When to Plant Pumpkin Seeds

A wheelbarrow full of pumpkin and squash varieties

Pumpkins come in all shapes, sizes and colours. From compact sugar varieties ideal for pies to sprawling giants grown for fun, there's a wide selection to suit different growing spaces and culinary goals. Squash are closely related and often grown alongside pumpkins, offering similar growing habits but a wider range of textures and flavours. Before planting, it's worth deciding what type suits your garden and what you'll use them for—whether carving, eating, or storing over winter.

When should you plant pumpkin seeds

In the UK, timing is everything with pumpkins. Sow too early and you risk stunted seedlings or losing them to late frosts. Too late, and the fruits may not have enough time to mature. The ideal time to start pumpkin seeds indoors is from mid to late April. If you're sowing directly outdoors, wait until late May or early June when the soil has warmed and all danger of frost has passed.

How to grow pumpkin seeds

Pumpkins need warmth, rich soil and plenty of space. Start by choosing a sunny, sheltered site. If you're growing from seed indoors, use small pots filled with multipurpose compost. Place the seed on its side about 2cm deep to reduce the risk of rotting. Keep the compost moist and warm—ideally around 18 to 21°C—until germination. Once seedlings develop two or three true leaves, they’re ready to be hardened off before planting outside.

How to sow pumpkin seeds

If sowing directly outdoors, wait until the soil is reliably warm. Create a small mound of soil to improve drainage and add well-rotted manure or compost to enrich the planting area. Sow two seeds per mound about 2cm deep and keep them moist. Once they germinate, thin out the weaker seedling, leaving the strongest to grow on. It’s crucial to protect young seedlings from slugs and sudden cold snaps during the early stages.

How to plant out pumpkins

After the risk of frost has passed—usually from late May onwards—harden off indoor-grown seedlings by gradually exposing them to outdoor conditions over a week. Plant them in well-prepared ground with plenty of space. Pumpkins are hungry and thirsty plants, so dig in compost or manure and leave at least a metre between plants. Water well after planting and continue to feed throughout the growing season.

How to care for pumpkin crops

Pumpkins thrive with regular attention. Water deeply, especially during dry spells, but avoid soaking the leaves to reduce the risk of mildew. A weekly feed with a high-potash fertiliser once the fruits start to form will help them swell. Pinch out the growing tips of trailing varieties once a few fruits have set to encourage them to put energy into ripening. Keep the area weed-free and support developing pumpkins with tiles or straw to prevent rot.

Harvesting pumpkins

Pumpkins are usually ready to harvest in September or October. You'll know they’re ripe when the skin hardens and the colour deepens. Tap them—they should sound hollow. Cut the fruit from the vine with a sharp knife, leaving a few inches of stem attached. Allow them to cure in the sun for 10 days or keep them indoors somewhere dry and warm. This helps harden the skin further and improve storage life.

Common issues with planting pumpkin seeds

Cold, wet weather is the enemy of pumpkins at any stage of growth. Seeds may rot if the soil is too damp, and young plants can be damaged by frost or eaten by slugs and snails. Powdery mildew can affect the leaves later in summer, particularly if plants are crowded or poorly watered. If fruits fail to develop, it may be due to poor pollination—encouraging bees and hand-pollinating flowers can help.

Climate and regional variation

In the UK, regional differences in temperature and frost dates can affect when to sow and plant out pumpkin seeds. In the South, you may be able to plant a week or two earlier than in the North. Use local last frost dates as your guide. You can also use cloches or fleece to warm up the soil earlier in the season and give your plants a head start.

Indoor vs outdoor sowing pros and cons

Indoor sowing gives you more control. It protects seeds from pests, bad weather and allows you to get a head start. However, it also requires space, warmth and the extra step of hardening off plants.
Outdoor sowing is simpler and less labour-intensive but carries the risk of seed rot or slug damage if the conditions aren’t just right.

Succession planting and planning

If you’ve got space and want to spread out your harvest, you can stagger sowing over a few weeks. This can be useful for avoiding a glut all at once, especially with smaller or culinary varieties. Just make sure all your plants still have enough time to mature before the first frost in autumn.

Using a soil thermometer

For those who want precision: pumpkin seeds germinate best in soil temperatures of 18–21°C. A simple soil thermometer can help you avoid sowing too early and increase germination success.

Moon planting (for the more traditional growers)

Some gardeners follow biodynamic or moon phase calendars to decide when to plant. For pumpkins, a waxing moon during a fertile sign is said to encourage strong leafy growth and good fruiting. While not scientifically proven, it's a method some swear by.