Good groundcovers reduce mulching & weeding

Hello Gardeners,

First, a little diversion about hummingbirds. Usually we think of attracting them with nectar-rich, tubular-shaped, deep red- and blue-colored flowers, right? Well...apparently there are other ways to attract them, as well.

My husband and I recently planted two, 10' tall, river birch trees (Betula nigra 'Heritage') We wanted a couple of fast-growing, medium sized trees to screen the view of a nearby house. We were surprised to be almost immediately rewarded with our first hummingbird visit. She sat quietly in the birch tree for a tiny moment, then seemed to pick at something on the branches. We used to see lots of them, nectaring on flowers at our previous home, but in three years of living here in Annapolis, nada-zip in the hummingbird department. So this first sighting feels special.

Hummingbirds, with their delicate little feet, love to perch on the numerous, slender branches of birch trees. And there seems to be something that interests them, within the peeling bark of these trees. I've read that although people often put out sugar water for hummingbirds, insects are actually a very important source of nutrition for these high-metabolism birds, with aphids and spiders among their favorite foods. So maybe there are little insect treats hiding in those crevices in the birch bark...

On to today's promised topic: how to reduce mulching by using carefully selected groundcover plants. You've probably heard why mulch is "necessary": it prevents weeds, retains moisture, and helps keep erosion in check. But if you can get a good, thick groundcover established, the benefits are the same as or better than mulch.

The leafiness and roots naturally help keep soil from eroding away and reduce evaporation, helping retain moisture for the other plants in the bed. It greatly reduces the need for weeding, since the weeds find a harder time getting a foothold where the groundcover has already declared victory. And finally, there is less work, because you don't have to replace with new mulch every year--you plant once, and except for adjustments and tweaking, you are done!

There is a trick to it, though. In order to get quick, lush, weed-suppressing growth that doesn't have a lot of bare spots, you have to match the groundcover's preferences to the type of soil, sun and moisture that you have. Yet you can't have a plant that is so aggressive it will overwhelm whatever else you want to have in the bed. 

I have a long, slightly nerdy list of about 14 groundcovers that I use often--some fiercely aggressive, some that need a little coaxing at first. My list shows the preferred growing conditions, bloom time and color, and notes about the wildlife each plant supports. But today I just want to share the several plants I probably use the most often.

There are three, relatively-adaptable favorites---groundcover plants I've been using for some time, that have performed well for reducing weeding and mulching. If you've worked with me on your landscape design, you more than likely have at least one of these in your landscape.

1. Iris cristata, Crested iris. The beauty of this plant is that the slender leaves spread into a pretty thick mat of graceful arches within a year or two. Once established, I rarely have to pull weeds among them. Good for either clay or sandy soil. Best in part sun or shade, unless the area is consistently moist (avoid dry, hot, and sunny). This has a short-but-lovely bloom time (blue). You can divide every 3 years to spread the area out (free plants!). Best time to divide is in August just after the plant has died back for the fall.

2. Chrysogonum virginianum, Green and gold. Prefers moist, alkaline soil but is remarkably adaptable as long as you take good care of it during establishment. There are several good cultivars. Most are selected for their shorter inter-nodal growth, which will make them more likely to form a mat that prevents weeds from weaving in to your garden. (In a later post I'll talk about how author/designer Larry Weaner uses the straight species, with its longer internodal growth, to creatively fill bare spots without making a solid mat--kind of an advanced technique that can be used in an already established bed). This plant is also semi-evergreen, so there is some presence protecting the bed even through the winter months.

3. Heuchera villosa 'Autumn Bride'. This plant amazes me with its sturdy resilience in the face of drought and poor soil. In the Mt. Cuba trial gardens, this cultivar got winning scores in all categories. 'Autumn Bride' tolerates full shade or (with a little more moisture) full sun. It is quite drought tolerant except in super hot sun, and rebounds pretty well from early season deer browsing (later in the season it gets hairy and tough, and the deer leave it alone). I use it to give a big, leafy texture in areas where I'm concerned about erosion and dry soil. It has a small-flowered, white bloom stalk in July, and the leaves turn blush-burgundy in autumn. Although a perennial, this plant usually persists through the winter (semi-evergreen).
So those are a few good ones. Do you have any favorite native groundcovers that have done well in your landscape? Send me a note--I'd love to hear about them!

Also, if you know anyone else who is interested in natives and might like to receive this newsletter, please forward to them. Thank you!

Chris Pax

Christina Pax