Groundcovers for Sun

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Variety of thymes creating a multicolored groundcover.

Looking for a groundcover for a sunny spot? Maybe because the lawn isn’t holding up well or because it’s on a slope or is otherwise hard to mow… or simply because you really don’t want to mow anymore? Here is a list of plants you might find suitable:

  1. ‘Angelina’ Sedum (Sedum rupestre ‘Angelina’), zone 3, FTR: none
  2. Barren strawberry (Waldsteinia spp.), zone 4, FTR: poor
  3. Barrenwort (Epimedium x rubrum), zone 3, FTR: none
  4. Basket-of-gold (Aurinia saxatilis, syn. Alyssum saxtile), zone 3, FTR: none
  5. Bearberry (Arctostaphylos uva-ursi), zone 2, FTR: moderate20170426WEN.jpg
  6. Bearberry cotoneaster (Cotoneaster dammeri), zone 5b, FTR: none
  7. Bergenia (Bergenia crassifolia, syn. B. cordifolia), zone 2, FTR: none
  8. Bigroot geranium (Geranium macrorrhizum), zone 3, FTR: none
  9. Bird’s foot trefoil (Lotus corniculatus ‘Pleniflorus’, syn. ‘Plenus’, zone 3, FTR: good
  10. Bishop’s weed (Aegopodium podagraria ‘Variegatum’), zone 3, FTR: poor
  11. Black mondo grass (Ophiopogon plansicapus ‘Nigrescens’), zone 7, FTR: none

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    Bleeding-heart (Dicentra formosa). Photo: J Brew, Flickr

  12. Bleeding-heart (Dicentra formosa and D. eximia), zone 3, FTR: none
  13. Brass buttons (Leptinella squalida ‘Platt’s Black’), zone 4, FTR: good
  14. Bugleweed (Ajuga reptans), zone 3, FTR: moderate
  15. Cambridge geranium (Geranium x cantabrigiense), zone 3, FTR: none
  16. Caucasian Sedum (Sedum spurium), zone 3, FTR: none
  17. Creeping juniper (Juniperus horizontalis), zone 2, FTR: poor
  18. Creeping speedwell (Veronica repens), zone 2, FTR: moderate
  19. Creeping thyme (Thymus serpyllum), zone 3, FTR: moderate
  20. Crested iris (Iris cristata), zone 3, FTR: none
  21. Crownvetch (Coronilla varia), zone 4, FTR: none
  22. Cutleaf stephanandra (Stephanandra incisa ‘Crispa’), zone 3b, FTR: none
  23. Dwarf knotweed (Persicaria affinis, syn. Polygonum affine), zone 3, FTR: moderate

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    Faassen’s catnip (Nepeta faassenii). Photo: Wouter Hagens, Wikimedia Commons

  24. Faassen’s catnip (Nepeta x faassenii), zone 3, FTR: none
  25. Foamflower (Tiarella cordifolia), zone 3, FTR: none
  26. Goldenstar (Chrysogonum virginianum), zone 4, FTR: poor
  27. Green carpet (Herniaria glabra), zone 4, FTR: good
  28. Hairy greenweed (Genista pilosa), zone 5, FTR: poor
  29. Heuchera (Heuchera cvs), zone 3, FTR: none
  30. Hosta (Hosta cvs), zone 3, FTR: none
  31. Houseleek (Sempervivum spp.), zone 3, FTR: none
  32. Iceplant (Delosperma cooperi), zone 5b, FTR: poor
  33. Ivy (Hedera helix and others), zone varies according to species and cultivar: 4-9, FTR: poor

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    Kamchatka sedum (Sedum kamtschaticum ‘Weihenstephaner Gold’). Photo Maja Dumas, Wikimedia Commons

  34. Kamchatka sedum (Sedum kamtschaticum), zone 3, FTR: none
  35. Labrador violet (Viola riviniana ‘Purpurea’, syn. V. labradorica), zone 4, FTR: none
  36. Lady’s mantle (Alchemilla mollis), zone 3, FTR: none
  37. Lamb’s-ears (Stachys byzantina ‘Silver Carpet’), zone 3, FTR: none
  38. Lily-of-the-valley (Convallaria majalis), zone 3, FTR: none
  39. Liriope (Liriope muscari), zone 6 ou 7, FTR: none

