Pumpkins When to sow and plant When to sow pumpkins
Pumpkins are tender, so frost decides the dates at both ends of the season. Sow too early and the plants wait indoors. Pick too late and the fruit will not keep.
In short
The RHS sows pumpkins indoors from mid to late April, at 18–21 °C. Plant them out, or sow outdoors, in late May or early June, after the last frost. Garden Organic sows indoors in May and plants out in June. Harvest before the first frost.
Pumpkins: what to do and when
Under cover and outdoors, for UK conditions. The weather differs from year to year and from north to south, so check your local conditions too.
When to sow pumpkins indoors
The RHS says pumpkins are best sown indoors in mid-spring. Its date is mid to late April.
Sow into 7.5 cm pots or modular trays. Set the flat seeds on their side, 1 cm deep, one seed in each pot or module. Keep the pots at 18–21 °C, either in a heated propagator or on a warm, bright windowsill with a clear polythene bag over them. Take the bag off once the seeds germinate.
Pumpkins are tender, the RHS says, so they must be protected from frost and cold. It keeps young plants indoors, in good light, until late May or early June.
Garden Organic sows a little later. Its growing calendar gives May for sowing indoors. It sows the seed in pots 1.5 cm deep, on their side.
So the two sources differ by a few weeks and by half a centimetre. Both agree that the seed goes on its side.
Sowing pumpkins outdoors
You can skip the pots. The RHS says pumpkins can also be sown a month or so later outdoors, in late May or early June, after the last frost.
Sow two or three seeds into each prepared site, 2.5 cm deep.
Garden Organic's guide does not give an outdoor sowing date. It sows in pots and transplants.
Planting out after the last frost
The RHS plants indoor-sown or newly bought plants outside after the last frost. First, harden them off to get them used to outdoor conditions. Garden Organic also hardens off and transplants, and its calendar gives June for planting out.
Site. The RHS wants a warm, sunny site with shelter from cold winds. Garden Organic says fertile soil in a sunny, sheltered site.
Soil. The RHS asks for soil that is fertile and moisture retentive but not waterlogged. Make a hole about 30 cm wide and deep and fill it with a mix of soil and organic matter.
Spacing. The sources differ here. The RHS spaces bush varieties 90 cm apart and trailing varieties 1.5 m apart. Garden Organic transplants 60–90 cm apart. The RHS adds that bush types stay comparatively compact but still take up at least one square metre.
Containers. The RHS says smaller varieties can potentially be grown in large containers, but most fare best in the ground. Plant one per growing bag or one in a container at least 45 cm wide.
Water, mulch and feeding
Pumpkins need plenty of water, especially when fruiting, the RHS says. It suggests sinking a 15 cm plant pot into the ground next to each plant and pouring the water into it. Use rainwater from a butt whenever possible. On hot days, water early in the morning or in the evening.
After planting, the RHS covers the soil with a thick layer of mulch. Leave a gap around the base of the stem, because dampness there could lead to rotting. Garden Organic also mulches, to conserve moisture.
Most pumpkins should not need feeding, the RHS says. The exceptions are plants grown for particularly large or giant fruits, and plants in containers. For those, start once the fruits begin to swell and apply an organic-based, high potassium liquid fertiliser every 10 to 14 days.
For bigger fruits, the RHS limits the number to two or three per plant, and just one for giant pumpkins. Put a tile, brick or piece of wood under developing fruits to keep them off damp soil. Garden Organic puts larger fruit on a tile to stop rotting.
When to harvest pumpkins
The RHS lets pumpkins mature and colour up on the plant before harvesting in autumn. Keep them on the plant for as long as possible, but harvest before the first frost, or protect the fruits with straw, fleece or cardboard. Frosted pumpkins cannot be stored.
Garden Organic's calendar gives a harvest window of July to October. It cuts the fruit when it has coloured and sounds hollow when tapped, but before frosts.
