It is the ‘ivy’ of ivy league schools. Nonetheless, Boston ivy, Parthenocissus tricuspidata, is neither an ivy, nor indigenous to Boston. It is from eastern Asia, and is related to grape vines. It is related to Virginia creeper too, which is actually native to Boston, Virginia and the eastern half of North America. It has become popular locally for freeway sound walls.
Boston ivy is an aggressive clinging vine that can climb to the top of a ten story building. Unfortunately, there are a few problems with that. It ruins wooden or painted surfaces, so can only climb concrete or masonry. It climbs over windows if it gets the chance. Thicket growth is difficult to remove if it is too high to reach. On rare occasion, mice can nest in it.
Otherwise, Boston ivy works well on freeways. Although deciduous, its vines discourage graffiti. Even while bare, its texture helps to muffle sound. Its exquisite autumn foliar color might begin to develop as early as late summer, and lingers until frost. Boston ivy is quite resilient to neglect. Shabby plants generate fresh new growth after major winter pruning.
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.
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.
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.
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.
Although rarely planted intentionally in home gardens, perennial pea, Lathyrus latifolius, is somewhat common near rural roadside ditches and in riparian situations. It naturalizes to a minor degree, generally where the soil retains a bit of moisture after the rain finishes. It can eventually become somewhat overwhelming in unrefined but irrigated landscapes.
Bloom is typically rich purplish pink during late spring or early summer. A few specimens might bloom white or pale pink. Seed for varieties that bloom in any of these three colors, as well as red, is available online. Flowers resemble those of annual sweet pea, but are more abundant, and lack fragrance. Their delicate foliage might be slightly bluish green.
Vines might be lean through their first season from seed, but can get six feet long. By the middle of summer, they begin to die back to their plump perennial roots. They last longer with watering. Without watering, they may finish before July. Vines that grow from mature roots as winter ends after the first season should be bigger, fuller and perhaps voracious.
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.
No other bloom is comparable to that of bougainvillea. It is often profuse enough to nearly obscure the foliage. The color is remarkably vibrant. Magenta is the most popular color. Purple might be the second most popular color. Other cultivars bloom in delightfully rich hues of pink, red, orange, yellow and white. Some bloom with double flowers. A few dwarf cultivars have variegated foliage.
Bougainvillea is a thorny vine that leans on its support, rather than cling to it. Like climbing roses, it must be tied or woven into trellises. Larger cultivars can mix with the branches of trees and big shrubs to eventually reach more than thirty feet high. Many cultivars stay much lower. Some grow slowly, and do not get more than three feet tall. The lush foliage is evergreen with regular watering.
However, bougainvillea does not want too much water, and actually prefers to get a a bit dry between regular irrigation. Excessive irrigation may promote vegetative growth while inhibiting bloom. Excessive fertilizer does the same. Sunny and warm exposure promotes fuller bloom. In late spring, the first and most profuse of perhaps a few bloom phases can continue for more than a month.
Grapevines that were not pruned aggressively enough last winter are tangled messes by now. Many grapevines that were pruned properly are tangled messes as well. That is their nature. Woody vines like grapevines grow rapidly and vigorously. They rely on other plants for support, and do what they must to get to the top. Woody vines are not concerned about the plants that support them.
Woody vines climb structures also. Some cling to stucco and siding with aerial roots or modified tendrils (holdfast discs), that ruin paint and promote decay. Woody vines with twining stems wrap around posts and beams, and then crush them as they grow. All sorts of vines can dislodge shingles, roof tiles, gutters, downspouts or window screens. Some sneak into basement or attic vents.
Even relatively docile woody vines can get out of control fast. Star jasmine performs well as ground cover, but can climb more than twenty feet up trees if neglected long enough. Pink jasmine, lilac vine and Carolina jessamine are tame enough for lattice, but get overgrown on top if not pruned down. American wisteria is much smaller than Chinese wisteria, but can still strangle small shrubs.
Woody vines are certainly worth growing. Chinese wisteria, autumn clematis, honeysuckle, bougainvilleas and various trumpet vines all have their attributes. They just require diligent maintenance and serious commitment. Most need more than just winter pruning. Some of the more vigorous sorts may need specialized pruning a few times annually. They also need serious accommodation.
Trellises and supportive structures must be resilient to the destructive forces of particular woody vines. For example, Chinese wisteria deserves a trellis or arbor of posts and lumber that its heavy vines will not crush. Boston ivy can climb bare concrete retaining walls, but must not attach to painted or wooden surfaces. No vines should climb on roofs, chimneys, vents, gutters or utility cables.
Just as importantly, woody vines require enough room to grow without crowding or climbing into trees or other plants.
As the simple name implies, ‘groundcover’ covers the ground. Groundcover plants stay lower than shrubbery, and function something like mulch. They insulate shallow roots of other plants, inhibit weeds, and some groundcovers inhibit erosion. Besides all their utilitarian functions, they provide appealing foliage, and some bloom nicely.
Lawn is probably the most common groundcover, and is also the most useful; but that is an entirely different and involved topic! Other groundcover plants are spreading perennials, plants with sprawling stems, or vines grown without support. Most are evergreen, since defoliated plants do not cover much of anything too well.
Gazanias and iceplants are popular perennial groundcovers. Their old stems tend to die out and decompose as efficiently as new stems pile up over them, which is why they do not get too deep. Gazanias can eventually get bald spots that need to be patched with new plants, or ‘plugged.’
(The debris from pruning the edges of easily rooted perennial groundcovers can be processed into cuttings known as ‘plugs’, which can go directly into bald spots. Plugs can be taken from dense spots if no edging is necessary. They should be watered regularly, or plugged in autumn to take advantage of rain while roots develop.)
Groundcover forms of ceanothus (wild lilac), juniper and contoneaster are really shrubs that extend their stems more horizontally than vertically. Honeysuckle and both Algerian and English ivies are vines that spread over the ground until they find something to climb. Their stems root into the ground wherever they need to.
Since most groundcover plants are naturally understory plants that grow below larger plants, many tolerate considerable shade. Periwinkle and the ivies are remarkably happy in partial shade. However, vines, particularly the ivies, will climb walls and trees for more sunlight if they get the chance.
Many of the perennial groundcovers and some of the vines are neater if mown or cut low annually. Periwinkle does not need to be mown, but can get rather unkempt before new growth overwhelms the old through winter. Mowing eliminates the old stems, and makes the new growth fluffier. Dwarf periwinkle stays too low to mow.