Kohlrabi · Philadelphia, Pennsylvania, United States
When to plant kohlrabi in Philadelphia
Main outdoor window
31 Mar - 14 Apr
The window this page is built around.
Timed from last spring frost
14 April
In Philadelphia, on your chosen risk.
Ready to pick
25 May - 14 Jun
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
10-24 Mar
Five weeks before your last frost, under cover or on a windowsill.
Sow for autumn
15 Jul - 5 Aug
Counting back 89 days from your first frost so the crop matures in time.
Sow direct
31 Mar - 14 Apr
Two weeks before your last frost.
Plant out
28 Apr - 12 May
Two weeks after your last frost.
Harvest
25 May - 14 Jun
Kohlrabi through the year
Against the frost risk in Philadelphia
Why these dates
Sow direct two weeks before the last frost and every three weeks after, avoiding high summer. A late-summer sowing crops into autumn.
Tolerates about -6C. The exposed stem is more vulnerable than a buried root would be, so a hard frost damages it directly.
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. Kohlrabi are timed from 5 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.
The median frost-free season here is 202 days, against 55 to 75 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Philadelphia
Other vegetables to time
Growing kohlrabi in Philadelphia
When should I plant kohlrabi in Philadelphia?
Aim for 31 Mar - 14 Apr in an average year. If you would rather not gamble on the weather, wait until 9-23 Apr - by then frost has finished in nine years out of ten.
When will kohlrabi be ready to harvest in Philadelphia?
Expect to start picking around 25 May - 14 Jun, based on 55 to 75 days to maturity from the planting date calculated for this location.
How much frost will kohlrabi tolerate?
Tolerates about -6C. The exposed stem is more vulnerable than a buried root would be, so a hard frost damages it directly.