Yes — Strong Match
shiso is grown as an annual, so season length decides it here, not a winter zone — and Rhode Island's typical season runs ~225 frost-free days against the ~80 shiso needs.
Sow by about Sep 5
Shiso is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 80 frost-free days and a typical Rhode Island season runs ~225 frost-free days, leaving 145 days of slack. That is room to sow as late as about Sep 5 and still finish before the usual first freeze (Nov 14).
Want more weeks at either end of that window? How to buy the weeks →
80 frost-free days required against Rhode Island’s ~225-day season. NOAA Regional Climate Centers ACIS 1991-2020 (28°F killing freeze), state median across counties, via stateClimateData.ts.
Shiso in Rhode Island — the short answer
Shiso in Rhode Island: full sun, against a state median of ~225 frost-free days.
- Rhode Island zones
- 6b-7b
- USDA PHZM 2023
- Frost window
- Mar 27 - Apr 3 – Nov 7 - Nov 21
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 210 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 70 days
- Growable Ground Plant Database
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.
Shiso is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Rhode Island site runs ~225 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 shiso against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Zone Comparison
Shiso Needs
- USDA Zones: Data pending
- Frost-Free Days: 80+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: High
Rhode Island Has
- USDA Zones: 6b-7b
- Last Hard Freeze (28°F): Mar 27 - Apr 3
- First Hard Freeze (28°F): Nov 7 - Nov 21
- Annual Rainfall: 44-52 inches
- Common Soils: Glacial till, Sandy loam, Coastal sand
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 Shiso in Rhode Island
The frost window
Across Rhode Island, the last spring hard freeze (28°F) clears between Mar 27 and Apr 3, and the first fall hard freeze lands between Nov 7 and Nov 21 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 218-day window you can count on — up to 239 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.
Frost tenderness
Shiso is frost-tender — FAO ECOCROP puts its killing temperature at 32°F — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
When to start the seed
Those dates are when shiso goes out, not when it starts. It is sown under cover about 4 weeks ahead, so counting back from Rhode Island's late-side last freeze of Apr 3 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 70 days to maturity (Growable Ground Plant Database), counting from the last hard freeze it ripens with 148 days to spare even in Rhode Island's tightest freeze scenario — room for a later start or a second sowing.
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
Frost-free days
Shiso wants 80+ frost-free days; a typical Rhode Island site sees ~225 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Shiso needs ~1400 GDD (base 50°F) to ripen. The state median runs ~2635 GDD (from PRISM 1991-2020 climate normals), so Rhode Island's typical season clears that easily.
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
Shiso likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Rhode Island's glacial till and sandy loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 5.5 and 6 — worth knowing before you decide whether a Rhode Island soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Rhode Island site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Rhode Island's soils run mostly fine sandy loam, but SSURGO maps the series, texture, and drainage under your exact parcel. Shiso needs about 19 inches of workable depth, so it is that horizon — not the surface — you are testing for. That map unit, not the state average, decides how shiso 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. Rhode Island soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant shiso for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before shiso goes in. What follows is Rhode Island’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Rhode Island — and how to grow with it.
We checked the federal record across Rhode Island — 7,250 documented sites across 7 of the 9 source types we track.
The most significant on record: 141 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Rhode Island carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources Checked
across Rhode Island
Severity Distribution
across Rhode Island
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Rhode Island, two things run higher than the national average across Rhode Island — Superfund (141 sites) and Toxics Release Inventory (446 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for Shiso in Rhode Island
Zone compatibility tells you about winter cold survival — but Rhode Island growers also need to think about:
Small lot sizes limit garden space in much of the state
Salt spray affects coastal plantings
Rocky glacial soils need clearing
Growing shiso here specifically
Rhode Island's soils run mostly fine sandy loam (Inceptisols), and whether that suits shiso's pH 5.5–7.5 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward shiso's 5.5–7.5 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Rhode Island grower, not just shiso — is covered on the Rhode Island growing guide.
Timing shifts within Rhode Island
Shiso needs about 80 days of frost-free season to complete its cycle. Even Providence County — Rhode Island’s shortest season at 210 frost-free days — clears that by 130 days, so season length isn’t the constraint anywhere in Rhode Island. What varies is your own parcel.
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"). Shiso's 80-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
Shiso draws honeybees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, shiso can only work that bloom inside Rhode Island's frost window — roughly 225 days, opening after the last 28°F freeze (Mar 27 - Apr 3) and closing at the first (Nov 7 - Nov 21), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant Shiso
Shiso is listed as toxic to dogs, cats (all) at a mild 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 Rhode Island this is a one-season plant and the first hard freeze (Nov 7 - Nov 21) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Shiso Varieties for Rhode Island
Rhode Island publishes no state variety trial for shiso, so we won't invent a "best for Rhode Island" list. Choose types rated to your USDA hardiness zone (6b-7b), and confirm winter survival and drainage against your own parcel.
Rhode Island Cooperative Extension
For Rhode Island-specific cultivar recommendations, planting calendars, and pest pressure for shiso, the canonical source is URI Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Shiso native to Rhode Island?
No — the USDA PLANTS Database lists Shiso as introduced rather than native in the Lower 48, so it is not part of Rhode Island's native flora. It grows here as a garden plant; pairing it with a few Rhode Island natives keeps local pollinators fed too.
Looking for plants that belong here? The Rhode Island 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 Shiso in Rhode Island
When can I plant Shiso in Rhode Island?
Rhode Island's last spring hard freeze (28°F) clears between Mar 27 and Apr 3, and the first fall hard freeze lands between Nov 7 and Nov 21 (NOAA Regional Climate Centers ACIS, 1991-2020). Shiso is frost-tender — its killing temperature is 32°F (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Shiso mature before first frost in Rhode Island?
Yes — Shiso matures in 70 days (Growable Ground Plant Database), and Rhode Island's dependable hard-freeze-free window runs 218 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 148 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 Shiso grown in across Rhode Island?
Rhode Island spans USDA hardiness zones 6b-7b (USDA ARS PHZM 2023). Shiso 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 Rhode Island site have?
A typical Rhode Island site sees ~225 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Shiso needs 80+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Shiso native to Rhode Island?
No — the USDA PLANTS Database lists Shiso as introduced rather than native in the Lower 48, so it is not part of Rhode Island's native flora. It grows here as a garden plant; pairing it with a few Rhode Island natives keeps local pollinators fed too.
How should I amend the soil for Shiso in Rhode Island?
Shiso prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Rhode Island soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Shiso actually grow on my specific land in Rhode Island?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores shiso 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 Rhode Island
State-level data is a sketch. Your Growable Ground report scores shiso against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Rhode Island shiso averages can't show:
We read public map data around Rhode Island — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Rhode Island shiso average
Explore More
Growing guides for shiso
Explore Rhode Island county by county
Rhode Island carries 5 counties with their own USDA zone — a sample of the growing pages for shiso there:
Where else shiso grows
Shiso's zone band crosses state lines — these are the states closest to Rhode Island 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 Rhode Island
Rhode Island has a growing page for 889 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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