Vertical gardens have become part of mainstream landscape design in both large-scale commercial and small urban designs. John Gabriele outlines a few of their features.
Vertical gardens pose one of the greatest challenges in plant cultivation.
The small volume of growing media in these systems will dry out much more rapidly than containers that have a greater volume of growing media. Therefore, maintaining these gardens can be a challenge, particularly during the heat of summer.
Installation of a drip-irrigation system is one way of overcoming the problem of possible water stress in vertical gardens, but installation will increase the cost of a project.
Twiners
One way of utilising the vertical space in a landscape without resorting to specialist vertical-garden systems is to grow climbing plants. Climbing plants have elongated stems and require some form of support to grow vertically. In nature climbers use trees, shrubs and rock faces to grow towards the light. Some climbers, known as lianas, can grow to heights of 50m in their native habitats, usually on thick, arborescent stems, in search of light so they can flower and fruit. They’re probably not the type of plant for the average urban landscape, however many ornamental climbers are a little more obedient.
Climbing plants use different modifications to grow on a support, and the mechanism by which these plants climb will influence the type of support provided for the plant when planning vertical gardens.
Climbers
Climbers can be classified as twiners; plants that wrap their stems around the support to assist them in growing vertically. The following selections are good examples of twining plants:
• Trachelospermum jasminoides (Star Jasmine) with its fragrant late-spring flowers, can always be relied upon to look good in any landscape setting. Star Jasmine grows slowly at first but, once its roots are well established, will take off. It displays reasonable drought tolerance and is also adaptive to shade, but with fewer flowers;
• Hardenbergia violacea (False Sarsaparilla) is one of the first to begin flowering. These delightful natives with their deep purple, pink or white pea flowers – depending on variety – tend to scramble to the top of their support. There are some varieties of Hardenbergia that are more shrub-like in their habit, so care should be taken when choosing plants from the nursery. Check you have the right variety for the purpose intended, otherwise an undesirable effect may be created;
• Pandorea jasminoides (Bower of Beauty) is another fantastic native climber that has bold glossy leaves and a stunning display of large, trumpet-shaped maroon-on-pink blooms. ‘Lady Di’ is a pure-white version. Look, too, for the low-growing Bellz range of Pandorea that has been bred in part for its precocious flowering. They produce clusters of flowers on short, robust stems and the plants branch naturally to provide a dense form. They can even be used as a low shrub in a water-wise, easy-care garden, but given support they will climb;
• Mandevilla cvs. are another very obedient type of twiners that are also well suited to pot culture where they can be grown on balconies, across trellis or wrought iron. They produce large, trumpet-shaped blooms in shades of red, pink or white, and can flower for up to nine months of the year. Mandevilla will flower profusely in a full-sun position, but care must be taken to ensure they receive ample moisture under such conditions.
Twiners are best grown on a trellis system and are exceptional selections for covering a weldmesh fencing or railing-type fences. Caution should be exercised though, when planting twiners or other climbers close to pool fences as their growth, and the vertical gardens they produce could provide a foothold for infants to climb and gain access to pools inadvertently.
Tendrils and scramblers
Tendril climbers have some form of modified stem or leaf producing a tendril that wraps around the support, Passiflora edulis (passionfruit), Pyrostegia venusta (Orange Trumpet Vine), Vitis vinifera (Alicante Bouchet, Ornamental Grape) use their tendrils to attach to their support, often a wire or bamboo trellis. Climbers with re-curved hooks or thorns are referred to as scramblers. Bougainvillea cvs. and Climbing Roses rely on this type of mechanism, but may also require additional ties to keep them attached closely to the support.
Pros and cons
The vigorous growth of many climbers can be difficult to control, making correct selection critical in reducing maintenance and possible damage to some surfaces. Climbers such as Jasminimum polyanthum (Sweet Jasmine) have a tendency to sucker and readily layer, potentially spreading beyond its intended site. Others can cause physical damage to landscape infrastructure due to their climbing mechanism, Hedera helix (English Ivy and Boston Ivy) fall into this category, as the adventitious roots of the ivy, and the sucker disks found at the end of the tendrils of Boston Ivy, cling to the vertical surfaces they climb upon. When stems are pulled away, the disks or adventitious roots can pull away bits of masonry or paint from vertical surfaces the plant was growing upon.
Some climbers can be problematic owing to their vigorous growth habits.
Cissus antarctica (Kangaroo Vine) and Hedera canariensis (Algerian Ivy) grow quickly to form a dense mass which can climb through and smother any plants beneath. The upside of such dense growth in these two species is where they are used as a groundcover they block out light to the ground and prevent other plants germinating – thereby suppressing weed competition.
Support systems
Almost any structure can be used to support a climber or be covered by a climber.
The type of support required depends on the use or purpose the climber is to serve, but whatever type of support is chosen, it should have enough strength to support the weight of the mature plant.
Support materials should be selected on their ability not only to support the mature weight of a climber, but also for their longevity and ability to blend aesthetically with the surrounding features and display the characteristics of the climber to full effect. A case in point is Wisteria sinensis. With its pendulant blooms it requires an arbor or pergola to be displayed to full effect, or, if grown on a fence or building façade, a strong wire support system.
Select support materials for climbers that will not rot or collapse in a few years. Treated timber, plastic-coated metal mesh or frames and stainless-steel wires are all worth considering. Most trellis and wire systems are designed as a one-dimensional frame which doesn’t necessarily provide the best support when installed against a solid wall. Spacing between the wall and support, if inadequate, can lead to failure in supporting the climber as plants mature and increase in weight. Taking this into consideration, there is a new product on the market called ArchBar Climber Trellis Mesh (CTM). This is a three-dimensional, galvanised, welded-wire trellis system, industrially powder-coated black, that creates both a vertical and espaliered green wall. The CTM allows the transformation of a blank concrete or masonry wall, fence, or facade into a soft, textured-vine surface into a green wall. ArchBar Climber Trellis Mesh comes in standard panels of 2233mm x 1220mm, consisting of a 50mm x 50mm apertured grid with a 50mm depth between front and rear mesh sections. Specific sizes of both aperture, depth and perimeter panel sizes may be manufactured pending on volume.
Versatile
Climbers have the versatility to cover or decorate fences, pillars and posts, pergolas, arches and arbors, deck railings and balustrades. They can be grown as groundcover or spill over in containers. Whatever the landscape situation, with careful selection and the right support, climbers can be a real focal point in a landscape.