Zucchini & Summer Squash
Cucurbita pepo
Two plants will feed a household. Three will make you unpopular with the neighbours.

Two plants is plenty
A healthy zucchini produces several fruit a week for two months. Two plants feed a family; the classic mistake is planting six and spending August trying to give them away.
Direct sow into warm soil
Seed rots in cold wet ground. Wait until soil reaches 65F, usually a week or two after last frost here. Sow two or three seeds per station and thin to the strongest. They grow so fast that transplants rarely gain much, though peat pots can buy a couple of weeks.
Bush habit needs floor space
Summer squash grows as a wide open bush rather than a runner - allow a three-foot circle per plant. It does not climb usefully. Generous spacing is also the main defence against mildew later on.
Pick small and pick daily
A six to eight inch zucchini is excellent; an eighteen-inch one is a watery marrow with tough seeds. In peak season they grow that much in two days. Leaving a giant on the plant also signals it to stop producing.
Squash vine borer
The main killer in this region. The adult moth lays at the stem base in early summer and the larva tunnels inside, so the plant wilts suddenly and dies. Look for a small hole with sawdust-like frass at the base. Defences: wrap the lower six inches of stem in foil or nylon, mound soil over lower nodes so the vine roots at several points, or sow a second crop in early July to outrun the single generation. You can also slit the stem lengthwise, remove the grub and bury the wound.
Squash bugs
Flat grey-brown bugs that cluster at the base and suck sap, causing wilting and eventually death. Check leaf undersides for bronze egg clusters and crush them. Adults resist most sprays; lay a board on the soil overnight and destroy the ones sheltering under it in the morning.
Poor pollination versus disease
If small fruit yellow and shrivel at the blossom end, that is failed pollination, not rot. The first flush of male-only flowers is normal. In a wet or bee-poor spell, hand-pollinate in the morning with a paintbrush or by touching a picked male flower to the female stigma.
Powdery mildew
Expect white powdery patches by August. Space for airflow, water at the base rather than overhead, and accept a finite plant life - a July sowing keeps you in squash. Resistant varieties help but do not eliminate it.
Harvest, blossoms and storage
Cut with an inch of stem rather than twisting. Male flowers - on thin stalks with no baby fruit behind them - can be picked and stuffed at no cost to your harvest. Fruit keeps only about a week in the fridge and does not store, but grates and freezes well for baking.
- Habit
- Bush
- Days to harvest
- 45-60
- Spacing
- 24-36 in
- Sun
- Full
- pH
- 6.0-7.5
- Soil temp
- 65F+
- Harvest at
- 6-8 in
- Sow
- Direct after frost