Grecian windflower · Philadelphia, Pennsylvania, United States
When to sow grecian windflowers in Philadelphia
Main outdoor window
21 Sep - 5 Oct
The window this page is built around.
Timed from last spring frost
14 April
In Philadelphia, on your chosen risk.
Ready to pick
1 Mar - 30 Apr
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 Philadelphia
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
21 Sep - 5 Oct
Four to six weeks before your first frost, so roots form before the ground cools.
In flower
1 Mar - 30 Apr
Grecian windflowers through the year
Against the frost risk in Philadelphia
Why these dates
Soak the tubers overnight before planting - they arrive bone dry and dehydrated tubers frequently fail. Plant 5cm deep in early autumn, any way up; the growing point is impossible to identify and the tuber sorts itself out.
Hardy to about -20C. Flowers early enough that a hard frost sometimes catches open blooms, which recover. Goes fully dormant by midsummer and tolerates dry summer shade better than most spring bulbs.
Grecian windflowers 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 Philadelphia instead of forwards from its start.
Hardiness is not the obstacle here. Philadelphia is zone 7a, 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 202 days, against 140 to 180 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Philadelphia
Other flowers to time
Growing grecian windflowers in Philadelphia
When should I plant grecian windflowers in Philadelphia?
Aim for 21 Sep - 5 Oct in an average year. If you would rather not gamble on the weather, wait until 10-24 Sep - by then frost has finished in nine years out of ten.
When will grecian windflowers be ready to harvest in Philadelphia?
Expect to start picking around 1 Mar - 30 Apr, based on 140 to 180 days to maturity from the planting date calculated for this location.
How much frost will grecian windflowers tolerate?
Hardy to about -20C. Flowers early enough that a hard frost sometimes catches open blooms, which recover. Goes fully dormant by midsummer and tolerates dry summer shade better than most spring bulbs.