Busy Road-side Bank

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Situation and conditions: Full sun; sandy soils; a short, steep bank, extended length along a busy main road; sprinklers are provided but little used; summer rainfall. A similar plant palette decorates a small business-park garden behind the bank.

Groupings and pairings make the design of this extended roadside bank work:

Use of various plant types and form:

• Upright rather than vigorously spreading shrubs, groundcovers and perennials, mostly with bold, rigid form.

• Different plant types for a layered effect

• Combining small and large leaf sizes that slot into each other like puzzle pieces

• Stiff leaves paired with soft and yielding foliage

• Prostrate groundcovers that spread to keep soil beneath shrubs and between perennials covered.

• Groundcovers and perennials with staying power whose spread ebbs and flows to fill gaps as they open up, or remain contained alongside equally matched companions.

• Very little exposed ground, crucial to prevent erosion and maintain healthy soils.

• Choosing plants that require little management.

  • Plectranthus ecklonii is cut back at the end of winter.

  • A yearly trim keeps Plumbago in shape and improves foliage density

  • Dead flower stalks can be removed after flowering - or seasonally.

  • Kniphofia, Scadoxus, Crinum bulbs: dead leaves retained as mulch; new growth pushes through in spring.

Soil protection designs:

• A gum pole wall holds back the steepest section.

• Plants with strong, fleshy roots (Agapanthus, Chlorophytum, Crinum, Asparagus, Strelitzia) anchor the topsoil to the stable substrate, plus, they store water making these species water wise.

• Mat-forming groundcovers small enough to fill gaps and slot in beneath shrubs and perennials provide all the benefits of mulch: Delosperma, Crassula multicava.

• Dense foliage with firm leaves intercept, scatter and soften the weight of raindrops, reducing soil erosion and compaction.

Sturdy, year-round structure:

A permanent structure of evergreen shrubs, perennials and aloes allow for the use of indulgent seasonal specials, like kniphofias and Scadoxus.

Shrubs and trees planted in scattered groupings are linked by linear blocks of mostly tidy perennials, groundcovers and succulents.

While some sections look a bit messy up-close, from afar the result is an attractive display of dense foliage cover year-round, a big improvement over a sterile bank of lawn grass that would require weekly mowing, dies back or looks tatty when stressed, and provides little in the way of wildlife food and habitat.

Think twice about using these plants in small area designs with a diversity of species: 

Barleria obtusa, purple-flowering Barleria repens, Asystasia gangetica, and Hypoestes aristata, are beautiful, robust and hardy plants, but think carefully about using them in places you have no plans to maintain more than a few times a year. Barleria and Asystasia are vigorous growers that quickly send out long searching stems that root where they touch the ground. And they clamber and twine up and over their neighbours. Seeds of the Ribbon Bush germinate easily and rapidly anywhere and clumps expand in size via suckering stems. This shrub can grow and flower in its first season, producing a multitude of seedlings throughout the bed. Save these gorgeous, easy-care plants for beds you can manage often, and large areas in need of their generous characteristics.​