Crown imperial · Kaifeng, Henan, China
When to sow crown imperials in Kaifeng
Main outdoor window
5-19 Oct
The window this page is built around.
Timed from last spring frost
22 March
In Kaifeng, on your chosen risk.
Ready to pick
1 Apr - 31 May
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 Kaifeng
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 bulbs
5-19 Oct
Four to six weeks before your first frost, so roots form before the ground cools.
In flower
1 Apr - 31 May
Crown imperials through the year
Against the frost risk in Kaifeng
Why these dates
Plant in early autumn, as early as the bulbs can be bought, and deep - 20cm. The bulbs have a hollow crown that collects water and rots, so plant them at a slight tilt or on a handful of grit. They resent disturbance and often skip a year after being moved.
Hardy to about -25C. The smell deters mice and voles, which is a genuine advantage in a garden where tulips get eaten. Needs cold winters and dislikes hot wet summers.
Crown imperials 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 Kaifeng instead of forwards from its start.
Hardiness is not the obstacle here. Kaifeng is zone 8a, comfortably inside the range this crop is rated for, so an established plant should come through an average winter without protection.
The median frost-free season here is 240 days, against 160 to 200 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Kaifeng
Other flowers to time
Growing crown imperials in Kaifeng
When should I plant crown imperials in Kaifeng?
Aim for 5-19 Oct in an average year. If you would rather not gamble on the weather, wait until 21 Sep - 5 Oct - by then frost has finished in nine years out of ten.
When will crown imperials be ready to harvest in Kaifeng?
Expect to start picking around 1 Apr - 31 May, based on 160 to 200 days to maturity from the planting date calculated for this location.
How much frost will crown imperials tolerate?
Hardy to about -25C. The smell deters mice and voles, which is a genuine advantage in a garden where tulips get eaten. Needs cold winters and dislikes hot wet summers.