Busy Roadside Bank

Hot, Sunny Bank

Drought-stressed Slope

April articles: Next

Successful Verge Plants offer up

design ideas for Resilient Gardens

Successful Verge Plants Page 2: Plumbago and grasses; Dry succulent bank

Thriving verge designs translate well into resilient home gardens.

 

I love to take weekend walks through the neighbourhood; from this vantage point, I get to see so much more than when whizzing past in the car. Of course, our need for security and privacy - from nosy, wandering gardeners, amongst others - means that high walls offer a limited view of these attractive spaces, often only revealing the top half of a boundary screen – and, of course, the verge. Yet even these meagre pickings can inspire fresh design ideas.

 

Successfully planted verges, for example, offer up a list of resilient species for our gardens as roadside plants battle challenging conditions to survive like:

 

  • Car fumes

  • Windy and exposed

  • Full-day sun without shade protection from trees

  • Little maintenance

  • No supplemental water

  • Nutrient-poor, sandy or rocky soils

  • Steep gradients

 

What makes a verge design successful?

Most importantly, plants must have staying power to survive long-term, certainly beyond the few short months after planting. And this refers to the design as well; combinations, groupings, companions, all should maintain themselves with minimal input from the gardener.

 

To accomplish this, the designer needs to: 

 

  • Know the conditions - gradient, aspect, exposure, soil quality - and choose plants to match them.

  • Use plants that suit your areas rainfall season and volumes, plus temperature variations through the day and through the seasons.

  • Be honest about how much spare time you have to manage this area and focus on low-maintenance species.

  • Know a plant’s growth needs and management requirements – individually and as a member of a community group.

  • Use well-balanced compositions where no single plant dominates the others and the majority of species have similar competitive strategies.

 

While the following are verge displays, they provide us with a list of successful low-input plants and attractive combinations we can easily replicate to create resilient home gardens.

 

The plant palette and designs translate well to the following garden situations and conditions:

Dry slopes, north-facing aspects, sandy soils; rockeries, verges, exposed sites, stony soils.

Busy Road-side Bank

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.​

S - Sun; Ss - Semi-shade; Sh - Shade   Fr - Frost hardy; Mod Fr - moderate frost

Shrubby backdrop:

  • Polygala myrtifolia (September Bush) S; Ss; Fr

  • Carissa bispinosa (Forest Num-num) Ss; Sh; S  Mod Fr

  • Erythrina lysistemon (Common Coral Tree) S; Fr

  • Portulacaria afra (Spekboom) S; Mod Fr

  • Aloe ferox (Bitter Aloe) S; Fr

  • Plumbago auriculata (Plumbago) S; Ss; Mod Fr

 

Other mid-level shrubs used:

  • Aloe arborescens (Krantz Aloe) S; Ss; Fr

  • Euryops pectinatus (Golden Daisy Bush) S; Fr

  • Strelitzia reginae (Bird of Paradise) S; Ss; Mod Fr

  • Coddia rudis (Small Bone Apple) S; Ss; Mod Fr

  • Hypoestes aristata (Ribbon Bush) S; Ss; Mod Fr

  • Plectranthus ecklonii (Large Spur Flower) S; Ss; Sh

  • Leonotis leonurus (Wild Dagga) S; Fr

Groundcovers:

  • Crassula multicava (Fairy Crassula) S; Ss; Sh; Mod Fr

  • Delosperma species:Try D. rogersii; D. cooperi; D. riylei. S; Mod Fr

  • Tulbaghia violacea (Wild Garlic) S; Fr

  • Chlorophytum comosum (Hen & Chickens) Ss; Sh; Light – Mod Fr

  • Asparagus densiflorus ‘Sprengeri’ (Emerald Fern) S; Ss; Mod Fr

  • Chlorophytum saundersiae (Weeping Anthericum) S; Ss; Sh; Fr 

 

Perennials, succulents:

  • Curio species (C. crassulifolius / C. talinoides) S; Light Frost

  • Sansevieria hyacinthoides (Mother-in-Law’s Tongue) S; Ss; Sh;   Mod Fr – mixed with a few exotic Sansevieria trifasciata

  • Aloe vanbalenii (Octopus Aloe) S; Mod Fr; Fr

  • Bulbine latifolia (Broad-leaved Bulbine) S; Ss; Mod Fr

  • Kniphofia species (Red-hot Pokers) S; Mod Fr; Fr

Specials:

  • Scadoxus multiflorus subsp. Katherinae (Blood Flower; Katharine Wheel) Ss; Sh

  • Crinum bulbispermum (Orange River Lily) S; Fr

Successful Verge Plants Page 2: Plumbago and grasses; Dry succulent bank