How to Grow Pumpkins in the UK

Pumpkins are perfectly suited to the UK climate. They’re a member of the winter squash family that includes the well-known butternut squash, the Atlantic Giant which is, as its name says, a huge pumpkin, and dozens of other varieties of all shapes and sizes. Pumpkins are popular at Halloween and delicious in all sorts of dishes, including risottos, pies, soups, and curries, and it’s perfect when simply roasted with salt and olive oil. And not only do pumpkins taste great, they’re packed full of vitamins.

So, how do you grow a pumpkin? This guide will give you all the information you need to cultivate this sensational squash in your garden or allotment.

Most of us think pumpkins are vegetables, and why shouldn’t we? We cook them like vegetables, we eat them as vegetables, and they’re with the other vegetables in the supermarket, but would you be surprised to know that pumpkins aren’t vegetables?

In fact, a pumpkin is technically a fruit! More specifically it’s a berry called a pepo, which is characterised by a hard outer rind and fleshy insides. Fruits develop from the ovary of a flower and contain seeds, which is precisely how pumpkins grow.

Before we get to the ins and outs of how to grow pumpkins in the UK, let’s take a quick look at the different types of pumpkins you can grow. The Jack O’Lantern is probably the best all-rounder, with sweet flesh for eating and a robust rind for carving. Crown Prince, while technically a squash, is highly regarded for its sweet flavour and dense texture, and the Queensland Blue, with blue-grey skin, is also very tasty.

Looking to go big? Try Big Max or Mammoth Gold, which can each weigh up to 45 kilograms, and Atlantic Giant has the potential to grow really big. And we do mean really big. The world record for the largest pumpkin ever grown was an Atlantic Giant and weighed 1,247 kilograms, or 2,749 lb. That’s about the same as a small family car!

Including squash and gourds, it’s estimated that around 23 million tonnes of pumpkins are grown every year, with about 30% grown in China, and smaller numbers in Ukraine, Russia, the USA, Mexico and Spain, but it’s much more fun to grow pumpkins at home! So how do you plant pumpkin seeds? Let’s dig into the answer.

This guide to how to grow pumpkins in the UK is pretty straightforward. You can plant pumpkins directly into their final growing site, though some gardeners prefer to give their plants a headstart and transport them into the garden when they’re ready. Starting seeds indoors helps them to establish strong roots and increases their chances of thriving in the cooler UK climate.

When To Start
Begin sowing pumpkins indoors in April or early May, about 2-4 weeks before the last expected frost.

What You Need
Small pots (7-9 cm in diameter) or seed trays, seed compost or a quality potting mix, and the pumpkin seeds for the variety you’ve chosen.

Sowing the Seeds
First, fill your pots with compost, leaving about 1 cm of space at the top. Then, make a hole about 2.5 cm (1 inch) deep in the centre of the compost and place one seed on its side in each pot to prevent rot. Cover the seed with compost, gently firm it down, and then lightly water the pots.

Germination
Place the pots in a warm location indoors, ideally between 18 – 21°C (65 – 70°F). Covering the pots with a clear plastic bag or using a propagator can help maintain humidity and warmth. Your seeds should germinate within 5 – 10 days.

After Germination
Once seedlings appear, uncover the plants and move them to a bright windowsill or under grow lights to ensure they get plenty of light. Keep the compost moist but not waterlogged.

Hardening Off & Transplanting
Before you take your plants outdoors, you’ll need to get them used to outside conditions. Start by placing them outdoors for a few hours a day in a sheltered spot, gradually increasing the time over a week. After the last frost, you can transport them permanently. Choose a sunny, sheltered spot with fertile, well-drained soil. Dig in lots of compost or well-rotted manure and space your plants about 1-2 metres apart, depending on the variety.

Once your pumpkin seedlings are transplanted outside, they require consistent care to thrive and produce a healthy harvest. Here’s what you need to do:

Watering

Pumpkins need regular watering to develop strong roots and vines. Water at the base of the plant to encourage deep root growth. Avoid overhead watering to reduce the risk of fungal diseases. Water in the early morning so that any water on the leaves can dry throughout the day.

Mulching

Apply a layer of organic mulch, such as straw or compost, around the base of the plants to help retain soil moisture. Mulch helps suppress weeds that compete for nutrients, and also keeps the soil temperature consistent, which is beneficial for root health.

Feeding

Once the vines begin to run, feed the plants every 2 – 3 weeks with a high-potassium liquid fertiliser. This is one of the most important steps in the process of how to grow and plant pumpkins.

Training & Pruning

Guide the vines away from other plants or paths. You can gently reposition them as they grow. For larger pumpkins, consider pruning the vines. Once a few fruits have set, you can trim back the ends of the vines to encourage the plant to focus energy on the existing pumpkins. You can also put a piece of wood or straw under developing pumpkins to prevent rot from ground contact.

Weeding

Keep the area around your pumpkins free from weeds to reduce competition for nutrients and water. And when you are removing weeds, try not to disturb the shallow roots of your plants.

Check your plants regularly for common pests like slugs, snails, aphids, and squash bugs. To avoid fungal diseases like powdery mildew, make sure there’s enough space between your plants to ensure good air circulation.

Pumpkins are ready to harvest when they have a uniform, deep colour and the rind is hard. The stem will also start to harden and dry. Use a sharp knife or pruning shears to cut the pumpkin from the vine, leaving about 5 cm (2 inches) of stem attached to prolong storage life. It’s not vital, but some gardeners put their harvested pumpkins in a sunny spot for a week or so to harden the skin.

To grow extra large pumpkins, you’re essentially following the same steps as growing normal-sized pumpkins, but with just a few other pointers to keep in mind.

Soil
Giant pumpkins need nutrient-rich soil with plenty of organic matter. Incorporate generous amounts of well-rotted manure or compost into the soil to a depth of at least 30 cm (1 foot). You also need to test your soil’s pH and nutrient levels. Aim for a slightly acidic to neutral pH of 6.5 to 7.0. Adjust as necessary with lime or sulphur.

Space
Each plant requires a large area, ideally 9-12 square metres (100-130 square feet), to allow the vines to spread and access sufficient nutrients. Plant the seedlings 3-4 metres (9 – 12 feet) apart to reduce competition.

Sustenance
Feed your plants every 1-2 weeks. Start with a high-nitrogen fertiliser to encourage vine and leaf growth. Once your pumpkins have set, switch to a high-phosphorus and high-potassium fertiliser to promote fruit development. And they’re very thirsty! Giant pumpkins require a lot of water – up to 30 litres per plant per day during peak growth periods.

So, we’ve explored each step of how to grow pumpkins in the UK. Along the way, we’ve answered questions, including how do you plant pumpkin seeds, as well as giving you some tips on its upkeep and care. Happy gardening!