Lupin · Philadelphia, Pennsylvania, United States
When to sow lupins in Philadelphia
Main outdoor window
31 Mar - 28 Apr
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.
Start indoors
9 Jun - 7 Jul
Eight weeks before your last frost, under cover or on a windowsill.
Sow direct
31 Mar - 28 Apr
Two weeks before your last frost.
Plant out
28 Apr - 26 May
Two weeks after your last frost.
In flower
1 Jun - 31 Jul
Lupins through the year
Against the frost risk in Philadelphia
Why these dates
Sow direct a fortnight before the last frost, or start indoors eight weeks earlier - the seed germinates much better if chipped or soaked overnight first. Plants flower in their second year and are usually past their best by their fourth, so sow a few every year. Cut the spent spikes to get a second flush.
Hardy to -30C. Slugs destroy the emerging spring crowns far more often than frost does, and a wet winter on clay rots the deep taproot.
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. Lupins are timed from 8 weeks before that frost for an indoor start, with planting out 2 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.
Do not expect a crop in the first year. A plant set out now should give its first worthwhile pick around year 1, and will then produce every year after that, which is what makes the planting decision worth getting right the first time.
Also in Philadelphia
Other flowers to time
Growing lupins in Philadelphia
When should I plant lupins in Philadelphia?
Aim for 31 Mar - 28 Apr in an average year. If you would rather not gamble on the weather, wait until 9 Apr - 7 May - by then frost has finished in nine years out of ten.
When will lupins be ready to harvest in Philadelphia?
Expect to start picking around 1 Jun - 31 Jul, based on 120 to 150 days to maturity from the planting date calculated for this location.
How much frost will lupins tolerate?
Hardy to -30C. Slugs destroy the emerging spring crowns far more often than frost does, and a wet winter on clay rots the deep taproot.