Overview
What zucchini need, how productive they are, and whether they suit your space.
Zucchini (courgettes) are summer squash, eaten young while the skin is soft. A single healthy plant gives three or four fruits a week, so two or three plants feed a family. They need warmth, sun, rich soil and steady moisture, and bees to carry pollen between their separate male and female flowers. Pick them small and often: leave a fruit to become a marrow and the plant slows down.
Quick facts
- Botanical name
- Cucurbita pepo
- Soil pH
- 6.0 – 6.5
- Feeding
- Heavy feeder
- Temperature
- 18 – 24 °C
- Hardiness
- Any zone, as an annual
- Time to harvest
- 50 – 65 days
- Propagation
- Seed
Optimal growth
Killed by frost
Growing details
- Spacing
- 90 cm (35 in)
- Sowing depth
- 13 mm (½ in)
- Frost sensitivity
- Frost tender
Growing calendar
- Start indoors: April, May
- Sow outdoors: May, June, July
- Plant out: May, June
- Harvest: July, August, September, October
In the UK, April or early May (RHS). Late May or early June under a cloche in the UK (RHS); a second US sowing in early to mid-July (UMD). After the last frost, usually from late May (Gardeners’ World). In the UK, July to October (Gardeners’ World); about 50 to 65 days after planting out (UMD).
Is this plant right for you?
- Very productive
- Beginner friendly
- Frost tender
- Needs space
- Hungry and thirsty
- Good in large pots
- Pick every day or two
Good to know
It is a hungry plant, so feed it regularly right through the growing season. Wait until the last frost has passed before it goes outside.
Before You Grow
Choose green, yellow or round, bush or climbing, and a warm, sunny spot with rich soil.
Prepare each planting site a few weeks ahead with plenty of compost or manure (RHS).
What you need
Seed or young plants
Two or three plants feed a family (Gardeners’ World). See choose your zucchini.
Small pots and warmth
For sowing indoors. See sowing.
A square metre per plant
In a warm, sunny spot. See growing conditions.
Compost or manure
Plenty, dug into each site. See soil.
Slug protection
Young plants vanish overnight. See pests.
A sharp knife
For clean picking. See harvesting.
Choose your zucchini
Varieties differ in fruit colour and shape, plant size, and how prickly the stems are (RHS).
Green zucchini are the classic: RHS AGM ‘Defender’, a popular heavy cropper with good disease resistance; ‘Tuscany’, for cooler areas; ‘El Greco’, with an open habit that keeps the fruit in view; and pale ‘Lorea’ (RHS, Gardeners’ World).
Yellow zucchini such as ‘Parador’ (RHS AGM) and ‘Gold Rush’ stand out among the leaves at picking time (RHS, Gardeners’ World).
Round varieties such as ‘Tondo di Nizza’ and ‘One Ball’ are ideal for stuffing (Gardeners’ World).
Compact varieties such as ‘Astia’ (RHS AGM) and ‘Venus’ suit pots. Climbing varieties such as ‘Black Forest’ and ‘Tromboncino’ can be trained up a stake (RHS, Gardeners’ World).
Seed or young plants. Young plants, sold in late spring and early summer, suit you if you lack the time or space to sow (RHS).
Other summer squash: yellow crookneck and straightneck, and scalloped patty pan, are grown the same way (Illinois, UMD). Parthenocarpic varieties set fruit without pollination (UMD).
Summer squash types compared
-
Green zucchini
- Shape
- Long, cylindrical
- Pick at
- 10 to 20 cm (4 to 8 in) long
- Examples
- ‘Defender’, ‘Tuscany’, ‘Black Beauty’
-
Yellow zucchini
- Shape
- Long, golden
- Pick at
- 10 to 20 cm (4 to 8 in) long
- Examples
- ‘Parador’, ‘Gold Rush’
-
Round zucchini
- Shape
- Ball
- Pick at
- Tennis-ball size
- Examples
- ‘Tondo di Nizza’, ‘One Ball’
-
Crookneck and straightneck
- Shape
- Yellow, narrow neck
- Pick at
- 4 to 5 cm (1½ to 2 in) across
- Examples
- ‘Early Summer’, ‘Saffron’
-
Patty pan (scallop)
- Shape
- Flat, scalloped
- Pick at
- 7.5 to 10 cm (3 to 4 in) across
- Examples
- ‘Sunburst’, ‘Peter Pan’
From the RHS, Gardeners’ World, Clemson and UMD. For a small space, a compact or climbing variety.
