Cool-season vs. warm-season grass - which do you have?
Short answer: Cool-season grasses such as tall fescue, Kentucky bluegrass and perennial ryegrass grow best at about 60 to 75°F and peak in spring and fall. Warm-season grasses such as bermudagrass, zoysia, St. Augustinegrass and centipedegrass grow best at about 80 to 95°F, peak in summer, and turn brown when dormant in winter.
What is the difference between cool-season and warm-season grass?
The difference is the temperature range where each group grows best. NC State Extension puts the cool-season optimum at 60 to 75°F. It puts the warm-season optimum at 80 to 95°F.
| Cool-season grasses | Warm-season grasses | |
|---|---|---|
| Optimum growth temperature | 60-75°F (15.6-23.9°C) | 80-95°F (26.7-35°C) |
| Peak growth | Spring and fall | Summer |
| Summer | May be stressed or go dormant; some leaves brown | Active growth |
| Winter | Stays green, growth slows | Dormant; all foliage turns brown |
| Shade and cold | Good winter tolerance, adequate shade tolerance | Poor shade and winter tolerance |
| Water | Needs more water than warm-season grasses | Needs less |
Celsius conversion: °C = (°F - 32) × 5/9. For example, (75 - 32) × 5/9 = 23.9°C.
UGA’s Turfgrass 101 lists the cool-season range as 65 to 75°F in one place and 60 to 75°F in another. Treat these ranges as approximate.
Which grasses are cool-season and which are warm-season?
| Group | Common lawn species |
|---|---|
| Cool-season | Tall fescue, Kentucky bluegrass, perennial ryegrass, annual ryegrass, fine fescues (creeping red, hard, chewings, sheep), rough bluegrass, creeping bentgrass |
| Warm-season | Bermudagrass, zoysiagrass, St. Augustinegrass, centipedegrass, bahiagrass, carpetgrass, buffalograss, seashore paspalum |
Species lists come from NC State, UGA and the University of Maryland. Table rows on summer, winter, shade and water follow UGA and Illinois Extension.
As a broad pattern, cool-season lawns dominate the northern US and warm-season lawns dominate the South. The middle band is more complicated.
What is the transition zone?
The transition zone is the band where temperate and subtropical climates meet, between the main cool-season and warm-season regions. The University of Maryland places Maryland in it, and Illinois Extension describes parts of Illinois the same way. Neither grass group is perfectly suited there year-round.
In this zone, both groups are planted:
- Maryland: UMD recommends tall fescue for most homes. