Top Of The Crops - Cucumber


Cucumbers are a refreshing addition to any salad.  There are some interesting varieties to trial. It is worth investigating the different tastes and textures to see which of the varieties suits you best.  There is the Carmen, which are dark-ribbed and wonderful for growing indoors, as is the Femden, which produces a slightly darker fruit to the Carmen.  The Marketmore yields well, though the fruit is smaller.  The Zeina offer a high yield of fruits and is the best option if you plan to share your crop with the family.  The team at First Tunnels love the taste of all our freshly harvested cucumber straight from our polytunnels.

Growing cucumber is satisfying because the fruit looks substantial and the plant offers crop after crop.  You will find that your friends will be impressed when you show them the cucumber you created with your own green fingers!

Here we guide you through the steps and the essential tips for growing cucumber.  You might fear that the cucumbers will end up pea-pod sized and meagre in quantity, but with our simple guide, you will be impressed with the size of your crop.


Growing Cucumber in a Polytunnel

One of the major secrets to success when growing cucumber, as it is with tomato and broad beans, is setting up the right growing conditions.  The right conditions are not just about creating the right temperature and protecting from frosts, but also forming a structure that can hold the plants in place. 

The specific growing conditions required by cucumbers makes the polytunnel the perfect environment.  You can train the plants using a length of string, which you will attach to your crop bar or the double ridge if there is one in your polytunnel.

The good news is that cucumbers grown in a polytunnel do not need pollinating.  If your polytunnel gets too hot, make sure it is well ventilated.  You can leave the doors open at each end and make sure you cover the plants with shade netting.

How to Grow Cucumbers

Step 1: Planting your cucumbers

  • Sow your seeds 2cm deep in 8cm pots.  Keep the pots indoors or somewhere warm, as you should keep them somewhere where they are not susceptible to frost.  Keeping them indoors will also keep the small, more vulnerable plants, free from slugs.
  • Try successional growing, or starting your planting in aggregated steps rather than planting all your cucumbers at the same time, then you will have a steady supply of cucumber rather than an explosion at harvest time.

Step 2: Transplanting

  • When you move your seedlings to your polytunnel, or to the outside, make sure you water them well.  Remember to place each plant 60cm apart.
  • Plant them the opposite side of your tunnel to where the sun mostly shines.  This decision will naturally encourage leaves to grow into the area and therefore not touch the edges of the polytunnel.  The same is true in a greenhouse.
  • Erect your structure for the training of the plants.  You will either use some string in your polytunnel or you will erect a trellis if growing outdoors.

Step 3: Growing Care

  • It is likely that your cucumber plant is an all-female plant that does not require or desire pollination. You may still get a few male flowers, and you should remove these.  Female flowers will have a small fruit growing at the base; male flowers will not.  
  • It would help if you pinched out the tops of each side shoot two leaves away from your female flower.  This pinching will provide adequate room for growth for your fruit.
  • Cucumber plants require heavy watering – but not soggy soil.  It would help if you increased this watering as more fruit arrive and start to expand.  The ground should be damp but not too soggy. As with most plants, watering just the right amount is going to be crucial to your success.  To keep the air humid in the polytunnel try watering the path, moisture in the air helps maintain water levels in the plant without making the soil boggy.
  • When you set up your training strings or trellis make sure that the leaves are going to be well away from the edges. In a greenhouse or polytunnel, these leaves should not touch the window or the plastic. This positioning will help to reduce the chance of disease in the plants.

An important tip: Complimentary planting helps with cucumbers, like with most other plants.  Peas and beans make particularly good companion plants for cucumber, and they will grow up the same vertical structure.

Step 4: Dealing with Pests and Problems

Growing cucumbers indoors makes them more susceptible to pests and diseases, though you will find your crop is superior. Cucumbers do not enjoy cold and soggy conditions.

  • Slugs and snails are a particular danger to young plants.  You can use the tried and tested beer trays to protect the cucumbers as they grow.
  • Mildew is also a problem.  You will see a white powdery appearance covering the leaf.  If you regularly water the plant, then this should be easily managed.
  • It is essential to keep your plants free of aphids, as these are a significant cause of disease spread.
  • When watering, avoid splashing the fruit.
  • Place a tile or stone under any fruit that may otherwise rest on the soil.
  • Keep the polytunnel well-ventilated, keeping the doors open at either end.
  • A robust and healthy cucumber plant is a resilient plant.  Therefore, as well as regular watering, you should try regular feeding too, with comfrey tea or tomato feed.  You should also use mulches and organic matter in the soil.
  • Make sure the soil in your polytunnel is recycled every two or three years to prevent diseases from building up in the ground.

An important tip: If you plant nasturtiums, radishes, and marigolds, you can help to distract or repel pests.

How to Harvest Cucumbers

As much as you want to grow the biggest fruit possible to impress your neighbours, it is best to harvest the cucumber when it is small.  This will increase your yield, and it will provide a much tastier fruit.  Generally, though not always, the bigger the cucumber, the more bitter the fruit.

Here are the steps for harvesting your successful crop of delicious cucumber:

  • The fruit will be ready for pickling before it is ready for slicing.  The growing season for cucumber is relatively long, usually somewhere between 50 and 70 days.
  • Generally, the fruit is ready between 8 and 10 days from the first female flowers appearing on the plant.  It would be best if you harvested well before the cucumber shows signs of yellowing.
  • If you are pickling the fruit, then aim for 2 to 6 inches long and a diameter of about an inch or just over.  For eating from fresh, you may wish to leave them to grow a little more – aiming for the full six inches or so.
  • Remove stunted and rotting fruit as quickly as you spot them, to help other fruits grow more effectively.
  • Use scissors to remove ripe cucumbers, or twist gently without pulling.  It is best to use the scissors to prevent damage to the vine from pulling, but the fruit should come away quite easily with a gentle twist.
  • Lay the cucumber gently into a basket as you harvest, as they are sensitive from bruising if handled too casually.

An important tip: If you grow cucumbers indoors, in a polytunnel or greenhouse, then the cucumber will grow slowly at first.  There will just be one or two which will likely be ready for harvest at first.  However, with patience, you will be pleased with how the plan delivers a full crop.  Harvest at regular intervals to extend the cropping period.


Sowing seeds: Between February and May.  Remember the benefits of succession planting.

Transplanting: Approximately three weeks after planting the seeds.

Harvesting: 50 – 70 days from planting of seeds, between June and September.


Until you have tasted a home-grown cucumber, you do not know what you are missing.  There is nothing wrong with shop-bought, except maybe that they are a little watery in taste and the crunch is not so crisp.

Cucumbers are relatively resilient plants that thrive indoors.  They love humid but well-ventilated air and will need a decent structure to help train them.  Remember the biggest secret to a healthy crop of cucumber is to keep them regularly watered without making the soil too boggy.  Also, bigger might mean bitter, so harvest the fruit when they are about 6 inches.  If you periodically harvest your plant will continue to crop through the season.  As you can see, the polytunnel creates the best environment for your cucumbers.  Although the cucumber will grow outdoors, it doesn't like the cold, and it needs the moisture level in the soil well-managed.

We hope that you enjoy growing your cucumber in your polytunnel.  There is nothing more satisfying for a gardener that to see the emergence of fruit on plants grown from seed.  

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