Drosera or Sundew
Collectors Corner Fact Sheet
The Drosera genus (common name - Sundew) is a very widespread group of carnivorous plants. It contains more than 160 species, scattered around the globe - about 65 species native to Australia. Charles Darwin was absolutely fascinated by sundews and spent considerable time studying them.In particular Drosera rotundifolia which can be found in England where he lived.Sundews vary in size from 1 cm. in diameter (pygmy drosera) to 60 cm (24") tall or more (Drosera regia,Drosera binata dichotoma and Drosera gigantea), and grow in a variety of environments - tropical rainforests in Queensland,the sandy dry plains of outback Western Australia(tuberous drosera),swamps near the beach and in alpine regions.Another well known group of drosera is the petiolaris complexwhich grow in tropical Australia.They grow in all continents except Antarctica and are concentrated in Western Australia. The species bear glands (often brightly coloured) on stalks or tentacles that are scattered over the surface of the leaves. The glands exude attractive nectar, adhesive compounds, and digestive enzymes. Insects that land on the leaves stick fast and are digested. Often nearby glandular tentacles are stimulated and also adhere to the insect, and on many species the entire leaf will coil around the insect. These motions are slow, taking minutes or hours to occur, although some species exhibit faster motion - for example, D. burmanni can produce 180º of tentacle movement in 30 seconds or less. Once an insect has touched a leaf, sometimes trying to eat the sticky glue, it will become hopelessly stuck, and moves about, touching more tentacles. The leaf will probably move other tentacles toward the stuck insect, and may even curl to further engulf the insect with tentacles (ie. an active trap). Then the digestive acids and enzymes are released to dissolve the insect. Afterwards the leaf opens and the insect shell is left to blow away.
The diversity of forms in this genus is impressive. While some species grow year-round, others die back to fleshy roots or tubers during dry seasons, others survive cold weather by forming densely packed hibernacula. Some species are tall, erect or viny plants, others are ground-hugging rosettes. Other than the usual problems associated with habitat destruction, most species do not have any particular threats. Some species, especially pygmy droseraforms of limited range in Western Australia, have gone extinct because of land development. As expected for a genus with so many types of plants, there is no prescription for growing every species. The two temperate species D. spatulata and D. capensis are pretty-well indestructible and make good starting plants for beginners. These, and various others, will do fine in a terrarium or in open air culture using a 2:1 peat and coarse sand compost mix. You can always tell when a sundew is healthy by the quantity of sticky glue (mucilage) droplets on the small tentacles. The leaves can be a variety of shapes, with some having long and thin leaves, while others may be spoon-shaped, or like a thick wedge; all have their sticky tentacles. Sundews have beautiful flowers, some with up to 50 on a stem, but only a small number open at any one time. Some species, particularly those from South Africa, can be seriously weakened due to growth of flowers. It is recommended that flower stems be removed in such cases. Pygmy Sundews (all are native to Australia) are tiny plants about the size of a fingernail - but even at this size, they manage to snare many tiny insects. These plants have a method of spreading their species that is unique to the pygmy sundews. As the cooler damper months of winter approach the plants produce additional non-sexual parts called gemmae, or winter buds - formed in the centre of the rosette. Each gemma is seed-like, but is living and must reach a suitable environment for growth or it will die - just as other living plant parts would die if damaged or allowed to become dry. When removed from the plant, and placed on the surface of the compost, each gemma will soon produce leaves and roots to form an exact genetic replica, a clone, of the parent plant. The pygmies can spread rapidly across a pot or terrarium base by means of their gemmae and the usual seed production from their flowers. There are two major, quite different, types of sundews. One type has roots like most plants, and will rejuvenate each year in spring to produce flowers, after dying back in winter. The other type has a tuber underground, and dies down to exist as just the tuber during the hot dry months in Australia. Most the tuberous Drosera plants are native to Australia. When the days shorten near winter, and the autumn rains come, its active growing time starts. Generally, Drosera plants like quite a bit of sun, and don't like to be over-watered. The common name for this genus of plants, sundew, was derived from the visual effect of sunlight shining, glistening, on their gluey tentacles. One particular plant, Drosera capensis from South Africa, can be used for demonstration. If you hold the potted plant almost between the observer and the sun, you will see this beautiful sundew effect.
