Generally — Most Areas
bottlebrush grass (zones 5-8) suits most of Montana (3a-6b) — zones 5-6 are in range, and the rest of the state is the exception.
Bottlebrush Grass in Montana — the short answer
Bottlebrush Grass in Montana: hardy in zones 5–8, full sun, against a state median of ~151 frost-free days.
- Plant zones
- 5-8
- 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
- Montana zones
- 3a-6b
- USDA PHZM 2023
- Frost window
- May 2 - May 13 – Sep 28 - Oct 7
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 59 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Montana spans zones 3a-6b, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score bottlebrush grass against your parcel's actual hardiness, soil, and sun.
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Montana is not one climate
Montana’s winter-low ladder runs across 56 counties, from zone 3.5 in Daniels County to zone 6 in Sanders County. That is 25°F between the two counties’ average coldest night — the difference between bottlebrush grass overwintering in the ground and coming under cover.
The middle half of 56 counties runs 4–5 zones, with a median of 4.5 zones — a 2.5-zone span end to end.
Measured across 56 Montana counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Montana Fits Best
Bottlebrush Grass is rated for zones 5–8 — a cold floor USDA puts at -20 to -10°F. Against Montana’s 56 counties that band holds in 17 of them, and the line runs at Beaverhead County (zone 5a), the coldest county still inside it.
Inside zones 5–8
17 counties
- Carbon County · zone 5a
- Gallatin County · zone 5a
- Granite County · zone 5a
3 of 17 shown
Below the zone 5 floor
39 counties
- Daniels County · zone 3b
- Roosevelt County · zone 3b
- Sheridan County · zone 3b
3 of 39 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Even within Montana's zones 3a-6b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for bottlebrush grass (USDA PHZM 2023):
Zone Comparison
Bottlebrush Grass Needs
- USDA Zones: 5-8
- Frost-Free Days: 90+
- Sun: Full Sun
Montana Has
- USDA Zones: 3a-6b
- Last Hard Freeze (28°F): May 2 - May 13
- First Hard Freeze (28°F): Sep 28 - Oct 7
- Annual Rainfall: 10-20 inches
- Common Soils: Sandy loam, Clay, Glacial till
Plant Zone Range (zones 5-8)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Bottlebrush Grass in Montana
The frost window
Across Montana, the last spring hard freeze (28°F) clears between May 2 and May 13, and the first fall hard freeze lands between Sep 28 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 138-day window you can count on — up to 158 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Winter standing
Montana runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for bottlebrush grass, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether bottlebrush grass is a permanent planting or a replant-every-spring crop for you turns on your own zone within Montana; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says bottlebrush grass survives winter in part of Montana, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Bottlebrush Grass wants 90+ frost-free days; a typical Montana site sees ~151 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Bottlebrush Grass tolerates a wide pH range (pH 5-8.2) — 3.2 units, acid ground through alkaline — so soil acidity is rarely what limits it in Montana. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Montana soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells), excessive (dry/moderately dry). If your Montana site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Montana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Bottlebrush Grass in Montana
Zone compatibility tells you about winter cold survival — but Montana growers also need to think about:
Very short growing season (60-100 frost-free days)
Low rainfall requires irrigation in most areas
Extreme winter cold (-40F possible)
What to actually do about these — and the constraints that apply to every Montana grower, not just bottlebrush grass — is covered on the Montana growing guide.
Timing shifts within Montana
Bottlebrush Grass needs about 90 days of frost-free season to complete its cycle. 55 of Montana’s 56 counties give it that outright. The tightest that does is Gallatin County at 114 frost-free days — 24 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Montana’s 56 counties the frost-free season runs from 59 days in Deer Lodge County to 170 days in Petroleum County — a spread of 111 days, which is why a single statewide planting date misleads. The median Montana county sees 151 frost-free days, leaving bottlebrush grass about 61 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Bottlebrush Grass's 90-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Montana Cooperative Extension
For Montana-specific cultivar recommendations, planting calendars, and pest pressure for bottlebrush grass, the canonical source is Montana State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Bottlebrush Grass native to Montana?
Bottlebrush Grass is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Montana. It can still earn a place in a Montana garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Montana growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Bottlebrush Grass in Montana
When can I plant Bottlebrush Grass in Montana?
Montana's last spring hard freeze (28°F) clears between May 2 and May 13, and the first fall hard freeze lands between Sep 28 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Bottlebrush Grass, so this page does not state whether it overwinters in Montana and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Bottlebrush Grass grown in across Montana?
Montana spans USDA hardiness zones 3a-6b (USDA ARS PHZM 2023). Bottlebrush Grass carries a range of zones 5-8, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Montana site have?
A typical Montana site sees ~151 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Bottlebrush Grass needs 90+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Bottlebrush Grass native to Montana?
Bottlebrush Grass is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Montana. It can still earn a place in a Montana garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Bottlebrush Grass in Montana?
Bottlebrush Grass tolerates pH 5-8.2 and well (dry spells), excessive (dry/moderately dry) drainage (FAO ECOCROP). That is a 3.2-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Montana site — amend for drainage and organic matter first.
Will Bottlebrush Grass actually grow on my specific land in Montana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores bottlebrush grass against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Montana
State-level data is a sketch. Your Growable Ground report scores bottlebrush grass against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Montana bottlebrush grass averages can't show:
We read public map data around Montana — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Montana bottlebrush grass average
Explore More
Growing guides for bottlebrush grass
Explore Montana county by county
Montana carries 56 counties with their own USDA zone — a sample of the growing pages for bottlebrush grass there:
Where else bottlebrush grass grows
Bottlebrush Grass's zone band crosses state lines — these are the states closest to Montana in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Montana
Montana has a growing page for 747 plants — a rotating sample of the rest of the shelf.
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