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Growing season

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 8 Apr
Daylight
10+ h
14+ h
10+ h
4 Mar
9 Apr
3 Sep
10 Oct
220 days
Frost-free
1 May
15 Oct
167 days
Effective
1 May
10 Oct
162 days

The growing season in Selfoss is approximately 162 days and is limited by both frost and daylight.

Last spring frost

The last spring frost normally occurs on in Selfoss. At the earliest, the last frost is over around and at the latest around .

No frost data available for this location.

Growing is often planned around the date when there is a 50% probability that the last spring frost has occurred. In Selfoss that is . If you want lower frost risk, choose 75% or 90%, i.e. a later date.

First autumn frost

The first autumn frost normally occurs on in Selfoss. At the earliest, frost can arrive around and at the latest around .

No frost data available for this location.

Growing is often planned around the date when there is a 50% probability that the first autumn frost has occurred. In Selfoss that is . If you want lower frost risk, choose 10% or 25%, i.e. an earlier date.

Daylight & Persephone Period

Plants need at least 10 hours of daylight to grow actively. The period with under 10 h is called the Persephone period.

From To Number of days
Daylight over 10 h 4 Mar 10 Oct 220
Persephone period 11 Oct 3 Mar 145
Plan the year's last sowing of cold-hardy plants in Selfoss so they are approximately 75% mature by 11 Oct when daylight drops below 10 h and growth starts to slow.

Daylight periods

Long-day plants like lettuce, spinach and coriander bolt when daylight gets too long. Plan sowing and harvest during periods when daylight is shorter (10-14 h). Early spring or late summer sowing gives the best results.

Season Light Period Days Advice
Shorter daylight 10-14 h 4 Mar – 8 Apr 36 Grow long-day plants like spinach, lettuce and coriander.
Longer daylight 14+ h 9 Apr – 2 Sep 147 High risk of bolting
Shorter daylight 10-14 h 3 Sep – 10 Oct 38 Grow long-day plants