediately after harvest without stratification is poor (5-20%), while seeds of the cultivar Akai Ryu stored in the refrigerator for three years germinate well (80%).

Drosera

The genus Drosera is extremely large, and the various species are quite diverse in their cultural requirements. These plants may be divided into several groups according to the best sowing methods.

1. Subtropical and tropical Drosera

This group consists of commonly grown sundews such as D. capensis, D. capillaris, D. cuneifolia, D. dielsiana, D. indica, D. montana, D. spatulata, etc.; but also includes very rare species such as D. glabripes, D. glanduligera, D. graminifolia, D. villosa, etc. Australian forest sundews present a special group. These include D. adelae, D. prolifera, and D. schizandra.

The common planting medium used for sowing is a mix of peat moss and sand (2:1). Temperature should be maintained between 19 to 25C. Seeds germinate within several days or weeks. D. glanduligera was sown at temperatures of 8-12C, and germination started after several weeks and continued for several months. The group of forest sundews (D.adelae, etc.) are sown at temperatures of 28-35C. Rare, especially South American species, took a long time to germinate, usually several months, with germination being very unpredictable. You must try it yourself. If your seeds were absolutely fresh then they should germinate within 4 weeks.

Seedlings are transplanted individually or in clusters into fresh planting medium as soon as the young plants are large enough. Repeated repotting will not cause damage.

2. Sundews needing a cold treatment

This group of the plants consists of American and European sundews; D. anglica, D. filiformis, D. intermedia, D. linearis, and D. rotundifolia; and New Zealand and Australian sundews; D. arcturi, D. binata, and D. stenopetala. Cold stratification is needed for germination of all these species. A mixed planting medium (peat moss and sand at 3:1) is used for these species. Seeds usually germinate within several weeks after stratification. D. binata does not need stratification if it is sown immediately after harvest. The fresh seed of D. arcturi stratificated at a temperature range of -5-12C germinates within 3 months. Germination of sown seed was approximately 5% after 5 months.

If outdoor cultivation is possible, European species can be sown immediately when seed is mature. Part of the seed will germinate that year, the rest in the spring. Experience has shown that seed can be sown outdoors during autumn (October- November) for germination in spring. The pots must stand in water all of this time, but they should be protected from rain. The pots are covered by snow during winter.

3. Pygmy Drosera

Australian pygmy Drosera; D. ericksoniae, D. nitidula, D. ocidentalis, D. pulchella, D. pygmaea, etc.; are sown on the surface of the common planting medium (peat moss and sand at 2:1) at temperatures of 15-25C. Thermal stratification or the addition of ash results in a more uniform germination rate and is beneficial when sowing some rare species (D. lasiantha, etc). Both procedures can be used for sowing common species as well. Germination is faster and the number of the seedlings higher with this method. Gibberellic acid can also be used. Seeds will start to germinate in a few weeks.

4. Tuberous and South African Drosera

Australian tuberous Drosera; D. erythrorhiza, D. gigantea, D. marchantii, D. menziesii, D. stolonifera, etc.; and rare South African Drosera; D. cistiflora, D. hilaris, D. pauciflora, D. regia, D. trinervia, etc.; germinate with difficulty and often require 3 or more years to germinate. To germinate successfully, use smoke and heat stratification (see above). Addition of ash or gibberellin leads to successful germination, but many trials are often needed. Seed is sown on the surface of the mixed medium (peat moss : sand at 1:1) within a temperature range of 10-18C. Some species germinate only after temperatures drop to 5-10C! The young seedlings reduced drought resistance, so during the dormant season the medium should be kept slightly moist. However, high humidity and water logged medium leads to loss of plantlets.

5. Specialities: D. petiolaris complex, D. dilatato-petiolaris, D. falconeri, D. lanata, D. ordensis, etc.

There are several species of very interesting sundews in Northern Australia which have been recently discovered and described. These magnificent robust plants have some special ecological requirements requiring further comment. I am sorry to say that there is little record of their successful cultivation.

The plants grow from November to May, usually in sunny localities at temperatures of 24-32C. Often they are found in both extremely peaty and sandy soils, sometimes submerged. Relative humidity ranges from about 50-90%. The plants flower in November and then again in May.

A dormant period occurs from July to October. During the dormant season rainfall is non-existent, and soils slowly go dry, in the end drying up completely. Relative humidity drops to 20-40% with a temperature range of 14-32C.

Seeds of species from the D. petiolaris-complex are sown on the surface of the planting medium (peat moss : sand at 3:1 or 3:2). Germination starts in a few weeks but sometime is prolonged for several months. Have patience! Seeds should be sown at temperatures of 25-35C, keeping the relative humidity high. Good ventilation is needed to prevent seeds and seedlings from succumbing to attacks by fungi. During winter, artificial light is needed because a lack of light will result in the death of these plants. If temperatures are too low, seeds can lapse into dormancy!

