|Lobelia tupa in front of Eucalyptus glaucescens|
I first got this plant many years ago from Heronswood and it was described as being marginally hardy. At that time I had no idea what to do with it or how to grow it and the only lobelias I had had experience with were the kind of more common lobelias that liked moist soil and that tended to flop around. Therefore, the first couple of years I grew it, it didn't do much, probably because I didn't put it in the right place. I only got the hang of it when I saw a slide at a garden talk that showed a huge plant of this growing out in the open in an arid landscape. So that clued me in to the fact that this is a drought tolerant plant, that it will get very large and that it is not a plant to crowd into a small spot. Full sun is also what it likes.
I have now been growing this for more than 15 years, and the oldest clumps I have are almost that old. As I said, Lobelia tupa will become very large, with my biggest clumps being probably 6 feet in diameter. The plant can also get quite tall, with the flower spikes in excess of 6 feet. Fortunately, if you grow this plant out in the open, it does not need staking.
Established clumps sometimes send out runners with new plants coming up several feet from the mother plant. These can be dug up and moved if you so desire. I have also had self sown seedlings in the garden. Indeed, the clumps against my blue wall seeded themselves extensively this year, so now I have lots of babies to put elsewhere in the garden. At first I didn't realize that all the weedy looking things around those plants were seedlings because they looked so much like all other common weeds. So if you want seedlings, be careful in weeding around established plants because it is not easy to tell seedlings from weeds at first.
Although Lobelia tupa has a reputation for being marginally hardy, I have not found this to be the case. I never protect my plants and they have never died from the cold.
Lobelia tupa is now available from many sources and local wholesalers grow it so I have found it in local nurseries. Seed can also be found from many sources including Chile Flora. These, of course, are native to Chile.