Helen McKerralPlanting a dry stone wall

With seventy square metres of dry stone retaining walls in the new garden area, the effect is currently rather stark… but, no worries. The big advantage of this kind of wall is that it can be planted! I popped in six thyme plants in late spring, but it was the wrong season so only three survived the scorching summer heat. Autumn will be much a better time for successful establishment.

Grass skink on stone wall with armeria

Grass skink on stone wall with armeria

As well as beautifying walls, small rockery and trailing plants help stabilise stones as their roots extend into crevices and prevent soil behind from washing out.

Plants with long and/or overlapping flowering times attract bees: Nepeta fassenii and Erigeron karvinskyanus ‘Profusion’ are two hardy ones. And then there are plants that are simply pretty: Armeria maritima, Viola labradorica ‘Purpurea’ and Dianthus. Some of the tougher cranesbills like South African Geranium reniforme with its leathery grey leaves, should do well, as should the compact Rhodohypoxis bauerii. In spring I’ll tuck seed of Alyssum into crannies and see what happens.

Geranium reniforme

Geranium reniforme

Culinary herbs in dry stone retaining wall

Culinary herbs in dry stone retaining wall

Endemic species attract native insects, birds and wildlife (little grass skinks, probably Lampropholis guichenoti, are ubiquitous in my garden, and love sunning themselves atop the stone walls). I’ll try to buy plants like Astroloma humifusum (tiny edible berries), Hibbertia sericea, Tetratheca pilosa, Stackhousia spp, Scaevola albida, Goodenia spp, Kennedia prostrata plus some of the lilies (eg Burchardia umbellata, Bulbine bulbosa, Arthropodium spp). All of them will grow equally well, if not better, under the stringybarks in the native area of the new garden, so I’ll mass them along the paths where these small plants can be easily seen.

Stone retaining wall with planting on opposite side of path

Stone retaining wall with planting on opposite side of path

Many compact culinary herbs will thrive in my walls and, in a modest vegetable garden where growing space is so precious, it makes sense to utilise areas that aren’t suitable for other crops. And why not include a few variegated and golden cultivars for added impact? Plain, variegated and golden oregano, marjoram, chives, prostrate rosemary (the truly prostrate one, not the more sprawling ‘Blue Lagoon’), borage, dill and thymes (Westmoreland, ‘Silver Posy’, lemon variegated) should all look terrific.

Prostrate rosemary growing in stone wall

Prostrate rosemary growing in stone wall

Three-corner garlic and blackberries

Three-corner garlic and blackberries

Of course, if I’d been as organised as this article suggests, I’d have planted the walls as I built them, popping plants into little pockets. But seriously, is anyone quite that organised? And perhaps it’s just as well that didn’t happen – three-corner garlic and blackberries that emerged in the first season had to be spot-sprayed because there was no way to physically remove them as in other parts of the garden. Having plants already established would have greatly compromised weed control.

Another article suggests that you deliberately leave openings and spaces in a wall for planting but ho-ho! That’s not a concern in my vernacular constructions and I have dozens, if not hundreds, of inadvertent planting pockets from which to choose! Another waller suggests that she doesn’t bother searching for that odd-shaped stone to fill that odd-shaped gap – she just leaves the space for planting. Now that’s more like it! Either way, planting pockets are not my problem!

What may be a problem is that smaller stones backfill the larger ones to improve drainage and strengthen the walls. Although soil and compost are gradually filling the spaces, big air pockets will hamper root development. I’ll prod in extra soil (some gardeners suggest sphagnum moss or even floral foam), and trust that roots will find their way to deeper moisture during winter, and chase it down as the soil dries in spring.

Thyme in dry stone wall

Thyme in dry stone wall

Many of the walls face south-west, so won’t become overly hot in summer. However, the half-circle wall around the seating area is heavily shaded and, if it were moister, would be ideal for ferns, native violets and other more delicate plants. But it’s only wet in winter, not in summer, so plants for this wall have me a bit stumped. The cliff beside the summer-only creek in Belair National Park, just down the road, should offer some ideas.

Armeria in dry stone wall

Armeria in dry stone wall

As well as using the walls, I can plant at the base along paths and steps where I can improve the soil, as well as on the opposite side of paths where small specimens won’t impede access.

Only a few young plants are in so far, but I’m thrilled with the improvement already. As long as I resist the temptation to pop in one of each plant, and limit my palette, it should be looking terrific by next summer!

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Helen McKerral

About Helen McKerral

Horticultural journalist, photographer, contributor to many garden magazines, and author of 'Gardening on a Shoestring'. Adelaide Hills, South Australia

One thought on “Planting a dry stone wall

  1. Jenny Deans on said:

    Helen – it’s wonderful to hear that you’re planting so many local natives – what a fabulous place your wall will be for skinks and birds. Do you get bandicoots too? If you have a wetter shady spot under the stingybarks see if you can get hold of some Olearia grandiflora it’s endemic here and is spectacular in flower and has striking large leaves. Looking forward to photos of this part of your garden growing!

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