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.

Star Jasmine

Star jasmine blooms with fragrant profusion.

This jasmine is quite a star. However, this star is technically not a jasmine. Star jasmine, Trachelospermum jasminoides, is instead related to mandevilla and oleander. For many years, it has been one of the most popular vines for home gardens as well as large scale landscapes. It works well either as a ground cover, or as a relatively docile climbing vine. 

As ground cover, star jasmine gets about two feet deep. It will be lower and more refined with shearing, but will likely bloom less. It tries to climb shrubbery and trees, so will need exclusionary pruning. However, on a chain link fence, star jasmine works splendidly as a shorn faux hedge. It grows fast to more than ten feet high, but can get significantly higher. 

The richly fragrant bloom is most profuse about now, and can continue sporadically until autumn. The inch wide and bright white flowers are shaped like stars, and hang in small clusters. After bloom, the distinctly glossy and dark green evergreen foliage is handsome alone. Individual leaves are a bit longer than two inches and a bit broader than one inch. 

Plants To Cover New Ground

Ground cover plants are quite variable.

Lawn is both the most common and the most horticulturally incorrect of landscape features. Not many landscapes lack lawn. After all, it is the most useful part. Yet, with few exceptions, it requires more water and maintenance than anything else, and in most situations, than everything else combined!

Other groundcover plants are not nearly so greedy. Some need only occasional attentions. Most want less water, and some need very little water or none at all once established. No other groundcover functions like lawn. However, they each have particular advantages.

Ideally, groundcover plants do more than just look good. Most cover otherwise exposed soil so that weeds or other unwanted plants do not dominate. Some groundcovers help to stabilize soil. A few even work as living mulch so that soil does not stay too harshly exposed for other plants to be comfortable in it.

Low growing shrubbery, like creeping ceanothus and some types of juniper, can get too deep and unmanageable for confined areas. They tend to work better where they have room to spread outward uninterrupted. Otherwise, the edges can get quite shabby if they need to be pruned back for confinement. Some sprawling cotoneasters tolerate pruning better, both on top and the edges.

Coarse vines, like honeysuckle, naturally stay low where they have nothing to climb, although they need occasional pruning to stay tidy and confined. High branched trees, like most types of eucalyptus, are beyond the reach of busy tendrils or twining vines. However, Algerian and English ivies, although considerably tidier and uniform, can cling directly to the trunk of any tree to become a wicked mess out of reach!

Old fashioned Hottentot fig (freeway iceplant) can be aggressive where it needs to be pruned around the edges, but is actually quite complaisant otherwise. It does not pile up too deeply because older stems decay as readily as they get overwhelmed by new growth above. Vigorous growth is an advantage for filling in quickly, and subduing weeds. ‘Real’ iceplants are smaller, more docile around the edges, and much more colorful when they bloom.

Algerian Ivy

Algerian ivy is big and bold.

Like so many fad plants that were formerly too popular, Algerian ivy, Hedera canariensis, now has a bad reputation. Ironically though, it earned its reputation for doing what it does best. It covers ground rapidly and efficiently. The problem is that it never seems to stop. It creeps anywhere it can, and climbs trees, fences and anything else that it can grab onto.

Aerial roots of climbing vines ruin paint and stucco, and accelerate rot of wooden fences and walls. Vines that get between planks or into cracks between bricks cause significant damage as they expand. Shrubby adult growth that blooms and produces seed develops where climbing vines reach the top of their support, or spontaneously in sunny locations. 

Nonetheless, with diligent edging for strict confinement and to prevent climbing, Algerian ivy works well as a resilient evergreen ground cover for large areas. Once established, it excludes weeds, and tolerates quite a bit of shade. Shrubby adult growth is uncommon if vines can not climb. Climbing vines may be harmless on bare reinforced concrete walls.

Algerian ivy is neither as finely textured nor as shallow as English ivy. Its broader leaves are about six inches wide, with blunter lobes. They stand higher on longer and distinctly blushed petioles. Algerian ivy is rare in nurseries now, but inhabits old landscapes, from which it sneaks into adjacent landscapes. Variegated cultivars are slightly more passive.