When to sow wallflowers in Halifax

Why these dates

Sow in early summer, six weeks after the last frost, and pinch the tips once to make the plants bush. Move them to their final position in autumn, twenty weeks after the last frost, so the roots settle before winter. Flowering starts the following April and runs six weeks.

Hardy to about -20C. Clubroot is a real risk because it is a brassica, so do not plant it where cabbages grew; rotate it around the garden as you would a vegetable.

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. Wallflowers are timed with planting out 20 weeks after it, and this page simply resolves those offsets against the frost date computed for Halifax.

Hardiness is not the obstacle here. Halifax 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 Halifax 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.

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