Two weeks before planting or sowing seed outdoors, make planting pockets 90cm (3ft) apart for courgettes, 1.2m (4ft) for marrows, 90cm (3ft) for bush plants of summer squashes and 1.5m (5ft) for trailing plants of summer squashes. Do this by making a hole about a spade’s depth, width and height and fill with a mixture of compost or well-rotted manure and soil. Sprinkle a general fertiliser over the soil. Plant one plant on top of each planting pocket.
For indoor-raised seedlings, plant outside on top of your planting pocket in early June, hardening off (acclimatising) before doing so. Do this by moving them into a coldframe for a week or if you don’t have a coldframe, move plants outdoors during the day, then bring in at night for a week, then the following week, leave them out in a sheltered spot all day and night.
You can also grow courgettes, marrows and summer squashes in growing bags or containers (at least 45cm/18in wide). Plant one or two per growbag, or one per container.
Keep the soil constantly moist by watering around the plants, not over them. They need plenty of water, so sink a 15cm (6in) pot alongside the plants when planting out. Water into the pot and it will help ensure that water goes right down to the roots and doesn't sit around the neck of the plant, which can lead to rotting.
Feed every 10-14 days with a high potash liquid fertiliser once the first fruits start to swell.
Powdery Mildew: Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.
Remedy: Keep the soil moist and grow in cooler locations.
More info on Powdery Mildew
No fruit, or fruit rotting when very small: This is a physiological problem, caused by the growing conditions, not a pest or disease. It is a problem when the weather in early summer is cool and this causes inadequate pollination.
Remedy: This is usually a temporary problem and once the weather starts to improve, so will pollination. You can try to hand-pollinate plants yourself by removing a male flower (no swelling at their base) and brushing the central parts against the centre of a female flower (female flowers have a swelling at the base – this is the beginning of the fruit). But this is a bit of a hassle, and normally the plant will correct this problem itself.
Grey mould: Can be a problem in densely sown crops, especially ‘cut and come again’ veg crops. Seedlings suddenly collapse. This is a problem normally in wet conditions, and is usually worse on weak or damaged plants. The mould usually enters through a wound but, under the right conditions, even healthy plants will be infected. You will see fuzzy grey mould on affected buds, leaves, flowers or fruit. Infected plant parts eventually shrivel and die.
Remedy: Sow thinly and when conditions are warm. Hygiene is very important in preventing the spread of grey mould. If you see it, remove the infected material and destroy. Grey mould is encouraged by overcrowding, so make sure you plant your seedlings, plants and squashes at the appropriate distance apart.
More info on Grey mould
Harvest courgettes when 10-12.5cm (4-5in) long.
Regularly picking courgettes while they are small will ensure a long cropping period.
Greg Wallace tempts us with his Grilled vegetable terrine.
‘Venus’ AGM: A compact courgette producing a large crop over a long season, with smooth, spine-free stems.
‘Supremo’ AGM: Its compact growing habit makes this courgette ideal for areas with restricted room.
‘El Greco’ AGM: Plants have an open growth habit, making picking easy of this prolific cropper.
‘Tiger Cross’ AGM: This is a marrow variety, producing large striped fruits, good for winter storage.