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    Golden moneywort (Lysimachia nummularia ‘Aurea’). Photo: European Environment Agency

  40. Moneywort (Lysimachia nummularia), zone 3, FTR: moderate
  41. Moss phlox (Phlox subulata), zone 2, FTR: none
  42. New Zealand burr (Acaena microphylla), zone 4b, FTR: poor
  43. Oregano (Origanum vulgare), zone 4, FTR: none
  44. Ornamental strawberry (Fragaria x rosea), zone 3, FTR: moderate
  45. Pachysandra (Pachysandra terminalis), zone 4, FTR: none
  46. Perennial dusty miller (Artemisia stelleriana ‘Boughton Silver’, syn. ‘Silver Brocade’), zone 3, FTR: none
  47. Periwinkle (Vinca minor), zone 2b, FTR: moderate
  48. Rozanne™ geranium (Geranium ‘Gerwat’), zone 4, FTR: none
  49. Scotch moss (Sagina subulata glabrata ‘Aurea’), zone 3, FTR: moderate
  50. Self-heal (Prunella grandiflora), zone 4, FTR: none
  51. Sensitive fern (Onoclea sensibilis), zone 3, FTR: none

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    Siberian cypress (Microbiota decussata) forms a dense, weed-resistant groundcover. Photo: Crusier, Wikimedia Commons

  52. Siberian cypress (Microbiota decussata), zone 3, FTR: none
  53. Snow-in-summer (Cerastium tomentosum), zone 2, FTR: poor
  54. Spotted dead-nettle (Lamium maculatum), zone 2, FTR: none
  55. St. John’s wort (Hypericum calycinum), zone 6, FTR: none
  56. Sweet woodruff (Galium odoratum), zone 3, FTR: none
  57. Sweetfern (Comptonia peregrina), zone 2, FTR: none
  58. White clover (Trifolium repens), zone 3, FTR: moderate
  59. Wintercreeper (Euonymus fortunei), zone 5b, FTR: moderate

    20170426H Ghislain118 (AD), www.fleurs-des-montagnes.net

    Woolly thyme (Thymus pseudolanuginosus) Ghislain118 (AD), http://www.fleurs-des-montagnes.net

  60. Woolly thyme (Thymus pseudolanuginosus), zone 3, FTR: moderate
  61. Yellow archangel (Lamium galeobdolon), zone 2, FTR: none

Keeping Them Under Control

Most groundcover plants are a bit to very invasive… and that’s normal, considering that we choose groundcovers specifically for their ability to cover ground. It does, however, mean that you should always plan on how you eventually intend to slow them down when they’ve filled up their allotted space and start looking for new territory. You could, for example, contain them with a walkway, paving stones, a short wall, logs, lawn edging or deep shade.

Groundcovers for Shade

If you are looking for suggestions of shade-tolerant groundcovers, see the article Groundcovers for Shade.20170426A

Getting Rid of Goutweed

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The variegated form of goutweed (Aegopodium podagraria ‘Variegata’) is the form most commonly seen in gardens.

Whether you call it goutweed (as we will here), ground elder, bishop’s weed or any one of over its dozen other common names, Aegopodium podagraria is one of the most common groundcovers used in our gardens… and also one of the most pernicious weeds known to man. Once established, it spreads out in all directions thanks to its numerous horizontal underground rhizomes. It’s a very domineering plant, choking out other vegetation and even preventing trees and shrubs from germinating. In addition, it readily leaves gardens to invade nearby fields and forests, causing inestimable damage to the environment in countries where is it not native. And it is terribly difficult to control once it does get loose!

Know Thine Enemy

First a description.

Goutweed is native to Eurasia where it commonly grows in the dense shade of forests. It’s a umbellifer, that is, in the Apiaceae family. It’s closely related to the carrot and, in fact, damaged roots and leaves of goutwood give off a characteristic carrotlike odor.

