“Our” garden world refers to the geography of Midwest USA with a Horticultural Zone of, let’s guess, 3.8 to 4.8……….So, then….
What are ground covers in the landscape garden which I grow and have something to write about?
Those plants whose forms tend to creep along the garden floor forming horizontal masses usually no higher than two or so feet, are called ground covers.
The most popular groundcover in Minnesota regardless of horticultural zone, is turf grass (lawn).
(Not all grasses are groundcovers. Miscanthus giganteus should by its Latin name suggest it is not fit for ground cover use. It is a beautiful grass with spectacular “plumes’ in late summer, but stands at an expanding clumb somewhere around twelve feet tall at maturity.)
Ground covers are essential landscape garden materials which provide negative space. that is space absent of forms, to allow the display of an individual plant or even a group of plants independent from mass plantings. (Another purpose might be to display the beauty of the ground cover itself.
When one sees a beautiful sculpture of a mature White Oak or Emerald Green Arborvitae , it is noticed because it arises as an individual from the negative (empty) space surrounding it rather being lost a forest.
I have many, many favorite groundcovers and use many of them as if they were fighting for space at the floor of a forest glade. Among them are:
Ajuga, but not all are reliably hardy nor spread readily. I prefer the Purple leaf or Gaiety ajuga to all others for they spread, spread and spread and show a mass of beautiful bluish blooms in mid spring. Nearly all of ajugas so-called improvements, such as Black scallop or Catlin Giant do not spread aggressively and cannot be counted on to live very long.
Burgundy Glow is a special ajuga, one with variegated bluish green and gray to cream foliage. But until about ten years ago the plant was NOT reliably hardy. It spreads only modestly, so I do not term it as a groundcover.
If you have a reliable watering system Lily of the Valley can make a spectacular mass and when large enough and in bloom, the unique fragrance of Lily of the Valley can be intoxicating without you ever having be bend down to pick a flower stem. Try to confine its space to about 100 square feet so the mat becomes so thick nothing, even tree seeds can penetrate its cover. The regular watering encourages its ability to expand and mass.
Lamiums are usually troublesome. I have all sorts for they seed readily and spread even ‘readilier”. They cover and cover in mass okay, but sometimes they run over and around everything else including valuable peonies taking over their space.
A few are more refined, but some of the ‘refined’ lose their propagated beauty. Anne Greenaway is an example. Beautiful bluish and limegreen with streaks of yellow and true green make this a beauty…..EXCEPT the plant can’t reliably hold its colors as it ages. It reverts to a dark gray-green mixture leaf pattern, but maintains an ability to bloom steadily from midMay to frost…..a sharp attractive purplish lavender.
I stay away from Herman’s Pride Lamiastrum. It is big and clumsy and I don’t want another yellow in the garden. It likes to live and do its thing….run over everything else.
Pachysandra is another once not-hardy plant that is now a wonderful regular in most of the grounds we landscape. Easterners love Pachysandra, an evergreen broadleaf, and when I was a kid those who visited or moved here from the Northeast would snobbishly look down their noses on gardens and gardeners who couldn’t grow the fragrant evergreen, Pachysandra.
Well, for about the last fifty years we can…..one of the reasons I love warming here in Minnesota reaching almost a horticultural zone 5 in the Twin Cities.
Again, in case you missed it, Pachysandra stays bright happy green all winter long. It makes a good mass, but watch out for lawn grass invasions with this as well as all of your non-grass ground covers. Lawn grasses are killers when uncontrolled in the landscape garden.
It does not do well in bright sun. Its foliage fades and even occasionally burns.
This Spring my Pachysandra has been blooming now for about three weeks and will continue until a windy warmup arrives.
Mayapple is a native Minnesota groundcover, It looks like a mass of eight inch umbrellas which opened yesterday this year, and will remain open in my garden until dormancy in mid to late September. It is a cute addition besides its cover which in frenzied manner aims to jealously own it ever growing space.
In about two weeks like a six year old kid, I will check underneath an umbrella or two to admire the single happy flower almost smiling at me. In a month it will have become a greenish balloon, or ‘Mayapple’ as it is called in lore.
Sweet Woodruff is another fragrant groundcover when grown in mass. It is daintier, and although fortunately just as weedy, as the already mentioned groundcovers, its mass isn’t thick enough to keep out an endless number of seedling invasions.
It is good that I like it. Once Sweet Woodruff is introduced into your grounds, it is likely to be there forever. Its delicacy saves it.
A ground cover which SHOULD NEVER BE PLANTED ANYWHERE NEAR A GARDEN, is Aegopodium….Bishop’s “Weed’, but more commonly called, perennial Snow on the Mountain.
It is a WEED of the horrible kind. It becomes uncontrollable in no time at all and suddently your garden is under siege.
Remember, the Landscape Gardener’s definition of a weed is: A PLANT OUT OF PLACE. Perennial snow on the mountain eventually because a plant out of place whereever it is grown.
Then there is Vinca…..Garden girls from out East prefer Periwinkle. Dart’s Blue is by far my favorite. It eventually grows several layers of wires covered with masses of small sized dark green shell like leaves, and like this very day show off splotches of sharp dark blue open faced flowers.
I do have an automatic irrigation system providing water on a reliable schedule from early April till shut down time in October. I cannot grow any Thyme as a result. I have a common sedum that would cover the Earth if I didn’t control it…and I cherish it every day it grows. It blooms yellow, but I have never been able to score its real Latin name.
It is the kind of sedum I can rip out of the garden and hand it over with or without soil to friends to take home with the following instructions…..plop or spread the clump onto open soil, then step on the clump and wait a day or two. If in June it will have double it space in a week……It is only and inch in height….two when in bloom.
Many of the sedums on the market do not defend their space well and fall to invaders….especially the tree kind. Many prefer drier soils than I have. I grow Coral Carpet in a drier location in full sun for half a day and it is doing okay….looks like a mass of reddish beads among its stone neighbors.
One hardy perennial groundcover grown for its floral color I must have in my landscape garden is Arabis caucasica….white rockcress. It spreads rapidly and in early spring, as now, it produces the whitest blooms in masse one could ever see. The white is so stark and pure, I have several areas roughly twenty five square feet each spread throughout a section of the grounds for repetition for rhythm on the grounds rather than a single white target. Like the blue-flowering ajuga, I grow this Arabis for its floral yield rather than its foliage, which appears wimpy and weak, but don’t mistake that for trouble. If it likes its location it will soon let you know.
In most grounds white arabis likes to advance its space and does so. Other arabis are not able to make this claim.
Some of the most beautiful and hardiest of all ground covers are the evergreen conifers….those in the catalogues called ‘spreaders’. As a group most tend to range from six inches to two and a half feet in height. Many, if the space for their expanse were available, could grow for decades and decades and reach fifty to two hundred or more feet, if not limited by invasive seedlings, for most have the ability to continue rooting as they wander around their world.
Coniferous ground covers will be a topic for another day.