Groundcover plants, such as this 'Angelina' creeping sedum, are dense enough to choke out most weeds.

Have you heard the gardening quip, “If you have too many weeds, you don’t have enough plants?”

That can be true, because one of the best ways to discourage weeds is to put plants you like better there first, especially ones that cover the ground densely. With your choices taking up space, there’s no room for weeds to elbow in.

Remember, bare soil is an open invitation for weeds.

If you’ve had another summer of battling weeds incessantly, September is one of the best months to add weed-blocking groundcover plants.

These botanical weed-blockers don’t necessarily have to be short ground-huggers. Unless you’re trying to grow them underneath another plant, groundcovers can be any dense, spreading or horizontally growing species.

Here are 20 good groundcover plants of varying size to consider in Pennsylvania yards – half for sun, half for shade, and a mix of natives and non-natives:

Sumac 'Gro-Low' is a native shrub with brilliant fall foliage.

Sumac ‘Gro-Low.’ A woody shrub with yellow spring flowers and showy red-orange fall foliage. Grows 2 to 3 feet tall, 6 to 8 feet wide.

Prairie dropseed grass is shown in its flowering stage.

Prairie dropseed. A short, clumping grass with arching plumes and maroon fall foliage. 2 feet tall, 2 to 3 feet wide.

'Zagreb,' shown below, is one of the best threadleaf coreopsis varieties.

Threadleaf coreopsis. A low, spreading perennial with fine leaves and yellow summer flowers. 18 inches tall, 2 feet wide.

Several juniper 'Grey Owls' are shown covering this sunny bank.

Juniper ‘Grey Owl.’ A silvery-gray needled evergreen with a spray-form habit. 3 to 4 feet tall, 6 to 8 feet wide.

'Scarlet Flame' is a rosy-blooming variety of moss phlox.

Moss phlox. A low, spreading, mounding, fine-leafed perennial with pink-lavender spring flowers. 8 to 10 inches tall, 2 to 3 feet wide.

The Drift series is a good line of low-growing, spreading roses. Below is Pink Drift around a tree trunk.

Groundcover or “landscape” roses. Low-growing, low-care shrub types that come in a variety of bloom colors, often flowering through much of the summer and into fall. The Drift and Flower Carpet series are two of the best known. 2 feet tall, 3 to 4 feet wide.

Catmint is a long-blooming perennial that does well in hot, sunny spots.

Catmint. A drought-tough perennial with silvery-gray foliage and blue flowers in early to mid-summer. 15 to 18 inches tall, 2 to 3 feet wide.

Several varieties of creeping sedum line this rock pathway.

Creeping sedum. A drought-tough succulent perennial with versions that either flower yellow in early summer or pink in late summer. Some varieties have golden or dark foliage as well. 8 to 10 inches tall, 2 to 3 feet wide.

Rozanne is a popular, long-blooming variety of hardy geranium.

Hardy geranium. A long-blooming, low-and-wide perennial with blue-purple or pink flowers for weeks in summer. 18 to 24 inches tall, 2 to 3 feet wide.

Leadwort is a fast-growing perennial that blooms blue in late summer and turns red in fall.

Leadwort. A spreading perennial with blue flowers in late summer and scarlet fall foliage. 15 to 18 inches tall, 2 to 3 feet wide.

Native foamflowers make good groundcovers in damp, shaded spots.

Foamflower. A spring-blooming perennial with pink or white bottle-brush flowers and attractive variegated foliage. 10 to 12 inches tall, 2 feet wide.

Coralbells come in several different leaf shades, including burgundy, chartreuse, and nearly black.

Coralbells. A wide-leafed perennial with early-summer pink or white flowers atop wiry stems. Leaves come in a variety of showy colors besides plain green. 12 to 18 inches tall, 24 to 30 inches wide.

This planting of Pennsylvania sedge under trees has a grassy appearance and virtually ends weed problems.

Pennsylvania sedge. A green-bladed grassy perennial with a clumping, arching habit. 1 foot tall, 24 to 30 inches wide.

White wood asters tolerate the shade and root competition of even big trees.

White wood aster. A mounding, late-summer-blooming perennial with daisy-like white flowers. 2 feet tall, 2 to 3 feet wide.

Christmas ferns are native perennials that form dense, weed-preventing colonies in shady areas.

Christmas, autumn, and wood ferns. All three of these native ferns are dense, spreading, upright, and resistant to deer. 2 to 3 feet tall, 2 to 3 feet wide.

Sweetbox is an underrated, under-used evergreen groundcover that's also very fragrant in early spring.

Sweetbox. A glossy, broad-leaf evergreen that produces small, fragrant, white flowers in early spring. 2 feet tall, 3 to 4 feet wide.

Spreading versions of Japanese plum yew make excellent groundcovers, especially where deer are lurking.

Japanese plum yew ‘Duke Gardens’ or ‘Prostrata.’ Horizontally growing varieties of green, soft-needled evergreens that deer don’t like. 3 feet tall, 5 feet wide.

Japanese forest grass comes in white- and gold-variegated versions and tolerates shade well.

Japanese forest grass. A clumping, arching ornamental grass that comes in green, gold, and green-and-gold variegated versions. 2 feet tall, 30 inches wide.

Helleborus are some of the first perennials to bloom -- and deer don't eat them.

Helleborus. A deer-resistant, glossy-leafed, mounding perennial with large, hanging, bell-shaped flowers of white, rose, pink, or lavender in very early spring. 18 to 24 inches tall, 24 to 30 inches wide.

Liriope is a tough, grass-like perennial that produces purple flower spikes in late summer.

Liriope. A grassy perennial with spiky late-summer lavender flowers that’s one of the best performers in dry shade under trees. 15 to 18 inches tall, 24 to 30 inches wide.

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