How to Grow Gourds in Australia

Gourds are frost-tender climbing annuals of the cucumber family, Cucurbitaceae, grown for young fruit to cook and mature fruit to dry. The four kinds are luffa (Luffa acutangula and Luffa aegyptiaca), bottle gourd (Lagenaria siceraria), wax gourd (Benincasa hispida) and small ornamental gourds (Cucurbita pepo). All want a long, hot season and a strong frame, and the usual failure is picking at the wrong stage.

Three mistakes that matter

1. Starting too late. Hard-shelled gourds need three to six months of warmth, and sponge luffa four to five months from first flowers. Sown late, the fruit is still green when frost arrives and ruins it for drying. Where summers are short, start seed in pots.
2. A flimsy frame. A vine in full crop carries heavy fruit, and a light trellis sags or collapses. Fruit lying on damp soil rots. Build a strong trellis, A-frame or pergola before sowing.
3. Picking at the wrong stage. Luffa, cucuzza and hairy gourd left too long turn tough and bitter, while drying gourds cut green shrivel or rot. Pick eating types young, and leave drying types until the stem is dry and brown.

When to plant

Gourd seed germinates in soil between 20°C and 30°C, so sow once the soil holds at least 20°C and frost has passed. Where the season is short, raise seedlings in pots three to four weeks ahead and plant out after the last frost.

At the cool edge of the window, a seedling heat mat keeps the pots warm enough for the seed.

Site, soil and setup

Luffas are not drought tolerant, yet they suffer in waterlogged ground, so give every gourd full sun and rich soil that drains freely. Fix the frame before sowing, because the vines run for metres.

Lay drippers or a soaker hose before planting. Overhead water trapped in the dense leaves invites mildew.

Sowing Seeds

Sow direct where summers are long and warm, and start in pots where spring is cool or short.

Sowing direct

• Sow 20 to 25 mm deep, two or three seeds to a station.
• Space stations 80 cm to 1 m apart along a frame, or 1.2 to 1.8 m apart where vines trail on the ground.
• Keep the soil moist but not wet; seedlings show in 1 to 3 weeks, bottle gourd and sponge luffa the slowest.

Starting in pots

• Sow two or three seeds per 10 cm pot, ideally a biodegradable one.
• Keep pots warm, as in When to plant, and remove the weaker seedlings to leave one.
• Harden off (accustom seedlings to sun and wind over a few days) before planting out after the last frost.
• Plant the whole pot or an unbroken root ball, since gourds resent root disturbance.

Pollination

Every gourd carries separate male and female flowers, and a female has a tiny fruit behind its petals. The main vine often opens male flowers first, and most fruit forms on the side shoots.

Smooth luffa, wax gourd and the ornamental gourds open yellow flowers by day, and bees work them. Angled luffa opens its yellow flowers at dusk and closes them soon after dawn. Bottle gourds open large white flowers in the early evening, each fertile for about a day, and night-flying moths visit them.

Too much nitrogen in hot weather pushes out extra male flowers, so a lush vine can flower hard and set little. Where young fruit shrivels, pollinate by hand.

• Pick a freshly opened male flower and strip back its petals.
• Press its pollen onto the centre of an open female flower, or carry it across on a soft brush.
• Pollinate bottle gourds and angled luffa at dusk, soon after the flowers open, and the others in the morning.

Care by growth stage

Steady water and a timely switch from nitrogen to potassium decide this crop. Weeks count from sowing.

If you prefer a conventional feed, use each at its label rate. Mix a controlled release granular (NPK around 14-5-10) into the bed at planting. Water on an all-purpose soluble (NPK around 23-4-18) fortnightly while vines run. From the first flowers, switch to a fruiting and flowering soluble (NPK around 15-4-26) fortnightly.

Pruning and Training

Stopping the main vine pushes out the side shoots, where most fruit forms; see Pollination. Tie young stems loosely until the tendrils grip.

• Main vine: pinch out the tip when it reaches the top of the support, and weave the side shoots into the frame.
• Bottle gourds, many small fruit: stop the main vine at about 3 m and let the side shoots run.
• Bottle gourds, fewer larger fruit: prune the vine harder, since heavy pruning gives fewer but bigger fruit.
• Long luffa, cucuzza and bottle types: train them over an overhead frame so the fruit hangs straight.
• Round winter melon: let it sprawl on the ground, trimming only to keep it in bounds.

Companion planting

Good partners bring in pollinators or escape the gourd's diseases; poor ones share its pests and diseases.

