You can plant cucumbers when the soil temperature is consistently warm, typically above 65°F (about 18°C). Here are some guidelines based on different growing conditions:
- For greenhouse cucumbers, plant them in a heated greenhouse as early as late March. For unheated greenhouses or polytunnels, sow seeds in April, and then plant the seedlings from late May once the temperature inside is above 12°C (53°F).
- For outdoor cucumbers, wait until the danger of frost has passed and the soil is warm enough, usually from early June onward, when local temperatures are reliably above 12°C (53°F).
- If you prefer to start indoors, sow seeds about 2-4 weeks before the last expected frost, then transplant the seedlings outdoors when the soil has warmed to at least 70°F (21°C).
- Direct sowing is usually best after the last frost when the soil temperature is warm enough to encourage germination (around 65°F or higher).
- In warmer climates or for a longer harvest, you can do succession planting by sowing new seeds about a month after the first planting.
In summary, plant cucumbers in late spring to early summer outdoors after the last frost and when soil temperatures are warm, or earlier in greenhouses or indoors for a head start.
