Cucumbers are relatively easy plants to grow, but every so often you’ll find cucumbers not growing straight. Even if you think you’ve done everything right, those perfect show cucumbers have just slipped the net again.
Don’t fret though, you can still eat curled cucumbers, and they’ll be just as crisp and delicious as ever. In this article, we’re going to break down the facts about curling cukes, explain why your cucumbers are not growing straight, and how to straighten out your next harvest.
Can you fix curling cucumbers?
Before we get into the how and why of cucumbers not growing straight, it’s important to get one thing straight but, sadly, it’s not your cucumbers.
Once a cucumber has begun to curl, it won’t straighten back out. Cucumbers that are curling as a result of under-watering, or under-feeding won’t continue to curl when you start watering more, but they will keep their kink.
Cucumbers that have grown curly due to under-pollination will continue to grow curly no matter what. You can fix this all next year, but for this year, just enjoy your wonky veg. Curled cucumbers are no better, or worse, tasting than straight cucumbers, and can in fact have a better crunch for salads as they have tighter cell structures along one side.
Why do cucumbers curl?
There are six common causes for curling cucumbers, and all can have interrelations, so we’ll break down each reason, and then take a holistic approach to tackle the problem.
- Irregular watering
- Insufficient nutrients
- Direct sun
- Poorly ventilated greenhouse
- Pollination problems
Irregular watering causes cucumbers to curl
Anyone who has ever grown their own cucumbers knows the vast difference between home-grown and store-bought cucumbers. Homegrown cucumbers are packed with flavour and an earthy freshness that carries through their watery flesh like no other vegetable you can grow.
That water carrying flesh is key to cucumbers not growing straight, and as your pollinated fruits begin to extend, they are being constantly warmed by the sun, and require regular watering to fill their cells evenly. If you skip a few days, they can quickly curl towards the sun, as those young cells dehydrate faster than their shaded neighbours on the other side of the fruit.
Insufficient nutrients lead to crooked cucumbers
Cucumbers are a fruit containing rows, and rows, and rows, of seeds. Those seeds develop larger and larger protective watery capsules around them as they develop (the bit we usually scrape out before chopping telegraph varieties into a salad).
High potassium and phosphorus feed like tomato fertilizers are ideal to help these fruits develop evenly, and should be applied at least once a week after flowering starts. These nutrients help the fruit develop more evenly, and skipping a week can cause tougher sections of growth that cause curling.
Direct sun actively curls cucumbers
In the same way that underwatering can lead to shaded parts of cucumbers filling up more quickly, direct sun can affect some cucumber varieties negatively too. Burpless cucumbers in particular are best grown either in full sun outdoors or in partially shaded greenhouses. They don’t enjoy the full summer heat like their cousins.
Avoid growing burpless cucumbers in direct sun if they are under glass as this quickly distorts their shape when they curl towards the sun as their cells can’t hold on to moisture as effectively.
Poor ventilation and high humidity can create curling cucumbers
Poorly ventilated greenhouses are one of the most common causes of cucumbers not growing straight. New greenhouse owners typically see these glasshouses as a place to produce the highest temperatures possible, but this can cause fungal problems and humidity to a point that pests can thrive.
Always ventilate your greenhouse for cucumbers. This might mean opening a window in the afternoon or leaving the door ajar on small greenhouses, but it’s worth the effort.
Damage and callousing stop cucumbers from growing straight
A whole host of problems, including high humidity and undernutrition, can lead to pests like cucumber beetles and squash bugs that bore into the skin of your fruits. The cucumber beetle (Acalymma vittatum) is a gorgeous yellow and black pin-striped creature with a glowing yellow collar holding up its jet-black head. But despite its beauty, it can cause real damage to your fruits, and they will curl around any callous.
Uneven pollination leads to curled cucumbers
The most common cause of curling cucumbers is uneven pollination. Cucumbers are mostly pollinated by bees and hoverflies, so attracting pollinators into your garden is essential for even pollination. A single visit from a bee just won’t do, as they require repeated pollination over the course of a couple of days.
If you don’t have many bees around the garden, visit your cucumber plants every day during flowering, and tickle the flowers with a fine paintbrush every day. The more they are pollinated, the more pollen is carried down the stigma to the ovules, and the more evenly the ovary swells.
Organic ways to grow straight cucumbers
We’ve got some great tips and tricks to grow straight cucumbers which we’ll share below, but if you remember nothing else, follow these golden rules for growing straight cucumbers:
- Mulch cucumbers generously with organic compost
- Grow cucumbers up a trellis
- Water cucumbers well, and regularly
- Feed cucumbers regularly
- Pollinate cucumbers thoroughly
Grow trailing cucumbers up trellis or frames
Not all cucumbers are the typical self-climbing varieties. Some cucumbers prefer to grow along the ground, but this causes uneven growth thanks to shady humidity on one side and evaporation on the other.
When you first plant your cucumber out into its final position, water it in really well, and then mulch lightly with garden compost (leaf mould is ideal for water retention). The mulch prevents surface evaporation and takes the strain off the roots as they establish in their new location.
When your cucumbers have put on a few feet of growth, mulch again once a month with garden compost for a nutrient boost as well as a protective cover for groundwater. This makes sure that cucumbers don’t dry out, and stops them from curling thanks to better access to moisture and nutrients.
As soon as your cucumbers begin to flower, you might find you need to water them every day. This is not too much!
Cucumbers are incredibly thirsty plants, and the combination of their insufferable thirst, with the high temperatures they enjoy growing in, can quickly deplete the most generous drenching. Not only does insufficient water cause curled cucumbers, but it can also cause bitterness, particularly if they are in hot dry spaces.
Any general-purpose plant food will be better than nothing for growing straight cucumbers, but I’ve always found that Tomorite or similar liquid tomato fertilizers work really well on cucumbers.
If you’re mulching regularly with good quality compost, liquid fertilizers are less necessary. Provided your cukes are planted in nutrient-rich soil, with a moisture retentive compost holding onto its goodness, there should be enough nutrients to produce straight cucumbers.
While you can go around hand-pollinating cucumbers, it’s a tricky and laborious business. By far the best way to pollinate cucumbers is to leave your greenhouse open and plant plenty of marigolds, nasturtiums, and sweet rocket around the garden.
The more bright, fragrant, and bee-friendly plants you have, the better pollinated your cucumbers will be. And, as we know, better pollination means straighter cucumbers.
Final thoughts on curling cucumbers
The key to keeping cucumbers straight is prevention rather than cure. Familiarise yourself with the tips and tricks above and use each and every one of them.
Cucumbers are really easy plants to grow, but if you’re growing for show, or just love the satisfaction of perfectly straight vegetables then you’ll need to provide the best care possible to avoid the risk of cucumbers not growing straight this season.