Growing subtropical Drosera
Subtropicals are perhaps the largest and most variable group of Drosera. Some, like D. capensis, are very easy to grow and can become weeds in your CP collection if left alone. Others (usually cool-growing South African species) can be quite temperamental if you cannot satisfy their cultural requirements successfully. While highland South American Drosera are technically subtropical, we've placed them in their own separate section due to their more specific care requirements. When reading this care guide, it is important to realize that easier species will have a wider range of tolerable conditions whereas difficult species will not.
In general, subtropicals are not very picky in regards to temperature; daytime temperatures within 65 - 80 degrees should be fine for most species. Most of the slightly more difficult species (usually cool-growing South African species like D. slackii) appreciate temperatures that stay below 75 degrees along with a nighttime drop. Other species, like D. madagascariensis, prefer temperatures on the warmer end of the spectrum (but will tolerate a wide range regardless). The takeaway from this is that, while there are general guidelines for temperature, it's important to do research on the specific temperature range that each species will prefer. For example, I grow D. capensis outdoors all summer in NJ where temperatures may occasionally reach up to 100F, and while the plants are clearly happier when we have cooler nights they still grow well all season. In contrast, my D. slackii tends to lose its dew when the ambient temperature exceeds 85F. Prolonged high temperatures will be damaging to all subtropicals, even D. capensis - it may be relatively difficult to fry, but it certainly is not impossible.
For most subtropicals, high light is an absolute necessity and will allow you to attain the beautiful coloration that is characteristic of many species. That said, be sure to slowly acclimate plants to brighter light levels, especially if they are fresh arrivals from a grower who gave them far less light than you provide. Both myself and other growers have found through observation that light is the most important factor in dew production for the majority of species.
High humidity certainly won't hurt any of these species, as long as you are not forgoing adequate light in favor of humidity. For the more difficult subtropicals, high humidity is a requirement. The more forgiving species won't have much difficulty adjusting to low humidity, though they may not grow as well as they would with optimal conditions. Species like D. capensis, D. venusta, and D. nidiformis, are very tolerant of low humidity and are the best candidates for windowsill growing.
Overall, whether you're an amateur (such as ourselves) or a seasoned CP expert, subtropicals are a great group of sundews that you will find very rewarding to grow! If you're looking to start your CP collection an easy subtropical like D. capensis is a great place to start.
-Alvin & Dan
-Alvin & Dan