Clethra is a perennial grown for its white blooms, which open in summer and return year after year. It's hardy across USDA zones 5 through 11. Its summer flowers are a real draw for honeybees, native bees, and butterflies.
Clethra — the short answer
Clethra: grown in zones 5–11, part sun, pH 4.5–7.
- USDA zones
- 5–11
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Soil pH
- 4.5–7
- USDA PLANTS
- Sun
- Part Sun
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — each tile names its own row's source, because per-field provenance varies.
Score Clethra on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether clethra actually takes — and those shift from one yard to the next. Enter your address and we'll score clethra against your land's real conditions.
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What Clethra is
Clethra grows as a perennial and reaches around eight feet at maturity. It blooms white in summer.
How to grow Clethra
Clethra grows in USDA zones 5 through 11. Clethra does best in part sun — at least 4 hours of direct sun a day — and soil from pH 4.5 to 7. It needs a growing season of at least 150 frost-free days and about 500 hours of winter chill, which is why climate matters as much as soil.
USDA Zones
5-11
USDA PHZM 2023
Soil pH
4.5 - 7
USDA PLANTS
Sun
Part Sun
Growable Ground plant catalog
Drainage
Data pending
Growable Ground plant catalog
Cold Hardiness
-23°F
The coldest temperature this plant is documented to survive.
USDA PLANTS
Mature Height
8 ft
Growable Ground plant catalog
Chill Hours
500+
Winter hours below ~45°F it needs to fruit — too-mild winters can leave it bloom-shy.
Growable Ground plant catalog
Frost-Free Days
150+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant clethra in part sun with at least 4 hours of direct sun.
Match the soil
Clethra prefers pH 4.5 to 7 (USDA PLANTS). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water steadily
Keep the root zone evenly moist through establishment. Match watering to the plant's drainage preference and your local rainfall.
Harvest at its peak
Cut clethra blooms in the cool of the morning, just as they open, for the longest display.
Where Clethra thrives
Clethra is hardy across USDA zones 5 through 11. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 5–11 spans average winter lows from -20°F to 50°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 29 outright and splits 21 more down the middle — and which side of that line your land sits on changes the answer.
Zones 5–11·Where Clethra growsOpen map →
Where Clethra stands, state by state
Clethra is rated for zones 5–11 — a cold floor USDA puts at -20 to -10°F. Across the 50 states and DC, 29 sit fully inside that band, the line runs through 21 more, and 1 sits outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 5–11
29 states
3 of 29 shown
The line runs through
21 states
3 of 21 shown
Clethra’s band covers part of each of these states — which side of the line your county sits on changes the answer, and each state page draws it.
Outside zones 5–11
1 state
- North Dakota · zones 3b-4b
Winter cold is the limit here — the same plant often works in a container that comes under cover. Each link is that state’s own growing hub.
State zone extents: USDA Plant Hardiness Zone Map (PHZM) 2023. A zone is a 10°F band of average annual extreme minimum temperature, so a state that splits the band contains the boundary — its own page draws the county line, and a parcel report resolves which side your land sits on.
What grows around Clethra
Growing guides for clethra
In rotation planning, clethra counts as a Other — beds recover best when other crops don’t follow each other in the same spot year over year. (Growable Ground derivation — crop-rotation group from botanical family)
Good to know
Good news for pet owners — clethra isn't known to be toxic to dogs or cats. (Source: ASPCA.)
Clethra is a standout pollinator plant — high value to bees and other pollinators. (Source: Xerces Society.)
Your land is one point inside Clethra's range
This page resolves to the species. Your state page draws the county line, and a report reads the parcel — the soil pH, drainage, sun, and frost dates on your exact ground, which no species average can see.
See if Clethra will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether clethra actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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How we know this about Clethra
The figures above are cited per row, not per site: the pH band names this plant’s own source column, the three temperature figures each carry their own, and days-to-maturity cites the publication that actually lists it. All of it comes from the Growable Ground Plant Database — a compilation over FAO ECOCROP, USDA PLANTS, and university Extension sources, published openly with per-field provenance.
Grounded inUSDA PLANTS Database•USDA PHZM•ASPCA
Frequently asked questions
Can I grow Clethra in my zone?
Clethra grows in USDA hardiness zones 5 through 11 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
When should you plant Clethra?
Time clethra to your own season rather than the calendar, leaving enough of the season for its 150-day frost-free need. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Clethra need?
Clethra does well in partial sun — around 4 hours of direct sun, and it takes some afternoon shade in stride. That flexibility makes it a good match for a bed the house or a nearby tree shades for part of the day. A Growable Ground report maps how the sun actually falls on your land, hour by hour, so you can set it where the light lines up.
What soil does Clethra need?
Clethra prefers soil pH 4.5 to 7 (USDA PLANTS). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Clethra attract pollinators?
Yes — clethra's flowers are a strong nectar and pollen source for honeybees, native bees, and butterflies. (Source: Xerces Society.)
Is Clethra safe for pets?
Clethra is not known to be toxic to dogs or cats based on available data. Always supervise pets around new plantings. (Source: ASPCA.)