Bupleurum (Thoroughwax) in Zone 3a & 3b
Bupleurum rotundifolium
When to plant bupleurum (thoroughwax) in zone 3b
Zones 3a and 3b share the same average frost dates in our data, so this page covers both.
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Bupleurum (Thoroughwax) tolerates either.
| Start indoors | Apr 11–Apr 18 |
|---|---|
| Direct sow / transplant outside | May 16–May 23 |
| Estimated bloom | Aug 14–Aug 21 (~90 days after planting) |
Spacing: 2 per square foot (square-foot-gardening spacing). Mature height: 2-3 ft.
Bupleurum, also called thoroughwax, is a chartreuse-toned filler flower that reads more like foliage than bloom in a bouquet, useful for softening bolder cut flowers without pulling attention away from them.
How bupleurum (thoroughwax) fits zone 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. Bupleurum (Thoroughwax) needs about 90 days from sowing to first harvest.
Good companions
No standout companions recorded yet for Bupleurum (Thoroughwax).
Where to buy bupleurum seeds
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See it growing
Search YouTube for "growing bupleurum (thoroughwax)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 3b calendar · Full companion planting guide · Full plant profile · Plan your beds in the Garden Designer →
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Growing Bupleurum (Thoroughwax) in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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