I'm not sure if this is the correct place for this, but several people have requested this information on growing Tuberous Drosera so I thought I might as well make it available to everyone.
Tuberous Drosera are a section of Drosera, mostly, though not exclusively originating from Western Australia. The conditions in this area of Australia is more or less, desert in the summer with cooler, wetter conditions in the winter. This group of Drosera have developed the strategy of growing during the cooler winter weather and waiting out the dry summer as a tuber buried underground. This survival mechanism is not exclusive to Drosera. A number of other plant groups also survive in this area as winter growers producing tubers to sit out the summer - orchids for instance.
As with other plants, its important to get the basics right, as is understanding their lifecycle.
Its important to get the soil right. You need a soil that is free draining but also one that will retain moisture and so not dry out too quickly. I use something simlar to the soil I use for my cacti and succulents. That is a gritty sand (with partical size variable from 1mm up to about 5mm) mixed with a good quality potting loam (soil based mixture). If loam is not available you can substitute peat. Use this 3 parts sand to 1 part soil or peat. The loam we get has added nutrients which is good for these plants. When the loam is mixed with the sand the amount of nutrients is very small and ideal for these plants. If you are using peat with no nutrients this is okay but you will need to give a weak 1/4 strength foliar feed every few weeks.
Use quite large pots. These plants do not have a large root system but large pots are easier to dry out slowly (see dormancy). I use pots that are about 110 mm across the top but they are 1/4 times the depth of a normal pot. This is simply because I can fit more pots into a growing area. If you cannot find this sort of pot, then use pots minimum size of 125 mm. Plant the tubers about 2-3 times the height of the tuber. For smaller tubers pant them about 2-3 cm deep. It doesn't matter too much, though of course the deeper they are planted, the more they have to grow to reach the surface of the soil.
Some tubers have a papery tube coming from the top of the tuber. This is the remains of the old stolon. The new stolon grows along the inside of this tube. I guess its easier than growing through the soil. If you damage this papery sheath its no problem. The solon will just grow up through the soil anyway.
Once planted water from above. I usually put the pots outside and let the rain do the watering here. Allow the soil surface to dry out between waterings until you see signs of new growth, at which time you can stand the pots in water.
These plants are winter growers. They will start into growth at anytime from September right the way through to January. I've actually had tubers reappear in February - just when I was beginning to think they were dead!
If you are ever tempted to dig into the soil to check to see if there is anything alive in it, be very careful. Its very easy to accidentally break the new growing point. I know because I've done it! Sometimes they regrow, other times they will just form a new tuber under the soil and not produce any top growth for that year.
Keep all tuberous Drosera at a winter minumum of 5C. I suspect some will actually take frost, in fact I know some will because one year I had a greenhouse heater failure. Its not something I would recommend though. At 5C the plants actually stop growing and remain in whatever stage of growth they have reached. The optimal temperature is probably closer to 8C or warmer. If you have to use a terrarium to get this sort of temperature do not let it get too humid. These are not tropical plants and will not tolerate permanent high levels of humidty.
The plants will continue to grow until dormancy. Dormancy is signalled by the die back of the above ground portion of the plant. This can happen quite rapidly. I have known a plant, that was looking superb a week before our society's Chelsea Flower Show display, and therefore reserved to show there, die back completely by the time I got to packing the plants to take up for the show.
Once the plants have entered dormancy you need to dry the pots out. The tuber is the means the plant used to survive the hot dry summers in Western Australia. But, you must not dry the pots out too quickly. I used to do exactly this - dry the pots out as soon as I could; it is was the reason why I used to lose so many plants over the summer.
Basically, there is a stolon connecting the tuber with the above ground portion of the plant. This stolon contains food reserves and in order for the tuber to have the maximum chance of survival, the stolon needs to channel these reserves back to the tuber. If you dry the soil too quickly the stolon shrivels and is useless. If you dry the soil slowly the stolon has a chance to send its reserves back to the tuber.
Use of large pots and the correct soil mixture help. What you also need to do is to leave the pot with the dried plant in water for about a week. Then move it somewhere that does not get direct sunlight. I use the lower shelf of my greenhouse bench. Here, even if the weather is quite hot, the pot will take a long time to dry out. Even if the surface of the soil looks dry the lower layers of soil will keep damp for quite a long time. It should take 4-6 weeks before the soil is completely dry. Even so, the centre of the pot will retain a tiny amount of moisture - though barely detectable.
I do not usually move the pots once they have dried. I have experimented with covering the pots with plastic and I know some growers give a brief spray of water once or twice during the summer months. It probably depends on how hot your summers are. Here in the UK its rare that we get very hot summers, though the summer before last was very hot for us and I did lose a few tubers, so its probably a good idea to water in very hot weather.
And there you have it. After the summer start watering the pots again - around the middle of September is about right.
Its a good idea to repot every few years. Not because the soil gets old so much as every year new tubers are formed, either as additional tubers, or as replacments. The new tubers are always formed lower down in the soil so eventually the tubers will be at the bottom of the pot. If you stand the pots in water (as I do) it will mean that the tubers are sitting in water too, which almost always leads to them rotting.