Cultivation of pygmy Drosera
Jan Flísek and Kamil Pásek
Pygmy Drosera comprise up a peculiar group that include the smallest sundews - small growth is a typical characteristic of this group. Most pygmy Drosera are found in southwestern areas of Western Australia. Only D. pygmaea is found in southeastern Australia and New Zealand too. In their natural habitat, plants grow during the moist winter season which has a lot of rainfalls. During the long, hot, dry summer the plants go dormant. These sundews prefer sandy soils mixed with loam and laterite gravel; they often grow in pure silica sand, around lakes, along the banks of seasonal creeks and channels, and often in open woodland and among low shrubs. More detailed information about the particular types of localities and life cycles were published by Allen Lowrie, a local expert in carnivorous plants, in his book „Carnivorous Plants of Australia, Vol. 2".
We have been cultivating pygmy Drosera for several years. We will try to provide the most important cultivation tips along with how we have tested these with our own experience and growing conditions. Remember, not all approaches published here are necessarily suitable to your growing conditions. Most pygmy Drosera are easy to grow. If you have a feel for the plants and invest some time to a determine what your suitable conditions are, the plants reward you with marvelous growth.
A suitable planting medium for growing of pygmy Drosera is coarse-fibred peat moss mixed with silica sand (fine-grained grit), or perlite in a ratio of 1:1-3. More common species can be grown in pure peat, but results of this are poor as compared to the above. Sometime using perlite encourages growth of algae and moss on the surface of the pot. Moss and algae will compete with the small plants, freshly germinated from gemmae. The surface of the planting medium can be covered with a 1-3 cm thick layer of pure silica sand, gravel or perlite, into which the plants are placed. However, we have not yet fully determined the best top-layer for these plants. Experiment! One disadvantage with the use of a sandy layer is that watering the medium with hard water leads to fast mineral build-up in the soil. The adhesive calcareous concretions (white patches) are rather difficult to remove. Spraying with soft water or placing the plants in the environment with higher air humidity can sometimes help. If air humidity is kept high, we do not recommend allowing the plants to sit in trays of water permanently. A layer of perlite is grown over quickly with omnipresent algae and moss that outcompetes the sundews. Full-grown sundews of the larger species (D. dichrosepala, D. enodes, D. scorpioides etc.) can survive, but moss will successfully outcompete small plants and minute species (D. occidentalis, D. microscapa etc.). It is beneficial to remove some of the moss and algae using small tweezers. While doing this, loosen the surface of the planting medium with the same tweezers.
Most pygmy Drosera are not particular about their relative air humidity. Air humidity of about 40-80% is sufficient. Such humidity is achieved by placing the plants in semi-closed glass-cases or aquaria with small air holes. However, plants can also be grown in trays of water on the windowsill. For watering, soft water is used (distilled or mineral-free water). Spraying of sundews is not necessary. Even medium hard water does not damage grown-up plants. Using soft water prevents quick mineral build-up and formation of calcareous concretions on the soil surface, which is especially dangerous for freshly sown gemmae and small germinating plants, on which mineral deposits will also form. The level of air humidity also influences the rate of mineral build-up. With higher air humidity, e.g. in a semi-closed aquarium, water evaporates from the planting medium more slowly. In this case frequent watering is unneeded, as compared to open cultivation on the windowsill. Thus build-up of soluble minerals is decreased in the terrarium. Pygmy Drosera are not suitable for planting in closed glass-cases where the air humidity ranges from 80 - 100%. In this environment the plants waste away and die. At the other extreme, pymies will tolerate intermittent radical declines in air humidity during the nice sunny days. However, all the sundews are hygrophytic and will not survive constant desiccation. Short-term desiccation (a few days only) is tolerated by the plants without any problems.
Pygmy Drosera love and require maximum lighting during all year seasons. The plants do not require a shield against the sun during the hot summer days. We choose the sunniest place with maximum daily exposure to sunlight for their cultivation. During the winter and autumn or when sowing gemmae you should use artificial light (fluorescent tubes, preferably tubes whose spectral balance more closely approximates that of the sun, but common types with cool-white light are sufficient), to substitute for decreasing sunlight. You will find it difficult to keep rare and unusual species in good condition during the winter without artificial light.
