Conditional — Some Areas
plumbago (zones 9-11) reaches only part of Alaska (1a-9a): zone 9 are in range, so where you are in the state decides it.
One zone short — what would close it
Plumbago is hardy to zone 9, and the warmest ground in Alaska is zone 8 — 1 zone short. Planted in open ground it will not survive a Alaska winter. To grow it here, grow plumbago in a hoop house or unheated greenhouse — its modeled 1.5-zone lift covers this gap.
A hoop house or unheated greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 9-11 (plant) against 1-8 (Alaska). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Plumbago in Alaska — the short answer
Plumbago in Alaska: hardy in zones 9–11, full sun, against a state median of ~147 frost-free days.
- Plant zones
- 9-11
- 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
- Alaska zones
- 1a-9a
- USDA PHZM 2023
- Frost window
- Apr 16 - May 15 – Sep 24 - Oct 29
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 85 days
- NOAA Regional Climate Centers ACIS station record, 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.
Alaska spans zones 1a-9a, 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 plumbago against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Alaska is not one climate
A single Alaska answer averages 28 counties whose growing seasons are 155 days apart — from 85 frost-free days in Southeast Fairbanks County to 240 in Sitka County. Which end of that your land sits nearer changes what plumbago can finish before the first hard freeze.
The middle half of 28 counties runs 118–196 days, with a median of 145 days — a 155-day span end to end.
Measured across 28 Alaska counties. NOAA Regional Climate Centers ACIS station record, 1991-2020, county 28°F killing freeze. 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 Plumbago Stands in Alaska
Plumbago is rated for zones 9–11 — a cold floor USDA puts at 20 to 30°F. No Alaska county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Alaska winters, not about plumbago.
Below the zone 9 floor
30 counties
- Aleutians East County · zone 3a-4b
- Aleutians West County · zone 3a-4b
- Anchorage County · zone 3a-4b
3 of 30 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.
Zone Comparison
Plumbago Needs
- USDA Zones: 9-11
- Sun: Full Sun
- Mature size: 6 ft tall
- Picking window: ~120 days of harvest
- Drought tolerance: High
Alaska Has
- USDA Zones: 1a-9a
- Last Hard Freeze (28°F): Apr 16 - May 15
- First Hard Freeze (28°F): Sep 24 - Oct 29
- Annual Rainfall: 10-160 inches
- Common Soils: Permafrost, Glacial silt, Volcanic ash
Plant Zone Range (zones 9-11)
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 Plumbago in Alaska
The frost window
Across Alaska, the last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 132-day window you can count on — up to 196 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
Alaska runs as cold as USDA zone 1, and no sourced winter-hardiness floor is on record for plumbago, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether plumbago is a permanent planting or a replant-every-spring crop for you turns on your own zone within Alaska; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — North Slope County, not the statewide average.
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.
Soil + Drainage Fit
Plumbago likes near-neutral soil (pH 5.5-7). That's the common-ground band across Alaska's permafrost and glacial silt — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6 and 6.5 — worth knowing before you decide whether a Alaska soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Alaska site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Alaska's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for plumbago is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how plumbago performs.
Check your parcel → Source: USDA NRCS SSURGO.
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. Alaska soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Plumbago in Alaska
Zone compatibility tells you about winter cold survival — but Alaska growers also need to think about:
Extremely short growing season (70-110 frost-free days)
Permafrost prevents deep root growth in many areas
Limited soil development in glacial terrain
Growing plumbago here specifically
Alaska's soils run mostly silt loam (Spodosols), and whether that suits plumbago's pH 5.5–7.0 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward plumbago's 5.5–7.0 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Alaska grower, not just plumbago — is covered on the Alaska growing guide.
Timing shifts within Alaska
Alaska isn't one climate. In North Slope County, the last hard freeze (28°F) holds until about Jun 7 — roughly 33 days later than the recorded state median — so plant plumbago to your county's window, not the statewide date.
County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Where in Alaska Plumbago Is Zone-Hardy
Plumbago is rated for USDA zones 9–11. No Alaska county reaches it. Even Yukon-Koyukuk County, the state’s mildest winter at zone 3a-4b, sits below the plant’s zone 9 floor — so in open ground this one needs winter protection here, or a container that comes under cover.
Across those 30 counties Alaska’s winter-low ladder runs from zone 3a-4b in Aleutians East County to zone 3a-4b in Yukon-Koyukuk County — 1.5 USDA zones of spread, which is 15°F between the two counties’ average coldest night of the year. None of that range reaches the band plumbago needs, so here the statewide answer really is the answer.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. Plumbago’s zone 9–11 band: USDA PLANTS / Growable Ground plant database. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Plumbago draws honeybees and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, plumbago can only work that bloom inside Alaska's frost window — roughly 147 days, opening after the last 28°F freeze (Apr 16 - May 15) and closing at the first (Sep 24 - Oct 29), per NOAA Regional Climate Centers ACIS station record, 1991-2020.
Recommended Plumbago Varieties for Alaska
Alaska publishes no state variety trial for plumbago, so we won't invent a "best for Alaska" list. Choose types rated to your USDA hardiness zone (1a-9a), and confirm winter survival and drainage against your own parcel.
Alaska Cooperative Extension
For Alaska-specific cultivar recommendations, planting calendars, and pest pressure for plumbago, the canonical source is UAF Cooperative Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Plumbago native to Alaska?
No — the USDA PLANTS Database lists Plumbago as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
Looking for plants that belong here? The Alaska 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 Plumbago in Alaska
When can I plant Plumbago in Alaska?
Alaska's last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Plumbago, so this page does not state whether it overwinters in Alaska 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 Plumbago grown in across Alaska?
Alaska spans USDA hardiness zones 1a-9a (USDA ARS PHZM 2023). Plumbago carries a range of zones 9-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Alaska site have?
A typical Alaska site sees ~147 frost-free days per year (derived from NOAA Regional Climate Centers ACIS station record, 1991-2020). Plumbago should be matched against that window, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like North Slope, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Plumbago native to Alaska?
No — the USDA PLANTS Database lists Plumbago as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
How should I amend the soil for Plumbago in Alaska?
Plumbago prefers pH 5.5-7 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Alaska soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Plumbago actually grow on my specific land in Alaska?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores plumbago 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 Alaska
State-level data is a sketch. Your Growable Ground report scores plumbago against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Alaska plumbago averages can't show:
We read public map data around Alaska — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alaska plumbago average
Explore More
Growing guides for plumbago
Explore Alaska county by county
Alaska carries 30 counties with their own USDA zone — a sample of the growing pages for plumbago there:
Where else plumbago grows
Plumbago's zone band crosses state lines — these are the states closest to Alaska 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 Alaska
Alaska has a growing page for 1,020 plants — a rotating sample of the rest of the shelf.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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