Vines Are Aggressive Social Climbers

English ivy can cling to anything.

Regardless of how appealing many of them are in home gardens and landscapes, vines are flagrantly exploitative. They rely on shrubbery, trees or anything they can climb on for support. As they reach the tops of their supports, they extend their foliar canopies above. Vines have no reservations about overwhelming and maybe killing their own supporters. 

Vines climb with clinging roots, twining stems, tendrils, twining leaves, or even thorns or spines. Some vines are annuals or perennials. The most aggressive or destructive sorts are woody plants. Some creep along the ground while young, and then climb when they find support. Some mature to support their own weight as they lose their original support. 

English ivy and Algerian ivy, in their juvenile forms, can be practical ground cover plants. However, when they encounter shrubbery, trees or buildings, they become clinging vines that can overwhelm their supports, and ruin infrastructure. As they mature, clinging vines evolve into shrubbier and obtrusively bulky adult growth that blooms and produces seed. 

Boston ivy, which incidentally is not actually ivy, is more practical as a clinging vine than the other ivies. It does not grow as ground cover anyway. Nor does it develop bulky adult growth. However, it also has limitations. Because it attaches to its supports with clinging tendrils, it is only practical for surfaces that it can not wreck, such as reinforced concrete.

Bougainvillea is a delightful and shrubby vine. It neither clings to surfaces nor grips onto support by twining. It simply generates long and vigorous canes that eventually lie down onto its surroundings. Long thorns help to anchor these canes in place. Canes should be satisfied with trellises, but sometimes mingle with shrubbery or trees, or spill over fences. 

Carolina jessamine, lilac vine and mandevilla climb with twining stems, but are relatively docile. Star jasmine, which performs well both as a ground cover plant and as a climbing vine, can crush flimsy lattice with its twining vines. Wisteria might crush substantial trellis beams. Passion flower climbs with wiry tendrils, but can be overwhelmingly voluminous. 

Gazania

Gazania is colorful until cool autumn weather.

The most familiar of the gazanias are the ‘trailing’ types commonly appreciated as ground cover. They are rather shallow, but dense enough to prevent most weeds from getting through. Their yellow or orange composite (daisy like) flowers bloom initially in spring, and then continue to bloom sporadically as long as the weather stays warm into autumn. Some trailing gazanias have interesting silvery foliage.

‘Clumping’ gazanias do not spread efficiently or thoroughly enough to be practical as ground cover over large areas, but bloom a bit more profusely with bigger flowers in shades of yellowish white, light yellow, bright yellow, orange, brownish orange and brownish red. The foliage gets a bit deeper to form irregular but dense low mounds. Clumping gazanias can be lined up as an informal border around blooming annuals or perennials, or incorporated individually into mixed urns or vertical gardens.

Gazanias are not too discriminating about soil quality or frequency of irrigation. They only need good sun exposure. Trailing gazanias are rather easy to propagate by cuttings made from scraps from pruning around the edges. Clumping gazanias do not get pruned as much, but are easy to propagate by division from dense clumps.

THE LOWDOWN ON GROUND COVER

Most euonymus are upright shrubbery. This one though, stays low enough to be useful as a shallow shrubby ground cover.

Of all the functions that the many and various plants in the garden serve, ground covers have the lowliest job description. Well, maybe it is just the lowest job; covering the ground. It is an important job though. Ground covers fill in the space between other desirable plants to obscure otherwise bare soil. They also control weeds. Some ground covers help to limit erosion. Others help to insulate the soil for plants with sensitive roots.

There certainly are all sorts of ground cover. Lawns are the most familiar. Many other ground covers are perennials like gazanias, African daisies and iceplants. Some, like ivies, honeysuckles and star jasmine, are vines. Others are low growing shrubs like certain coprosmas, cotoneasters and junipers. Some lay about as flat as carpeting. Some get a few feet deep.

Many perennial ground covers as well as some of the vines and low growing shrubbery provide colorful flowers. Japanese honeysuckle and star jasmine are not as colorful, but provide delightful fragrance. Some of the cotoneasters have colorful berries in winter. Although not seen, many ground covers are appreciated more for their network or roots that help to stabilize soil that might otherwise erode. One feature that most ground cover plants have in common though, is their foliage that is dense enough to keep weeds out, as well as to obscure the soil below.

Like all other plants in the landscape, ground cover plants need maintenance. Lawns probably need more maintenance than any other ground cover, since they need to be mowed, weeded, fertilized and watered quite regularly. Vine ground covers need to be pruned so that they do not get into trees and shrubbery. Some ground covers look best if mowed annually (typically at the end of winter) or even more frequently. Some of the deeper ground cover shrubs should be pruned down to stay low. Almost all ground covers need to be edged for confinement.

