Rock Soapwort in Zone 5a & 5b

Saponaria ocymoides

When to plant rock soapwort in zone 5b

Zones 5a and 5b share the same average frost dates in our data, so this page covers both.

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

Start indoors	Not typically started indoors
Direct sow / transplant outside	Apr 26–May 3
Estimated bloom	Apr 25 '28–May 2 '28 (First real harvest the season after planting)

Spacing: about 2 square feet per plant (square-foot-gardening spacing). Mature height: 6-9 in.

Rock soapwort is a trailing rock-garden perennial, and it is a different plant from the soapwort already in this dataset.

How rock soapwort fits zone 5's season

Zone 5b's frost-free window runs about 148 days, from May 10 to October 5. Rock Soapwort 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.

Rock Soapwort is hardy in zones 2-9, so in zone 5b 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 Rock Soapwort.

Where to buy rock soapwort seeds

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