PlantyBoxPot and soil
At least 40-50 litres (10-13 gallons) per plant, with rich compost-based mix. Choose compact or bush varieties, not trailing ones.
Light and position
Full sun, 6-8 hours at least. Plant out once nights stay above 12-14 °C (54-57 °F).
Watering
Plenty and regularly: about every 2 days, daily in hot weather, always at the base and never on the leaves, which easily get powdery mildew.
Feeding
Roughly every 10 days, with a balanced feed at first and a potassium-rich one once flowers appear.
Harvest
Zucchini 15-20 cm long with glossy skin. Bigger ones get watery and seedy.
How to harvestCut at the base every 2-3 days in peak season. Male flowers are edible too.
Common problems
Poor pollination: balconies lack insects. Hand-pollinate in the morning, brushing pollen from a male flower (thin stem) into a female one (tiny fruit at its base).
Powdery mildew, very common in late summer. Remove the worst leaves, water only the soil and keep air moving.
Normal in strong heat if they perk up by evening. If they're still limp in the morning, it's thirsty.
FAQ
How big a pot do zucchini need?
At least 40-50 litres (10-13 gallons) for one plant. In smaller pots it grows but crops poorly and goes thirsty.
When should I pick zucchini?
When they're 15-20 cm (6-8 in) long and glossy. Bigger ones turn watery and seedy and slow the plant down.
Can you eat zucchini flowers?
Yes, especially the male ones (thin stem, no fruit): pick them in the morning, leaving some for pollination.