Cultivation Summary for some temperate species (eg. D. binata)
Pots - 5-8 inches.
Compost - 2 parts peat,1 part washed sand.
Climate - temperate
Light - Full sun to part sun.
Water - Stand pot in 1cm of water all year round.Better results are achieved by watering from the top of the pot once a day.
Propagation - Division of clumps,seed,leaf cuttings.
Humidity - moderate
Notes - do not mist leaves too often
Pygmy Drosera are miniature rosetted Drosera, of the section/subgenus Lamprolepis and Bryastrum.Drosera are a type of carnivorous plant that catch prey by using sticky drops of fluid on their leaves.The Pygmy Drosera are amongst the smallest of all Drosera with most types being less than 4cm across.As individual plants they can be insignificant but growing en masse in a pot or the wild they can be showy and spectacular.
The trapping mechanisms of pygmy drosera which are just highly modified leaves are shown in greater detail below.The tentacles with sticky fluid and even the leaf itself have limited powers of movement that can be surprisingly fast.When an insect is captured the tentacles and leaf wrap around the insect as with most drosera.Some species such as Drosera pygmae can have such quick tentacle movement that it is plainly visible through a magnifying glass.To see this for yourself remember the plant needs to be healthy ,the temperature warm and the speedy movement is usually restricted to a few marginal tentacles.
The insects that are captured by pygmy drosera are minute in size but there is no shortage of them which partly explains why the plants are so successful.
There are approximately 45 different species growing mainly in south-west Western Australia but there are two unusual species growing elsewhere.Drosera pygmae,that also grows in Eastern Australia and New Zealand and D.Meristocaulis * (although this plant is genetically close to pygmy drosera perhaps it should not be included in the group as it has not been seen to produce gemmae) which grows only in the tropics of South America at high altitude. Their habitat generally is hot and dry in summer,cool and wet in winter with some species growing in wetter environments near permanent water.Some forms of the unusual D.Pygmae can grow in sub alpine conditions that get snow in winter.Pygmy drosera can tolerate extremes in temperature better than most other drosera.In most of their habitats summer temperatures can get to well over 40 C and winter temperatures may go just below 0 C.The soil is sand based with varying amounts of peat.Some species grow in laterite/loam type soils and clay based soils.Most species are out in the full sun with little to shelter them but once again there are exceptions such as D.Pulchella which can grow in shadier conditions.Typical places to find pygmy drosera include the borders of permanent or winter wet swamps,creeks or lakes.Heathlands,forests and even hilltops.
Apart from being carnivorous,the plants have many interesting characteristics to enable them to survive in their environment. One such characteristic is the central white stipule bud which shields the sensitive center of the plant from the intense summer sun.Relative to the size of the whole plant the stipules are enormous in pygmy Drosera.
Very long roots allow the plant to deal with relatively dry conditions in summer.Soaking up precious moisture deep within the soil.The roots can be 30cm long or more making them gigantic compared to the size of the plant above the ground.Even so many pygmy drosera have a period of slowed growth or dormancy over summer depending on the conditions.Often they can only manage to gather enough water to survive during this time.
These are produced in the center of the plant only once a year at the beginning of winter and provide a means of asexual reproduction.The timing ensures that the best growing conditions of the year are just ahead,giving the young plants the best possible start in life.Several dozen gemmae can be produced by each plant and each of those can produce a mature plant in 6 months or so under natural conditions.So a group of pygmy drosera can increase in number at an astronomical rate given a few good seasons.Each species of pygmy Drosera has unique gemmae.Many plants that start out as gemmae will flower by the next summer.
