Experiment: What can grow under black walnut, AND under the dog?
I'm going to try an experiment, and I'd like your input!
I have a mature black walnut in my side yard near some dogwoods. It is on a gentle slope. For years we have kept our dog under this tree, and we let the tree get long branches so there is plenty of shade for her. (We move her when it starts dropping the nuts, lol!)
This somewhat dry hillside is eroding due to its perpetual nudity (it's hard to see the nudity under the tree from this pic, but I assure you, it's bare.) The only thing that has ever grown well under the walnut-and-dog combination is ground ivy, which I can't stand the smell of! There used to be wispy grass, but the dog has long since compacted the soil so tightly that it won't grow. Even if we fluff the soil and do grass plugs, they only make it about one season before dying. Seeding is fruitless. And of course there is regular watering and fertilizing, courtesy of the dog. ;-)
Recently I've moved some white yarrow (Achillea millifolium) under the tree and near the dripline (at the base of the post in tehe right-hand side of the pic.) I figure yarrow is so tough, such a thug in the garden, it should be able to hold its own here. So far, I'm right. It's not flourishing, but it is surviving ok and looks pretty good. It's a little short, but blooming.
I just planted some creeping Jenny (Lysimachia nummularia) at the base of the tree. Everyone says that this stuff tries to take over the planet, especially in wet locations. Hopefully it can at least survive in this location. So far it looks healthy though I don't see growth yet - hasn't been down a week yet, so I imagine it's just getting its roots in now.
I'm trying Ajuga reptans, too. This always seems to look bad when just transplanted, so perhaps it will perk up later. I'm trying it in several spots around the tree base.
I've planted a slip of Houttunyia. People say this is one of the most invasive groundcovers they've ever seen. Perhaps it will be kept to a dull roar in the compact, dry, walnut-poisoned dirt?
I have a small clump of variegated Bishop's Weed (Aegopodium podagraria 'Variegatum') which I plan to plant near the yarrow at the dripline. Again, people say this one's a thug, so here's hoping.
Can you think of anything else you'd like to try in such an inhospitable environment? If I can find some to try, I'll do it and I'll post the results as they either die or flourish!