Generally — Most Areas
heliotrope is grown as an annual, so season length decides it here, not a winter zone. Alaska's typical season runs ~147 frost-free days against the ~90 heliotrope needs — a workable window, but start indoors to bank time.
Sow by about Jul 11
Heliotrope is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 90 frost-free days and a typical Alaska season runs ~147 frost-free days, leaving 57 days of slack. That is a workable window rather than a generous one: sow by about Jul 11 — and start indoors to bank time — so it finishes before the usual first freeze (Sep 29).
Want more weeks at either end of that window? How to buy the weeks →
90 frost-free days required against Alaska’s ~147-day season. NOAA Regional Climate Centers ACIS 1991-2020 (28°F killing freeze), state median across counties, via stateClimateData.ts.
Your yard isn't the whole zone.
Heliotrope is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Alaska site runs ~147 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score heliotrope against your land's actual frost dates, sun, and soil.
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Zone Comparison
Heliotrope Needs
- USDA Zones: Data pending
- Frost-Free Days: 90+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~90 days of harvest
- Drought tolerance: Low
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
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Heliotrope 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.
When to start the seed
Those dates are when heliotrope goes out, not when it starts. It is sown under cover about 10 weeks ahead, so counting back from Alaska's late-side last freeze of May 15 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 80 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 52 days to spare even in Alaska's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — North Slope County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
Frost-free days
Heliotrope wants 90+ frost-free days; a typical Alaska site sees ~147 (NOAA Regional Climate Centers ACIS station record, 1991-2020). That leaves a workable window — start indoors to bank time.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS station record, 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
Heliotrope likes near-neutral soil (pH 6-7.5). 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 7 — 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 heliotrope is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how heliotrope performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Alaska soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Heliotrope in Alaska — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: Data pending (USDA PLANTS Database)
- State Zones: 1a-9a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 16 - May 15 to Sep 24 - Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 80 days
What Else to Consider for Heliotrope 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 heliotrope here specifically
Alaska's soils run mostly silt loam (Spodosols), and whether that suits heliotrope's pH 6.0–7.5 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward heliotrope's 6.0–7.5 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Alaska grower, not just heliotrope — 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 heliotrope to your county's window, not the statewide date.
Heliotrope needs about 90 days of frost-free season to complete its cycle. 27 of Alaska’s 28 counties give it that outright. The tightest that does is North Slope County at 98 frost-free days — 8 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Alaska’s 28 counties the frost-free season runs from 85 days in Southeast Fairbanks County to 240 days in Sitka County — a spread of 155 days, which is why a single statewide planting date misleads. The median Alaska county sees 147 frost-free days, leaving heliotrope about 57 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"). Heliotrope's 90-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Heliotrope draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, heliotrope 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.
Good to Know Before You Plant Heliotrope
Heliotrope is listed as toxic to dogs, cats (all) at a moderate level (Cornell). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Alaska this is a one-season plant and the first hard freeze (Sep 24 - Oct 29) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Heliotrope Varieties for Alaska
Alaska publishes no state variety trial for heliotrope, 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 heliotrope, the canonical source is UAF Cooperative Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Heliotrope native to Alaska?
No — the USDA PLANTS Database lists Heliotrope 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 Heliotrope in Alaska
When can I plant Heliotrope 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). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
Can Heliotrope mature before first frost in Alaska?
Yes — Heliotrope matures in 80 days (USDA PLANTS Database), and Alaska's dependable hard-freeze-free window runs 132 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 52 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Heliotrope grown in across Alaska?
Alaska spans USDA hardiness zones 1a-9a (USDA ARS PHZM 2023). Heliotrope carries a range of zones Data pending, 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). Heliotrope needs 90+ frost-free days, 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 Heliotrope native to Alaska?
No — the USDA PLANTS Database lists Heliotrope 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 Heliotrope in Alaska?
Heliotrope prefers pH 6-7.5 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 Heliotrope actually grow on my specific land in Alaska?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores heliotrope 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 heliotrope against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Alaska heliotrope 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 heliotrope average
Explore More
Growing guides for heliotrope
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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