Growing Season: Sundbyholmsön
Södermanland, Sweden
Growing season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
15 Apr
Daylight
10+ h
14+ h
10+ h
28 Feb
13 Apr
31 Aug
14 Oct
228 days
Frost-free
10% frost-free
7 May
10 Oct
90% frost risk
156 days
Effective
7 May
10 Oct
156 days
The growing season in Sundbyholmsön is approximately 156 days and is limited by frost.
Last spring frost
The last spring frost normally occurs on 7 May in Sundbyholmsön. At the earliest, the last frost is over around 24 Apr and at the latest around 15 May.
| Frost-free probabilityFrost-free prob. | Date | Grower's risk level | Explanation |
|---|---|---|---|
| 10% | 24 Apr | High risk | Frost 9 out of 10 years after this date |
| 25% | 30 Apr | Frost 3 out of 4 years after this date | |
| 50% | 7 May | Normal risk | Frost every other year after this date |
| 75% | 12 May | Frost 1 out of 4 years after this date | |
| 90% | 15 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 Sundbyholmsön that is 7 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 10 Oct in Sundbyholmsön. At the earliest, frost can arrive around 1 Oct and at the latest around 26 Oct.
| Frost probabilityFrost prob. | Date | Grower's risk level | Explanation |
|---|---|---|---|
| 10% | 1 Oct | Low risk | Frost 1 out of 10 years on or before this date |
| 25% | 3 Oct | Frost 1 out of 4 years on or before this date | |
| 50% | 10 Oct | Normal risk | Frost every other year on or before this date |
| 75% | 18 Oct | Frost 3 out of 4 years on or before this date | |
| 90% | 26 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 Sundbyholmsön that is 10 Oct. 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 | 28 Feb | 14 Oct | 228 |
| Persephone period | 15 Oct | 27 Feb | 137 |
Plan the year's last sowing of cold-hardy plants in Sundbyholmsön so they are approximately 75% mature by 15 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 | 28 Feb – 12 Apr | 44 | Grow long-day plants like spinach, lettuce and coriander. |
| Longer daylight | 14+ h | 13 Apr – 30 Aug | 140 | High risk of bolting |
| Shorter daylight | 10-14 h | 31 Aug – 14 Oct | 45 | Grow long-day plants |