A Gardening Journal
Fabulous in the Fall: Variegated Shrub-Mint
- Published: November 29 2016
Fall foliage is so much the province of woody plants that we're shocked—shocked!—that there are even a few slaggards. Perennials are the yin to this yang: only a few provide a credible show of fall foliage. Here's the gold standard—or, rather, the golden standard—thread-leaf amsonia.
This post celebrates another seasonal champ, variegated shrub-mint. Spring and summer, the green foliage of Leucosceptrum japonicum 'Mountain Madness' is splashed with white. For fall, most of that green has been ditched for pink and dark purple that would make any coleus proud. (The banana-sized green leaves are those of prairie dock.)
And how about the fluffy white flowers? It's highly unusual for any perennial to flower so vigorously even as its fall foliage develops. (Although its blue flowers are stunning, hardy plumbago—Ceratostigma plumbaginoides—is famous, in part, because the combination of flowers and fall foliage that are full-on simultaneously is so rare.)
All of these pictures were taken in mid-October. Besides mums and asters, there're fewer blooming plants to tempt pollinators—just fall-flowering witch hazel, autumn crocuses, tree ivy, the earliest hellebores. So, creatures that visit shrub-mints are enthusiastic, and include bees, butterflies, and hummingbirds.
Despite that attention, fall flowering could be risky: Will there be time for fertilized flowers to mature to viable seeds? Even so, if the plant is native to a climate with a much longer growing season, there might not be time for those seeds to germinate and grow into winter-hardy plants. If not, could the seeds remain viable through the months of cold and wet between now and return of growing weather in March or April? And even if the seeds do remain viable month after chilly month—meaning, in part, that they don't just rot away—that also ensures that they remain all the more appealing to foragers.
In addition to Mountain Madness, I grow four other cultivars of Leucosceptrum across two species, L. japonicum and L. stellipilum. Some colonies are nearly a decade old, and all remain energetic and floriferous, so there has been ample opportunity for almost any combination of pollination and germination. And yet I can't recall a single volunteer that could have arisen from seed, as would be the case if a plant appeared elsewhere in the garden than right alongside the colonies. My colonies all increase in size—and how!—but I've never seen a "popper upper," say, thirty feet away from the nearest colony that I established myself.
Yet another possible piece of this puzzle is that all species of Leucosceptrum are native to Japan. Is there some secret sauce in its environments or climates that facilitates germination of this genus's seeds? Perhaps the range of preferred pollinators is very narrow, and those of New England just aren't effective despite their diversity and enthusiasm.
Mountain Madness blooms for weeks and, yet, without the ultimate success of the effort: seed-driven propagation. I don't know how the Mountain part of this cultivar's name arose but, from its seedly perspective, the Madness seems evident.
Here's how to grow prairie dock.
Here's how to grow variegated shrub-mint.
Here's another astonishingly showy shrub-mint, Gold Angel.