How to Choose your Groundcovers
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By Anno Torr
Many perennials and bulbs ‘cover’ the ground effectively and are often included in this plant category, but, for this article, we focus on plants that typically grow close to the soil surface but can range in size from 10 cm to around 30 cm. They differ widely in foliage colour, texture, density, woodiness of stem, succulent or grassy characteristics, and so their effect, both aesthetic and environmental, varies too. And, while we so often choose plants for their attractive flowers - and why not - our focus here is, function; what does this plant need to do? Then match it to a plant’s ability to cope with the sun, wind exposure, soil type, aspect and gradient, drought and wet conditions.
Rocky slopes where lawn maintenance is tricky: Choose plants that need little management, spread quickly, have strong roots that will withstand the pressure of moving water and wind, are evergreen, and long-lived.
Between pavers: Clumping or non-vigorous species able to cope with the reflective heat off pavers, and perhaps take some light foot traffic.
As a no-mow lawn: Evergreen, mat-forming, plants that don’t die off from the centre, take foot traffic and trimming.
Beneath trees: Plants for shade and dry soils if beneath dense, evergreen canopies.
Between shrubs: Takes some shade, won’t compete too much with the shrub for water and nutrients and is happy to spread across the ground rather than using other plants as a jungle gym.
To edge a flower bed: Not too vigorous, and won’t clamber into shrubs or smother perennials.
On seasonally/ periodically wet ground: Choose groundcovers that cope with damp and dry conditions, preferably evergreen to prevent soil erosion, compaction and cracking in the dry season.
As living mulch: Dense, mat-forming leaf growth, spreads quickly, and is evergreen.
To prevent soil erosion: Plant with strong roots, grows readily on sloping ground, has dense, mat-forming foliage and stems that spread quickly, is evergreen, handles high winds and heavy rains.
Their variety and problem-solving versatility provide gardeners with a plant for almost every situation. But take note; while the majority are low-maintenance, they are not no-maintenance. That said correct choice reduces the management required.
Space plants according to their rate of growth and how rapidly you want to cover the soil. Consider water availability (drought conditions and water restrictions) and size of the area which affects your budget. Highly visible beds – entrance, entertainment area - may need fast cover, as will areas prone to erosion, like banks, or expansive newly landscaped beds. That said you could establish large areas gradually to limit water use and plant costs and cover the balance of the ground with thick mulch that is easily removed when you’re ready to plant again. Plus, this organic cover will provide you with crumbly, healthy soils for the new plants. Planting in staggered rows covers ground more rapidly, plus helps to reduce erosion on slopes.
Another cost-saving measure is to use cuttings of succulent groundcovers and plant them close together to ensure rapid cover. Firm around the stems to provide good soil-root contact. If planting many, water small groups as you go to prevent them drying out. Make use of cuttings only in your regions rain season as they will need regular watering for the first few weeks. High heat also affects cuttings and landscapers tend not to plant them in January and February.
Watering: It is difficult to find the balance between too much and too little water during the establishment phase; too much and plants may not establish a deep-spreading root system. Too little, on the other hand, encourages shallow rooting resulting in plants that dry out rapidly and drought-prone. So, how much is enough? Keep a watch on your regions weather report and try to establish plants just before rain is due. They will still require water as you plant out, around 2 - 3 cm of water per plant to moisten the entire root zone for the average plant. Add a thick mulch layer to prevent water evaporation.
Mulch depth: A mulch layer 5 – 8 cm deep is enough to block light and suppress weed germination, and prevent soil-borne diseases spreading onto plants from rain splash. Too thick a layer – over 10 cm – limits or blocks oxygen from getting to plant roots. This anaerobic environment suffocates roots causing root rot. Symptoms can include; yellow foliage, lack of growth, dieback, and small leaves.
Control weeds that will compete for water, nutrients and sunlight. Weeds can also suppress strong growth preventing a dense mat-forming.
