To cope with a slope, part two: What flopped

    I was away for Irene’s visit to Philly, but returned to find that my slope was mostly intact.

    The precariously balancing trees I mentioned in my last post were still upright, and the smaller plants I put in around them hadn’t washed away. This summer I’ve been experimenting with perennials that can survive on a hill that’s hard to work on. The soil here is extremely barren, and the steep grade adds an additional challenge.

    Gravity can be the nemesis of slope gardening. Woody plants are rigid enough to remain upright, but with their softer stems perennials and annuals  have a propensity to break apart or topple over, particularly when heavy with flowers. There’s something disheartening about a flower stalk listing at an angle. The same can be said for the subsequent efforts gardeners make to truss the plants back upright. Stakes, cages, and twine- I might be tempted to go there on a flat piece of ground, but not someplace where I’m already nervous about having both hands free to catch myself if I start tumbling into the street.

    Over the years I’ve noticed that multi-stemmed plants fare better in steep locations than plants with one main branching stem, which tend to split at the joints when not resting on level ground. Sturdiness is a requirement, and this often is unrelated to the size of a plant. I’ve had success so far with the large native joe-pye weed staying upright, as well as various types of goldenrod. And now I’m trying a native black-eyed susan, Rudbeckis ‘Herbstonne’ that seems to be defying gravity, even as it reaches four feet tall.

    Some of the other plants I’m using are shorter and meant to sprawl, so a sloped site is fine for them. Low asters, the small evening primrose ‘Fireworks’, and orange butterfly weed look good here. As do daylilies, the most common ornamental plant for steep grades. To my eye, daylilies are more effective on a hill than on flat ground.

    So what were the flops? The bee balm I thought might look nice is now sprawled over the ground like a plate of limp spaghetti. The other failure so far is a short coreopsis. I did not heed my own advice, and this single stemmed plant broke apart right at the crown almost immediately.

    How did your garden fare in our recent weather event? Any surprises, good or bad?

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