Winter aconite · London, England, United Kingdom
When to sow winter aconites in London
Main outdoor window
8-22 Oct
The window this page is built around.
Timed from last spring frost
14 April
In London, on your chosen risk.
Ready to pick
1 Feb - 31 Mar
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in London
Each window is a range, not a single day. Earlier in the range buys you a longer season; later in it buys you a safer one.
Plant the tubers
8-22 Oct
Four to six weeks before your first frost, so roots form before the ground cools.
In flower
1 Feb - 31 Mar
Winter aconites through the year
Against the frost risk in London
Why these dates
Plant dry tubers as early in autumn as you can get them, 5cm deep, after an overnight soak. Expect a proportion to fail regardless. The reliable method is to beg a clump from an established planting just after flowering and plant it in leaf.
Hardy to -30C and flowers in midwinter, opening whenever the temperature rises above about 10C and closing again. Needs cold winters and cool summers; useless in a hot climate.
Winter aconites are anchored to the first autumn frost rather than the last spring one, so the planting window on this page counts backwards from the end of the season in London instead of forwards from its start.
London sits in zone 9a, which is milder than this crop wants, and a winter that never really arrives is its own problem. The dates below still describe the right time of year; the open question is survival rather than timing.
The median frost-free season here is 219 days, against 100 to 150 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in London
Other flowers to time
Growing winter aconites in London
When should I plant winter aconites in London?
Aim for 8-22 Oct in an average year. If you would rather not gamble on the weather, wait until 19 Sep - 3 Oct - by then frost has finished in nine years out of ten.
When will winter aconites be ready to harvest in London?
Expect to start picking around 1 Feb - 31 Mar, based on 100 to 150 days to maturity from the planting date calculated for this location.
How much frost will winter aconites tolerate?
Hardy to -30C and flowers in midwinter, opening whenever the temperature rises above about 10C and closing again. Needs cold winters and cool summers; useless in a hot climate.