Trimming and deadheading:
Pruning, or trimming, help stimulate growth by causing new buds to grow from the base or along the plant stem. Annual trimming slows the development of woody growth and keeps them attractive. Cutting back can induce repeat flowering in some species like Dianthus. Cut off infected foliage immediately.
Asystasia gangetica - Creeping Foxglove: 30 – 60 cm; creeping Foxglove; rambling, clambers up and over other plants, roots from spreading stems. Use in large areas, under trees, on verges, down shady slopes. Prefers nutrient-rich soils and mulch. Trouble-free in the right place. Not good for small areas and gardens. Moderate frost; good summer rains.
Asparagus densiflorus ‘Sprengeri’ - Emerald Fern; 30 cm x 90 cm; fast, spreading, rooting stems; needle-like foliage; good for security; plant on steep banks, verges, large shady areas under tree. Trouble-free; suppress weeds; control erosion; very strong, deep roots – stabilise soils; light to moderate frost; moderate water, needs water during establishment, so plant in the rainy season; will cope with seasonal drought. Can be cut back to ground level. Woodland plant from year-round to summer rainfall regions.
Chlorophytum comosum - Hen and chickens; 30 x 40 cm; fast-growing, spreading bulbous plant; use in shade under trees, in large or small areas; moderate frost; moderate water; stabilise soils, slopes.
Plectranthus madagascariensis - Madagascar Spurflower/ Variegated Plectranthus; 15 x 45 cm; spreads via rooted stems; clambers a bit, but light so doesn’t smother; spreads rapidly; enjoys humus-rich soils, moderate water and frost; semi-shade.
Plectranthus verticillatus - Money Plant: 20 x 50 cm; semi-succulent foliage; spreads fast; good for large areas, roots from spreading stems; use under trees in place of lawn, needs moderate water, light to moderate frost; high water areas, banks, enjoys humus-rich soils and mulch; copes with wet and dry soils.
Crassula multicava - Fairy Crassula: 20 x 30 cm; moderate frost; low to moderate water; drought-hardy; water wise; succulent leaves; under trees, lawn replacement for no-traffic areas; rooted runners; spreads quickly; small and large areas; easy to manage; looks good year-round; rocky ground; slopes, banks.
Plectranthus ciliatus - Speckled Spur-flower: 50 cm; moist subtropical shade to semi-shade; spreads along the ground up to 50 cm; handles root competition and light trampling; shallow roots; water wise; good as a lawn replacement under trees; large areas, slopes; mulch.
P. neochilus - Lobster Flower; 50 x 1 m; dry soils; drought-hardy; fast-spreading groundcover, good for dry, rocky areas, to stabilise soils, banks, control erosion; spreads from rooted runners and self-seeds; more compact when dry in full sun; moderate frost.
Pelargonium reniforme - Kidney-leaved Pelargonium; 20 x 35 cm; lovely neat foliage for small areas in full sun; dry soils; edge a flower bed or paving; amongst perennials as a mulch; steep slopes, rocky ground; spreads from tuberous roots, fast-growing, drought-resistant; sandy soils; won’t take wet soils; trim for a second flush of flowers. Frost hardy, low water needs.
Geranium incanum - Carpet Geranium; 35 x 50 cm; soft, feathery foliage, fast-growing, large or small areas, easy to manage; edge bed, among shrubs and perennials; sloping bank, self-seeding; trim back to retain more compact stronger growth; frost hardy; moderate water.
Dimorphotheca jucunda - Trailing Mauve Daisy; 25 x 60 cm; frost hardy; moderate to low water; sun; rapid spreading groundcover; slopes, large areas, rocky ground, stabilise soils, control erosion; spreads from rooted runners.
Carpobrotus edulis - Yellow Sour Fig; 15 x 90 cm; trailing succulent, spreads rapidly from rooted runners; tough, drought hardy, water wise; hold soils on gentle slopes, roadsides; sandy soils; dune conditions; parking areas; winter rainfall region.
C. dimidiatus - Natal Sour Fig; robust, spreading succulent; large areas; salt spray, sandy soils; drought resistant; bind soils; control erosion; steep banks roadsides; dense cover; any soil type – sandy to clay; for large gardens; care-free; summer rainfall, winter rainfall; light frost; sun; am sun; pm sun.
