|Battle of the Invasives
Since the plants I grow have to be easy, I end up with a lot of tough customers that want to take over. What happens when two of these meet?
Lily-of-the valley will overrun any shade but in one part of my woods, it's been overgrown by fast-creeping, 12- to 18-inch tall Yellow Archangel, Lamiastrum galeobdolon. (I have 'Variegatum,' with silver chevrons marking the green leaves; supposedly other varieties are slightly less aggressive.) Just across a path from there, the lamiastrum is locked in a standoff (so far) with sweet woodruff which although certainly invasive too, wouldn't have seemed to me capable of competing: it grows a bit lower, and not so dense.
On the north side of my house, an English ivy is creeping under established lily-of-the-valley which so far, doesn't seem troubled by it. But no lily-of-the valley is sprouting up within the established ivy. On the edge of the bed, ivy's creeping out into the lawn. Mowing doesn't seem to deter it. Rather, it seems to be learning: Many leaves are chopped in half by the mower, and though they look ungainly, they're healthy. But just as many leaves are small, and escape the mower by growing low. There seem to be more of them than I'd expect to find on these well-established runners; is this like the leaves on bonsai trees growing smaller in response to their conditions?
On the front of the ivy bed, pachysandra is sprouting up in it, a bit taller. Though the pachysandra is broad-leaved, ivy will take dense shade; I wonder if they will coexist.
Magenta-flowered Geranium sanguineum, the original bloody cranesbill, grows 18 to 24 inches tall. It spreads slowly, but anything adjacent that it can overtop, is a goner for example thyme and bugleweed normally invasive themselves. Named varieties of this cranesbill are less aggressive, for example I also have lancastriense, which grows lower and sports flowers in a light pink with darker veins. I actually like the pink better; it's not such an overwhelming color but the magenta self-seeds more prolifically, popping up all over my garden. Only bigger plants withstand it, for example tall New England asters (which are also slow-but-strong spreaders and enthusiatic self-seeders).
If I plant some of this magenta cranesbill at the edge of the worst lamiastrum patch, will it contain the lamiastrum?