When to sow garden phlox in London

Why these dates

Plant out in spring after the last frost, or in autumn. Thin each clump to five or six stems in spring: crowded growth is what triggers the mildew, and a thinned plant flowers just as well. Divide every three years.

Hardy to -30C and fully dormant in winter. Needs a cold season to perform and is unsatisfactory in frost-free climates.

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. Garden phlox are timed with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for London.

London sits in zone 9a, which is milder than this crop wants, and a winter that never really arrives is its own problem. The dates below still describe the right time of year; the open question is survival rather than timing.

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.

See every crop timed for London →