American Pumpkin

How to grow American Pumpkin

Written by the GardenDecoded editorial team · Last reviewed 21 July 2026 · Written for UK gardens · How we research our guidance

Planting

Sow seed on its edge in individual pots indoors in late April, and plant out after the last frost once the plants have two or three true leaves. Harden off properly — a cold check sets them back badly. Plant into a pocket of compost, 90 cm apart for bush courgettes and more for trailing pumpkins, and water into a sunken pot or pipe alongside the plant to get water to the roots.

Pruning

Remove old and yellowing leaves through the season to improve air movement around the base. On winter squash and pumpkins, stop the trailing stems in late summer and thin the fruit to two or three per plant if you want them to ripen properly.

Propagation

From seed each spring. Home-saved seed crosses freely with other squashes nearby, so results are unpredictable.

Pests and diseases

Powdery mildew coats the leaves white by late summer and is close to inevitable — keep the roots moist and remove the worst leaves. Cucumber mosaic virus causes mottled, distorted growth and means pulling the plant out. Slugs destroy young plants, and grey mould rots small fruit in wet weather.

Value to wildlife

The large open flowers are readily worked by bumblebees.

Notes

Pick courgettes at 10–15 cm and pick often — one marrow left on the plant slows everything else down. Poor fruit set early in the season is usually a shortage of male flowers or of pollinating insects in cold weather, and normally corrects itself; hand-pollinate with a male flower if it does not.

This guidance was researched and written by GardenDecoded — see our editorial policy for how guides are checked and reviewed.

Other names for this plant

These names have all been used for Cucurbita pepo but are no longer the accepted name. You may still meet them on old labels, in books, or in nursery catalogues.

Others in Cucurbita