Ok what I can say about this plant is this.
Last year I grew some from seeds, planted the little seedlings among Sempervivum in 3 hypertufa pots at my kitchen window in very light soil - lots of sand, tiny grit and perlite and some soil. They thrived, bloomed, produced seeds and now I can see also some seedlings in the pots. All 3-4 plants are still alive, growing larger, and in fact are blooming (not profusely as in the spring) but still...
OK. Then I sowed some more seeds (left from the first batch). I planted 2-3 plants out in the garden. Raised beds, but the soil was just mixed with larger grit. I kept watering cause hot summer was on them. This may have killed them.
Either too hot or too much water. I watered more when I saw they were withering. I guess they needed less, not more.
All my windows are facing north-ish. Not really sunny spot. But the sempervivum and Thlapsi are doing great.
I am not sure you can find any "advice" in what I wrote. It's just my experience with this lovely plant. I also have a bunch of seedlings now. In a plastic pot, on balcony again, facing north.
ONly the window between them and what the winter brings.