Where zucchini grow best
Zucchini are tender, warm-season plants: frost injures them (RHS, UMD).
Temperature. They grow best at an average of 18 to 24 °C (65 to 75 °F) (Clemson). Cool weather early in summer can stop fruit setting until it warms up (RHS).
Sun and shelter. A warm, sunny, sheltered spot (RHS, Gardeners’ World), with at least six hours of direct sun, better eight to ten (UMD). In shade, plants grow and crop poorly.
Space. Bush plants spread about 1 m (3 ft): the RHS and Gardeners’ World give each about a square metre, 90 cm (3 ft) apart. US extensions plant closer, 60 to 90 cm (2 to 3 ft) (Illinois, Utah State).
Early crops. Black plastic and row covers warm the soil and protect young plants; remove the covers at flowering so bees can reach the flowers (Utah State, UMD).
- Best growth
- 18 to 24 °C (65 to 75 °F)
- Space per plant
- About 1 m² (60 to 90 cm apart)
- Sun
- At least 6 hours; 8 to 10 is better
Soil
Zucchini are hungry plants that do best in rich, moisture-retentive, well-drained soil (Gardeners’ World, Utah State).
Planting sites. A few weeks before planting, dig lots of compost or well-rotted manure into each site, about a spade’s depth and width (RHS). If you garden no-dig, mulch each site instead.
pH. 6.0 to 6.5 (Clemson).
Roots are shallow, so mulches help (Illinois).
Planting
Sow in warmth, plant out after frost, and give each plant room.
Seed needs warmth: 18 to 21 °C (65 to 70 °F) indoors (RHS), or soil at 16 to 18 °C (60 to 65 °F) outdoors (Clemson, Utah State).
When to sow and plant zucchini
Indoors in April or early May for an earlier crop, especially in colder areas (RHS, Gardeners’ World). US extensions sow about three weeks before planting out (UMD).
Planting out after all risk of frost, usually from late May in the UK (Gardeners’ World), once the soil has warmed. Bought plants go out at the same time (RHS).
Outdoors in late May or early June, under a cloche (RHS, Gardeners’ World). In the US, once soil is 16 to 18 °C (60 to 65 °F) (Clemson, Utah State).
Second crop. UMD sows again in early to mid-July for a late-summer harvest.
- Indoors April to early May.
- Out after the last frost.
- A second sowing in July (US).
How to sow zucchini
Indoor sowing gives earlier crops and keeps seedlings away from slugs until they’re bigger (RHS).
-
Sow on edge
One seed per 7.5 cm (3 in) pot, on its side, about 1.3 cm (½ in) deep, in moist compost (RHS, Gardeners’ World).
-
Keep warm
At 18 to 21 °C (65 to 70 °F) in a propagator or under a clear bag on a sunny windowsill (RHS).
-
Pot on
Move the strongest seedlings to larger pots and discard the weaker ones (Gardeners’ World).
-
Or sow direct
Two or three seeds 2.5 cm (1 in) deep at each site, 90 cm (3 ft) apart, under a cloche. Thin to the strongest by cutting the others off with scissors (RHS, UMD).
Planting out
Handle zucchini gently: they dislike root disturbance (UMD).
-
Harden off
Over a week or two, stand plants outside by day and bring them in at night, so they get used to outdoor conditions gradually (RHS).
-
Plant into the prepared site
Without disturbing the roots, at least 90 cm (3 ft) apart (RHS).
-
Sink a pot
A 15 cm (6 in) pot sunk beside each plant takes water straight to the roots (RHS).
-
Water and mulch
Water well, then mulch generously, keeping it off the stem (RHS, Gardeners’ World).
-
Protect from slugs
Straight away: young plants can be eaten overnight. See pests (Gardeners’ World).
Care
Watering, feeding, pollination, pots, and crops to grow alongside.
Water at the base, not over the leaves, to keep mildew and rot down (RHS, Clemson).
Care by growth stage
Young plants
Weeds: until leaves cover
Protect from slugs and cold. See pests.
Flowering
Water: keep just moist
Male flowers come first. See pollination.
Fruiting
Pick: every day or two
Feed and pick often. See feeding and harvesting.
Late summer
Leaves: remove tatty ones
Remove mildewed leaves. See diseases.
End of season
Frost: plants die
Clear the plants; dispose of any with vine borer damage. See pests.
Watering zucchini
Moisture is the key: a constantly just-moist soil lets plants crop to their full potential (Gardeners’ World).
