Late season ground cover

The explosion of growth in spring pretty well covered in the last posts, what’s to keep our gardens free of weeds in the late season?

Several of the ground covers so far disappear completely in the heat of summer, especially if the year is hot and dry. While these conditions don’t easily give rise to weeds either, so problems seldom come from it, there are some instances where you want a thick cover beginning in the heat of summer, and at its peak at the onset of fall.

For example, if you have a bed really well stuffed with early rising, but late season dormant perennial vegetables like Valerian, rhubarb, Camassia, the bed goes just about bare once the days get long and hot.

The other category is plants that get long and lanky in the end of the season, like Asparagus, and tiger lilies. These don’t shade their ground very well, but are tall enough to stay above the weeds themselves.

Given the two separate situations, I’m covering two separate plants for ground cover post number nine.

Down near the ground, with plants that only keep sparse leaves for gathering energy over summer, like Turkish rocket, it’s best to use blue mist flower (Conoclinium coelestinum). Although similar in form to annual Ageratum, this plant is perennial. It doesn’t show itself until about June, when it slowly begins growing in an upright fashion that later flops over, covering quite a bit of ground around it. Usually the vines top somewhere between one to three feet long. The flowers, in late September-early October, are a pretty addition themselves.

The ones below are in my friend’s ornamental garden, with a lovely ground cover of golden Lysimachia nummularia next to it.

Blue mist flower has long, white, very shallow roots that run and sprout up, filling the cracks in the planting quickly. It pulls out about as easily as cobwebs from dusty corners, and doesn’t come back from the smallest micron of root like some weeds. What’s more, it cohabits quite well, not stressing other plants like many weeds -unless of course they’re buried under the vines, which are again easily removed. Overall it’s quite easy to manage.

Towering up to 6 ft by September, alongside our lanky end of the season plants like tiger lily, Asparagus and the like is Tartarian aster (Aster tataricus). A bit later than blue mist flower, Tartarian aster unfurls its light blue flowers around late September, and well into October in my climate.

Until July, it’s just a thick mat of leaves, when all at once they shoot up in leafy spires, leaving the ground beneath in darkness. In ornamental gardens, like my step grandmother’s garden above, I’ve seen it work well with peonies, which are just looking drab as the asters shoot up. This covers the peonies from view, but it’s not so aggressive as to grow through the peonies leaves. This leaves a little spot of sun to continue feeding the peonies until they are satisfied and ready for dormancy, the cycle happening year after year quite successfully.

For how lush the leaves look in spring, I keep wondering if they wouldn’t make a tasty cooking green at least. My searches for references has turned up very little. Plants for a Future database has hopeful, but very scant information on its edibility. I may just try it sometime if I can’t find a good reference and report the results. Many asters are edible, so I don’t think it would be poisonous. The roots are used in Chinese medicine for certain lung conditions.

It also runs quite successfully, so you don’t need many initial plants to eventually fill a large space. From my observation, established plants run at least a foot a year. With an initial spacing of two foot distance between plants, the space should be filled in two to three years.

Pulling is quite easy. It’s best done late in the year when, due to the long stems, pulling can be done while standing upright. More importantly, these late season bloomers are quite vulnerable to losing their precious energy store for the winter by keeping so much energy in their stem so late. Snapping off the big stem just at or before blooming weakens them severely. 

Building so much biomass in the fall, both these plants still provide good ground cover in spring, so planting something other than useful crops to cover the ground is hardly necessary. Often their is too much biomass, which stacks higher than some plants can stretch. This makes excellent mulch the next spring if removed for new beds, or if broken up and shoved against the ground to make a thick, water retaining, weed blocking cover. 

Given they show off when everything else is going drab, every garden should have at least a little patch of one of these niche-in-time filling ground covers.