Ageratum (Flossflower) in Zone 9a & 9b

Ageratum houstonianum

When to plant ageratum (flossflower) in zone 9b

Zones 9a and 9b share the same average frost dates in our data, so this page covers both.

Method: Start indoors: Start indoors from seed, then transplant outside. Ageratum (Flossflower) needs a head start most zones can't give it by direct-sowing alone.

Start indoors	Dec 28–Jan 4 '27
Direct sow / transplant outside	Feb 22–Mar 1
Estimated bloom	May 8–May 15 (~75 days after transplanting)

Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 1-2 ft.

Ageratum, also known as flossflower or blue mink, is a fuzzy-textured filler flower that's a classic choice for the back of a bed or a mass planting, needing no pinching or staking along the way.

How ageratum (flossflower) fits zone 9's season

Zone 9b's frost-free window runs about 293 days, from February 15 to December 5. Ageratum (Flossflower) needs about 75 days from transplant to first harvest.

Good companions

No standout companions recorded yet for Ageratum (Flossflower).

Where to buy ageratum seeds

See why we recommend these suppliers →

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See it growing

Search YouTube for "growing ageratum (flossflower)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)

← Back to the full zone 9b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →

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Growing Ageratum (Flossflower) in USDA zone 9b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.

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