When to sow astilbes in Manhattan

Why these dates

Plant dormant crowns in autumn or early spring, at soil level, in ground that stays reliably moist. Mulch after planting. In a dry summer it needs watering as a matter of routine rather than in emergencies.

Hardy to -35C and needs winter cold to break dormancy. Drought, not frost, is what kills it; a plant in dry shade will fail in its first summer.

Astilbes are planted once and then left in place, so there is no sowing offset to resolve. What matters in Manhattan is the shape of the year: this crop is dormant through the winter and is planted while it sleeps, any time between leaf fall in autumn and the restart of growth in spring, so long as the ground is neither frozen nor waterlogged. That is why the window below spans the cold months rather than sitting in the middle of the growing season.

Hardiness is not the obstacle here. Manhattan 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 2, and will then produce every year after that, which is what makes the planting decision worth getting right the first time.

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