Cosmos · Tongchuanshi, Shaanxi, China
When to sow cosmos in Tongchuanshi
Main outdoor window
2-16 Apr
The window this page is built around.
Timed from last spring frost
26 March
In Tongchuanshi, on your chosen risk.
Ready to pick
11 Jun - 1 Jul
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 Tongchuanshi
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
26 Feb - 12 Mar
Four weeks before your last frost, under cover or on a windowsill.
Sow direct
2-16 Apr
One week after your last frost.
Plant out
2-16 Apr
One week after your last frost.
In flower
11 Jun - 1 Jul
Cosmos through the year
Against the frost risk in Tongchuanshi
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 Tongchuanshi.
The median frost-free season here is 226 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 Tongchuanshi
Other flowers to time
Growing cosmos in Tongchuanshi
When should I plant cosmos in Tongchuanshi?
Aim for 2-16 Apr in an average year. If you would rather not gamble on the weather, wait until 20 Apr - 4 May - by then frost has finished in nine years out of ten.
When will cosmos be ready to harvest in Tongchuanshi?
Expect to start picking around 11 Jun - 1 Jul, 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.