Pygmy Drosera are generally repotted in an emergency only, the best time being at the end of dormancy after producing gemmae. In our conditions this occurs in early spring, when plants are starting to grow. Common species and hybrids (D. x Lake Badgerup, D. x Carbarup, etc.) tolerate repotting very well except during their growing season. Rare species (D. dichrosepala, D. scorpioides, etc.) are very sensitive to repotting and we do not recommend trying it. If you decide to repot them, you must perform it very carefully, ensuring you include as much media as possible! A careful way of "rejuvenation and repotting" is to delve deep into the plants original media, using tweezers. During repotting we can also rejuvenate the plants by removing old leaves. Even though pygmy Drosera are annuals in the wild, they can grow in the same planting media for several years without any repotting. When the plants are fully-grown, they will generally tolerate opportunistic moss, which covers the surface of the pot.
Although several pygmy Drosera can been potted in a smaller pot (6x6 cm), the larger pots are better suited (e.g. 10x10 cm). Larger planting medium volume means that it will break down slowly and insures a more stable pH, so growing plants do not need to be repotted for some time. The root system of pygmy Drosera are threadlike and very long. Therefore, the plants prefer a deeper planting medium. As well, moist soil conditions are maintained more easily, necessary during summer dormancy especially, when the rare species require a slow desiccation of the soil followed by maintenance of lightly moist conditions. Pygmy Drosera are ideal plants-owing to their miniature "bonsai-like" - growth for "window" CP growers with minimal free space available for their hobby. With a bit of effort, you can grow a large collection on the windowsill that included many species!
Pygmy Drosera should be cultivated next to a window with southern or southeastern exposure, directly in trays, or in a ventilated glass-case or aquarium on the windowsill. These plants should be grown in outdoor growing areas (hotbed, greenhouse) during summer. Common species can be cultivated outdoors in open gardens or on balconies, even allowing it to rain on them. Rarer species should be protected from the rain during the summer rest period. The sundews are moved to the outdoors during early spring. The sundews love this method of cultivation; after the first "shock" and subsequent formation of new leaves, the plants will get a beautiful coloration and will form robust rosettes of leaves resembling those found in their native habitat. The plants flower prolifically during the spring to summer, some producing large quantities of miniature seeds for their propagation. From our observations, this occurs when there is no rain or several days, prior to wet autumn weather. The plants tolerate high summer temperatures during the day. As autumn approaches, the sundews should be protected from foul weather and rainfalls with a glass covering or a transparent foil. We move them indoors or into a heated greenhouse with the onset of the first autumn freeze. Our experience from the 1992-1999 with these plants has shown that they will tolerate even the first light frosts (up to -5°C), but we do not recommend exposure of your plants to such stress if it is not necessary. We must emphasize that outdoor summer cultivation of pygmy Drosera is not necessary and the plants may be cultivated, for example, on the indoor windowsill year-round with no apparent problems.
During winter we move the plants indoors or into a greenhouse. The plants require maximum light, especially during the short, dark autumn and winter days. Rare species will not do well when provided with insufficient light! We keep the plants within a temperature range of 15-25°C in winter. By late autumn to early winter the plants start to form gemmae from the central bud. Gemmae are brood bodies for propagation of pygmy Drosera. Some species form gemmae in two (exceptionally three) waves (autumn and spring), often forming dozens of gemmae. Mature, already falling gemmae may be sown on the surface of suitable planting media or around the mother plants, where they will germinate within several days or weeks. After several next weeks they will be fully grown. It is not that rare to grow a plant from gemmae in autumn and have it forming gemmae in spring (D. roseana, D. pygmaea)!
We should pay pecial attention to the dormancy period of these plants. In their native habitat some species stop growing during the hot summer season, and new leaves are protected against killing droughts by forming a bud in the crown area composed of the leaf stipules. These stipules form a shiny white bundle of hairs or bristles at the center of the rosette. As soon as unfavourable conditions pass with the first autumn rains, the plants restore their full growth. In our conditions this rest period occurs in summer, usually during the hot, dry season in July and August. The plants then gradually start to produce gemmae with a lowering in temperatures during the autumn. The length and beginning of dormancy is very different for individual species and is often variable. Even the most experienced grower cannot avoid &q! uot;light" the occasional loss of "less brawling" plants during this period.
Some of the more common species stop growing for a few days or weeks only. Their rosette of leaves has only small signs of forming the central bud during dormancy. After temperatures decrease, plants usually continue production of new leaves. This group consists of: D. mannii, D. nitidula, D. paleacea, D. pygmaea, D. pulchella, all the hybrids, plus others. The growing containers can stay in water all year round with summer restriction of watering being unnecessary.
Many rare species more or less go into intensive dormancy during the summer. They form a tight polymerous bundle of hairs or bristles at the rosette center and stop growing for a few weeks. These species require reduction of water during the rest period. Keep the planting medium barely moist! The plants tolerate high air humidity, but could die during long summer rains. With outdoor cultivation we must protect our plants from direct rain. The plants start growing again with a fall in temperature during autumn; at this time watering commences once again. Except for the dormancy period, these species can sit in water constantly. Examples from this group include D. androsacea, D. helodes, D. echinoblastus, D. leioblastus, and others.
