Saving squash seed
Generous seed, but the hardest isolation in this catalogue. Squash cross readily, so bagging and hand-pollination are the only reliable method in a garden.
- Life cycle
- Annual
- Pollination
- Insect-pollinated, separate sexes
- Isolation
- 500 m–1 km, or bagging
- Seed life
- 4–6 years
- Yield
- 1 fruit gives 200–400 seed
Squash have separate male and female flowers on the same plant, and insects move pollen between them and between plants. Within a species they cross freely, which means a courgette and a pumpkin of the same species grown together will produce seed that is neither.
The good news is that the species boundary is real: Cucurbita pepo and Cucurbita maxima do not cross. If you grow one of each, both come true.
The protocol
- 1
Know your species
Courgettes, most summer squash and some pumpkins are pepo. Many winter squash and marrows are maxima. Check before you plan — this is the difference between success and a wasted season.
- 2
Bag a female flower the evening before
Identify a female by the miniature fruit at the base. Tie a paper bag or mesh over it before it opens.
- 3
Hand-pollinate in the morning
Pick a male flower that has just opened, peel back the petals, and press its centre into the female's stigma. Do it before mid-morning; the flowers close by afternoon.
- 4
Re-bag and leave
Tie the bag back over the pollinated flower and leave it until the fruit is clearly swelling. Then remove it.
- 5
Let the fruit over-ripen
Leave it on the plant well past eating stage — 40 to 60 days after pollination for winter squash. The seed must be fully mature inside.
- 6
Scoop, wash, dry
Cut open, scoop the seed and pulp, rinse in a sieve under running water, then ferment two days in a jar before a final rinse and a week of drying.
What goes wrong
Trusting distance in a garden. The textbook figure is 500 m to a kilometre. In a domestic garden that is unachievable, which is why bagging exists.
Harvesting the fruit too early. Seed from an eating-stage courgette is immature and will not germinate. Let it turn into a marrow.
Crossing within pepo. Courgette seed saved near an ornamental gourd will give bitter, inedible fruit next year. Bitterness in squash is cucurbitacin and it can be genuinely toxic.
Saved seed from this crop?
Germination rates, what came true and what crossed — post it and let other growers learn from it.
All 14 protocols
Annual, biennial and vegetative crops all save differently. The index compares them side by side.