Planting cucumbers: when, where & how?

Sebastian
Sebastian
Sebastian
Sebastian

As a horticulture student I mainly studied crops and cultivation techniques. It fascinates me how many diverse plants can grow from small, nearly identical seeds.

Favourite fruit: blueberries, grapes, raspberries, pears
Favourite vegetables: mushrooms, peppers, kohlrabi, onions, garlic

If the idea of growing cucumbers at home seems a bit daunting, do not let it put you off trying, as cucumbers are actually relatively easy to grow. Read on to find out more about how to grow cucumbers and when and where to plant them.

Planting a cucumber plant
Young cucumber plants need ideal growing conditions to thrive [Photo: Samoilova_Olena/ Shutterstock.com]

Eating your own home-grown and fresh cucumbers in the middle of summer is a delight that is easy to achieve with the right care and know-how. Cucumbers (Cucumis sativus) can be grown in a greenhouse or a warm spot in your garden or patio and, if properly cared for, can produce delicious fruit for you and your family to enjoy all season long.

When to plant cucumbers

Cucumbers are a summer season plant that can produce harvestable fruits in as little as 10 – 12 weeks from sowing, when grown in the right conditions. With varieties suited for growing either indoors or outdoors, a greenhouse is not strictly necessary for growing cucumbers.

If you are wondering when to plant your cucumbers, here in the UK they can be started from seed relatively early in the season as long as they are kept indoors on a windowsill or in a propagator, as they require a minimum temperature of 20 °C to germinate. Cucumbers can also be sown outdoors in early summer, but only after the risk of frost has passed, which is usually around May to June depending on where you live.

Cucumbers are tender plants, so plant them outside from June onwards, once the frosts have passed and the temperatures have risen to above 12 °C . 

Cucumbers being grown in pots
Cucumbers grow well in pots and containers [Photo: Razumhelen/ Shutterstock.com]

Where to grow cucumbers

Cucumbers are sun and heat-loving plants and prefer to be grown in a greenhouse or in a sheltered south or west facing location. Cucumbers prefer high humidity, which is why they are so often grown in greenhouses, and they also prefer a free-draining fertile soil. Our Plantura Organic Tomato & Vegetable Compost is ideal for growing cucumbers in containers since it provides the young plants with all the nutrients, they need for the first few weeks after planting out.

Potted cucumber plant with Plantura compost
If you would like to grow cucumbers at home, pay close attention to location and soil

If growing cucumbers outside directly in the ground or in a soil trench inside a greenhouse, it is best to add some well-rotted manure or garden compost to the planting area prior to sowing to enhance fertility levels or to apply a slow-release granular fertiliser, like our Plantura Tomato Food, and work it into the soil.

Tip: To promote plant and soil health and help prevent any diseases, it is recommended to not plant cucumbers in the same spot year after year, but rather practice crop rotation on a minimum 3-year cycle.

Organic Tomato & Vegetable Compost, 40L
Organic Tomato & Vegetable Compost, 40L
  • Perfect for tomatoes & other vegetables such as chillies, courgettes & more
  • For strong & healthy plant growth as well as an abundant vegetable harvest
  • Peat-free & organic soil: CO2-saving composition

Planting cucumbers

Ready to plant out cucumber seedlings can be purchased from most garden centres or online retailers, but cucumbers are not difficult to grow from seed, and while a little patience is required, the results can be very rewarding.

A cucumber seed being sown
Sow cucumber seeds indoors in seed or module trays [Photo: UncleFedor/ Shutterstock.com]

Sowing cucumber seeds

Cucumber seeds are available in a wide range of varieties, with typical green fruits ranging in size from small to large to even quite unusual yellow types like the lemon cucumber. When growing cucumbers from seed, the soil needed for sowing differs from that required for planting out. To germinate, cucumber seeds require a free-draining, low-nutrient compost, such as our Plantura Organic Herb & Seedling Compost.

If the cucumber plants will grow undercover, such as in a greenhouse, start the cucumber seeds indoors in late March to April. If you want to grow your cucumber plants outdoors, wait until late April to early May to start the seeds indoors so that the frosts will have passed and the soil will have warmed up by the time they are ready to be planted out.

To sow cucumber seeds indoors, fill a seed or module tray or small pot with seedling compost and sow the seeds on their side at a depth of 1 – 2 cm. Water well. If using module trays or pots, seeds can be sown individually or in pairs. For pairs, thin weakest seedling out after germinating. Place in a propagator or on sunny windowsill at a minimum of 20 °C and keep the soil moist.

Young cucumber plants in planting tray
Cucumbers can be grown from seed or purchased as young plants to grow at home [Photo: ZhakYaroslav/ Shutterstock.com]

Cucumber seeds usually germinate within 7 – 10 days and can be grown on until they have at least two true leaves before being pricked out into 9 cm pots filled with nutrient-rich potting compost.

If you want to sow the cucumber seeds directly in the garden bed, you can do so from June onwards. First remove any weeds and stones and rake to a fine tilth to prepare the previously enriched soil. Sow the cucumber seeds at a depth of 1 – 2 cm, leaving 60 cm space between seeds to allow for enough room to grow. Water well.

If cold weather is forecasted or night temperatures begin to dip, use a cloche or layer of fleece to shield the seedlings and ground from the elements.

Cucumber plants with cloche covering
Using cloche or a layer of fleece helps to protect your cucumber plants [Photo: Oksana Ageeva/ Shutterstock.com]

Planting out cucumbers

Cucumber plants are ready to be planted out in a greenhouse when they have at least three to four leaves and a strong root system. Whereas, when planting out cucumbers in the garden bed, let the seedlings grow a little larger and become more robust before gradually hardening them off and planting them outside at the mercy of the weather and slugs and snails.

When it comes to how to plant cucumbers out, it is important that they have enough room to grow and that there is adequate air circulation between them to prevent disease. Growing cucumbers vertically raises them off the ground, which not only improves airflow between the plants but also saves space. The ideal spacing for cucumber plants is 60 cm apart for vertical-growing cucumbers and 90 – 100 cm apart for plants that trail along the ground.

To plant cucumbers, gently remove them from their current pot and place in a pre-dug hole at the same depth as they were previously planted. Water thoroughly. Insert a support if growing vertically, taking care not to injure the roots. There are two main styles of supports for vertically grown cucumber plants: Either tie the leading stem to a cane or stake or place a cucumber trellis beside the plant carefully for it to sprawl over.

Cucumber plant growing up a vertical trellis
Use a vertical trellis to support your cucumber plant [Photo: Veirina/ Shutterstock.com]

Keep the soil moist and feed with a slow release or liquid fertiliser to ensure a bountiful crop of cucumbers over the summer months. Read our specialist article for more advice on how to feed your cucumber plants over the growing season.

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