Begonia darthvaderiana was discovered in 2013 near West Kalimantan. It slightly resembles Begonia chlorosticta in its growth, and it’s temperamental nature. It has been making its way into the hobby gradually over the past year, and I am happy to now be growing this species.
This species should be grown in terrarium culture only, not an open-air environment. Like many of the more sensitive Begonias, care should be taken not to leave water standing on the leaves, but rather, moistening of the roots directly at the root base to maintain constant high moisture to prevent drying out. I have been growing this species on sphagnum only, but have seen others grow it in potting soil with success. It does not like temperatures above 80F, and should ideally be maintained between 70-75F. Even short spikes above 80F can cause the plant to wilt quickly. Having heard horror stories about its difficulty, I have been pleasantly surprised with how they are taking to propagation.
*update* After having kept this species for nearly eight months, lots has happened! The plants that I had on sphagnum crashed after about 4 months. They were given no ventilation and condensation appeared to be causing leaves to melt, however, I do not believe this to have been the primary issue. To address the melting, I kept them rooted in sphag, and sprinkled some clay around the plants, and potting soil. They did not improve much and of the 25 or so plants I had, all seemed to be suffering simultaneously, even though they were housed in three different containers. All this happened over the summer, starting in July and continuing through August/Sept. The temperatures were slightly warmer than they had been, but did not go above 80F, and usually stayed under 75F. Somewhat impulsively, I put some gypsum around the circumference of a few plants, and those lost all their leaves within a few days. Lesson learned! gypsum is not stable and quickly dissolved into the substrate when moistened, and was too strong for this species (at least in the amount I used). I used it because these plants were melting so quickly, I thought something drastic was needed, but in retrospect I should have been a bit more conservative. I experimented with airing out the bins daily for short periods of time but it did not seem to make a difference. I did this for about a month. Even sensitive Begonias when happy seem to put out moderate growth, so that even after one or two weeks there are noticeable changes, so every two or so weeks I changed something about how the plants were kept. In this case I am very grateful to have had so many plants to experiment on. I initially received six or seven plants but they were propagating so readily I took leaf cuttings whenever possible and within a few months had more than 25 plants (albeit small ones). Those plants made it possible to try out the different growing conditions with a few plants to test each variation in care and to maintain a group of ‘control’ plants. I even tried not caring for a few weeks and refused to look at them. That didn’t work either although they did not melt any faster than they had been when I was being attentive. Unfortunately, I do not have any images of the entirety of the darths melting, (it was a sad sight!) as I was too concerned at the time to take any pictures. Here is an image of the particular way these plants melt though, which can be more dangerous than the classic ‘turn to goo’ type of melting as it occurs when the plants are seemingly healthy in every other way. Randy Kerr calls it ‘ashing’, which seems an apt term. It is different from other types of plant cell death and in my experience only occurs in some sensitive SE Asian species.
Here is the more typical melting, which darths are also very prone to. If this happens, it is best to cut off any damaged tissue and to do so very liberally. If the plants’ rhizome is intact that is enough, so even if you must cut all the leaves off, I think it is the best solution. I have salvaged many this way.
It’s now December, and after some aggressive repotting and change in potting mix, the remaining plants I have are growing more robustly than they were when I first recieved them. They are housed in gently ventilated bins, under daylight spectrum 1800 lumen LEDs with a printer paper shade cloth over them. They are in clay pots, with a mix of potting soil, perlite, crushed lime, and turface. They are fertilized twice a month with urea free orchid fertilizer. It seems the primary issue was one of potting medium. I think that like many Begonias, if kept on sphagnum for more than a few months, they suffer nutritional deficiencies that effect (in this case) their ability to resist melting. Since this change, the leaf edges are intact, and only one out of the fifteen or so plants has any observable malady of the leaves. That particular plant, though, is flowering, so I don’t think it’s too unhappy 🙂 This is consistent with observations I have had with rhizomatous species on LFS long term. The soil I use is happy frog brand, and the first ingredient is aged forest product. I think LFS sphagnum especially is not very similar to the growing medium of these Begonias in the wild, at least in terms of nutrient content and complexity. Even if you fertilize on sphagnum, the types of nutrients that are available are limited to what is in the fertilizer, and so the dosage and type would need to be perfectly calibrated. We know rainforests have nutrient-poor soils, but they are a lot more complex than simple N, P, K measurements. Of course, that doesn’t mean the most ingredient rich medium is best, it depends on the ingredients, but I do think its reasonable to be skeptical of using sterile mediums for growing long term.
The flowers, with the female flower opening first, and the males soon to follow.