Unlikely — Zone Mismatch
koronivia grass (zones 10-13) does not overlap with Delaware's zone range (7a-8a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Koronivia Grass is hardy to zone 10, and the warmest ground in Delaware is zone 8 — 2 zones short. Planted in open ground it will not survive a Delaware winter. To grow it here, grow koronivia grass under glass — a greenhouse is the only lift this wide the engine models.
A greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 10-13 (plant) against 7-8 (Delaware). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
Delaware spans zones 7a-8a, but your yard has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score koronivia grass against your land's actual soil, sun, and frost.
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Zone Comparison
Koronivia Grass Needs
- USDA Zones: 10-13
- Frost-Free Days: 90+
- Sun: Full Sun
- Mature size: 2 ft tall
- Drought tolerance: Medium
Delaware Has
- USDA Zones: 7a-8a
- Last Hard Freeze (28°F): Mar 23 - Mar 23
- First Hard Freeze (28°F): Nov 17 - Nov 19
- Annual Rainfall: 42-48 inches
- Common Soils: Sandy loam, Silt loam, Tidal marsh
Plant Zone Range (zones 10-13)
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 Koronivia Grass in Delaware
The frost window
Across Delaware, the last spring hard freeze (28°F) clears between Mar 23 and Mar 23, and the first fall hard freeze lands between Nov 17 and Nov 19 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 239-day window you can count on — up to 241 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
Koronivia Grass is frost-tender — its listed minimum temperature is 68°F (USDA PLANTS Database) — 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.
When to start the seed
Koronivia Grass is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Delaware's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Days to maturity vs. the window
At 120 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 119 days to spare even in Delaware's tightest freeze scenario — room for a later start or a second sowing.
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
The zone check says koronivia grass does not survive a Delaware winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Delaware under protection.
Frost-free days
Koronivia Grass wants 90+ frost-free days; a typical Delaware site sees ~241 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Koronivia Grass needs ~3000 GDD (base 50°F) to ripen. The state median runs ~3732 GDD (from PRISM 1991-2020 climate normals), so Delaware'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
Koronivia Grass tolerates a wide pH range (pH 4.5-7.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Delaware. 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 and 6 — worth knowing before you decide whether a Delaware soil test result is a problem or just a number. Drainage matters: this plant wants poorly (saturated >50% of year), well (dry spells). If your Delaware site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
SSURGO maps about 19.8% of Delaware as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Koronivia Grass sits mid-range for drought tolerance, so either extreme can cost you — your soil map unit, not the state average, is the real answer.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Delaware soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Koronivia Grass in Delaware — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 10-13 (USDA PLANTS Database)
- State Zones: 7a-8a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 23 - Mar 23 to Nov 17 - Nov 19 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 120 days
What Else to Consider for Koronivia Grass in Delaware
Zone compatibility tells you about winter cold survival — but Delaware growers also need to think about:
Sandy soils in southern DE drain too quickly
Salt spray damage near the coast
Rising water tables in low-lying areas
Growing koronivia grass here specifically
Koronivia Grass roots run medium and prefer pH 4.5–7.5, but drainage comes first here: SSURGO maps about 19.8% of Delaware as poorly or somewhat-poorly drained, and wet ground rots its roots before pH ever matters.
Plant koronivia grass on a raised, gravel-amended berm so water drains fast and the roots stays dry. How to handle it →
What to actually do about these — and the constraints that apply to every Delaware grower, not just koronivia grass — is covered on the Delaware growing guide.
Timing shifts within Delaware
Koronivia Grass needs about 90 days of frost-free season to complete its cycle. Even Sussex County — Delaware’s shortest season at 238 frost-free days — clears that by 148 days, so season length isn’t the constraint anywhere in Delaware. 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"). Koronivia 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.
Delaware Cooperative Extension
For Delaware-specific cultivar recommendations, planting calendars, and pest pressure for koronivia grass, the canonical source is University of Delaware Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Koronivia Grass in Delaware
When can I plant Koronivia Grass in Delaware?
Delaware's last spring hard freeze (28°F) clears between Mar 23 and Mar 23, and the first fall hard freeze lands between Nov 17 and Nov 19 (NOAA Regional Climate Centers ACIS, 1991-2020). Koronivia Grass is frost-tender — its listed minimum temperature is 68°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Koronivia Grass mature before first frost in Delaware?
Yes — Koronivia Grass matures in 120 days (USDA PLANTS Database), and Delaware's dependable hard-freeze-free window runs 239 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 119 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 Koronivia Grass grown in across Delaware?
Delaware spans USDA hardiness zones 7a-8a (USDA ARS PHZM 2023). Koronivia Grass carries a range of zones 10-13, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Delaware site have?
A typical Delaware site sees ~241 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Koronivia 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.
How should I amend the soil for Koronivia Grass in Delaware?
Koronivia Grass tolerates pH 4.5-7.5 and poorly (saturated >50% of year), well (dry spells) drainage (FAO ECOCROP). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Delaware site — amend for drainage and organic matter first.
Will Koronivia Grass actually grow on my specific land in Delaware?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores koronivia 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 Delaware
State-level data is a sketch. Your Growable Ground report scores koronivia grass against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Delaware koronivia grass averages can't show:
We read public map data around Delaware — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Delaware koronivia grass average
Explore More
Growing guides for koronivia grass
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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