Hyssop · London, England, United Kingdom
When to plant hyssop in London
Main outdoor window
28 Apr - 26 May
The window this page is built around.
Timed from last spring frost
14 April
In London, on your chosen risk.
Ready to pick
1 Jun - 30 Sep
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 London
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
17 Feb - 17 Mar
Eight weeks before your last frost, under cover or on a windowsill.
Plant out
28 Apr - 26 May
Two weeks after your last frost.
Harvest
1 Jun - 30 Sep
Hyssop through the year
Against the frost risk in London
Why these dates
Very hardy, to about -25C.
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. Hyssop 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 London.
Hardiness is not the obstacle here. London is zone 9a, 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.
Growing hyssop in London
When should I plant hyssop in London?
Aim for 28 Apr - 26 May in an average year. If you would rather not gamble on the weather, wait until 19 May - 16 Jun - by then frost has finished in nine years out of ten.
When will hyssop be ready to harvest in London?
Expect to start picking around 1 Jun - 30 Sep, based on 90 to 110 days to maturity from the planting date calculated for this location.
How much frost will hyssop tolerate?
Very hardy, to about -25C.