Getting your garden ready for spring: a South African checklist in plain words

Spring on the Highveld does not arrive on the first of September. It arrives on a Tuesday in mid August when the wind turns hot and dusty, the peach trees blossom a fortnight before it is safe, and then a cold front comes through the following weekend and burns the lot. Anyone who has gardened in Gauteng for a few years knows the routine. The Cape has its own version, with the winter rain tailing off and the ground finally warm enough to work, and the coast barely notices a change at all. So a spring checklist for South Africa has to be a little flexible about dates, and honest about frost.

What follows is the order we work through our own display beds and pots at the nursery every year, roughly from early August to mid October. It is not a rigid list. Some years the frost is done by the last week of August, other years it bites into September. Watch the forecast, watch your own garden, and treat this as a sequence rather than a schedule.

When spring actually starts where you live

The South African Weather Service publishes a seasonal outlook each month, and it is worth a look in August, because a warm dry spring and a cold wet one call for different timing. Inland, the average last frost falls somewhere between late August and mid September, with the low-lying and open areas around Centurion, Midrand and the East Rand catching frost later than the ridges. In the Free State and the Eastern Cape interior it can run into October. Along the coast from Durban to Cape Town frost is rare or absent, and spring is really about warmer soil and longer days rather than survival.

The single most useful thing you can do is remember the date of your own last frost each year. Write it in a notebook or a phone note. After three or four years you will know your garden's pattern better than any regional average, and you will stop losing seedlings to a September you should have seen coming.

Leave the frost damage alone a bit longer

Brown, mushy leaves on the plectranthus and blackened tips on the hibiscus are ugly, and the urge to cut them off in early August is strong. Resist it. That dead growth is insulating the living tissue beneath, and if you prune it away and another frost comes, you lose the next layer too. The Royal Horticultural Society's advice on frost damage is the same as ours: wait until new growth appears low on the plant, then cut back to just above it.

Once the frost has passed, spring pruning is about shaping and encouraging new growth. Roses get their hard prune in late July or August inland. Summer-flowering shrubs, hydrangeas, buddleja and the like, can be cut back now because they flower on this year's wood. Spring-flowering shrubs should be left until after they bloom or you will cut the flowers off. Divide overgrown clumps of agapanthus and clivia now too, while they are waking up. SANBI's page on Agapanthus praecox is a good reminder of how little this plant asks, it grows almost anywhere and only wants splitting every few years when the flowering thins out.

Refresh what is in your pots

Potting soil is not permanent. After a season or two it compacts, the bark breaks down, the nutrients are gone and the mix shrinks away from the sides of the pot so water runs straight down the gap without wetting the roots. Spring is the time to fix that. For small and medium pots, tip the plant out, shake off the old mix, trim any circling roots and repot with fresh outdoor potting soil. For big pots that cannot be moved, scrape out the top ten centimetres and replace it with a mix of fresh potting soil and bark compost, then water well.

If you are planting up a new concrete pot this spring, do it properly from the start. There is a right way to fill and plant a concrete pot that keeps it draining and stops the freeze and thaw stress that cracks cheaper pots, and we have written it up in how to plant your concrete pot to reduce cracks. Our own pots are cast from a Fibre Concrete Mix that handles Highveld frost without complaint, but good drainage still makes every pot last longer and every plant happier.

Top-dress the beds and give the lawn a hand

Beds get a generous layer of compost forked lightly into the top few centimetres or simply spread as mulch and left for the worms to pull down. If you are not sure of the difference between compost, fertiliser and soil, and plenty of people are not, this explainer sorts it out. The RHS guide to compost covers what it does in the soil. In short, compost is food for the soil and fertiliser is food for the plant, and in spring the soil needs feeding first.

Lawns wake up hungry after a Highveld winter, especially kikuyu and LM that have gone brown and thin. Wait until they are actively growing again, usually mid September inland, then mow low once, rake out the dead thatch and spread a thin even layer of lawn dressing over the whole area. Brush it in so the grass tips show through, water well, and within three weeks the lawn is level, green and thick. Doing this before the summer rains arrive means every storm feeds the grass rather than washing bare soil away.

Check drainage holes, feet and trays

Turn every pot you can lift and look at the hole. Over winter roots, compacted soil and the odd snail block drainage holes, and a pot that cannot drain in a January thunderstorm drowns whatever is in it. Poke the hole clear with a screwdriver. Pots that stood directly on paving through winter often have a damp, stained patch underneath, which is a sign the base has been sitting in water. Lift them onto concrete pot feet so air moves underneath and water runs away. On a stoep or balcony where the run-off would stain the floor, a drip tray under the feet catches it.

Clean the pots themselves

Concrete pots pick up two things over winter: a green film of algae on the shady side and, sometimes, a white chalky bloom on the surface. The white bloom is efflorescence, dissolved salts from the concrete and the water that have migrated to the surface and dried there. It is harmless and it brushes off with a stiff dry brush; stubborn patches come away with a scrub of diluted white vinegar and a rinse. Algae shifts with a brush and soapy water. Do not pressure wash a concrete pot at close range, as it roughens the surface and makes the next season's algae grip harder. A clean pot in spring also lets you check for any hairline cracks before the summer rains find them first.

Plan the planting, then hold your nerve

By late August the nurseries are full of tomato, basil and marigold seedlings, and every instinct says buy. Buy if you like, but keep them under cover or on a protected stoep until your own frost date has passed, and harden them off for a week before they go into open ground. Sow beans, squash and pumpkins directly once the soil is warm to the touch in the morning, usually October inland. In the Cape you can move earlier, and along the warm coast most of this can start in August. Perennials, shrubs and indigenous plants can go in any time from now on, and the sooner they are in, the better their roots will be before the heat of December.

Spring preparation is mostly about the ground under the plants rather than the plants themselves, which is why the compost, potting soil and lawn dressing matter more this month than anything flowering in the nursery. Once the frost is done and the soil is fed, everything else falls into place. Our soils, compost and pebbles are all in one place, and they are what we reach for first every August. For the rest of the year, our season-by-season garden care guide picks up where this leaves off.

Frequently asked questions

When does spring start in South Africa?

Officially on 1 September, but for gardeners it is when the last frost has passed. Inland that is usually late August to mid September; coastal gardens rarely see frost and can start earlier.

When should I prune frost-damaged plants?

Wait until new growth appears low on the plant, then cut back to just above it. Pruning too early removes the dead layer that protects living tissue from a late frost.

Do I need to replace potting soil every year?

Not entirely. Repot small pots every year or two with fresh mix; in large pots, remove and replace the top ten centimetres with fresh potting soil and compost each spring.

What is the white powder on my concrete pot?

Efflorescence, harmless mineral salts that migrate to the surface and dry there. Brush it off with a stiff dry brush, or use diluted white vinegar for stubborn patches, then rinse.

When should I apply lawn dressing in South Africa?

Once the lawn is actively growing again, usually mid September inland. Mow low, rake out thatch, spread a thin even layer and water well, ideally before the first summer rains.