It is interesting to note that recent experience shows that most species from this group germinate reliably at 16C, e.g. D. caduca, nevertheless some such as D. falconeri require high temperature near 35C to start germination.

Drosophyllum (Drosophyllum lusitanicum)

The minute black seed is enclosed in a hard coat. 3-5 seeds are sown in clay pots (12 -18 cm in diameter) on the surface of moist, well-drained planting medium (peat moss: sand : perlite at 2:1:1). Seeds germinate without light and can be covered with an opaque lid. As soon as the young seedling appear, the lid should be removed so that the seedlings can receive enough light.

Several methods are known to yield successful germination. 4-10% sulphuric acid has been used to break the hard exosperm with seeds allowing them to germinate. We can recommend the following methods at the present time: 1. Remove the tip of exosperm until white endosperm appears or grind off exosperm with a file or sand paper, then sow the seeds; 2. use the first method and soak the seed in a solution of gibberellic acid for 24 hours; 3. soak the seed in a solution of "smoke water" for 24 hours before sowing. In all cases it is recommended to soaking seed in pure water for 24 hours to be able to cut the exosperm.

Seeds germinate in a few weeks, and relative humidity need not be high. If you use gibberellin, seeds will germinate within one week. Otherwise germination happens within 2-3 weeks. Seedlings die when given high relative humidity. As soon as the seedlings appear, reduce humidity and start ventilation. Seedlings also require a lot of light. The key for maintaining Drosophyllum plants is to keep the soil damp but not wet.

Recent experience has shown that Drosophyllum can be grown easily, e.g. on a windowsill, when the plants are watered from below according to need. The planting medium should be kept damp but not wet. It is not necessary to use two pots as has been written previously. Mr. Jan Flisek has also shown that seed was able to germinate in light. During the first months after germination, about 40% of plantlets died. After the plants mature, the danger of damping off or of death due to drying is minimal.

Genlisea

Seeds of species from the genus Genlisea are sown on the surface of the common planting medium (peat moss : sand at 3:1) at temperatures of 25-35C. They will usually germinate within several weeks or months. Two months after germination the plantlets reach a size of 4 mm in diameter. Recently, a new method for sowing was published which had been used for the genera Utricularia and Heliamphora. Seeds are sown in pots filled with a mixture of peat moss and sand (1:1). The pots are kept in water so that the level of water reaches at least 4 cm below the brim of the pot. Each pot should be watered from above three times per day for five or more minutes per watering. These seeds also require a lot of light, at least artificial light, and a photoperiod of 10-12 hours. The seed also need fluctuating temperatures with day temperatures above 35C and below 18C at night. Good ventilation is also necessary from the start of sowing, but excessive drying must be avoided.

The second procedure for Genlisea seeds is based on sowing on the surface of pure peat moss. Seeds are located in the centre of the pot (about 30 seeds per 1cm2) and sprayed with a small amount of GA3. Water from below only! Seeds of species from the genus Genlisea usually show low viability. Successful germination is obtained when utilising gibberellic acid, and artificial light is recommended.

Heliamphora

Unfortunately, I do not have any meaningful observations of sowing this genus because the seed is very rare and expensive. The sole suitable method recommended is the sowing procedure given above for the genus Genlisea

The common method of cp seed sowing leads to death of the seedlings following fungal infection, so we can only presume that there is neither a short period of viability nor the presence of any unknown dormancy-promoting factors in seed from this genus.

On the other hand, some experiments have shown that fresh seed germinated with no special conditions and without the need for any stratification. The seed was sown on the surface of pure cut living sphagnum or pure peat moss, keeping the pots in a closed aquarium. Seeds germinated from one week until a few months had passed at temperatures of 22C. The fresh seed of H. heterodoxa sown immediately after harvest have not germinated at all, but the seed of H. nutans stored in the refrigerator for 1-2 years germinated after one month with a rate of germination of about 5%. The seedlings grew very slowly, 3 mm for 2 months, and then died. Sown seed requires a lot of light. Unfortunately the young seedlings grow slowly and a high loss rate is likely. Pots must not stay in water, and watering should be from above using mineral-free water. The young seedlings are more sensitive to higher temperatures than the older plants which is why we protect them from direct sunlight during summer with maximum temperatures of 18-25C.

Ibicella and Proboscidea

Cut a thin slice of exosperm before sowing and then let the seed soak for 24 hours in a solution of gibberellic acid. Mr. Jan Flisek recommends removing all exosperm. Seeds are sown in large pots (16 x 16 cm), germinating within a few days or weeks. Relative humidity should be 60%, and temperature should be 20-30C. If you do not remove the exosperm, germination will be prolonged over several months. Proboscidea usually germinate within 4 days to several weeks after sowing when using GA3, and Ibicella germinate within 6 to 8 weeks using GA3.

