Tuberous Drosera are native to southern Australia, Tasmania, and New Zealand. A few species like the Drosera peltata-complex and Drosera macrantha are widespread but most are narrowly endemic to the state of Western Australia. Tuberous Drosera live in areas where winters are mild and rainy while summers are hot and dry. The tubers sprout in early fall and begin vigorous growth with the first rains. By late spring the plants have bloomed and they die back to the underground tubers. The tubers over-summer in warm barely damp soil.
Most tuberous Drosera are quite challenging to grow unless you can provide their exact requirements. The Drosera peltata-complex species and Drosera stolonifera are the most forgiving of adverse conditions and recommended for beginners. As long as the plants are kept cool and get lots of light, they are very tough and easy to grow. Most can take light frost. But temperatures above 25°C (78°F) can cause them to die back and will kill seedlings. If the plants have not built up enough nutrients in the tuber to recover from the warm temperatures, the plants are history.
Most tuberous Drosera do NOT make good terrarium plants. They get too large, do not need the high humidity, and terrariums tend to get too warm. If you live in a so called Mediterranean climate you should grow tuberous Drosera outside all year. If you live in a colder climate and your house is cool enough you can grow the plants under lights. LED lights would be best because they are not hot like fluorescent lights. Or you can grow them in a garage or basement under lights. Try to keep the light cycles natural.
Tuberous Drosera seed must be planted in summer or early fall since these species are winter growing. The seed of some species germinate best if they have experienced a period of warm stratification in damp soil. In the northern hemisphere this means you must plant the seeds by the first week of August (down under that would be February). The soil surface needs to be kept damp during stratification. Cold stratification such as is used for Sarracenia and temperate Drosera is NOT effective with tuberous Drosera.
Drosera hookeri, Drosera auriculata, and Drosera macrantha do not require the warm stratification and will germinate if planted by the first week of September (March in the southern hemisphere) or if grown inside kept in a 10°C to 20°C (50°F to 70°F) temperature range until you get germination. The seeds appear to require cycling temperatures or temperatures in the middle of that range to germinate. Expect the seeds to start germinating in October and November (April and May in the southern hemisphere). Seeds planted late may germinate in the spring. Depending on your growing conditions this will likely end in tears as the temperatures could get too warm and the seedlings not live long enough to make tubers.
Some tuberous Drosera species with hard seeds germinate better if they are scarified before planting. These species include Drosera stolonifera and Drosera gigantea. Please see the page on Drosera seed scarification for more information.
Tuberous Drosera require very deep pots and can not be transplanted when growing because their roots are very long and very fragile. Use 16 cm deep nursery #1 ("gallon") pots to start seeds. A 1:2 mix of peat and sand with some sphagnum moss in the bottom blocking the drainage holes works well. Let the pots sit in about 2 cm of water. In mild winter areas you may leave the pots outside and let nature takes its course. In other areas you may start the seeds in a greenhouse that allows the temperature to get down to a few degrees above freezing at night. The perfect location is in the trays with your Sarracenia plants although it is probably best to protect the pots from rain and top watering as the rain could wash out the seeds and encourage moss, liverworts, and other weeds.
If the seeds don't germinate the first winter, don't throw out the pot! Let it dry out during the summer and try again the next winter. These plants require some patience.
After the seeds germinate, the challenge is to give them enough light at cool temperatures to produce tubers sufficiently large to get the plants going again the next winter. Most species appreciate a foliar feeding of half strength Miracid every two to three weeks. Only mist the leaves; don't fertilize the soil.
Do not force the plants to go dormant. This is especially important for seedlings. If there is a heat spell in the spring, put them in a cool location to delay dormancy as long as possible.
When the plants do die back, let the pots dry out. For most species you can let the pots get completely dry if they are stored in a humid location out of the sun. Drosera gigantea and Drosera sulfurea should never be allowed to dry out completely. A technique for storing the pots with tubers over the summer is to allow the soil to become just damp and then put the pots in plastic bags or in a terrarium in a shady location or under a greenhouse bench. A terrarium with gravel and some water in the bottom works best as it is easy to keep an eye on the pots and to check for new growth in the fall.
The only time you can transplant tuberous Drosera is when they are dormant. If you are getting too many plants in a pot, carefully dig up some of the tubers a month after they die back and put them in new pots at the same depth they were originally at in the old pots. They are usually 5 to 10 cm deep. Don't throw out the soil in the top 10 cm of the pot unless you also want to throw away small tubers. Don't wait until the fall to do the transplanting as many species try to get a jump on winter by sending up a sprout to just below the soil surface in late summer. Do enjoy these wonderful ephemeral plants!
— John Brittnacher
For more information please see:
Powell, Charles L. II (1989) Tuberous Drosera. Carniv. Pl. Newslett. 18(1):21-26 ( PDF )
Gibson, Robert (1994) Carnivorous plants of New Zealand: A review. Carniv. Pl. Newslett. 23(3):74-81 ( PDF )
Gibson, Robert (1992) Observed variation in Drosera auriculata and Drosera peltata. Carniv. Pl. Newslett. 21(3):75-78 ( PDF )
Gibson, Robert (1999) Carnivorous Plants of New South Wales, Australia. Carniv. Pl. Newslett. 28(2):59-69 ( PDF )
Gibson, Robert (2013) Variation in floral fragrance of tuberous Drosera. Carniv. Pl. Newslett. 42(4):117-121 ( PDF )
Bourke, Greg (2014) Growing tuberous sundews. Carniv. Pl. Newslett. 43(2):71-73 ( PDF )
Many stalk forming tuberous species produce rosettes as seedlings and when they first emerge in the fall from tubers. This is Drosera hookeri.
Drosera stolonifera is another species that forms rosettes for a few weeks or months before it bolts.
After a few months for seedlings or a few weeks for plants with tubers, the main stalk will appear. This is Drosera auriculata from a tuber.
D. hookeri leaves and flower buds.
Tubers may be stored in plastic zip-lock bags in a dark location. Plant them with the "eye" up. You may find it easier to maintain mature plants if the top 3 cm of the soil is pure sand.
Drosera hookeri (part of the Drosera peltata-complex) from Dubbo, NSW, Australia.
Drosera auriculata. These plants are 25 cm tall.
Drosera auriculata up close.
Drosera rupicola tubers dug up too early. If you have lots of them it is fun and interesting to dig them early and watch the tubers form. Tuberous Drosera have thick roots while growing and the tubers are formed after the top and leaves die back and while the roots shrivel.