How much. Deeply, 2.5 to 5 cm (1 to 2 in) a week, soaking the soil about 15 cm (6 in) deep (Utah State, Clemson). Pots may need watering daily in hot weather (RHS).
When it matters most. Fruit set and development (Clemson). Dry soil means few female flowers; see pollination.
How. At the base, not over the leaves, which spreads mildew and rot, and in the morning (RHS, Clemson, Gardeners’ World).
Mulch with compost or manure to hold moisture, keeping a gap around the stem (RHS).
Feeding zucchini
Zucchini are hungry plants (Gardeners’ World).
In the ground. Rich, manured soil usually needs no feed (RHS); Gardeners’ World gives a weekly high-potash feed such as tomato food.
In containers. A high-potash liquid feed every 10 to 14 days once the first fruits swell (RHS); Gardeners’ World starts weekly once flowering begins.
US extensions side-dress with a little nitrogen once the plants start to spread or flower (Utah State, UMD).
Not too much nitrogen: it makes leaves at the expense of fruit (Clemson).
Yellow leaves in pots usually mean the compost has run out of nutrients (Gardeners’ World).
Flowers and pollination
Zucchini have separate male and female flowers. The female has a tiny fruit behind it; only females become zucchini (Illinois, Clemson).
Males first. Plants make male flowers for one to two weeks before the first females. This is normal (UMD).
Bees do the pollinating. Poor pollination gives no fruit or misshapen fruit, and is common in cool or rainy weather when bees are inactive (Clemson, UMD, RHS). UMD avoids pesticides while plants are flowering; Clemson sprays only late in the evening, when bees have stopped working.
Hand pollination. If fruits don’t set, pick an open male flower, strip its petals and brush its pollen onto the centre of an open female flower (UMD).
Only male flowers? Usually dry soil: water generously and feed with potash (Gardeners’ World).
Parthenocarpic varieties set fruit without pollination, so they can stay under insect netting all season (UMD).
Zucchini in containers
Compact or bush varieties grow well in large containers in a warm, sunny spot (RHS).
Container. At least 45 cm (18 in) wide and deep; plants still spread about 1 m (3 ft) above ground (RHS, Gardeners’ World). A growing bag takes one or two compact plants (RHS).
Compost. Peat-free soil-based or multi-purpose, with well-rotted manure or compost added (Gardeners’ World).
Care. Pots dry out fast and run short of food; see watering and feeding.
Growing with other crops
Zucchini spread wide, so pair them with crops that grow up.
Climbing beans
Grow together · Wants the same conditions
Beans climb canes while zucchini fill the ground beneath; both like the same rich, warm soil (Gardeners’ World).
Sweet corn
Grow together · Wants the same conditions
Tall corn with low zucchini makes two crops in one bed (Gardeners’ World).
Where squash grew last year
Keep apart · Traditional practice
Squash vine borers overwinter in the soil near last year’s plants, so a fresh spot may help (Illinois, UW-Madison).
Problems
Slugs, poor pollination, powdery mildew and rot are the usual troubles.
Common zucchini problems
Match what you see to its likely cause.
Flowers but no fruit
- Male flowers
- Dry soil
- Few bees
Early flowers are male; later, dry soil or poor pollination. See pollination.
Tiny fruits rot or shrivel
- Cold
- Poor pollination
Cool early-summer weather stops fruit setting (RHS). Remove the rotting fruits, and hand-pollinate if bees are scarce. See pollination.
Fruit rotting from the flower end
- Damp
- Calcium
In wet weather, rot spreads from the faded flower: remove soggy flowers and don’t water from above (Gardeners’ World). A dark, dry rot is blossom-end rot, a calcium problem: mulch, keep the soil evenly moist, and don’t overfeed (Clemson).
Plant slows down
- Marrows left on
Large fruits left on the plant stop new ones forming (Illinois, Gardeners’ World). See harvesting.
More problems with zucchini
Common pests
Slugs and snails
Can demolish young plants overnight and eat flowers and fruit (Gardeners’ World, RHS). Protect plants as soon as they go out: crushed eggshells or a copper ring around the stem, or a biological control; wildlife-friendly pellets only as a last resort (Gardeners’ World).
Squash vine borer
In North America, larvae tunnel into the stem base and the plant wilts. Cover plants with netting while moths are laying, and remove it at flowering. Planting early helps. To save a plant, slit the stem, remove the larvae, and mound soil over the wound (UW-Madison, Illinois).
