Growing Zucchini in a Short Season: Planting, Pollination and Harvest
Zucchini has a reputation for overproducing, and in a warm summer one or two plants really can feed a family. In a short, cool season it needs a little more help: warm soil, a quick indoor start and good pollination. Then the only problem is keeping up with the harvest.
The short answer
- Start indoors 2 to 3 weeks before planting out, or direct sow once soil is at least 18°C.
- Plant out about 2 weeks after your last frost, when days and nights stay at 18°C or warmer.
- Most varieties need 48 to 60 days.
- Pick at 15 to 20 cm long, at least every second day.
Based on the University of Saskatchewan zucchini guide.
How many plants?
One or two plants are usually enough for a family of four. In a short season it is still worth planting a spare in case one is lost to cutworms or a cold snap.
Starting indoors
- Sow 2 seeds 1 cm deep per pot and keep the strongest.
- Seeds sprout in 5 to 6 days at about 24°C.
- At least 14 hours of light a day; a fan builds sturdier stems.
- Harden off at least 3 days and plant out at 10 to 14 days old.
USask’s example: in Saskatoon, start seeds around May 7 and plant out in late May or early June. In the far north (Wollaston Lake), start around June 1 and plant out around June 20.
Planting
- Space transplants 25 cm apart in rows 90 cm apart; direct-sown hills 90 to 120 cm apart.
- Rich, well-drained soil with compost. Water in with a starter fertilizer.
- Black plastic mulch, row covers or low tunnels keep plants warm early on.
- In containers, use at least 19 litres (5 gallons), ideally a dark pot to warm the roots, and a compact bush variety.
Varieties
- Green zucchini (NDSU, via USask): Raven, Spineless Beauty, Green Machine, Payload, Cashflow, Desert, Portofino.
- Yellow: Gold Rush, Easypick Gold. Yellow fruit is much easier to spot.
- Other summer squash: Sunburst and Flying Saucer (pattypan), Zephyr (straightneck), Sundance (crookneck).
- Containers: Raven, Peter Pan, Goldy, Gold Nugget.
Pollination
Male flowers appear first, and many drop off; that is normal. Female flowers, with a tiny zucchini at the base, follow 7 to 10 days later. Remove row covers once flowers open. In cold or wet weather, hand-pollinate early in the morning by transferring pollen from a male flower to the centre of a female flower.
Water and feed
About 2.5 cm of water a week early in the season and twice a week from mid-July. Mulch thickly, keeping it off the stems. Feed with a balanced soluble fertilizer weekly before fruit set and twice weekly after.
Harvest
- Pick at 15 to 20 cm long. Smaller fruit is more tender.
- Check plants at least every second day. A zucchini can double in size in a couple of warm days.
- Cut with a knife, leaving at least 3 cm of stem, early in the day.
- Handle gently; it bruises easily. It keeps 1 to 2 weeks in the fridge.
Common zucchini problems
| Problem | Likely cause | Fix |
|---|---|---|
| Small fruit rotting at the tip | Poor pollination or wet weather | Hand-pollinate; mulch to keep fruit off wet soil |
| White powder on leaves | Powdery mildew | Space plants, water at the base, remove the worst leaves |
| Plants wilting despite watering | Squash vine borer or bacterial wilt | Check the base of stems; row covers early |
| Huge, seedy fruit | Missed harvests | Pick every day or two at 15 to 20 cm |
Using the harvest
- Freeze shredded zucchini in measured bags for winter baking.
- Grill, roast or sauté young fruit; they cook in minutes.
- Stuff the flowers: male flowers, which do not form fruit, are delicious stuffed or fried. Leave a few for pollination.
- Bake: zucchini bread and muffins use up oversized fruit.
Varieties for cool summers
In a short or cool season, early, compact varieties perform best. Look for plants listed at around 45 to 55 days, open-habit bush types that make picking easier, and varieties with powdery mildew tolerance. Yellow and round types such as Eight Ball add variety and grow just as easily.
Planning next season? Save this guide to your Pinterest board so it is there when you need it.
Gear that helps
- Biodegradable seed starting pots: Squash, pumpkins and cucumbers dislike root disturbance. Plant the whole pot.
- Soil thermometer: Soil temperature, not the calendar, tells you when seeds will actually sprout.
- Floating row cover fabric: Light enough to lay over crops; it keeps out insects and adds a little warmth.
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Frequently Asked Questions
When should I plant zucchini outside?
About two weeks after your last frost, when the soil is at least 18°C and nights stay at 18°C or warmer.
How many zucchini plants do I need?
One or two plants are usually enough for a family of four.
Why are my zucchini flowers falling off?
Early male flowers normally drop. If small fruit shrivels, pollination is poor; hand-pollinate early in the morning.
What size should zucchini be picked?
About 15 to 20 cm long. Pick at least every second day.
Why are my small zucchini rotting at the end?
Usually poor pollination or wet weather. Hand-pollinate in the morning and keep fruit off wet soil with mulch.
Can I eat zucchini flowers?
Yes. Male flowers, which do not form fruit, are delicious stuffed or fried. Leave some for pollination.