Pygmy Drosera can be propagated via seed or brood bodies (gemmae). Description of how to sow seed was published in K. Pásek's article: How to sow seeds of carnivorous plants. So let's pay attention to sowing gemmae. Gemmae are sown shortly after they "ripen" on the surface of the growing medium (described above), giving the germinating plants plenty of space to grow undisturbed. They can be gently pushed into the soil, but this is not necessary. Never cover them! Sown seed should be placed somewhere with good exposure to sunlight. The rare species should be grown using artificial light during the winter. Germinating gemmae require light; especially they are placed in warm conditions! Cultivation and substrate are the same as for adult plants. Pay attention to high air humidity! Gemmae start to germinate, in bulk, within several days or weeks. Germinating sundews have the same requirements as fully grown plants. If you cannot sow gemmae immediately, you can store them for a short time. Gemmae must be kept in moist conditions (do not allow them to dry), e.g. between the sheets of moist filter paper in the refrigerator (0-5°C). Gemmae can be stored by this way for several weeks, but every day of storage withers and impairs their viability. Under these circumstances fungi often attack the gemmae. Any storage must be restricted to as short a period as possible. Within several months after sowing, the plants will be fully grown and some of them may begin to produce their first portion of „spring" gemmae. And so another amazing circle of nature continues.
Aphids love Pygmy Drosera. They usually pick the rarest and most precious species, while leaving the other common ones alone. If it becomes necessary to spray affected plants with a chemical spray, be very careful. We recommend trying it on some common species to determine any possible "undesirable" effects. This prevents the dissapointing loss of a rare plant. Pygmy Drosera dislike any „chemicals" in general, especially pesticides, and that is why we keep such interventions to a minimum. Pirimor was not effective at all, because aphids had survived. On the other, Karate was found to be effective and is safe for the plants (only tentacles will dry up for a time).
Fungus attack is another important factor that affects and, in many cases, can kill pygmy Drosera in cultivation. Fungi is often seen during autumn and winter weather, especially in areas with poor or no ventilation. Fungus often attacks freshly sown gemmae, but will also infest grown plants. It can appear on the surface of the planting medium (mostly due to using poor quality peat moss), and will later spread and start to damaging sown and weak gemmae or plants, especially when light levels are low and humidity high. If an infestation appears, spraying the affected plants immediately with a systemic fungicide is necessary (!!!). Alternatively, affected parts can be dusted with a fungicide. The spray can be used as a preventative measure when sowing gemmae or transplanting plants. Fungus often attacks pygmy Drosera if the plants are overcrowded, growing in mass clusters. In this case, simply remove and destroy the source of the infection, spraying the remainder of the affected plants with a systemic fungicide. Avoid sowing the plants too close together. We must remember that the little gemmae will quickly grow into plants a few centimeters in diameter and need plenty of space to grow. If you have sown gemmae „thickly", it is recommended that you report a part of the young plants either after germination or later - within a few months. Pygmy Drosera tolerate currently available fungicides (Topsin, Euparen, Fundazol) relatively well while other brands can not be used for treating your plants. Pymy sundews are like other sundews in that they do not require feeding.
Pygmy Drosera are offered by Allen Lowrie. A portion of gemmae (5-10 gemmae) is available for 10 AU$. He offers a wide range of pygmy Drosera species. Unfortunately few other foreign firms offer pygmy Drosera for sale, which is a shame considering the beauty of these plants.
While writing this article some interesting questions have arisen. These may serve to you as possible questions to contemplate and investigate, as we only have ambiguous responses for the present.
How would one grow pygmy Drosera in laterite and loamy substrates, frequently found in their native habitat? Can the plants propagate by leaf cuttings, as is common in other groups of Drosera? What is the best method for storing gemmae and what is their maximum viability? Can summer dormancy be broken artificially, eventually leading to no necessary summer dormancy? What is about autogamy and heterogamy of the individual species, and the ability to produce crossbreeds? When you know the answers to these questions, we would appreciate it if you notify us about them.
Pygmy Drosera are a strange mystery of nature. Looking at how harsh conditions are in their natural habitat, and nevertheless the plants survive and propagate, we realize what an amazing life strategy nature has created for this group of plants. We must admire her perfection at all points. We believe that the marvelous group of miniature Australian "dwarfs" will attract you not only with their beauty, but with their life history as well. We wish you luck with their cultivation.