Dear Miss Floribunda,
Because of a dry spring season and now long stretches without sustained rain, I’m using a lot of mulch on my garden. I’ve found from bitter experience that wood chips just compact the soil, steal nutrients as they decompose, and, ironically, keep moisture from reaching the roots of my plants. This year I’ve used the lighter shredded wood mulch, but I’m finding that while some seedlings I’ve planted got smothered, plenty of weeds are doing just fine.
I’m thinking of saving fallen leaves this coming autumn, mowing them, and using them as mulch. However, a large part of my garden is on an incline, which is the reason I’ve replaced certain portions of grass that became too difficult to mow with a few small shrubs. I wonder if the leaves wouldn’t blow or slip away. I’ve also heard of “green” groundcovers that create a protective carpet composed of other plants, but wouldn’t that compete with the plants I have? I’d appreciate some guidance here.
Mulch Obliged on Oliver Street
Dear Mulch Obliged,
I have turned for advice to my groundcover guru, Kathy Jentz: publisher and editor of Washington Gardener magazine; editor of The Azalean, Water Garden Journal and Fanfare; co-author of The Urban Gardener; and most recently author of Groundcover Revolution. (The following interview was edited for brevity.)
Floribunda: Ms. Jentz, what do you think Mulch Obliged should do?
Jentz: I advise using groundcover plants as green mulch. Once they are in the ground, you don’t have to worry about replacing them again — as opposed to the twice-yearly chore of mulching with wood chips or shredded bark. Green mulch suppresses weeds, holds in moisture and moderates the soil temperature — keeping soil cooler in summer and warmer in winter — at least as well or better than non-living mulch.
F: Would these compete with the plants already in place?
J: That should not be an issue. Most groundcovers combine well and can be layered in the same bed with perennials, bulbs, and shrubs, plus trees.
F: What do you think of using fallen leaves as mulch?
J: I think it’s a great idea, and inexpensive, but one large thunderstorm can wash it away, especially if there is a slope. Also, think of the labor involved in that and other kinds of conventional mulching. People don’t always calculate the price of their own labor when comparing costs.
F: Doesn’t the cost of purchasing plants add up a bit? How would you compare the expense of acquiring plants with buying mulch twice a year?
J: It‘s true that upfront expense is greater with green mulch. In time, however, you save money as well as effort. Once the plants are established, they never have to be replaced.
F: What are some of the best plants to use as ground covers instead of grass?
J: Carex is the groundcover that most resembles turf grass, but I’ve provided 40 profiles in my book to help gardeners make an informed choice. Some groundcovers are good in sun, others in shade. Some thrive in boggy spots with poor drainage, while others do well in dry spots. Some spread quickly, others more slowly. Some tolerate clay and even somewhat salty soils. Many are native and attract pollinators, and the list goes on. To make quick reference easy, I’ve provided detailed charts as well.
F: Personally, I’d like to know what to plant in my garden under a large tree with prominent roots where nothing will grow. I think this is a fairly typical example of what a lot of homeowners encounter.
J: You are probably contending with dry shade, and so I’d recommend epimedium. I would advise getting small plugs rather than plants in larger pots grown in nurseries because you don’t want to damage the tree roots when you dig. Also, nursery-grown plants take longer to acclimate to a new situation, and they don’t naturalize as well.
F: I am hoping that you can find time to come to Hyattsville to give a talk about this topic in the near future. In the meantime, what in general would you like my readers to know?
J: The trend today is to replace most turf grass with groundcovers. Along with the many ecological advantages, such as lower water use and the elimination of the need for chemical fertilizers and weed killers, they require much less maintenance and are less expensive in the long run. Visually, they are much more interesting.
F: Yes, indeed. Thank you very much for giving me your time.
Please check the Hyattsville Horticultural Society’s website, hyattsvillehorticulture.org, for information about upcoming events.