When to plant potato in Portsmouth

In Portsmouth, typical last spring frost is March 23 and typical first fall frost is December 1. Typical last spring frost: March 23. Potato in Portsmouth is a good fit outdoors. The suitable growing window of 239 days covers the 70–125 days this plant usually needs.

Potato

How to grow Potato Portsmouth climate Weekly temperatures and windows

Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Potato in Portsmouth is a good fit outdoors. The suitable growing window of 239 days covers the 70–125 days this plant usually needs.

When to plantMarch 17 – August 9

Harvest: May 26 – January 2
Season vs crop: 239 grow days vs 70–125 needed
Typical frost (last spring – first fall): March 23 – December 1

Potato in Portsmouth is a good fit outdoors. The suitable growing window of 239 days covers the 70–125 days this plant usually needs.

Planting conditions

Direct sow
Harvest

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 row239

Days to harvest70–125 days from planting

Mar 17 – Aug 9

Direct sow

May 26 – Jan 2

Harvest

Activity	Window	Notes
Direct sow	Mar 17 – Aug 9	Plant outdoors in this window.
Harvest	May 26 – Jan 2	Expected harvest from typical days to harvest.

Direct sow
Harvest

Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost (35 seasons (1991–2025)). Adjust a week or two for your conditions.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (15 – 24 °C59 – 75 °F15 – 24 °C (59 – 75 °F)) and tolerable (7 – 30 °C45 – 86 °F7 – 30 °C (45 – 86 °F)) ranges.

Ideal / plantable
Tolerable
Too cold
Too hot
Outside window

Planting uses sow / plant-out rules; growing shows daytime air against this plant’s ideal and tolerable ranges.

Key dates

Typical last spring frostMarch 23

Low-risk last spring frostApril 14

Typical first fall frostDecember 1

Low-risk first fall frostNovember 17

Frost-free days252

Outdoor sow dateMarch 17

Direct sow windowMarch 17 – August 9

Suitable growing windowMarch 17 – November 10 (239 days)

Expected harvestMay 26 – January 2

How these dates are judged

Ideal conditions: Daytime air from 15 – 24 °C59 – 75 °F15 – 24 °C (59 – 75 °F).
Suitable conditions: Daytime air from 7 – 30 °C45 – 86 °F7 – 30 °C (45 – 86 °F).
Last frost and first frost: Typical spring and fall frost dates for Portsmouth, shown in the key dates.
Days to harvest: 70–125 days from planting, 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. Air ratings on the weekly chart colour only weeks inside that same window — see weekly temperatures and windows.

Other plants for Portsmouth

Calculated by Plan & Plant. Method. Data 35 seasons (1991–2025).

Frost and suitability dates are typical figures from climate statistics.

Based on 35 years (1991–2025) of ERA5-Land data from Open-Meteo, for an area of about 10 km. Typical dates, not a guarantee.

Dates for Portsmouth use ERA5-Land cell 50.80, -1.09. How we calculated this · Algorithm 2026-10-season-10.

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