the spring bank holiday is the busiest weekend of the year for garden centres and tender veg are popular with grow-your-own enthusiasts.

To avert disaster, however, plant with care or sow your own seed.

Tender tomatoes, courgettes and cucumbers frizzle and die at the first frost and grow poorly in a dreich Scottish May. For good results, they need a steady warm temperature, preferably 18-20C. Courgettes are the easiest of these tender veg to get going as soon as the weather warms up.

Courgettes thrive in a cool greenhouse or polytunnel - I always have a couple in the tunnel as insurance against a poor summer. But you should get good results in the open ground or a container.

Late frosts are a genuine risk here, so if you're desperate to get planting now, be prepared to protect your courgettes. Make a square of cloche hoops round the plants to support fleece and keep the fabric above the leaves to prevent damage. Fan-shaped sticks are an alternative to hoops. If you're caught unawares and a frost is forecast, use a large pot as an emergency cover, remembering to remove it in the morning.

When planting in the open ground, choose a sunny spot - the sun rarely gets strong enough to damage courgettes in Scotland. The plants need space, too, so plant them in rich, moist soil in a row, one metre apart.

In days gone by a hot bed was the usual technique for warming the soil and bringing on crops more quickly. Gardeners would dig a square, spade's-depth hole, put in a generous helping of fresh horse muck and cover with a mix of soil and compost. It's a method often used with courgettes. The courgette is planted in the warming soil, with the plant's neck slightly above ground level. Since few of us have a horse tethered to the front gate or can follow a cuddy, armed with a shovel, fresh grass clippings are a hot 21st-century alternative. Grass doesn't retain its heat as long as horse muck, but it helps.

I also like to cover the soil with a permeable membrane. This keeps in the heat and moisture while preventing weeds. Small courgette plants have brittle stems that can snap in the wind and roots may not establish well when the plants are buffeted by the wind. Prevent this by covering with fleece or surrounding the plant with small twigs to act as windbreaks.

When buying plants this weekend, don't buy one simply labelled "courgette". You need a variety to suit your growing conditions. Unlike other varieties, Partenon is self fertile. It harvests well even during a cool, damp summer when there are fewer insects around for pollination. Other varieties form small, compact bushes and are suitable for containers: Sunstripe, with yellow fruits and striking white lines, Midnight and Venus. Varieties such as All Green Bush, Alfresco and Rondo di Nizza are good spreaders, and do well outdoors.

Rather than buying plants this weekend, there's still time to sow seed. Fill 8cm pots with compost and sow one seed per pot, 2-3cm deep, placing it flat or on its side. After a month, when the third true leaf starts growing, harden them off for a week by putting the plants outdoors during the day, and bringing them in at night. Then plant them out. Your courgettes will be ready for planting when there's less chance of a late frost. Gardeners in the south of England can get a longer crop with a second sowing in early June, but that doesn't work here - without a strong sun in September, the fruits become rather tasteless.