Sweet alyssum · Xinji, Hebei, China
When to sow sweet alyssum in Xinji
Main outdoor window
23 Mar - 20 Apr
The window this page is built around.
Timed from last spring frost
30 March
In Xinji, on your chosen risk.
Ready to pick
12-27 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 Xinji
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 Feb - 2 Mar
Eight weeks before your last frost, under cover or on a windowsill.
Sow direct
23 Mar - 20 Apr
One week before your last frost.
Plant out
23 Mar - 20 Apr
One week before your last frost.
In flower
12-27 May
Sweet alyssum through the year
Against the frost risk in Xinji
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 Xinji.
Hardiness is not the obstacle here. Xinji is zone 7b, 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 223 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 Xinji
Other flowers to time
Growing sweet alyssum in Xinji
When should I plant sweet alyssum in Xinji?
Aim for 23 Mar - 20 Apr in an average year. If you would rather not gamble on the weather, wait until 7 Apr - 5 May - by then frost has finished in nine years out of ten.
When will sweet alyssum be ready to harvest in Xinji?
Expect to start picking around 12-27 May, 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.