What is a good way to deal with a gravelly area with a lot of shade? Are there good groundcovers that would be low maintenance? Can the plants grow right in the gravel, or do I need to do something to the soil?
If it’s pure gravel, you can just make a border (with rocks and/or wood, preferably non-treated) and fill it with 9-12″ of soil. (No need to remove the gravel.) You buy soil by the cubic yard, so to figure out how much, multiply the length (feet) x width (feet) x depth (.75 or 1), then divide by 27 to get the number of yards. One yard of soil is 3′ x 3′ x 3′, or 27 cubic feet. My guess is that you need less than a yard, but it settles.
You can save money by buying the soil in bulk. Otherwise, you have to buy it by the bag, and they might come in cubic feet. If there is only some gravel, you may be able to get by with the soil/gravel mix that you have. See how much hardpan there is by digging around a little.
If you have lots of weeds in the gravelly area, try mulching the whole area with a thick layer of wood chips (freely available from arborists) Smothering weeds depends upon complete darkness more than anything.
Once you’ve done that, you can plant right away. Here are some plant suggestions. I’ve
included links to pictures, but you can always find more on Google images or
the Missouri Botanical Garden’s PlantFinder.
- Lobularia maritima, known as sweet alyssum: You can plant seeds of this and it will come up this year. It’s best to mix it with something else, since it dies down in winter (but self-seeds vigorously and will return). The white seeds the fastest (year to year), but it’s nice to mix with purple. Both varieties smell good and attract
beneficial insects. - Fragaria x ananassa ‘Pink Panda’: A strawberry-potentilla hybrid that grows fast and spreads easily, is good weed suppresser, and blooms twice a year with pink flowers. This is an excellent groundcover, will probably be evergreen.
- Pachysandra: This plant is evergreen, and though it is not as fast growing as some groundcovers, it does spread.
- Hardy Geranium spp.: Geranium x oxonianum ‘Claridge Druce’ is a variety that spreads well. Another good variety is Geranium endressii ‘Wargrave’s Pink’; in particular, it seeds itself well. Geranium macrorrhizum has many cultivars, a pleasant scent, and self-seeds readily.
- Galium odoratum: Also called sweet woodruff, this plant is prettily scented, probably evergreen here, and spreads fairly rapidly. It produces white flowers in early spring, and it would be particularly good to mix with something taller, like Geranium species.
- Oxalis oregana: This native plant looks like a shamrock, and though it is slow to establish, once it has it’s very
tough and spreads. If you don’t get the native Oxalis oregana be careful, as the other species are very aggressive. - Euonymus spp.: These woody groundcover plants are evergreen, and come in lots of varieties like
E. fortunei ‘Emerald ‘n’Gold’ and ‘Emerald Gaiety’. Do be sure to get a groundcover and not a shrub version of the plant. ‘Emerald and Gold’ is the most robust choice. - Convallaria majalis: Also known as lily of the valley, this is a vigorous (aggressive!) groundcover.
- Maianthemum dilatatum: Called false lily of the valley, this native plant is a good choice for shade groundcover.
- Polystichum munitum: The native swordfern (or another fern species) might work. P. munitum is basically evergreen, though you might need to cut out some dead fronds in late winter, and makes a good mix with something else. Other deciduous ferns are higher maintenance.
There are also a couple of plants to avoid!
- DON’T plant Aegopodium podagraria ‘Variegatum’: Commonly called bishop’s weed, and frequently used as a groundcover, this plant is very invasive.
- DON’T plant Lamium galeobdolon (formerly known as Lamiastrum), either: Yellow archangel is very invasive in Pacific Northwest forests.