Marrows are easy to grow and provide a large harvest in a relatively short time. They are closely related to courgettes, squashes and pumpkins, and all are grown in basically the same way. They need a warm, sunny position, out of cold winds, with rich, moisture-retentive soil.
Jobs to do now
- Water every 14 days in dry spells
- Water-in a balanced fertiliser such as Growmore at 70g (2½oz) per square metre if growth is not vigorous
- Harvest first fruits if ready
Month by month
Marrows are easy to grow from seed. They are best started off indoors in pots, but you can also sow them outdoors in the spot where they are to grow.
For earlier crops or in cold regions, start them off indoors from mid- to late April at 18–21°C (65–70°F). Sow the seeds individually on their side, 1.5cm (½in) deep, in 7.5cm (3in) pots of seed compost.
In late May or early June, prepare your sowing site by digging in lots of home-made compost or well-rotted manure, to about the depth and width of a spade’s blade. Then sow two or three seeds in the centre, 2.5cm (1in) deep. Cover with a cloche, jar or plastic, and leave the covering in place for two weeks, or as long as possible, after germination. If more than one seed germinates, remove the smaller, weaker seedlings to leave just the strongest one.
If you don’t have space or time to grow marrows from seed, you can buy young plants from garden centres in spring. If you buy in late May or early June, they can usually be planted outdoors straight away (check with the shop when you buy them), as long as there is no longer any risk of frost.
Indoor-raised plants must be hardened off (acclimatised to outdoor conditions) before planting outside in June. Do this by moving young plants into a coldframe for a week. If you don’t have a coldframe, move them outdoors during the day, then bring them in at night for a week. Then the following week, leave them out in a sheltered spot all day and night.
Marrows need a sunny spot and rich soil, so prepare the planting site for indoor-raised plants as follows:
Make a hole about a spade’s depth and width
Fill the hole with a mixture of home-made compost or well-rotted manure and soil
Sprinkle a general purpose fertiliser, such as Vitax Q4 over the soil at a rate of two handfuls per square metre/yard.
Then plant one marrow in the centre. If you’re growing several, space them 90cm (3ft) apart.
You can also grow marrows in growing bags or large containers (at least 45cm/18in wide). Plant one or two per bag or one per container.
Marrows are thirsty plants and need regular and generous watering as they grow. When you water, try not to splash the leaves. A useful tip is to sink a 15cm (6in) pot into the ground alongside your plant. Then water into the pot, so the 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 potassium liquid fertiliser, such as tomato feed, once the first fruits start to swell.
Marrow fruits should be supported off the soil on a piece of tile or glass.
Marrows can be harvested from mid-summer, at 20–30cm (8–12in) long, for use straight away. Or they can be left to mature later in the season, for storing into winter.
Regular harvesting will encourage further fruits. The last marrows should be harvested before the first frost.
Marrows for storing should be fully ripened in the sun until the skin is hard. Then place in a cool, dark, frost-free place, such as a garage, where they should keep for several months.
If growing for show, keep just one marrow on the plant, removing any others that start to form, so the plant puts all its energy into ripening just one large fruit.
Marrow — bush type
Marrow — trailing
Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.
Keep the soil moist and grow in cooler locations.
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.
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.
A usually grey, fuzzy fungal growth which can begin as pale or discoloured patches. Grey mould ( botrytis) is a common disease especially in damp or humid conditions. Spores enter plants via damaged tissue, wounds or open flowers. Mould can also damage ripening fruit such as strawberries. Black resting spores survive over winter.
Remove damaged plant parts before they can become infected. Cut out infected areas into healthy tissue and clear up infected debris. In greenhouses, reduce humidity by ventilating and avoid overcrowding of young plants and seedlings.
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