Both cut with a long stalk. The RHS says at least 10 cm, and Garden Organic says 10 cm.
Curing and storing
To harden the skins, the RHS lays pumpkins out in the sun for a week to 10 days. This is called curing, and it helps them keep well. Garden Organic lets the skin harden in the sun for 10 days if you plan to store them.
Store fully ripened pumpkins in a well-ventilated place at 10–15 °C, the RHS says, with the fruits not touching. Depending on the variety, they should keep for at least three months, and up to six in ideal conditions. Check them regularly for signs of rot.
Sowing and planting pumpkins: what the RHS and Garden Organic say
| Job | RHS | Garden Organic |
|---|---|---|
| Sow indoors | Mid to late April, 7.5 cm pots or modules, 18–21 °C in a heated propagator or on a warm, bright windowsill under a clear polythene bag | May |
| Sowing depth | 1 cm indoors, seed on its side, one per pot. 2.5 cm outdoors | 1.5 cm in pots, seed on its side |
| Sow outdoors | Late May or early June, after the last frost, two or three seeds per site | Not given |
| Plant out | After the last frost, once hardened off | June, once hardened off |
| Spacing | Bush types 90 cm, trailing types 1.5 m | 60–90 cm |
| Harvest | Autumn, before the first frost | July to October, before frosts |
| Stalk | At least 10 cm | 10 cm |
| Curing | In the sun for a week to 10 days | In the sun for 10 days if storing |
How to do it
- From mid to late April, sow one seed per 7.5 cm pot or module, flat on its side and 1 cm deep, the RHS says. Keep the pots at 18–21 °C, in a heated propagator or on a warm, bright windowsill under a clear polythene bag.
- Grow the young plants on indoors, in good light, until late May or early June.
- Harden them off to get them used to outdoor conditions before planting out.
- Choose a warm, sunny site, sheltered from cold winds, with fertile soil that holds moisture but does not get waterlogged. The RHS says pumpkins generally grow less well in cooler sites.
- For each plant, dig a hole about 30 cm wide and deep and fill it with a mix of soil and organic matter.
- Plant out after the last frost. The RHS spaces bush varieties 90 cm apart and trailing varieties 1.5 m apart.
- Or sow outdoors in late May or early June, after the last frost: two or three seeds per prepared site, 2.5 cm deep.
- After planting, cover the soil with a thick layer of mulch, leaving a gap around the stem so it does not stay damp and rot.
- Protect the young plants from slugs and snails, especially in damp weather.
Common questions
When should I sow pumpkin seeds in the UK?
The RHS sows indoors from mid to late April, at 18–21 °C in a heated propagator or on a warm windowsill under a polythene bag. Garden Organic sows indoors in May. Outdoors, the RHS sows in late May or early June, after the last frost.
Can I sow pumpkins straight into the ground?
Yes. The RHS says pumpkins can be sown outdoors a month or so after the indoor sowing, in late May or early June, after the last frost. Sow two or three seeds per site, 2.5 cm deep.
How deep should I sow pumpkin seeds?
Indoors, the RHS sows 1 cm deep and Garden Organic 1.5 cm deep, both with the seed on its side. Outdoors, the RHS sows 2.5 cm deep.
When can I plant pumpkins outside?
After the last frost, once hardened off, the RHS says. It keeps young plants indoors until late May or early June. Garden Organic's calendar gives June for planting out.
How far apart should pumpkins be?
The RHS spaces bush varieties 90 cm apart and trailing varieties 1.5 m apart. Garden Organic transplants 60–90 cm apart.
When are pumpkins ready to pick?
When they have matured and coloured up on the plant, in autumn, and before the first frost, the RHS says. Garden Organic also listens for a hollow sound when the fruit is tapped.
Sources
We wrote this page using the sources below.
- How to grow pumpkins, Royal Horticultural Society (RHS)
- Pumpkins and squashes, Garden Organic