How to Grow Gherkins in Australia

A gherkin is a pickling cucumber (Cucumis sativus) picked young, or the West Indian gherkin (Cucumis anguria), a separate species with small, spiny fruit. Both are frost-tender vines of the cucurbit family, Cucurbitaceae, grown for crisp little fruit to pickle or eat fresh. They crop happily through an Australian summer, and the usual mistake is letting the fruit grow past pickling size.

Three mistakes that matter

1. Letting fruit grow on. Small fruit grow fast and soon pass pickling size, and fruit left to fatten grows a hard skin and slows the setting of new fruit. Once picking starts, check the vines every day or two, as Harvesting Fruit describes.
2. Sowing into cold soil. Seed sown into cold soil often fails to germinate, and chilled seedlings sit still. Wait for the soil temperature given in When to plant, or start seed in pots somewhere warm.
3. Letting the bed dry out. Dry spells and uneven watering turn fruit bitter and dry. Water deeply at the base two or three times a week in dry weather, under a straw mulch.

When to plant

Sow once the soil holds at least 16°C, ideally 20°C, and the last frost has passed. Picked often, vines crop for weeks, so two sowings a season usually do, the second keeping jars filling into autumn.

At the cool edge of a window, start seed in pots on a seedling heat mat, above 21°C by day and 16°C at night. At the late edge, sow early enough for vines to crop before autumn chills slow them.

Site, soil and setup

Put the support in before sowing, so no stake is driven through the roots later.

Rotate beds, since powdery mildew and other cucurbit diseases build up where cucumber, pumpkin, zucchini or melon grew before.

Container growing

One plant needs a pot at least 30 cm wide and deep, holding 13 to 15 L. A 40 cm pot of about 28 L is better. Use premium potting mix enriched with compost, with a small trellis fixed in at planting. Of the four lines, 'German Pickling', a compact spreading vine, suits a pot best.

• Water: keep the mix evenly moist, and in hot spells expect to water daily.
• Feed: fish and seaweed blend at 25 mL per 9 L fortnightly, then liquid potash at the label rate fortnightly from the first flowers.
• Position: full sun out of the wind, close to the back door, where daily picking is easy.

Sowing Seeds

Sow direct into warm soil, or start in pots where spring is slow. The four lines differ mainly in vine size, so space them to suit.

Slicing cucumbers have their own cucumber guide; the cucamelon, sold as Mexican sour gherkin, is another plant again.

Sowing direct

• Sow two or three seeds per station, 10 to 20 mm deep.
• Keep the surface moist; seedlings usually show in 4 to 10 days.
• Thin each station to its strongest seedling.
• Mulch with 5 to 7 cm of straw once the soil is warm, keeping it clear of the stems.

'National Pickling' comes as fungicide-treated seed, which may be dyed. Wear gloves, wash your hands after sowing, keep the seed away from children and animals, and never eat it. The crop it grows is safe to eat.

Starting in pots

• Sow one or two seeds per biodegradable pot, 3 to 4 weeks before planting out.
• Keep them as warm as When to plant describes, and thin to one seedling.
• Plant out at two or three true leaves, without breaking up the root ball.
• Harden off (accustom seedlings to sun and wind outdoors) over 7 to 10 days first.

Pollination

Each vine carries separate male and female flowers, and bees carry the pollen between them. The first flowers are male, so early flowers that drop without fruiting are normal. A female flower sits on a tiny fruit. On the West Indian gherkin, males grow in clusters of two to four at each leaf joint, and females appear only on side branches.

Where bees are scarce and small fruit shrivel, pollinate by hand early in the morning.

• Pick a freshly opened male flower, the one with no small fruit at its base, and peel back its petals.
• Touch its pollen lightly onto the centre of an open female flower, or carry it across with a small soft paintbrush.

Care by growth stage

Steady water and potassium decide this crop. Weeks count from sowing and shift with warmth and variety.

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 the vines run. From the first flowers, switch to a fruiting and flowering soluble (NPK around 15-4-26) fortnightly.

Pruning and Training

A trained vine saves room, dries fast and shows its fruit. Tie young stems loosely to the trellis until the tendrils take hold.

• Pickling lines: pinch out the growing tip at five to seven leaves, to push out fruiting side shoots.
• Their side shoots: pinch out any that reach eight to ten leaves without a female flower.
• West Indian gherkin: leave the side branches alone, because they carry every female flower.
• Top of the trellis: pinch out any leading tip that reaches it.

Companion planting

Good neighbours lend support or feed the insects that eat aphids; poor ones share the gherkin's pests.

