Astilbe in Zone 4a & 4b

Astilbe x arendsii

When to plant astilbe in zone 4b

Zones 4a and 4b share the same average frost dates in our data, so this page covers both.

Method: Direct sow: Direct-sow outside. Astilbe doesn't transplant well, or doesn't need the extra time indoors.

Start indoors	Not typically started indoors
Direct sow / transplant outside	May 1–May 8
Estimated bloom	Apr 30 '28–May 7 '28 (First real harvest the season after planting)

Spacing: about 2 square feet per plant (square-foot-gardening spacing). Mature height: 1.5-4.5 ft.

Astilbe gives feathery plumes in shade, which is a rare combination. It asks for one thing in return and it does not negotiate.

How astilbe fits zone 4's season

Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Astilbe takes about 1 growing season to reach full flowering, so what matters here is how many of these seasons it gets, not whether one is long enough.

Astilbe is hardy in zones 3-9, so in zone 4b it stays in the ground through winter and comes back rather than being replanted. Allow about 1.5 ft of spread at maturity.

Good companions

No standout companions recorded yet for Astilbe.

Where to buy astilbe seeds

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