When to plant zucchini in Leeds

Where are you growing?

Not realistic outdoors

Not realistic in greenhouse

Tight fit in a cold frame

Zucchini in Leeds is doable with planning under fleece. 45 suitable days are enough for fast varieties (45 days) but not slow ones (60 days).

When to plantJuly 23 – August 27

Harvest: September 6 – October 26
Season vs crop: 45 grow days vs 45–60 needed
Typical frost (last spring – first fall): March 27 – December 25

Zucchini in Leeds is doable with planning under fleece. 45 suitable days are enough for fast varieties (45 days) but not slow ones (60 days).

Estimate. Protection varies with the cover, the weather and how you vent it.

Fleece adds about 1–4 °C on frosty nights, depending on its weight. Remove it on warm days.

Fleece also cuts light: about 5–10 % for light fleece, up to 50–70 % for heavy grades. Take it off by day once frosts are over.

Cover dates are modelled from weather-model data using published greenhouse studies. They are not measured in your greenhouse. A max–min thermometer inside will tell you more.

Planting conditions

Direct sow

Local activity windows for this place and growing method. Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost.

Suitable growing days in a row45

Days to harvest45–60 days from seed

Jul 23 – Aug 27

Direct sow

Activity	Window	Notes
Direct sow	Jul 23 – Aug 27	Plant outdoors in this window.

Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost. Adjust a week or two for your conditions.

Protected frost and sowing dates are modelled estimates from weather-model data and published greenhouse studies, not measured in your greenhouse. A max–min thermometer inside will tell you more.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (21 – 32 °C) and tolerable (13 – 35 °C) ranges, from modelled cover temperatures for the growing method you selected.

Planting uses sow / plant-out rules (frost, soil germination, night, and last-sow): green when plantable, blue diagonal when nights or soil are too cold, amber cross-hatch when too hot, faint for other calendar limits. Growing shows daytime air against this plant’s ideal and tolerable ranges across the year.

Key dates

Typical last spring frostMarch 27

Safer last spring frostMarch 27

Typical first fall frostDecember 25

Safer first fall frostDecember 25

Frost-free days272

Outdoor sow dateJuly 23

Direct sow windowJuly 23 – August 27

Suitable growing windowJuly 23 – September 5 (45 days)

How these dates are judged

Ideal conditions: Daytime air from 21 – 32 °C.
Suitable conditions: Daytime air from 13 – 35 °C.
Last frost and first frost: Typical spring and fall frost dates for Leeds, shown in the key dates.
Days to harvest: 45–60 days from seed, from typical days to harvest.
Sowing window: Dated sow and harvest bars use frost dates, soil minima, night limits, and last-sow count-back from typical crop timing. The year strip and weekly chart use the same window: air ratings only colour weeks inside it.

Growing window for Zucchini: Jul 26 – Aug 15 (21 days)

Planting window for Zucchini: Jul 26 – Aug 27 (33 days)

Usually too cold: Jan 1 – Jul 12

Outdoors: weekly temperatures and windows

Temperatures across the year for Leeds. Shaded bands are this plant’s ideal and tolerable daytime air ranges. Growing is daytime air suitability; Planting is sow / plant-out conditions (same colour language). Window brackets mark each stretch.

Ideal range
Tolerable range
Possible min to max
Average min to max
Suitable
Tolerable
Too cold
Too hot

Selected week · tap a week or use the arrows

Week 30 · Jul 20 – Jul 26

Average 13 to 20 °C · Possible 9 to 26 °C

Growing: tolerable

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 13 to 35 °C; it is suitable when that average range also overlaps the ideal 21 to 32 °C band and possible readings stay within 0 °C to 35 °C. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 0 °C) makes it too cold. When a sowing window is calculated, weeks outside that window are uncoloured even if air is in range.

Based on average frost dates.

Show all 53 weeks

Cover method weekly charts

Outdoor weekly chart is above. Open a cover chart only if you grow under fleece, a cold frame, or an unheated greenhouse.

Other plants for Leeds

Calculated by Plan & Plant · Method · Data 2019–2026

Frost and suitability dates are typical figures from climate statistics. Microclimates vary; they are not a guarantee.

How we calculated this

Data: ERA5-Land via Open-Meteo, cell 53.80, -1.55, years 2019–2026 (not a 30-year climate normal yet).
Typical and safer dates: Typical last frost is the date after which half of winters in this sample had no more frost; safer is later in the sample so fewer winters still frosted.
Crop rule: Local windows for Zucchini from frost dates, temperature ratings, and crop timing rules.
Confidence: Provisional — short or thin sample for this place.
Full methodology (algorithm 2026-10-season-6).

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