It is really difficult to garden on steep slopes but creating a terrace with loffel stones opens up the possibility of creating a vertical garden feature, quite literally a beautiful flowering wall.
Loffel stones are precast concrete rings that interlock, each with a cavity that can be filled with soil. Although the cavities are not very deep, they contain enough soil for shallow rooted plants to grow in.
Getting started
Being quite shallow the soil tends to dry out fast, so a good starting point for an existing wall is to fill each hollow with good soil that consists of one part compost to two parts topsoil . Add bonemeal or superphosphate to the mix and some water retention granules to keep the soil moist for longer.
If a new wall is to be built, ensure that your building contractor uses a good topsoil mixed with compost, and make sure they don’t fill it with rubble.
Watering
Keeping the soil moist on a continuous basis is the biggest challenge because there is nothing worse than a wall with dry and frazzled flowers.
The best solution is a micro-irrigation system along the wall with sprinklers. It can be an automatic system or a simple manual system that its linked to a tap. Depending on the size of the wall, it could also be watered by a handheld hose.
The amount of watering also depends on how much sun or shade the wall receives.
Choose the right plants
The most suitable plants are those with small or shallow root systems and they should be hardy, heat and drought tolerant as most retaining walls are hot and sunny.
To create and interesting and colourful flowering wall, plant blocks of single varieties and colours to achieve a massed effect.
For a green wall, use spreading or trailing groundcovers with different coloured foliage to produce a pleasing pattern.
5 hardy growers for a flowering wall
Lobularia (alyssum) ‘Easy Breezy’ is a very compact variety that grows into a mounded plant covered by a profusion of sweetly scented flowers. ‘Easy Breezy’ flowers continuously through winter and attracts butterflies and bees.
Petunias are available in a huge range of colours and growth habits. A very showy variety is Petchoa ‘BeautiCal’, which is a cross of petunia and calibrachoa. They have the spread of calibrachoa but with bigger petunia flowers.
For a more cascading effect consider Petunia ‘E3 Easy Wave’ which only grows 15 to 30cm high but has a spread of 65 to 80cm. The plants hold their shape and stay lush. They are available in a large range of colours.
Calibrachoa ‘Cha-Cha’ is a vigorous grower with large cascading blooms in shades of apricot, hot pink, fuchsia and red. The mounded, low growing plants have a controlled spread of 30 to 60 cm. They like sun and have a long flowering season.
‘Tacari’ ivy geraniums are semi trailing plants that keep their shape, producing a full effect with large flowers above the leaves. There is a large range of colours and ivy leaf geraniums are particularly hardy with succulent type leaves.
Verbena ‘Cadet’ is an upright growing verbena with a compact growth habit, while Verbena ‘Firehouse’ has a more spreading growth of 45 to 55 cm. Both varieties are very healthy and rebloom so quickly they appear to flower non-stop. The flowers attract butterflies.
Some tips
Start with small plants or healthy, well established seedlings that can grow into the cavities. Bigger plants will be hard to plant and may not establish as easily.
Use either compact or spreading plants, depending on the effect you want. With spreading plants, it may not be necessary to fill every cavity and you may also be able to skip a row. Start planting at the top of the wall and work your way down.
General care
Don’t neglect watering as plants dry out quickly in their shallow planters.
Feed once every three months and cut back straggly growth to keep plants lush and healthy.
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Article and images supplied by Alice Coetzee.