A mixture of peat moss, sand (or perlite), and composted manure (and eventually some granular fertiliser) at 15:4:1 proves to be a good sowing medium. After germinating the seedlings need good ventilation. The plants grow quickly and have even bloomed 6 weeks after sowing.

Nepenthes

The long, slender seeds are sown on the surface of cut living sphagnum or the common medium (peat moss : sand at 2:1). Germination is a long process lasting several months at temperatures from 12-30C. Some seeds may germinate within several days (11), while others may take several months (6-8) after they are sown. My seed of N.albomarginata started to germinate just after one year. The prevailing opinion is that viability Nepenthes seed is significantly limited and that they will not germinate after several months of storage. We cannot confirm or deny this. Nevertheless some species are known to behave otherwise, e.g. N. fusca which germinates 90% after storage for 14 months. The viability of the seed of N. bicalcarata or N. ampullaria is limited to a few weeks. Seed of N. pervillei germinated after they had been stored in the refrigerator for 3 years.

Nepenthes seed are often contaminated by fungal spores in nature. My experience from recent work has shown that approximately 17 species collected in their natural localities (at the same time) germinate rather irregularly. Seeds of some species; N. sanguinea, N. singalana, N. ramispina, N. densiflora, N. lavicola, and N. mikei start germinating after 2-3 months, but only after a local attack by an unknown fungus which spontaneously disappears within 2-3 weeks. Seeds of other species; N. dubia, N. inermis, N. ovata, and others have not germinated in 8 months since sowing.

Pinguicula

In order to discuss sowing Pinguicula, it is convenient to group plants according to native environmental similarities.

Seed requiring a cold stratification period consist of European, Japanese, South American and Asian species that form dormant buds (hibernacula) to survive the frozen winter season. These include P. alpina, P. grandiflora, P. leptoceras, P. longifolia, P. macroceras, P. vallisneriifolia, P. vulgaris, etc. Some species that do not form winter buds also require a cool stratification period for successful germination. There is no freezing weather in their native localities, temperatures falling to 0-15C in winter. These plants reduce their growth but their habits stay the same. Species include P. caerulea, P. crystallina, P. crystallina ssp. hirtiflora, P. lusitanica, P. lutea, P. primuliflora, P. pumila, etc.

Seed of these species need cold stratification, and we can use some of the methods described, e.g. for those species in the genus Drosera requiring a cold period. Outside cultivation is best for these species. Many of them are difficult to grow indoors or in the greenhouse. Seed starts to germinate within two or more weeks after stratification ends.

The other Pinguicula plants from this group are sown on the surface of the planting medium at temperatures of 15-25C, with the best time for sowing being the spring. Fluctuations of temperature between day and night are beneficial, as are generally lower temperatures.

For better germination of some species; e.g. P. mundii, P. vallisneriifolia; stratification at temperatures of 5-10C for a short time (1-4 weeks) helps. The seed will germinate in a few days or weeks.

There are two types of planting media for sowing species of Pinguicula. Basic or alkaline growing media is suitable for species preferring basic soil; P. alpina, P. crystallina, P. dertosensis, P. longifolia, P. lusitanica, P. vallisneriifolia, etc. This consists of peat moss, chalky clay, washed gravel, and rubble of limestone, sometime mixed with plaster stone (2:1:0, 5:1), or so called soft travertine (structural fluvial spumy stone), what is (for laymen) a soft porous conglomerate of limestone which absorbs water. This has proven to be good for sowing and cultivating many species which like lime, such as the Mexican species. Seeds are sown directly on moist stone, staying in a dish that also serves for cultivating the seedlings later. Ecological observations of butterworts growing in nature on vertical rock faces - P. alpina, P. crystallina,  P. longifolia, and P. vallisneriifolia  - have shown that these species prefer to be sown and cultivated on vertically slanted medium which water flows through. This method f cultivation is not necessary.

For the other species; P. corsica, P. grandiflora, P.leptoceras, P. lutea, P. primuliflora, P. pumila, P. vulgaris, etc.; we use a planting medium composed of peat moss and sand at 3: 1.

The Mexican succulent species; P. acuminata, P. agnata, P. gracilis, P. moranensis, P. potosiensis etc.; are sown on the surface of a planting medium composed of peat moss, washed gravel, chalky clay, and rubble of limestone (2:1:0, 5:1) at temperatures of 20-28C. As an alternative medium we use a mixture of peat moss, dusty perlite, and rubble of limestone (1:1:0,5), or soft travertine. Seed will germinate in a few days (7) or weeks. You must provide good ventilation early after the seedlings have appeared. An interesting fact is that species germinating on medium with soft travertine grow more quickly than on other media.

