Growing subtropical Drosera
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Among Drosera species, the subtropicals usually make the best terrarium and greenhouse sundews.  They generally do well in a moderate temperature range of 10°C to 35°C (50°F to 95°F) and don't have dormancy or light cue requirements.  Many are long lived. Even annuals such as Drosera burmannii can live for years if you remove flower stalks as soon as they appear.

Drosera species that could be classed as subtropicals are found in South America, southern Africa, southern and eastern Asia, and Australia. There are at least a hundred species of Drosera in these regions. Some such as the tuberous, pygmy, and wooly sundews of Australia are special cases that need to be considered separately because of their particular requirements.  But most are just variations on the same theme. They have been referred to as DRS's or <expletive> rosetted sundews because they are so hard to tell apart without ripping off leaves and checking flowers and seeds under a hand lens.

Most subtropical Drosera aren't very picky about soil. They can grow well in pure sphagnum moss, live, long fibered or shredded, as well as the standard peat:sand "CP mix" which can be anything from 30% to 100% peat. Growing plants in CP mix with live sphagnum on top is very effective for the larger or stalk forming species.  Things to watch for are inferior grades of sphagnum and peat and non-silica sand. The best sphagnum is from New Zealand and Chile.  For peat look for Canadian or German sphagnum peat.  The best sand is uniform size sand-blasting silica sand about 1.2 mm in diameter (16 mesh in USA).

Everyone has their favorite seed planting medium. They also have anecdotes to tell why their way is so wonderful and the way everyone else does it is, well, you know. You just have to find what works best for you given the materials you have available and the conditions you can provide. You can try a high proportion of sand, putting sulfur in the soil, using sterilized material, waving a magic wand.  They all work for some people. And then there are pots. Don't get me started on pots! Some people have obsessions about round vs. square, tall vs. short, large vs. small. IT DOESN'T MATTER.  Mostly.

One thing there is no argument about is you sow seeds on the surface of your medium of choice. Don't burry the seeds. For any seeds but bog plant seeds, you don't top water a seedling pot. It can be fatal. With Drosera it is different. The soil surface should be lightly misted after the seeds are placed. It helps germination and settles the seed around large sand particles. Make sure you label the pots and include the date so when it seems like forever since you planted the seeds you can see it has only been a few weeks.  Some seeds may take a month or more to germinate.

What you do next depends on what works best for you. Everyone has their own preferred routine. I put pots with seeds in plastic zip-lock bags under but not too close to fluorescent lights. You could also use an aquarium in a greenhouse. The purpose of the plastic bag is to maintain very high humidity and to keep out fungus gnats. Fungus gnat larvae will eat the seedlings. A temperature between 20°C to 25°C (70°F to 80°F) works best. The seeds should germinate in a few weeks. When the new plants have a few true leaves, remove the pots from the plastic bags and put them in a bright terrarium or greenhouse.

Most Drosera seeds are small and result in tiny, slow growing seedlings. It takes patience to grow carnivores from seed. The biggest problem in starting seeds is usually dealing with the moss, fungi, and cyanobacteria (blue-green algae) found naturally in the sphagnum and peat.  It is not uncommon to transplant seedlings into new media a few times as the seedlings get overwhelmed with guk.  Use a fine forceps, bright light, and magnifying glass. Be careful not to damage the roots.

Once the plants are large enough you can try feeding them small insects or get some dried blood worms at a pet shop. The dried blood worms can be dipped in water and placed on the dewy leaves--don't feed a plant that isn't dewy. If the food gets moldy, use less next time. A dab of 70% isopropanol (rubbing alcohol) from a small paint brush will kill the fungus.

Do not put fertilizer of any kind in the soil. If it it does not directly kill the plants, it will change the soil chemistry which may make the plants rather unhappy. Once the plants are more than a cm wide they do respond to light misting with dilute, high nitrogen fertilizer. It is best to use hydrated dried blood worms on the leaves instead of spraying with fertilizer, but if you feel you must use fertilizer, use foliar fertilizer with care.

It can easily take two years to get mature plants. The hardest part is getting the seedlings to a size you can feed them with hydrated dried blood worms. Once you can do that the plants should grow quite quickly.

For more information please see:

Chandler, Graeme (1978) The Uptake of Digestion Products by Drosera. Carniv. Pl. Newslett. 7(1):11-13 ( Part 1 )

Chandler, Graeme (1978) The Uptake of Digestion Products by Drosera. Carniv. Pl. Newslett. 7(2):51-54 ( Part 2 )

Nolan, Garry (1978) On the Foraging Strategies of Carnivorous Plants: II. Biological Stimulus versus Mechanical Stimulus in the Fast-Moving Periphery Tentacles of the Species Drosera burmanni. Carniv. Pl. Newslett. 7(3):79-81 ( )

Haberlandt, Gottlieb (from Sinnesorgane Im Pflanzenreich, Trans. By Carla R. Powell) (1982) Insectivores: Drosera and Drosophyllum. Carniv. Pl. Newslett. 11(3):66-73 ( )

Degreef, John D. (1989) Early history Drosera and Drosophyllum. Carniv. Pl. Newslett. 18(3):86-89 ( )

Degreef, John D. (1989) The Droseraceae during the glaciations. Carniv. Pl. Newslett. 18(2):45-46, 52-54 ( )

Drosera aliciae
Drosera aliciae. These plants are 5 cm across.

Drosera seedlings
Seedlings with one true leaf.

 

Drosera dielsiana
Drosera dielsiana. This plant is 3cm across.

Drosera natalensis
Drosera natalensis, from South Africa.
Drosera asendens
Drosera ascendens from South America.
Drosera venusta
Drosera venusta from South Africa.  This species grows best under cool conditions.
Drosera trinervia
Drosera trinervia.

Drosera madagascariensis
Drosera madagascariensis from Botswana in a 5 cm pot.

Drosera nidiformis
Drosera nidiformis. These plants are in a 5 cm pot.

Drosera admirabilis from South Africa. These plants are 25 mm across.  The one in the middle is a few years old. This species generally looks like a miniature Drosera aliciae although some taxonomists confuse it with D. cuneifolia.


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