Foxglove · Philadelphia, Pennsylvania, United States
When to sow foxgloves in Philadelphia
Main outdoor window
26 May - 23 Jun
The window this page is built around.
Timed from last spring frost
14 April
In Philadelphia, on your chosen risk.
Ready to pick
1 Jun - 31 Jul
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.
Sow direct
26 May - 23 Jun
Six weeks after your last frost.
Move to final position
1-29 Sep
20 weeks after your last frost.
In flower
1 Jun - 31 Jul
Foxgloves through the year
Against the frost risk in Philadelphia
Why these dates
Sow on the surface in early summer, about six weeks after the last frost; the seed is dust-fine and needs light. Move the rosettes to their final position in autumn, twenty weeks after the last frost, and they will flower the following June. Leave one spire to seed and you will never sow it again.
Hardy to about -20C as an overwintering rosette, which is the form it spends the winter in. It needs that cold winter to trigger flowering, so it performs poorly in zone 10 and is treated as an annual bedding plant there.
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. Foxgloves are timed with planting out 20 weeks after it, and this page simply resolves those offsets against the frost date computed for Philadelphia.
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.
This is a two-season crop, so the dates above describe a sowing in one year and a flowering in the next. The plant spends the winter in the ground as a small rosette, which is why the frost-free season in Philadelphia does not limit it the way it would limit a tomato: it is not trying to finish before the cold arrives, it is trying to be well enough rooted to sit through it. Sowing too late is the real risk, because a plant that goes into winter undersized often fails to flower at all the following year.
Also in Philadelphia
Other flowers to time
Growing foxgloves in Philadelphia
When should I plant foxgloves in Philadelphia?
Aim for 26 May - 23 Jun in an average year. If you would rather not gamble on the weather, wait until 4 Jun - 2 Jul - by then frost has finished in nine years out of ten.
When will foxgloves be ready to harvest in Philadelphia?
Expect to start picking around 1 Jun - 31 Jul, based on 330 to 380 days to maturity from the planting date calculated for this location.
How much frost will foxgloves tolerate?
Hardy to about -20C as an overwintering rosette, which is the form it spends the winter in. It needs that cold winter to trigger flowering, so it performs poorly in zone 10 and is treated as an annual bedding plant there.