Sweet alyssum · Zhaodong, Heilongjiang, China
When to sow sweet alyssum in Zhaodong
Main outdoor window
20 Apr - 18 May
The window this page is built around.
Timed from last spring frost
27 April
In Zhaodong, on your chosen risk.
Ready to pick
9-24 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 Zhaodong
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
2-30 Mar
Eight weeks before your last frost, under cover or on a windowsill.
Sow direct
20 Apr - 18 May
One week before your last frost.
Plant out
20 Apr - 18 May
One week before your last frost.
In flower
9-24 Jun
Sweet alyssum through the year
Against the frost risk in Zhaodong
Why these dates
Sow direct a week before the last frost, or start indoors eight weeks earlier for immediate effect. Shear the whole plant back by half when it stops flowering in midsummer heat and it will flower again within three weeks. Self-seeds into paving cracks and is welcome there.
Takes light frost to about -6C and often keeps flowering after the first autumn frosts have finished everything around it. In zone 9 and warmer it flowers through winter and behaves as a short-lived perennial.
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. Sweet alyssum are timed from 8 weeks before that frost for an indoor start, with planting out 1 weeks before it, and this page simply resolves those offsets against the frost date computed for Zhaodong.
Hardiness is not the obstacle here. Zhaodong is zone 4a, 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 161 days, against 50 to 65 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Zhaodong
Other flowers to time
Growing sweet alyssum in Zhaodong
When should I plant sweet alyssum in Zhaodong?
Aim for 20 Apr - 18 May in an average year. If you would rather not gamble on the weather, wait until 28 Apr - 26 May - by then frost has finished in nine years out of ten.
When will sweet alyssum be ready to harvest in Zhaodong?
Expect to start picking around 9-24 Jun, based on 50 to 65 days to maturity from the planting date calculated for this location.
How much frost will sweet alyssum tolerate?
Takes light frost to about -6C and often keeps flowering after the first autumn frosts have finished everything around it. In zone 9 and warmer it flowers through winter and behaves as a short-lived perennial.