Tropical species which grow continuously; P. albida, P. benedicta, P. casabitoana, P. cladophila, P. jackii, P. lignicola, etc.; should be sown on the surface of a mixture of peat moss and sand (3:1) at temperatures of 20-35C. P. filifolia will germinate within one month from sowing at temperature 25C, and after two months the plantlets reach a height of 1.5 cm. Viability of the sown seed was very low, about 2%. Unfortunately I cannot give more information due to a lack of practical experience.

A special note should be made about relative humidity. All Pinguicula species enjoy very high humidity. As soon as the young seedlings have appeared, we must harden them and start careful aeration. All butterworts from the first and third groups require high humidity (40-70%) and good ventilation. The Mexican species like lower humidity and good ventilation. However, during winter the planting medium tends to dry, so the plants should be sprayed with water. When the plantlets reach a height of 4- 8 mm, they can be transplanted.

An interesting method of sowing was described by Mr. M. Studnika. It is probably useful for all species in the genus Pinguicula. The seed is sown into a transparent pot filled with pure water. The pots are then placed in a bright site at room temperature. Water washes germination inhibitors, ABA, away, and seeds will germinate more successfully and more rapidly. If you use this method, dormant species do not need cold stratification. As soon as the young seedlings appear, they must be transplanted onto the surface of a suitable medium. High humidity should be maintained for at least one week. Then you can start to harden off your plantlets.

Polypompholyx (Utricularia)

Seed is sown on the surface of the common moist medium (peat moss : sand at 2: 1) at temperatures of 15-25C. 100% relative humidity is necessary. Seed germinates within several weeks or months after sowing. There are probably some inhibitors of germination in the seed because a portion of the seeds will eventually germinate after one year. The use of GA3 is recommended, using the method described above for Genlisea.

Polypompholyx is an annual and must be sown each year. It will not self-pollinate, and so should be pollinated by hand to insure seed production. The plant grows to the adult stage in 2 to 4 months.

Roridula

Although Roridula is not carnivorous, many people grow it due its similarity to true carnivorous plants.

The instructions for sowing is described in the book by Mr. Adrian Slack: Fleischfressende Pflanzen fur Haus und Garden (Carnivorous plants for house and garden). Seeds of the genus Roridula are sown on the surface of the moist planting medium (peat moss : sand at 3:1) with pH in the range 4.5-5.5. The best time for sowing is from January to February. Bury the sown seed under a thin layer of the medium and place pots outdoors at freezing temperatures for three days. Then return the pots to 22-25C. Without this procedure the time of germination is highly variable, and all processes are prolonged. Even germinating seeds can survive temperatures of -25C. The planting medium must be moist, not waterlogged. 1-2 years old plants can be transplanted. Mr. Z. Jeek writes in his book that Roridula is a pyrophyte and needs some method of heat stratification to germinate successfully. Another author describes a procedure of stratification by pouring warm water at 60C over the seeds.

Sarracenia

Sarracenia seed require a cold treatment before they are capable of germinating. These methods have already been described above. Utilizing gibberellic acid results in a high rate of successful germination. There is another interesting method useful for germination of seeds from this genus. Put the seed into a small plastic bag, adding water to the bag before placing it in the refrigerator for 48 hours. I do not know if this procedure is useful for all species or to what degree it is successful.

Seed are sown on the surface of the moist planting medium (peat moss : sand at 3:1) at temperatures of 18-28C and 60-100% relative humidity. Seeds germinate within a few weeks or over a period of several months, but can take as long as 1-1.5 years. You must begin to harden the young seedlings after several weeks, with careful ventilation being best. Seedlings can be transplanted when they have produced 2 or 3 leaves (traps).

I have made an interesting observation about the seed of S. purpurea ssp. purpurea. The seed, which had germinated during the past year, being sown on the surface of living sphagnum in spring, were left in the garden exposed to the vagaries of weather during winter. The seed germinated during the next spring.

Utricularia

Seed are sown on the surface of moist planting medium (peat moss : sand at 3:1), and are not covered by the growing medium. They prefer intermediate temperatures (20-30C) and high relative humidity. The method described for starting the seed of members of the genus Genlisea is also suitable. Seeds start to germinate within a few weeks, and the plantlets grow quickly. These can be transplanted in small clusters during early growth.

The Australian tuberous bladderwort (U. menziesii) and the annual Australian bladderworts require heat stratification to germinate similar to tuberous Drosera. Seeds of European and North American species require cold stratification for germination.


Copyright (c) Kamil Psek, 1999