Squash bugs
Suck sap and leaves wither. Trap them under boards and hand-pick adults and eggs (Utah State).
Cucumber beetles
Striped or spotted beetles feed on leaves and spread bacterial wilt (Utah State). Illinois treats them with a suggested insecticide at first sight; watch for them on fruit in September. Parthenocarpic varieties can stay under netting to keep them out (UMD).
Common diseases
Powdery mildew
White coating on the leaves, worse when plants are dry or crowded. Space plants, mulch, water regularly, and remove affected leaves promptly (Gardeners’ World, RHS).
Grey mould
Fluffy grey growth in damp weather. Cut out affected parts and clear dead growth (Gardeners’ World).
Mosaic virus
Mottled, crinkled leaves and misshapen fruit, spread by aphids. Control aphids and remove badly affected plants (Utah State).
Bacterial wilt
Vines wilt and die. Cucumber beetles spread it, so controlling them is the defence; rule out vine borer first (Utah State, UW-Madison).
Harvest & Use
Pick at 10 to 20 cm (4 to 8 in), every day or two in summer.
Harvesting zucchini
Zucchini are ready about 55 days after planting (Clemson) and grow fast, ready 3 to 5 days after the flower opens (Utah State) or 4 to 8 days (Illinois). Expect three or four fruits a week from a plant in good weather (RHS).
Size. Small is best: 10 to 12.5 cm (4 to 5 in) for the RHS; US extensions pick at 15 to 20 cm (6 to 8 in) and no more than 5 cm (2 in) across (Illinois, UMD). Patty pans at 7.5 to 10 cm (3 to 4 in) across.
Signs. Tender, glossy skin that a thumbnail still marks easily (Clemson, UMD).
Often. Every day or two in summer (Clemson). Remove any oversized fruit so the plant keeps producing (Illinois).
How. Cut with a sharp knife or secateurs, and wear gloves: stems are prickly. Handle gently, as the skins bruise (RHS, Illinois).
Flowers. Pick male flowers (without a fruit behind) to stuff or fry, so you don’t reduce the crop, but leave a few for pollination (RHS, Gardeners’ World, Illinois).
- Pick small.
- Every day or two.
- Cut, don’t pull.
Storing and using zucchini
Zucchini are best eaten fresh (Gardeners’ World).
Fridge. Unwashed, in a plastic bag in the crisper drawer (Illinois). Keeping times vary: Utah State gives 2 to 4 days at 7 to 13 °C (45 to 55 °F), Clemson up to a week, and UMD 5 to 14 days at 0 to 10 °C (32 to 50 °F) with high humidity.
Gluts. Turn them into chutneys and pickles (Gardeners’ World). Grate larger fruits into breads and bakes, or hollow them out for stuffing (Illinois).
Cooking. Steam, fry or grill; round varieties are ideal stuffed and baked (Gardeners’ World).
More to Explore
Short answers, guides that pair well with zucchini, and the sources behind this one.
Frequently asked questions
Why are my zucchini flowers not producing fruit?
Early flowers are male; later, dry soil or few bees. See pollination.
How many zucchini plants do I need?
Two or three feed a family. See choose your zucchini.
How far apart should zucchini be planted?
About 90 cm (3 ft) in the UK; US extensions plant from 60 cm (2 ft). See growing conditions.
When should I pick zucchini?
Small, at 10 to 20 cm (4 to 8 in), every day or two. See harvesting.
Can I grow zucchini in a pot?
Yes, a compact variety in a pot at least 45 cm (18 in) wide and deep. See containers.
Why are my zucchini rotting at the end?
Damp weather rot from the old flower, or blossom-end rot. See common problems.
What is the white powder on my zucchini leaves?
Powdery mildew. See diseases.
Can you eat zucchini flowers?
Yes, pick male flowers to stuff or fry, leaving a few for pollination. See harvesting.
Related guides
Sources
- How to grow courgettes (opens in a new tab) Royal Horticultural Society
- Growing summer squash (zucchini) in a home garden (opens in a new tab) University of Maryland Extension
- Summer squash (opens in a new tab) University of Illinois Extension
- Summer squash (opens in a new tab) Clemson Cooperative Extension
- Summer and winter squash in the garden (opens in a new tab) Utah State University Extension
- Squash vine borer (opens in a new tab) University of Wisconsin-Madison Extension
- How to grow courgettes (opens in a new tab) BBC Gardeners’ World