Hi Sara!

I, too, know the challenges of managing a sloped yard! I'm glad you wrote in to us because we can definitely help you select the right plants for this project to be a success. 

To answer your questions: Do not use pre-emergents (herbicide) and make sure to familiarize yourself with the Montgomery County laws banning the use of chemical herbicide, pesticide and fertilizer. It is wise to avoid using these products on slopes especially since the runoff potential is high and the purpose of the bans is to prevent contamination of our waterways. 

The area looks like it is ready for planting, especially as the mulch continues to decompose and provide a nice planting medium. Fall (now) is a great time to plant on the slope. We recommend against vinca and pachysandra, as they are considered non-native and invasive species. Check out our recommendations for native groundcovers for shady slopes: https://extension.umd.edu/resource/native-plants-shady-slopes

When you source the plants, you could look for some deeply rooted 'plugs', which are smaller sized plants that will allow you to spread them across the large area. Plugs are typically a fraction of the cost of quart-sized plants. 

Until the plants grow in and provide shade to reduce weed germination, you'll need to do periodic weeding (hand pulling). 

Jamie



Hello Sara.
Just off the top of our heads, try investigating Sweetbox (Sarcococca), Packera, and Woodland Phlox.


Christine



Hello Sara,

We think the vining weed in the pictures might be Honeyvine Milkweed, and if so, it's a native plant but one that is known to be aggressive and hard to control in gardens (and is thus considered a weed). It looks superficially like Bindweed, another very common and hard-to-kill (and non-native) vining weed, but the leaf arrangement of Bindweed differs from Honeyvine. Concrete identification would be much easier with blooms on the plants, but we realize you may not want them to get that mature again. Both weeds can be fairly tap-rooted and will easily regrow after being cut or pulled where the entire root doesn't come up.

Although Monarch caterpillars can reportedly eat Honeyvine, they seem to prefer their Milkweed cousins so you don't necessarily have to keep the plants for that reason. Either repeated pulling/cutting every time new leaves appear (so the plants don't have time to renew their energy stores with photosynthesis) will eventually exhaust the plants, or you can spot-treat them with a systemic herbicide, being careful to only get their leaves contacted with the spray. A repeat treatment might still be necessary. You can plant the bed while this eradication process is underway, but realize that might make spotting any re-sprouts and avoiding contacting any desirable plants in the process more difficult. The aforementioned herbicide regulations in Montgomery County pertain to chemicals used on lawns, not garden beds.

Anything that isn't a fern or moss will technically flower (though grasses and sedges don't have blooms that look like stereotypical flowers and are often ignored), though some species have less showy blooms or a short flowering period, so won't be prominent if you prefer them subtle. The Sweetbox (evergreen and non-native, but non-invasive), native Wild Ginger (not evergreen), and European Ginger (evergreen but not native) all do bloom but aren't considered very showy. The Sweetbox blooms are very fragrant and appear around February-March, but the Ginger blooms are held at soil level underneath the leaves and are not brightly colored.

Partridgeberry blooms are showy for their size (though still small and sometimes sparse) and the plants make a nice evergreen groundcover, albeit much slower-growing than most other plants for such use. It would take many years for a patch of several plants to form a solid carpet, so site them accordingly so they don't get lost amid any taller-growing companions. It's always advisable to mix species in a groundcover planting so they add resilience in the face of potential future issues from unusual weather or a pest or disease outbreak, since not all species in the mix will have equal vulnerabilities. Plus, a mix of species adds more wildlife value, especially if the plants used are locally native.

Native evergreen groundcover options are limited, so you might need to prioritize where in the bed you want to have winter foliage...perhaps closer to the walkway or top of the slope where they will be more visible, or scattered so they maintain interest throughout the bed. Even among non-native but well-behaved species, evergreen foliage is an uncommon trait and leaves can still look a bit tired by the end of the season.

Christmas Fern (Polystichum acrostichoides) is fairly evergreen and is one of the only ferns in this area to retain its leaves in winter, though by the end of winter it too can look a bit bedraggled depending on the weather. Fresh fronds regrow in spring and any beat-up fronds can be clipped off in late winter if desired; otherwise new foliage simply covers them up eventually. They are not a spreading groundcover because they clump instead, but depending on plant spacing and whether running plants are grown between them, they can serve the same function. They often grow on slopes in our woods.

Depending on how dry or moist this site tends to be, combined with how many hours of direct summer sun it receives, that will help you narrow-down candidate species best suited to those conditions. If deer visit the yard (even if it's only over night, which is what they often do), their browsing preferences will also slim-down the plant list to those they least prefer to eat.

Miri



We don't have a specific brand of herbicide to recommend; any systemic formulation that includes other weedy vines (it probably won't list this one specifically) on its label should suffice. Any vigorous perennial weed sometimes needs more than one application to subdue it, so follow label directions about the interval between sprays. All herbicides bear some environmental impact risk, but when used as directed their risks are minimized.

Vinca and Japanese Pachysandra (not to be confused with our native Pachysandra, which looks a little different) tend to be the go-to options for landscapers or gardeners who aren't familiar with the wider range of options; plus, they're evergreen and very shade-tolerant, which makes them popular. Not many gardeners realize that both are invasive and cause harm to wild habitat and compete with wildflowers and other native plants. Despite neither being currently regulated by the MD Dept. of Ag., as several other invasive species are, that may change in the future. For now, nurseries are still allowed to sell them, which is unfortunate.

We recommend using more than just the one Phlox species for the entire slope, though it's certainly a good starting point. Spacing recommendation information can vary from supplier to supplier, but in general, each plant will cover roughly a square foot once it establishes, though that amount of space can of course change as the plant ages. Spacing between plants will depend on what other species they share the bed with and how quickly you need them to fill in; keep in mind that, as with any plant, overcrowding at too early an age can promote disease outbreaks because it reduces air circulation between plants. The counterpoint is that denser plantings help out-compete weed seedlings so fewer weed intrusions while the planting is maturing will need to be dealt with. There's no single best approach to how to plant groundcovers for those reasons. As for soil preparation, alter the soil type as little as possible so it doesn't change how moisture percolates through the soil layers. You can add a bit of compost if needed to loosen compacted soil, but only use just enough to make its texture a bit more crumbly; incorporate it thoroughly with the native soil when planting.

Our native species of Phlox are relatively common in garden centers, especially those carrying a few (or mostly) native plants. We don't keep track of nursery offerings or make recommendations for particular businesses, so you would need to check around. They're probably available at several central Maryland nurseries and online as well via regional suppliers of natives. Those sold online tend to be younger, which are not only cheaper (pre-shipping, at least) but also easier to plant because their root balls are smaller. Options for pot sizes, quantities, and cultivar selection are probably at their peak in spring, since these are spring-blooming perennials, but popular natives are often available in summer and early autumn as well, depending on what amount of inventory the wholesale growers have ready to ship. You could always get some started now and add more next spring if needed.

Using mulch between plants is the best way to minimize weeding, though as you mention, it's not likely to be eliminated entirely. About two inches should be plenty, and keep it from touching the plant crowns (where stems emerge from the soil), once again to maintain air circulation to minimize disease risk. A winter blanket of some sort is not needed for our cold-hardy natives, but a "mulch" of fallen leaf litter that is left in place would be the type of insulation they're accustomed to in the wild; plus, decomposing leaf litter adds nutrients and organic matter to the topsoil, which improves plant health over the long term. Granted, on a slope, a leaf litter mulch might not remain in place all winter, but that's fine -- it wouldn't necessarily be there all winter on natural woodland slopes either where this species of Phlox grows.

Miri