I grow at least four perennials that emerge in the late summer or fall, remain green all winter and then go dormant as summer approaches (Dentaria (Cardamine) diphylla, Arum italicum, Sternbergia lutea, and Cyclamen hederifolium). Weird. I suppose that makes sense in a Mediterranian climate where the winters are mild and moist and the summers are hot and dry, and that is exactly where three of these four are native. But somehow they survive in climates with cold winters and relatively moist hot summers. Dentaria diphylla, on the other hand, is native to the eastern U.S. So where did it acquire this inverted growing season behavior? I bring this up not for botanical reasons but rather horticultural. How do you take advantage of this habit to enhance your garden? I mean, what a gift to have plants that grow when others aren't. They need to be paired up with compatible companions, but there's the rub.
I pride myself in my efforts to orchestrate the sequence of emergence and decline of perennials in my garden and have several combinations that I shamelessly tout as exemplary. But, alas, this growth habit I am calling "inverted" is challenging. I think I found a nice combination for the Cyclamen. I combined it with Carex platyphylla (Silver Sedge). The sedge is low growing enough that when the otherwise dormant Cyclamen sends up its flowers in mid summer they poke through the sedge and make a nice display. As the Cyclamen leaves are emerging late in the growing season the sedge leaves make room for them as they go dormant. It is all very tidy, but I haven't been able to do anything comparable with Arum italicum or especially Dentaria diphylla. (For hardiness reasons I grow Sternbergia in a pot.) Arum italicum produces stalks with bright red fruit in August when the leaves are gone. It makes an interesting affect on bare ground, so there is a reward for not finding a sort of mirror image growing companion, but I would be more satisfied if I could. I have been growing Dentaria diphylla for six or seven years and only recently realized why it was so unsatisfactory in the summer. I just have to apply myself to this challenge. That (and so much more) is what I love about gardening.