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The upper leaves are twice ternate. Each of the three leaflets is divided in turn into three leaflets.

The lower leaves are divided into three toothed, pointed leaflets while the upper leaves are twice ternate (each of the three leaflets is in turn divided into three more leaflets). While the species, A. podagraria, has plain green leaves, the form most commonly grown in gardens is A. podagraria ‘Variegata’, with variegated foliage: green leaves are edged in white. When variegated goutweed self-sows, though, it gives entirely green plants. That explains why entirely green plants often appear near plantings of the variegated form. The green form is even more vigorous and invasive than the variegated variety and when the two grow together, the green variety may eventually smother out the variegated one.

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Goutweed in bloom: the flowers look a lot like wild carrots.

Goutweed can reach 50 to 100 cm tall when in bloom in mid-summer, topped par domes (umbels) of tiny white flowers. Its stems are hollow. Its roots can dig down deeply into the soil, sometimes to a depth of several yards (meters).

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Goutweed rhizomes.

Goutweed mainly spreads via its creeping rhizomes and, like many plants that have chosen vegetative propagation as their main means of reproduction, rarely self-sows. That’s good news for gardeners, because at least you don’t have to worry (much) about having to suppress the plant’s flowers to prevent it escaping by seed.

Since goutweed will grow in almost any environment – sun or shade and soil that is rich or poor, moist or dry, acidic or alkaline, etc. – and has no natural enemies outside of its native Eurasia, once it has escaped, you can’t count on Mother Nature stopping it.

Controlling Goutweed

The very easiest way to get rid of goutweed is to move away. Yes, change houses. That may seem excessive, but I assure you that more than one gardener has sold their home because of an uncontrollable goutweed infestation that made gardening impossible.

I’m not a fan of herbicides and hesitate to use or recommend them. Even so, goutweed is amazingly resistant to herbicides and even non-selective herbicides, such as glyphosate (RoundUp), that kill almost everything  green, are not very effective on goutweed, so multiple applications will be required if you use them. In addition, non-selective herbicides are not easy to use in a garden setting, as they kill everything, not just weeds, but ornamentals as well.

Hand pulling is rarely effective. Goutweed is one of those plants you can’t simply pull up: the roots reach down deep into the soil and simply won’t let go. In addition, any rhizome that escapes your control will result in a new plant. Even if you try your best at hand pulling, goutweed will generally soon be growing as densely as before.

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Cultivating to control goutweed just makes things worse.

Cultivating does an even worse job than hand pulling. It tends to chop the roots and rhizomes into pieces, some too small to be readily noticed and which are therefore left in the ground. And yet each piece will soon be a new plant. Cultivating therefore tends to create an even denser patch than the original one.

Rototillers and other motorized cultivators are probably the worst way to try and eliminate goutweed. Not only do they chop rhizomes into pieces (and we know what result that will give!), but then they also spread them far and wide!

It is possible to eliminate goutweed by deep digging then sifting the soil to remove all roots and rhizomes. Dig down to a depth of 2 feet (60 cm), then screen the soil using a soil sieve: ½ inch/1.25 cm screening will do. While there may well be roots going even deeper, the plant is very unlikely to regenerate from such a depth. Of course, this is a major job, even if you use a bulldozer or excavator to remove the soil (recommended), because properly sifting soil is a very slow process..

Moving short, to about 1-inch (2,5 cm), will also eliminate goutweed, as this removes the plant’s access to its sole source of energy, sunlight: by chopping the plant so far back you’ll eliminate its leaves entirely, you’ll prevent any photosynthesis. However, you’ll have to repeat the process regularly, as the plant’s reaction to having its leaves cut off is simply to produce new ones as soon as possible. Even mowing to a more moderate height, one appropriate for lawn grasses (2 ½ to 4 inches/6 to 10 cm) will at least weaken goutweed considerably. That’s one reason it rarely spreads very far into closely cropped lawns.

Why not try eating your enemy? Goutweed is a popular vegetable in many countries. Spring shoots are soft and tasty, cooked or raw. One the plant starts to bloom, though, the leaves become bitter.