The flowers are spectacular and in many cases enormous compared to the size of the plant.Many have a metallic lustre which is very attractive.Also some are sweet smelling as are the flowers of Drosera roseanna.The flowers usually only last for a day so as to maximize chances of producing seed.That way a few days later there can be more flowers producing more seed.Pygmy drosera plants do not put all their eggs (or seeds) in one basket(seed pod).There is another reason for this strategy and that is the rains may decrease sooner or later.If the rains decrease later the pygmy drosera will produce more flowers and seed ,most likely ending up with more seed than would be produced from just the one big flower.
Pygmy Drosera Cultivation
The techniques below are based on several years of trial and error as well as consultation with various growers within Australia.
In cultivation they are best treated as annuals with no dormancy period.It is true that in their natural habitat most go into a state of slowed growth or dormancy in the summer months but it is not necessary for most species.Most species can also probably survive for several years in cultivation without a dormancy.The techniques below will probably not work for the unusual D.Meristocaulis which requires similar conditions to Heliamphora.
Pots 5 inch standard pot with a minimum of 3 inches.Pygmy drosera have long roots,the bigger the pots the healthier the plants.Bigger pots also hold a more constant temperature which is important on hot ,sunny days.
Light 50% to 100% sun.Approximately, the more sun the smaller and redder your plants will be.
Water Good quality water,preferably rainwater.
Watering Keep the pot moist continuously by carefully watering the top once a day.Alternatively the pot can be standing in about 1cm water constantly but this is not as good as the previous technique.Some species benefit from a drying out of their pot 2 or 3 times over summer for about 1 week in between watering.It is not necessary and for this to work the plants need to be in 5 inch pots or larger otherwise they will die.The species that tend not to like this are ones like D.Pulchella and D.Occidentalis which grow in wetter environments than other pygmy drosera.
Humidity Pygmy Drosera prefer moderate humidity,about 50% humidity.
Compost A loose peaty mixture such as washed sand or perlite and good quality sphagnum peat.Better results are obtained by treating the species individually and adjusting the ratio of sand in the mix according to their preferences.A minority of species such as D.Barbigera require laterite type soils to do well.Some hard to grow species such as D.hyperostigma benefit from the presence of dolomite in the compost,for more information Click hereBiological fungus controls such as Trichoderma when mixed into the compost have also been found to be beneficial.
Climate Mediterranean climate similar to Perth,Australia (Linked climate data copyright by Australian Bureau of Meteorology).Hot dry summers and cool wet winters.
Photo period 10 hours in winter.14 hours in summer.
Gemmae are sprinkled on the surface of compost in pots as for mature pygmy drosera.For a better strike rate plant the larger gemmae (eg silvicola,sewelliae,scorpioides) with the pointy end in the soil.They are also treated like mature pygmy drosera except for one thing.Until they form their first leaves they should be misted once a day.Be sure to plant your gemmae early if possible,that is a month before mid-winter as these plants will end up being bigger a lot quicker than plants from gemmae planted 3-4 or more weeks later.That can often mean the difference between the plant flowering that year or not.Another thing to keep in mind is that a week or so after germination you may find that some gemmae have produced what looks like an aerial root.This is due to the root not being able to find a proper place in the soil to dig in.If you are short on gemmae you may want to carefully bury the root in the compost whilst keeping the main green part still visible.Otherwise that particular plant may die.
Seed propagation is a lot more difficult.Some species germinate readily from seed such as the D.Pygmae complex and D.Omissa(D.Ericksonae).However many species do not. Perhaps allowing the seeds to sit under a hot sun over summer may help as may smoke treatment.Many species will need another clone to produce seed so that fresh seed is not easy to get.For best results sow the seeds in early Autumn onto compost for mature pygmy drosera.
Some of the tall growing species such as D.Scorpioides may be decapitated and the top planted.This will usually only work if the plant has aerial roots and is in good condition.For example decapitation is usually not a good idea just after gemmae production.Plant in compost as for mature pygmy drosera and keep well waterred with high humidity for the first few weeks.
These are known to work for some pygmy drosera.For best results choose a young mature leaf, cutting close to the leaf base.Place on sphagnum moss with the cut end in the sphagnum slightly.Keep humid and in shade.
COPY AND PASTED FROM VCPS http://www.vcps.org/descriptions.html
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