Get the jump on spring by starting vegetables indoors

Unfortunately, it is not the midday temperatures, but the soil temperature, which is much lower, that dictates the time to sow seed, says Kirchhoff’s Marlaen Straathof.

“Tomatoes, brinjals, mild-to- medium-hot chillies and sweet peppers need a soil temperature of between 17°C and 19°C, which means waiting until the end of September if you want to sow them directly into the ground,” she says.

One way to get around this in August is to sow seeds in seedling trays and germinate them indoors.

Placing the seed tray in a plastic bag and blowing it up, like a mini-greenhouse, creates a micro-climate that traps in the moisture so that the soil stays moist.

“Basically, apply the same rules as you would when sowing in the garden,” says Straathof.  “Keep the seed trays in a warm room that receives morning sun.”

Her advice is not to put seed trays too close to a window, because night temperatures are still cold. Alternatively, the trays should be moved away from the window in the evening.

“It is that sudden drop in temperature that does the damage and if there is humidity in the plastic bag, the water can freeze,” she says.

Trays in a sunny location need regular monitoring to make sure the soil doesn’t dry out. Seeds need to be in consistently damp, but not soggy, soil to germinate.  If necessary, place the seed trays on saucers or even the black plastic trays used in vegetable packaging.

Don’t let them stand in the water, otherwise the soil stays too wet and cold and the roots will rot.

The seed trays can also be placed on folded paper towels or ordinary towels to absorb the water.

Spring veggies, like lettuce, that has a short season, can also be started early in seed trays, as can spinach and Swiss chard and the various squashes: cucumber, gem squash, baby marrows, patty pans and pumpkin.

From this week, seed companies will be stocking spring and summer seed on their shelves. Most vegetable seed is “open pollinated”, which, says Straathof, has been tried and tested for South African conditions.