Pumpkins in the UK are best started indoors in late winter to early spring and then moved outside after the danger of frost has passed, with plenty of warmth and sun for fruit development. A practical approach is:

• Indoor start: Sow seeds indoors from mid-April to late April in pots or modules, using compost that drains well. Keep them warm (ideally around 18–24°C / 65–75°F) until they germinate. This aligns with common UK guidance for indoor sowing in spring.

• Transplanting outside: After the last frost date and when the soil has warmed, usually in May, transplant seedlings into the garden. Choose a sunny, sheltered spot with rich, well-drained soil. Space plants widely (about 90–120 cm / 3–4 ft apart) to accommodate sprawling vines.

• Direct outdoor sowing: In milder parts of the UK, some gardeners sow directly outdoors from April to May, but protection against late frosts and a warm growing season improve germination and yield.

• Frost risk and timing: Pumpkins are a heat-loving crop and do not tolerate frost. If unusually cold conditions persist, delay transplanting or start indoors longer to ensure robust plants.

• Harvest window: Most pumpkin cultivars need about 90–120 days from sowing to mature fruit. Plan for harvest in the autumn, aiming for fruit that ripens fully on the plant before lifting.

Tips for success

• Start indoors in modular trays or small pots, then pot up as seedlings grow to reduce root disturbance when transplanting.

• Provide consistent moisture, especially during fruit formation, and feed with a balanced, tomato-type fertilizer after transplanting.

• If aiming for Halloween pumpkins, work backwards from your target harvest date (roughly late September to October) to determine when to start indoors and when to transplant. This helps ensure 12–16 weeks of growth after transplant before fruit development reaches maturity.

Assumed plan for typical UK garden (temperate climate)

• Indoor sowing: April
• Outdoor transplant: May after last frost risk
• Harvest: September to October, depending on variety

If you’d like, share your location (roughly by region) and whether you’re starting indoors or direct sowing, and a couple of pumpkin variety types you’re considering. This will help tailor the timing to your specific frost dates and desired Halloween-or-early-autumn fruit.