Ground cover plants must be selected for their appropriateness to particular applications. For example, most low growing shrubbery needs space, so is best for larger areas. Smaller iceplants that may not be aggressive enough for big areas are great for tight spots, or for mixing with other perennials. Tough Algerian ivy that is so useful for freeway embankments may be too aggressive for home gardens. As with all plants in the garden, careful selection helps to get the best ground cover plants for each particular situation where ground covers are needed.

Lantana

Lantana sports two colors per bloom.

All flowers that need help with getting pollinated do what they can to attract pollinators. The tiny flowers of lantana, Lantana camara, actually put forth a bit of extra effort to improve the efficiency of their pollinators, by becoming less attractive once pollinated. Within each tightly set flower cluster, pollinated flowers fade to an alternate color to inform pollinators that their services are no longer needed. This prioritizes flowers than still await pollination. Consequently, each small cluster exhibits flowers of two different colors. The choices are red, orange, yellow, pink, purplish pink or white.

The small and aromatic leaves are arranged in alternating pairs on thin stems that do not get much higher or wider than three feet. Established plants can survive with very minimal watering, but bloom better with somewhat regular watering. The summer bloom is very attractive to butterflies.

Trailing lantana, Lantana montevidensis, has limber stems that sprawl a few feet over the ground without getting a foot deep. It cascades nicely over retaining walls or from large planters. Flowers are shades of lavender, or sometimes white.

Creeping Thyme

Creeping thyme is pleasantly aromatic, but not quite as flavorful as culinary thyme.

Trendy landscape designers like to set flagstone walkways slightly out of step to compel visitors to the garden to stroll through a bit slower. Between the stones, it is in style to grow creeping thyme, Thymus spp., as a very shallow groundcover that relinquishes its delightfully herbal aroma with any misstep. It stays too low to trip on, tolerates a bit of trampling, and needs only minor trimming where it creeps a bit too far onto stones or pavement. Creeping thyme can also be plugged into retaining walls of broken concrete or stone. The grayish green foliage is very finely textured. While the weather is warm, minute lavender flowers bloom in subdued phases that come and go slowly. Some varieties have more pinkish flowers, lighter green foliage or exhibit different aromas.

Rosemary

Trailing rosemary cascades over retaining walls.

It is as familiar for culinary application as it is for home gardens, even with its new name. Rosmarinus officinalis is now known as Salvia rosmarinus, but the common name is still just rosemary. Like many Mediterranean culinary herbs, it is a member of the Lamiaceae Family. Since it is native to Mediterranean regions, it is quite happy within local climates. 

While many culinary cultivars of rosemary are shrubby or upright, the most popular home garden cultivars are trailing types. Trailing rosemary disperses its woody stems laterally, but can eventually get deeper than two feet. Shrubbier cultivars get at least twice as high in less time. The finely textured dark green foliage is evergreen and pungently aromatic.

Bloom is generally most profuse from late spring through the middle of summer, but may never really stop. It can continue in sparser sporadic phases whenever the weather gets warm, and even throughout the year. The tiny flowers are various shades of blue. Purple, white and pale pink bloom is very rare. Bloom is appealing to bees and other pollinators, including hummingbirds.

Knotweed

Knotweed by any other name. . .

There are no fancy varieties, but many different fancy names for knotweed. It used to be known as Polygonum capitatum, but is now easier to research as Persicaria capitata. The many common names include pink knotweed, pink clover, pink fleece flower, pinkhead, pink bubbleweed and smartweed. Obviously, the tiny and spherical blooms are pink, about the color of bubble gum. Each small leaf has a distinctive brown chevron, which makes the collective foliage rather bronzy. The wiry stems can not stand much more than three inches high, but creep indefinitely, rooting as they go. Knotweed is an excellent but potentially invasive groundcover, and is also a nice component to mixed plantings in large urns or behind retaining walls, where it can cascade several inches over the edges. A bit of partial shade is no problem. Bloom continues through the end of summer, and resumes at the end of winter.

Much Ado About Mulch

Not many weeds get through mulch.

Mulch was not invented by humans. Most plants make some sort of mulch naturally. Even desert plants that live on bare ground shed foliage that decomposes to be recycled back into the soil, and provide nutrients for the roots below. Redwood, most pines and most eucalyptus are extreme mulchers that generate thick layers of foliar debris that benefit their own roots, but inhibit the growth of competing trees. Knotweed, Hottentot fig (freeway iceplant), ivy (both Algerian and English) and other dense groundcovers are their own mulch, and also work well for substantial plants that grow amongst them.

