Why won't my cucumbers grow?

It's a familiar scenario in the vegetable garden: you've sown or transplanted some beautiful cucumber plants, watered them conscientiously, they've started to climb their trellis or run across the ground, the first flowers have arrived... and then nothing. Or almost nothing. No fruit. Or maybe a few mini-cucumbers that wilt and fall off. What was the cause?

1. Pollination: the keystone of fruiting

Cucumbers, like many cucurbits (courgettes, squash, melons...), do not bear fruit automatically as soon as the plant flowers. There's an essential step involved: pollination. The principle is simple:

• The male flowers produce pollen.
• The female flowers, on the other hand, need to receive this pollen in order to develop into fruit.

In nature, this work is generally done by pollinating insects: bees, bumblebees, sometimes even certain beetles or butterflies.

How to recognise male and female flowers

• The male flower is borne on a slender stem, without a bulge.
• The female flower has a small green bulge just below the flower, resembling a mini cucumber.

The problem is that if the female flower is not pollinated, this little fruit will abort. It will yellow, dry out and fall.

2. When the insects aren't there...

With the intensive use of pesticides, the dwindling number of hedgerows, and the sometimes capricious springs, pollinating insects can make themselves scarce. And without them, there's no natural pollination, so no cucumbers. Here are two solutions that can really make a difference:

a) Attracting pollinating insects

• Sow melliferous flowers around the vegetable garden: cosmos, borage, marigolds, phacelia, lavender, clover...
• Avoid chemical treatments, even "organic" insecticides.
• Diversify your vegetable garden to provide shelter and cover for beneficial insects all year round.

b) Pollinate manually

When bees are scarce, the gardener can play matchmaker:

• Locate an open male flower.
• Take a fine brush or directly the male flower.
• Apply the pollen to the centre of a female flower.

One application is often enough. The fruit will start to swell the next day.

3. Other common causes of problems

a) Too much or too little watering

Cucumbers have a big appetite for water. Water stress stunts growth or causes the fruit to abort.

• Water regularly, especially in hot weather.
• Use mulch to conserve moisture.
• Beware of excess water in heavy soil.

b) Poor or unbalanced soil

Cucumbers are greedy, especially for potassium in order to fruit well.

• Apply mature compost at planting.
• Make a regular contribution of nettle or comfrey purin.

c) Too much shade or not enough heat

This is a midsummer plant:

• Full sun exposure essential.
• Greenhouse growing possible in cool climates.

d) An excess of male flowers

Some old varieties produce more male flowers at the beginning of the season. Be patient: the female flowers arrive later.

F1 hybrid varieties are often parthenocarpic: they fruit without pollination.

4. Summary of possible causes

5. Choosing the right variety

• 'Tanja' or 'Marketmore' for the open ground.
• 'Iznik' or 'Picolino' for container growing.
• Varieties parthenocarpic in greenhouse or conservatory.

Cucumber growing requires vigilance, but it is rewarding. Good pollination (natural or by hand), regular watering, nourished soil and sunshine are often enough to guarantee fine harvests. And if, despite your best efforts, this season is a little shy, don't be discouraged: every year is different, and every failure makes progress. Good growing to you, and may your cucumbers be long, juicy and plentiful!