How to grow Zucchini

Cucurbita pepo · courgette, summer squash

Fast-growing summer squash grown from seed, either directly sown or started indoors. Produces abundant harvests over a long season when picked young.

Zucchini — Photo: Evan-Amos, Public domain, Wikimedia Commons

Quick facts

Type	Vegetable
Family	Cucurbitaceae
Light	Full sun
Soil pH	6–7
Frost	does not tolerate frost
Soil for sowing	from 15 °C
Germination	7 days
Seedlings ready	25 days
Sowing to harvest	45 days
Where it grows	Greenhouse, Open ground, At home

When to plant

Sow for seedlings about 5 weeks before planting out.

Plant out in open ground about a week after your last spring frost, once the soil is warm.

In an unheated greenhouse everything moves about three weeks earlier.

The first harvest comes about 45 days after the shoots appear.

Care

Greenhouse

Stage	Watering	Temperature	Feeding
Germination	every 1 days	20…25 °C	—
Seedlings	every 2 days	18…25 °C	balanced (NPK), 10 days into the stage
Growth	every 3 days	18…28 °C	nitrogen, 14 days into the stage
Flowering	every 3 days	18…30 °C	phosphorus and potassium, at the start of the stage
Fruiting	every 2 days	18…30 °C	potassium, at the start of the stage; potassium, 14 days into the stage

Open ground

Stage	Watering	Temperature	Feeding
Germination	every 1 days	15…25 °C	—
Growth	every 4 days	15…28 °C	nitrogen, 14 days into the stage
Flowering	every 4 days	15…30 °C	phosphorus and potassium, at the start of the stage
Fruiting	every 3 days	15…30 °C	potassium, at the start of the stage; potassium, 14 days into the stage

At home

Stage	Watering	Temperature	Feeding
Germination	every 1 days	20…25 °C	—
Seedlings	every 2 days	18…25 °C	balanced (NPK), 10 days into the stage
Growth	every 2 days	18…26 °C	nitrogen, 14 days into the stage
Flowering	every 2 days	18…27 °C	phosphorus and potassium, at the start of the stage
Fruiting	every 1 days	18…27 °C	potassium, at the start of the stage; potassium, 14 days into the stage

Growing notes

Light

Requires full sun — at least 6–8 hours of direct sunlight daily for strong growth and fruiting.

Soil

Rich, well-drained soil with plenty of compost; neutral pH is ideal.

Care

Keep soil consistently moist but not waterlogged; drought stress reduces yield. Hand-pollinate flowers in greenhouses if bees are absent. Harvest every 2–3 days; large fruits reduce further flowering.

How to tell it is ripe

Fruit is young and slim, about 10–20 cm long and no more than 5 cm across: this is the best eating stage.
Skin is still shiny and glossy.
Over-mature fruit grows large, hard-skinned and seedy and turns into a marrow.
The rind of a young fruit is easily pierced with a thumbnail.
Cut with a knife or secateurs, wearing gloves against the prickly stems, and pick every day or two because the fruits grow fast.

Pests and diseases of Zucchini

Bacterial wilt
Blossom-end rot
Broad mite
Cucumber beetles
Downy Mildew
Leaf Curl Virus
Squash bug
White mould (Sclerotinia)
Whitefly

Sources

Figures cited from these sources.