Grows well with

• Dill left to flower, whose umbels feed hoverflies, and hoverfly larvae eat aphids.
• Nasturtium, a trap crop that draws aphids away from the vines.
• Sweet corn or sunflower, a living stake for the vines to climb.

Keep apart

• Potato, a host of the 28-spotted ladybird.
• Pumpkin, zucchini and squash, which share cucumber fly and powdery mildew.
• Tomato, another host of cucumber fly and cucumber mosaic virus.

Harvesting Fruit

Picking starts about 8 to 11 weeks after sowing; go by size, picking while the fruit is small and firm.

• Go over the vines every day or two once fruit sets.
• Pick in the cool of the morning, when fruit is crispest.
• Cut the stalk with secateurs, leaving a short stub, because pulling can snap the vine.
• Remove any oversized, damaged or misshapen fruit, so the vine keeps setting.

Refrigerate fruit as soon as it is picked and pickle it within 24 hours, since gherkins left standing longer can turn hollow. For eating fresh, it keeps up to a week in the fridge in a perforated bag.

Slice a sliver from the flower end before pickling, since it can hold an enzyme that softens pickles. Pickle only to a tested recipe, such as the National Center for Home Food Preservation's, and never cut its vinegar. Too little acid lets the bacteria behind botulism grow. West Indian gherkins also eat well raw or cooked like zucchini.

Common problems

Bitter fruit. Cucurbitacin, a bitter compound, moves into the fruit when heat or dry soil stresses the vine. It gathers at the stem end and under the skin, so trim and peel mild cases. Taste one fruit before pickling a batch.

Flowers but no fruit. If female flowers shrivel after the early male flush, pollen is not reaching them; see Pollination.

Curled or pinched fruit. Poor pollination, or a dry spell while the fruit filled; hand-pollinate when bees are scarce and keep the watering steady.

Leaves wilting at midday. Common on hot afternoons; if the leaves perk up by evening, all is well, and if not, water more deeply.

Pests and diseases

Gherkins share their pests with cucumber, pumpkin and melon, so check under the leaves twice a week.

Cucumber fly (Zeugodacus cucumis). A native fruit fly and a major cucurbit pest in Queensland, the Northern Territory and north-east New South Wales, whose maggots feed inside fruit. Net the trellis or bag young fruit, keeping mesh off the fruit, and freeze stung fruit before binning it. It ignores the male lures used in Queensland fruit fly (Bactrocera tryoni) traps. Read more

Pumpkin beetle (Aulacophora hilaris). An orange-yellow beetle, 6 to 7 mm long, with four large black spots. Adults chew big holes in leaves, and a few can strip a seedling, so pick them off by hand.

28-spotted ladybird (Epilachna vigintioctopunctata). Pale brown to reddish, 6 to 10 mm long, with 28 black spots, unlike the aphid-eating common spotted ladybird (Harmonia conformis). Adults and spiny, creamy-yellow larvae skeletonise leaves; squash them and the yellow egg clusters beneath.

Melon aphid (Aphis gossypii). Pale green to yellow colonies curl the shoot tips. Worse, they spread cucumber mosaic virus, which stunts vines and leaves fruit small, distorted and discoloured. Spray colonies with insecticidal soap, and pull and bin any plant with the virus. Read more

Powdery mildew (Podosphaera xanthii). White powder spreads over the leaves, and a bad attack can stop fruit setting. 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 leaf veins, with dark fuzz beneath on damp mornings. Remove affected leaves and open up the canopy. A copper fungicide registered for cucurbits only prevents it, so spray healthy vines when wet weather is expected. Read more

Prevention first

• Water the soil, not the leaves, in the morning, and space vines so air moves through them.
• Rotate beds as Site, soil and setup describes, and bin spent vines rather than composting them.
• Pull sowthistle, nightshade and amaranth weeds, which harbour aphids and mosaic virus.
• Spare the bees by keeping sprays to a minimum while vines flower; any pyrethrum goes on late in the day, away from open flowers.

Tips

1. In hot inland gardens, a light shadecloth over the trellis on summer afternoons reduces scarring on the fruit.
2. To save seed, grow one pickling line only, because every Cucumis sativus cucumber crosses with every other. The West Indian gherkin crosses only with its own kind. Leave a fruit to turn yellow, soak the scooped seed in water for 2 to 4 days, then dry it until it snaps.
3. For the jar, choose a pickling line over a slicer: pickling lines have thicker skins, drier flesh and smaller seeds, so they stay crunchier.