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Virginia sweetspire Little Henry is a native shrub that's tolerant of occasionally wet soil.
(George Weigel)
Q: I have poor soil and a slope in my backyard, so I get water accumulation at the base of the slope. The problem is I have a shed near the base of the slope, which doesn't leave me room for trees or large shrubs that could soak up the water. Can you suggest any smaller plants or even ground covers that might help?
A: That site calls for plants that are tough enough to deal with days of potential sogginess but also periods in a dry summer where it's hot and dry – not to mention lousy soil.
Since you don't have trees in that area to provide shade all day, you'll also need plants that are sun-tolerant either all or most of the day. Given the shed-related size constraints, that'll leave you with perennials, groundcovers and possibly some compact flowering shrubs.
Mixing that altogether, here are 10 that I like:
1.) Dwarf Virginia sweetspire Little Henry (Itea virginica). A white-flowering native shrub that grows about 3 feet tall, slowly colonizes with runners (but not invasively) and has brilliant scarlet fall foliage.
Summersweet '16 Candles' is a compact native shrub tolerant of damp soil.
2.) Dwarf summersweet (Clethra alnifolia). Another native flowering that gets bottle-brush flowers of white in late spring, then yellow fall foliage. 'Hummingbird,' 'Compacta' and '16 Candles' are three good ones that top out at 3 feet tall or less.
3.) Indian grass (Sorghastrum nutans). A native grass that grows about 5 feet tall but can be kept to 3 feet of width. Turns yellow in fall.
4.) Red switchgrass (Panicum virgatum). Another native grass that grows about 4 feet tall with a 3- to 4-foot spread. Gets dainty pinkish seed heads in late summer and burgundy fall foliage.
5.) Sweet flag (Acorus). A damp-soil-tolerant grassy plant that grows 1 to 2 feet tall.
6.) Blue flag iris (Iris versicolor). A strappy-bladed perennial that gets blue flowers in late spring. Siberian iris also is a good choice.
7.) Gayfeather/blazing star (Liatris). A native perennial with summertime bottle-brush flowers of lavender.
8.) Dwarf goldenrod (Solidago). A native perennial with late-summer arching flower spikes of gold. Contrary to popular belief, these aren't heavy sneeze-producers. And they're tolerant of pool and wet soil. Look for shorties like Little Lemon, 'Baby Gold' and 'Golden Fleece.'
Turtlehead is a native perennial flower that prefers damp soil.
9.) Turtlehead (Chelone). Another late-summer native perennial, this one blooms in either white or pink spikes. I like the pink 'Hot Lips' variety best. This one works best out of the afternoon sun.
10.) New York and New England asters. Late-summer to early-fall native perennials that bloom mostly in purple.
There are lots of others that probably would work, but these give you a nice mix of shrubs, grasses and low perennials with bloom times that spread out over the season.
You can also mitigate some of the sogginess by loosening the soil and working in 2 or 3 inches of compost to create slightly raised beds before planting.