There are a few advantages to mulch. Although ground cover mulches consume some degree of moisture, mulches benefit plants by retaining moisture at the surface of the soil. Mulches also insulate the soil, so that it is more comfortable for roots that want to be near the surface. Most weed seeds that get covered by thick mulch can not germinate and emerge through it. Those that try to germinate on top probably can not get their roots through to the soil below. Besides, mulch simply looks better than bare soil.

Mulch is generally spread in early spring, before weed seeds are completely germinated, and while the soil is still damp. However, moisture retention is still a concern through the warm and dry weather of summer. A thin layer of finely textured mulch added over thinning groundcovers (without completely burying the foliage) can rejuvenate tired old stems by giving them something more to root into. This works well for knotweed, English ivy and even trailing gazanias.

Mulches should generally be well composted so that they do not take too many nutrients out of the soil for their own decomposition. However, uncomposted coarse wood chips, like those often recycled from tree services, are even more effective at controlling weeds while fresh, and they tend to decompose before they become a bother to larger plants.

Small volumes of mulch can be purchased in bales at nurseries and garden centers. Composted redwood soil conditioner is a popular soil amendment that can alternatively be a nice finely textured mulch to spread thinly over small areas or in planters. Larger volumes of more coarsely textured and less expensive mulching materials can be obtained by the yard from garden supply stores.

English Ivy

Rampant English ivy can overwhelm trees.

Compared to Algerian ivy, English ivy, Hedera helix, may seem to be more complaisant. As ground cover, it mostly stays a bit lower, with smaller leaves, and a more refined foliar texture. It is generally easier to maintain and to mow if it does not get too deep. However, where it naturalizes, English ivy is more aggressive and more invasive than Algerian ivy. 

If contained, English ivy is a splendidly dense and evergreen ground cover that excludes most weeds. Containment is very important! English ivy must not climb into shrubbery or trees. It otherwise overwhelms its support and disperses seed. Although reasonably safe on bare concrete walls, it ruins wooden, painted and stucco surfaces. Growth is very fast! 

‘Hahn’s’ is likely the most popular cultivar of English ivy. It branches well, to fill out fast as ground cover. Cultivars that are variegated with white or yellow grow significantly slower, but provide elegant foliage for big pots or planters of mixed annuals or perennials. Foliar lobes are variable. For example, lobes of ‘Needlepoint’ are distinctly narrow and pointed.

Ground Cover Works Like Mulch

Ground covers, simply speaking, cover ground.

Weeding otherwise bare and unused ground is no fun. Nor is weed whacking. Mulching inhibits future weed growth, but requires occasional replenishment. For many situations, ground cover plants are more practical. Once established, many sorts effectively exclude most weeds. Even more contain dust, and inhibit erosion of the surface of the soil below.

As the terminology implies, ground cover plants are simply plants that disperse laterally, over the surface of the ground. Many migrate by subterranean stems known as rhizomes, or by stems on the surface of the soil, known as stolons. Some are vines that behave like stolons. Also, many are merely prostrate shrubbery that does not stand upright very high. 

Ground cover plants generally require more maintenance than mulch, and most want for some degree of irrigation. Conversely they require less effort than weeding. Furthermore, ground cover plants can live on slopes that are too steep for mulch to adhere to, and are more appealing than mulch. They might be as colorful or fragrant as other sorts of plants. 

Prostrate shrubbery, such as creeping cultivars of juniper, manzanita and ceanothus, are best in areas that are big enough to accommodate their width at maturity. Within confined spaces, they need pruning around the edges, which exposes unappealingly bare interior stems. Prostrate shrubbery generally gets higher than other types of ground cover plants. 

The many vines that work as ground cover probably stay lower than prostrate shrubbery, unless of course they climb into bigger shrubbery and trees. Algerian ivy and English ivy are famously aggressive if they overwhelm other vegetation. Also, they can cling to walls and ruin paint and siding. Star jasmine climbs too, but does not cling, and is more docile. 

Perennial ground cover plants, such as various iceplant, trailing gazania, trailing African daisy and pigface (freeway iceplant), tend to stay lower than other types. Most require no grooming over their upper surface, so only need trimming around the edges. Scraps from trimming during winter can become cuttings for bare patches or elsewhere in the garden. Several types root efficiently.