My Favorite Method

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Use black tarp to cut off all light and goutweed will die.

I find the easiest environmentally friendly way of getting rid of goutweed (other than moving) is to cover the sector with black tarpaulin. Without light, the plant will be unable to carry out photosynthesis, causing it to weaken and die. You’ll need to cover about 3 feet (90 cm) beyond the goutweed patch’s original spread, however, or it will try to creep out from under the tarp. Make sure the tarp lets in absolutely no sunlight. Some geotextiles, for example, are not effective, because they let some light through: before you buy it, hold a piece to a light to make sure it is opaque. Sometimes good ol’ black plastic tarp, available in any hardware store, is the best choice.

Place the tarp in the early spring, before or as the leaves come up. Leave it on for a full year to totally starve the plant of any light. You can cover the tarp with mulch and or put flower pots on it if you want to beautify the area as the treatment proceeds.

When you remove the tarp in the spring of the second year, the goutweed will be dead, having exhausted all its reserves. If you find one or two pale shoots still alive, just cut them to the ground: they’ll be so exhausted they won’t grow back.

Really thick mulch will also shade out goutweed all on its own. Not just a few inches, but a good foot (30 cm) of it. Mow the plant down first and pour it on. Again, a full year of darkness, starting in spring, will be needed.

A Vertical Barrier

Eliminating goutweed from your yard is not however enough: you also have to keep it from coming back.

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An extra deep lawn border will keep goutweed out.

The problem is that goutweed rarely stops at property lines. If you have a goutweed problem, your neighbor is likely to have one too. And if he doesn’t collaborate in controlling it, the plant will simply cross back over into your yard. If so, install a vertical barrier into the ground between the two lots… before you start your treatment. Although goutweed roots can grow deeply down into the soil, its rhizomes usually run horizontally within a mere 2 inches (5 cm) of the surface. That means a simple lawn border could theoretically stop them. But not just any lawn border! The rhizomes tend to grow downwards when they hit an obstacle, although not very deeply. A 4- or 6-inch bordure (10-15 cm) will not be deep enough. Use an extra-deep border, 8 inches (20 cm) or more.

A horizontal barrier, such as a sidewalk or a driveway, between an infested area and a clean one can also be fairly effective, but sometimes a few rhizomes will make it across over time and, if so, will need to be controlled rapidly before a new colony starts up.

Should You Try to Save Plants From an Infested Bed?

Since treating goutweed usually means covering or digging up an entire garden, one question that always comes up is how to save any plants that are growing in the sector being treated. Can you dig up and save shrubs, bulbs, perennials, etc., planting them somewhere else temporarily?

Yes you can, if you’re very, very careful. Dig up the plant and rinse off all its soil. Remove any goutweed rhizomes you see growing through its root ball. Now pot it up. Do not plant it in another part of the garden until it has undergone a 3-month quarantine in its pot. If no goutweed has appeared after 3 months, you’ve successfully eliminated it and you can replant the potted plant.

Often divisions of the plant are easier to control for rhizomes (with fewer roots, you’ll better to able to see them) and are therefore a better choice than trying to save the mother plant.

Easier yet, take cuttings. You can take cuttings of most perennials, shrubs, and even conifers, and since the cuttings grow aboveground while goutweed rhizomes grow below, there will be no risk of them hosting goutweed rhizomes.

Should Goutweed Be Banned?

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Banning goutweed: an idea whose time has come.

Despite the environmental devastation caused by goutweed in North America, Australia, New Zealand and other countries where it has escaped from culture (it’s easy enough to find entire forests where there is no regeneration whatsoever of local trees and where all native understory plants have been entirely eliminated by goutweed), goutweed, and especially its variegated form (A. podagraria ‘Variegata’), is still widely sold to unsuspecting gardeners in nurseries throughout the temperate world. In some American states, however, including Connecticut, Massachusetts and Vermont, the import and sale of goutweed is now banned, a step that at least helps slow the plant’s invasion.

Isn’t it time for the sale of goutweed to be banned in your area as well? That’s certainly something worth thinking about.