Cosmos · Jieshou, Anhui, China
When to sow cosmos in Jieshou
Main outdoor window
25 Mar - 8 Apr
The window this page is built around.
Timed from last spring frost
18 March
In Jieshou, on your chosen risk.
Ready to pick
3-23 Jun
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 Jieshou
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.
Start indoors
18 Feb - 4 Mar
Four weeks before your last frost, under cover or on a windowsill.
Sow direct
25 Mar - 8 Apr
One week after your last frost.
Plant out
25 Mar - 8 Apr
One week after your last frost.
In flower
3-23 Jun
Cosmos through the year
Against the frost risk in Jieshou
Why these dates
Sow direct around the last frost date. Pinch young plants once to produce a bushier, more productive plant.
Frost-tender at both ends, but flowers freely until the first autumn frost stops it outright.
Seed packets and extension guides express timing as weeks either side of the last spring frost, because that is the only reference point that travels. Cosmos are timed from 4 weeks before that frost for an indoor start, with planting out 1 weeks after it, and this page simply resolves those offsets against the frost date computed for Jieshou.
The median frost-free season here is 246 days, against 70 to 90 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Jieshou
Other flowers to time
Growing cosmos in Jieshou
When should I plant cosmos in Jieshou?
Aim for 25 Mar - 8 Apr in an average year. If you would rather not gamble on the weather, wait until 10-24 Apr - by then frost has finished in nine years out of ten.
When will cosmos be ready to harvest in Jieshou?
Expect to start picking around 3-23 Jun, based on 70 to 90 days to maturity from the planting date calculated for this location.
How much frost will cosmos tolerate?
Frost-tender at both ends, but flowers freely until the first autumn frost stops it outright.