Planting ground cover in an active drain-way - Ask Extension
Adding close up pic from "Planting ground cover in a drain-way" part 1 message
Knowledgebase
Planting ground cover in an active drain-way #868185
Asked May 13, 2024, 12:28 PM EDT
I recently put in a retaining wall to help me more easily mow my yard (without a grass covered hill). Its installation revealed an ancient cobblestone gutter under the dirt from where the hill used to extend. It's really lovely but really difficult to maintain. Weeds come up constantly. I use a weed preventative that is only supposed to be applied twice a year but because it is an active drain-way, even if I apply it on a dry day, when the rains some, they will always bring new silt into the gutter which creates opportunity for weeds to grow. I will send more close-up pictures in a separate inquiry since the size of the one picture I attached takes up too much space.
So I thought what if I could plant creepers or something amidst the cobblestone to help crowd out weeds? But not sure I could establish them-- it's not like I can dig a hole or roughen the surface amidst the cobblestones. Especially now in spring there will be rains which will take seeds into the storm drain. I was thinking of microclover or something pretty.
Do you know the technique for planting or seeding or putting down ground cover in a densely covered cobblestone area? If technically and financially it is not feasible, (the gutter is LOOOOOng. It runs the whole length of my property --100" or so.) another option might be to put down a grass seed and weed preventative. Someone was telling me how happy they were with a "weed and seed" product for his lawn. That way, although I would need to mow it, it would look ok to have a bed of grass in front of the wall instead of jagged sporatic weeds throughout.
Kindly advise. But don't restrict your response to these options above if you have alternatives to suggest! Look for more close-up pics in a separate inquiry.
Baltimore City County Maryland
Expert Response
Adding close up pic from "Planting ground cover in a drain-way" part 1 message
We would not recommend using a pre-emergent herbicide (which includes weed-and-seed products) in a location with some erosion or which empties into a waterway/stormwater route, and keeping established plants vigorous in this kind of location may be challenging over the long term. (For example, having them be tolerant enough of drought, like last year's notable shortfall of rain, to survive without having to be intentionally irrigated.) If some plants do succeed and thrive well enough to put on lush growth, they will obstruct the view of the cobblestones, so we're not sure if that would render keeping them in place a bit moot, but can share some ideas.
Do you think you can squeeze-in plugs? Plugs are young plants that have fairly compact root balls, as they are younger than nursery pot sizes but older than seedlings. (Plugs do come in different ages/sizes, but most available to the public are "deep" plugs since they have better survival after planting, which puts their root mass at about 1.5 inches wide and around 3-4 inches deep, like the attached photo example.) Plugs may give you more flexibility since they get a jump start on growth compared to sowing seed, are sometimes more readily available than seed (though this can really depend on the plant species), and are easier to establish in the sense that you don't need to worry as much about trying to distinguish between seedlings of the desired species and weed seedlings, since either can change leaf characteristics as they mature, so might not always be recognizable until it's harder to remove the unwanted plants without disturbing the roots of the desirable plants.
One compromise could be to sow seed in containers first, essentially creating your own plugs, and then transplanting them while still fairly young into their final locations, which may help them get a competitive edge over any weed seedlings that appear later. Not directly sowing seed into the soil there also reduces the risk of them eroding away before they can establish in case we have heavy rain.
Plant species candidates will depend on site conditions like how much direct summer sun it receives (it looks like it would be semi-shady, but it's hard to tell), how deep the soil that collects there can get, and if deer browse in the area. Assuming a mostly-sunny or partly-sunny exposure, here are some ideas, though the list is not exhaustive. We are leaning towards native species in case their seeds wash into wild areas or are spread by wildlife into nearby parks. Botanical names are in parentheses.
Miri
Do you think you can squeeze-in plugs? Plugs are young plants that have fairly compact root balls, as they are younger than nursery pot sizes but older than seedlings. (Plugs do come in different ages/sizes, but most available to the public are "deep" plugs since they have better survival after planting, which puts their root mass at about 1.5 inches wide and around 3-4 inches deep, like the attached photo example.) Plugs may give you more flexibility since they get a jump start on growth compared to sowing seed, are sometimes more readily available than seed (though this can really depend on the plant species), and are easier to establish in the sense that you don't need to worry as much about trying to distinguish between seedlings of the desired species and weed seedlings, since either can change leaf characteristics as they mature, so might not always be recognizable until it's harder to remove the unwanted plants without disturbing the roots of the desirable plants.
One compromise could be to sow seed in containers first, essentially creating your own plugs, and then transplanting them while still fairly young into their final locations, which may help them get a competitive edge over any weed seedlings that appear later. Not directly sowing seed into the soil there also reduces the risk of them eroding away before they can establish in case we have heavy rain.
Plant species candidates will depend on site conditions like how much direct summer sun it receives (it looks like it would be semi-shady, but it's hard to tell), how deep the soil that collects there can get, and if deer browse in the area. Assuming a mostly-sunny or partly-sunny exposure, here are some ideas, though the list is not exhaustive. We are leaning towards native species in case their seeds wash into wild areas or are spread by wildlife into nearby parks. Botanical names are in parentheses.
- Sedge (Carex, many species) -- grass-like in appearance but not technically related, these perennials are occasionally evergreen, but not always; some spread with runners while others are more clumping, which type used will influence the spacing between plants; some handle drought better and some handle wet soil better, so the publication on the linked page will help sort-out which species might be the most suitable
- Pussytoes (Antennaria, several species) -- low-growing, spreading, with not-very-showy flowers but they do serve as a host plant for one of our butterfly species
- Eastern Columbine (Aquilegia canadensis) -- somewhat of a dainty-looking plant, but grows in the wild in just these kinds of places (in pockets of organic matter between boulders in semi-shade), and self-sows readily if not dead-headed; attracts hummingbirds
- American Alumroot (Heuchera americana) or Hairy Alumroot (Heuchera villosa) -- grows in similar locations as the columbine, and can also self-sow; tiny flowers support small native bees, but also might attract hummingbirds; semi-evergreen
- Lyre-leaf Sage (Salvia lyrata) -- self-seeding, clump-forming perennial with showy flowers (though the bloom window is fairly short)
- Wild Stonecrop (Sedum ternatum) -- unlike the other sedums commonly grown in gardens, this native is a woodland species, preferring semi-shade; evergreen; creeping, though somewhat slow to spread
- Partrigeberry (Mitchella repens) -- evergreen; slow ground-hugging creeper that can also be found rambling between rocks in the wild; showy, though very tiny, flowers and berries
- Blue Star Creeper (Isotoma fluviatilis, may also be listed as Laurentia fluviatilis) -- ground-hugging
- Dwarf Golden Sweet Flag (Acorus gramineus 'Minimus Aureus') -- short golden-leaved, grass-like plant that's actually related to Irises (though no showy flowers); fairly evergreen; this dwarf form stays just a few inches high, but there is a taller version that's about twice its size; vigorous creeper
Miri
