How to grow a loofah plant

The loofah plant (Luffa cylindrica) is a vigorous, frost-tender climber grown for its large, cucumber-like fruit. These can be either picked while very young for cooking or left to mature to full size and then used to make exfoliating sponges. Other names for the plant include luffa, vegetable sponge, washing gourd and sponge gourd.

Growing a loofah plant is possible in the UK when given a very warm, sheltered site and plenty of space. Its long stems are clothed with self-clinging tendrils and large, lobed, green leaves up to 25cm across. In summer, large yellow flowers are followed by long, slender, green fruits. The loofah plant is a tender annual and lasts for only one growing season – it dies in autumn as the days shorten and the nights become cold.

How to grow a loofah plant

Sow seed indoors from late winter to early spring and grow on in a warm, well-lit place under cover. Harden off before planting outdoors after all danger of frosts has passed. For much more reliable results, plant in a greenhouse or polytunnel, as the extra warmth, humidity and shelter from wind will benefit the plant greatly. Water regularly and feed weekly to boost fruiting. To harvest loofah fruit to use as sponges, you’ll need a long, warm growing season for the fruit to mature fully. Harvest young fruits for eating or leave to mature so they can be made into sponges.

Where to grow a loofah plant

Grow a loofah plant outdoors against a sunny, sheltered wall or fence, or for more reliable results in a greenhouse. Plant in rich, fertile soil with good drainage. A loofah plant can grow 3m in height, so it must have a large, sturdy support such as a trellis or strong, galvanised wires.

How to plant a loofah plant

If planting outdoors, harden off plants raised under cover to acclimatise them to the outside for 10-14 days, before planting out in early summer, once frosts have passed. Water in immediately after planting.

Hardening off will not be necessary if planting into a protected environment, but if your greenhouse or polytunnel is considerably cooler or sunnier than the environment in which seedlings were raised, ease them into their new surroundings with some protective horticultural fleece or shade netting for the first week or so.

How to care for a loofah plant

Water regularly to keep the soil evenly moist. Throughout summer, apply a high-potash liquid fertiliser weekly to boost flower and fruit production. If growing fruit for sponges, allow no more than six fruits to develop and mature, so the plant can concentrate its energy on developing good-sized fruits.

How to prune loofah plant

No pruning is required but train and tie in the vigorous shoots at least weekly. If growth is too abundant for the site, trim back stems as required.

How to harvest loofahs

In autumn, once fruits are mature, the colour of the loofah fruits turns from green to brown. Leave the fruits on the plant for as long as possible, ideally until late autumn when the weather turns wet and cool. If you can't do this, harvest them sooner and leave them in a sunny, airy place to dry fully. Once dry, peel off the skin and shake out the seeds, which sometimes need encouragement by tapping the fruit on a hard surface. You can store these in a paper bag in a cool, dry place for sowing next year.

Before using your loofah sponge for the first time, rinse thoroughly in warm water and allow to dry. A teaspoon of bleach in the water can help to preserve it for longer. Then use as you would a shop-bought loofah, either whole or cut into slices to make sponge pads.

How to propagate the loofah plant

Unlike other cucurbits such as courgettes and squashes, loofah plants don't cross-pollinate. This means it's easy to get predictable results when you sow with loofah seed that you saved the previous year. When you remove the seeds from the dried fruit, simply keep them in an envelope and store in a cool, dry place. Sow them indoors from late winter to early spring, into small pots of moist seed compost. Keep at a temperature of 20-24°C for seeds to germinate reliably. Once seedlings are large enough to handle, transplant them into individual pots and grow on. Don't plant outside until all risk of frost has passed.

Pests and diseases of loofah plant

The loofah plant is mainly free of pests and diseases, but powdery mildew may appear as a grey coating on the leaves if plants get too dry during hot weather. Avoid this by keeping the compost evenly moist.