Arctotis stoechadifolia - Trailing Arctotis;20 x 50 cm; dry banks and slopes; edging plant, front of bed, paving; fun; fast-spreading from rooted runners; tolerates high winds; loose sandy soils; winter rainfall; short-lived (replace after 3 years); rocky ground. Frost hardy.
Chaenostoma (= Sutera cordata and pauciflora) and hybrids - Trailing Phlox; 10 cm x 40 cm; will take damp soils so plant at the edge of paving, pathways, driveways where seasonal runoff collects; under trees; hold soils on slopes; between sleepers and perennials; spreads via rooted runners; can die back from the centre; semi-shade to sun; trim to keep compact; moderate frost; moderate water.
Delosperma herbeum - White Mountain Vygie: 12 x 20 cm; succulent spreading groundcover for small areas; small gardens; sun; moderate frost; low to moderate water needs; summer rainfall; rocky ground; slopes; edge a bed. Try other species: D. cooperi, D. rogersii and D. lydenburgense.
Crassothonna cacalioides (= Othonna carnosa) - Othonna; 10 x 60 cm; fast-spreading succulent groundcover; large areas; rocky ground; gentle slopes and banks; holds soils, controls erosion; mulch; traffic areas; spreads via rooted runners; drought resistant; needs little attention; low water needs; frost hardy; windy areas.
Helichrysum petiolare; 25 x 60 cm; large areas, vigorous spreader; hot dry areas; slopes, rocky ground; spreads via rooted runners; sandy soils; does not enjoy damp soils; sun; dies back if watered too much; summer and winter rainfall; coastal; frost hardy; low water needs; cut back to control and keep compact.
Gazania rigens - Trailing Gazania; 20 – 40 cm; trailing, mat-forming; roots from runners; dry soils; high winds; salty air; sandy soils; large areas; slopes; roadsides; bind soils; does not like wet soils; summer and winter rainfall; trim for more flowers and to prevent woody growth and die-back.
Dymondia margaretae - Silver Carpet; 5 – 25 cm; prostrate groundcover; spreads rapidly, stabilises soils on gentle slopes; between pavers and stepping stones; lawn substitute; around plants whose roots prefer to be undisturbed; sandy; coastal; light frost.
Bulbine frutescens - Stalked Bulbine; 30 – 40 cm; quick, spreading; drought-hardy; copes with dry and poor soils, slopes and rocky ground; good for parking areas.
Arctotheca calendula - Cape Weed; 10 x 50 cm; fast spreading for large areas; mat-forming; good for gentle slopes; lawn substitute; water wise and drought hardy; propagates via runners; handles sandy soils, salt air and rocky ground, as well as stream banks. Can be used on seasonally or periodically wet ground. Winter and summer rainfall.
Lampranthus coccineus - Red Vygie: 45 x 60 cm; Trailing, succulent leaves; good for steep banks; moderate growth speed; handles salt air and winter rainfall.
Aptenia cordifolia - Aptenia; 15 x 60 cm; semi-succulent spreading groundcover; creeping stems; handles salt air, sandy soils and dune conditions; steep banks and rocky ground; controls erosion; fast-spreading. Large areas; sun and shade, damp and dry.
Oscularia deltoides - Dassievygie: 20 – 40 cm; succulent; water wise; strong, trailing groundcover; copes with rocky ground; occasional light frost; steep ground; sandy soils; dry soils; parking areas.
Portulacaria afra prostrata - Dwarf Spekboom 10 – 20 cm; creeping, mat-forming; binds soils; good for banks, sun and shade. Summer and winter rainfall; moderate frost; dry soils and normal soils; evergreen.
Ruschia lineolata - Carpet of Stars: 5 cm x 60 cm; prostrate succulent; dense foliage; fast; sun to semi-shade; drought-hardy, evergreen, copes with sandy soils and moderate frost; woody root system; needs replacing after 3 – 4 years. Winter rainfall.