Dahlia · Guangzhou, Guangdong, China
When to sow dahlias in Guangzhou
Main outdoor window
24 Jan - 21 Feb
The window this page is built around.
Timed from last spring frost
10 January
In Guangzhou, on your chosen risk.
Ready to pick
1 Jul - 31 Oct
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 Guangzhou
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 tubers
24 Jan - 21 Feb
After the last frost, once the soil has warmed. This crop is never fully dormant, so it cannot be planted bare-root in winter.
In flower
1 Jul - 31 Oct
Dahlias through the year
Against the frost risk in Guangzhou
Why these dates
Plant tubers two weeks after your last frost, once the soil has reached about 13C, 15cm deep with the crown upward. For earlier flowers, start them in pots under cover six weeks before that and plant out as growing plants. Pinch the leading shoot at 40cm to get a bushy plant rather than one tall stem.
Top growth is blackened by the first touch of frost at about -1C, which is what ends the season. The tuber below ground survives a light frost but not a frozen soil, so in zone 7 and colder lift it a week or two after the tops are killed, dry it off and store it somewhere frost-free.
Dahlias are planted once and then left in place, so there is no sowing offset to resolve. Nor is there a dormant season to plant into: this crop keeps its leaves and keeps growing through the winter, which is exactly why cold damages it. The window on this page therefore waits until the last frost in Guangzhou has passed and the soil has begun to warm, giving the roots the longest possible run before the cold returns.
Hardiness is not the obstacle here. Guangzhou is zone 10a, comfortably inside the range this crop is rated for, so an established plant should come through an average winter without protection.
Also in Guangzhou
Other flowers to time
Growing dahlias in Guangzhou
When should I plant dahlias in Guangzhou?
Aim for 24 Jan - 21 Feb in an average year. If you would rather not gamble on the weather, wait until 14 Feb - 14 Mar - by then frost has finished in nine years out of ten.
When will dahlias be ready to harvest in Guangzhou?
Expect to start picking around 1 Jul - 31 Oct, based on 80 to 110 days to maturity from the planting date calculated for this location.
How much frost will dahlias tolerate?
Top growth is blackened by the first touch of frost at about -1C, which is what ends the season. The tuber below ground survives a light frost but not a frozen soil, so in zone 7 and colder lift it a week or two after the tops are killed, dry it off and store it somewhere frost-free.