When to plant zucchini in Phoenix

Where are you growing?

Not realistic outdoors

Comfortable in greenhouse

Comfortable in a cold frame

Zucchini in Phoenix is a good fit under fleece. The suitable growing window of 68 days covers the 45–60 days this plant usually needs.

When to plantMarch 24 – May 18; September 4 – September 28

Harvest: May 8 – July 17
Season vs crop: 68 grow days vs 45–60 needed

Zucchini in Phoenix is a good fit under fleece. The suitable growing window of 68 days covers the 45–60 days this plant usually needs.

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
Harvest

Local activity windows for this place and growing method. Blue fill is usually too cold for this plant.

Suitable growing days in a row68

Days to harvest45–60 days from seed

Mar 24 – May 18

Direct sow

May 8 – Jul 17

Harvest

Activity	Window	Notes
Direct sow	Mar 24 – May 18	Plant outdoors in this window.
Harvest	May 8 – Jul 17	Expected harvest from typical days to harvest.

Blue fill is usually too cold for this plant. 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 (70 – 90 °F) and tolerable (55 – 95 °F) 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

Frost-free days365

Outdoor sow dateMarch 24

Direct sow windowMarch 24 – May 18

Suitable growing windowSeptember 4 – November 10 (68 days)

Expected harvestMay 8 – July 17

How these dates are judged

Ideal conditions: Daytime air from 70 – 90 °F.
Suitable conditions: Daytime air from 55 – 95 °F.
Last frost and first frost: Typical spring and fall frost dates for Phoenix, 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: Apr 5 – May 18 (44 days)

Planting window for Zucchini: Apr 5 – May 30 (56 days)

Usually too cold: Oct 26 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Phoenix. 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 14 · Mar 30 – Apr 5

Average 53 to 79 °F · Possible 38 to 97 °F

Growing: too cold

Planting: too cold

A week is in range when its average low and high sit inside the tolerance band 55 to 95 °F; it is suitable when that average range also overlaps the ideal 70 to 90 °F band and possible readings stay within 32 °F to 95 °F. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 32 °F) 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 Phoenix

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 33.45, -112.07, 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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