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Heden
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Growing Season: Heden

Bollnäs, Gävleborg, Sweden

Growing season

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 23 Apr
Daylight
10+ h
14+ h
10+ h
2 Mar
11 Apr
1 Sep
12 Oct
224 days
Frost-free
10% frost-free
14 May
25 Sep
90% frost risk
134 days
Effective
14 May
25 Sep
134 days

The growing season in Heden is approximately 134 days and is limited by frost.

Last spring frost

The last spring frost normally occurs on 14 May in Heden. At the earliest, the last frost is over around 5 May and at the latest around 24 May.

Frost-free probabilityFrost-free prob. Date Grower's risk level Explanation
10% 5 May High risk Frost 9 out of 10 years after this date
25% 7 May Frost 3 out of 4 years after this date
50% 14 May Normal risk Frost every other year after this date
75% 18 May Frost 1 out of 4 years after this date
90% 24 May Low risk Frost 1 out of 10 years after this date
Growing is often planned around the date when there is a 50% probability that the last spring frost has occurred. In Heden that is 14 May. 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 25 Sep in Heden. At the earliest, frost can arrive around 4 Sep and at the latest around 2 Oct.

Frost probabilityFrost prob. Date Grower's risk level Explanation
10% 4 Sep Low risk Frost 1 out of 10 years on or before this date
25% 18 Sep Frost 1 out of 4 years on or before this date
50% 25 Sep Normal risk Frost every other year on or before this date
75% 30 Sep Frost 3 out of 4 years on or before this date
90% 2 Oct High risk Frost 9 out of 10 years on or before this date
Growing is often planned around the date when there is a 50% probability that the first autumn frost has occurred. In Heden that is 25 Sep. 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 2 Mar 12 Oct 224
Persephone period 13 Oct 1 Mar 141
Plan the year's last sowing of cold-hardy plants in Heden so they are approximately 75% mature by 13 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 2 Mar – 10 Apr 40 Grow long-day plants like spinach, lettuce and coriander.
Longer daylight 14+ h 11 Apr – 31 Aug 143 High risk of bolting
Shorter daylight 10-14 h 1 Sep – 12 Oct 42 Grow long-day plants