How to grow marrows

Marrow seeds are readily available from garden centres and online seed stockists. In spring, you may also find young marrow plants on sale in garden centres and online. These are useful if you don’t have the time or space to grow from seed, but the choice of varieties may be limited. If you buy after the last frost, they can usually be planted out straight away – although do check with the seller to make sure they have been hardened off.

For a longer cropping season or more reliable results in colder regions, start marrows off indoors from mid- to late April. 
 
Sow the seeds into 7.5cm (3in) pots or a modular tray filled with moist peat-free seed compost. Position the seed on its side, 1.5cm (½in) deep, sowing one per pot/module, to minimise root disturbance when planting out later. Water in, then keep at 18–21°C (65–70°F) in a heated propagator. Alternatively, place on a warm sunny windowsill and cover with clear plastic bags until the seedlings appear. Keep young marrow plants indoors until after the last frost, in a warm, bright spot and water regularly. For more sowing tips, see our guides below.

You can sow marrow seeds outdoors in late May or early June. If possible, warm the soil for a couple of weeks ahead of sowing, especially in cooler locations, by covering the ground with cloches or plastic-free fleece. The soil should be at least 13°C (56°F) for successful germination.

Sow two or three seeds in the centre of each prepared site, 2.5cm (1in) deep, then water well. Cover with cloches or plastic-free fleece, and leave in place for as long as possible after germination. If more than one seed germinates per sowing site, remove the smaller, weaker seedlings to leave just the strongest one.

Germination outdoors may be less reliable than indoors, and the young seedlings are vulnerable to slugs and snails, especially in damp conditions. Outdoor-sown marrow plants will usually start cropping later than those sown earlier indoors.

Marrows generally crop best in the ground, but compact or bush varieties can also be grown in a large container. Just bear in mind that plants will need regular watering and feeding to swell the large fruits. Also make sure there is plenty of space around the outside of the container, so the marrow plant can spread out its large leaves. Overcrowding and poor air circulation encourage fungal diseases.

Choose a container that’s at least 45cm (18in) wide, fill it with peat-free soil-based or multi-purpose compost, then plant one young marrow plant in the centre. 

Marrows need regular and generous watering, especially when flowering and fruiting, and when growing in containers. Aim to keep the soil or potting compost consistently moist. During hot spells, plants may need watering daily, and this is best done early in the morning or in the evening so the moisture doesn't simply evaporate.

Use rainwater from a butt if possible, and when you water, try not to wet the leaves, as this can encourage fungal diseases such as powdery mildew. For more water-wise advice, see our guides below.

Cover the ground around marrow plants with a thick layer of mulch to help hold moisture in the soil, reduce the need to water, and deter weed germination. Use garden compost or well-rotted manure, but leave a gap around the base of the stem, to keep dampness away, which could cause rotting.

Marrows growing in the ground don’t generally need feeding, unless the soil is very poor. But if you want particularly large fruits for exhibition, or are growing marrows in containers, then it’s worth feeding regularly – apply a high potassium organic liquid fertiliser, such as tomato feed, every 10–14 days once the first fruits start to swell.