Grows well with

• Flowering herbs and annuals nearby, which draw bees and the beneficial insects that hunt pests.
• Beans, peas, onions and sweet corn, which are not cucurbits and so do not catch its downy mildew or gummy stem blight.

Keep apart

• Potato, named for the twenty-eight-spotted potato ladybird, which also chews cucurbit leaves.
• Other cucurbits such as pumpkin, cucumber and bitter melon, which share its beetles, mildews and gummy stem blight.

Harvesting Fruit

The sign of readiness depends on the kind of gourd and on whether it is for the kitchen or for drying.

• Cut with secateurs, leaving 3 to 15 cm of stem on a drying gourd.
• Carry each gourd in both hands, never by the stem, since a fresh gourd is mostly water.
• Pick eating types every few days to keep the vine cropping.
• Bring drying gourds in before frost, which spoils fruit that is not fully mature.
• Set aside any gourd with soft spots, and dry it apart from the rest.

Fresh luffa keeps 2 to 3 weeks at 12 to 16°C, handled gently. A mature, waxy winter melon keeps for months at 13 to 15°C in dry air.

Dry gourds in a shed or on a verandah with good airflow, never inside the house. Wipe each with rubbing alcohol, and wait until it is light, with seeds rattling, after several weeks to a few months. For a sponge, soak a dried luffa in warm water until the skin slips off, shake out the seeds, and let the sponge dry.

Cook young luffa, cucuzza and hairy gourd like zucchini, in stir-fries and soups.

Common problems

Slow or patchy germination. Gourd seed has a hard coat, so it comes up slowly and unevenly; keep it warm and just moist.

Flowers but no fruit. Early flowers are mostly male, and an unpollinated female fruit shrivels and drops; see Pollination.

Huge vines, few gourds. Too much nitrogen, especially in hot weather; see Pollination and Care by growth stage.

Bitter fruit. Luffa turns bitter as it ages, and any cucurbit can carry the bitter toxin cucurbitacin. Spit out and discard a bitter gourd, since it causes vomiting and cramps, and cooking does not destroy it.

Fruit rotting underneath. It sat on damp soil; see Three mistakes.

Drying gourds that collapse. They were cut before the stem browned, or frost reached them first; see Three mistakes.

Pests and diseases

Luffa and wax gourd shrug off most pests, but all gourds share their troubles with pumpkin and cucumber.

Pumpkin beetle (Aulacophora hilaris). An orange beetle 6 to 7 mm long with four black spots, chewing large holes in leaves. A few can strip a seedling, so pick beetles off at the twice-weekly check. The twenty-eight-spotted potato ladybird, orange with 28 black spots, and its spiny larvae also scrape leaves to lace; pick them off too.

Cucumber fly (Zeugodacus cucumis). A native fruit fly and a major cucurbit pest in Queensland, the Northern Territory and northern New South Wales. Its maggots tunnel young fruit. Bag or net fruit once set, and freeze or heat-treat stung fruit before binning it. Read more

Melon aphid (Aphis gossypii). Pale green to yellow colonies under leaves curl the shoot tips and spread viruses. Use insecticidal soap at its label rate, and keep sprays to a minimum while bees work the flowers. Read more

Two-spotted mite (Tetranychus urticae). Pale or bronzed patches along the veins in hot, dry weather, then silvery leaves and fine webbing. Angled luffa is the most prone; check leaf undersides with a magnifying glass. Read more

Powdery mildew (Podosphaera xanthii). White powder on the older, lower leaves first; luffas rarely get it badly. Remove the worst leaves and spray 1 part full-cream milk to 10 parts water. Read more

Downy mildew (Pseudoperonospora cubensis). Angular yellow patches boxed in by the veins, with dark down beneath on damp mornings; 6 to 12 hours of wet leaves favours infection. In wet spells, a copper fungicide registered for cucurbits protects new growth; follow its label rate and withholding period. Read more

Prevention first

• Grow on a frame with room between plants, so leaves dry quickly.
• Water at the roots in the morning, never over the leaves at night.
• Walk the vines twice a week, turning leaves to check the undersides.
• Clear spent vines once the harvest is in, rather than leaving them on the bed.

Tips

1. Save seed only from open-pollinated types, since F1 hybrids such as 'Fong Show' do not come true. Luffa, bottle gourd and wax gourd cannot cross with one another, but varieties within one species can.
2. The small warted gourds are the same species as zucchini, so bag and hand-pollinate the flowers when saving seed of either.
3. Turn a bottle gourd into a birdhouse or planter, drilling the holes only once it is completely dry.