Unlikely — Zone Mismatch
Guinea grass (zones 9-13) does not overlap with Delaware's zone range (7a-8a). Growing outdoors is unlikely without significant protection.
One zone short — what would close it
Guinea Grass is hardy to zone 9, and the warmest ground in Delaware is zone 8 — 1 zone short. Planted in open ground it will not survive a Delaware winter. To grow it here, grow guinea grass 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 9-13 (plant) against 7-8 (Delaware). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Guinea Grass in Delaware — the short answer
Guinea Grass in Delaware: hardy in zones 9–13, part sun, against a state median of ~241 frost-free days.
- Plant zones
- 9-13
- 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
- Delaware zones
- 7a-8a
- USDA PHZM 2023
- Frost window
- Mar 23 - Mar 23 – Nov 17 - Nov 19
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 238 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.
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 guinea grass against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Where Guinea Grass Stands in Delaware
Guinea Grass is rated for zones 9–13 — a cold floor USDA puts at 20 to 30°F. No Delaware 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 Delaware winters, not about guinea grass.
Below the zone 9 floor
3 counties
- Kent County · zone 7b
- New Castle County · zone 7b
- Sussex County · zone 7b
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
Guinea Grass Needs
- USDA Zones: 9-13
- Frost-Free Days: 70+
- Sun: Part Sun
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 9-13)
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 Guinea 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
Guinea Grass 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
Guinea 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.
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 guinea 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
Guinea Grass wants 70+ frost-free days; a typical Delaware site sees ~241 (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
Guinea Grass tolerates a wide pH range (pH 3.5-8.4) — 4.9 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 7 — worth knowing before you decide whether a Delaware soil test result is a problem or just a number. Drainage matters: this plant wants 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. Guinea 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 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. Delaware soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Guinea 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 guinea grass here specifically
Guinea Grass needs sharp drainage and sends deep roots; its growing tissue takes cold to about 32°F (FAO ECOCROP), but in Delaware, about 19.8% of soils are poorly-drained (SSURGO), and standing water is what actually kills it.
Build guinea grass up on a coarse, free-draining mound so its roots never sit in saturated soil. How to handle it →
What to actually do about these — and the constraints that apply to every Delaware grower, not just guinea grass — is covered on the Delaware growing guide.
Timing shifts within Delaware
Guinea Grass needs about 70 days of frost-free season to complete its cycle. Even Sussex County — Delaware’s shortest season at 238 frost-free days — clears that by 168 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"). Guinea Grass's 70-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 guinea 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 Guinea Grass in Delaware
When can I plant Guinea 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). Guinea Grass 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.
What hardiness zone is Guinea Grass grown in across Delaware?
Delaware spans USDA hardiness zones 7a-8a (USDA ARS PHZM 2023). Guinea Grass carries a range of zones 9-13, 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). Guinea Grass needs 70+ 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 Guinea Grass in Delaware?
Guinea Grass tolerates pH 3.5-8.4 and well (dry spells) drainage (FAO ECOCROP). That is a 4.9-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 Guinea Grass actually grow on my specific land in Delaware?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores guinea 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 guinea grass against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Delaware guinea 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 guinea grass average
Explore More
Growing guides for guinea grass
Explore Delaware county by county
Delaware carries 3 counties with their own USDA zone — a sample of the growing pages for guinea grass there:
Where else guinea grass grows
Guinea Grass's zone band crosses state lines — these are the states closest to Delaware 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 Delaware
Delaware has a growing page for 1,013 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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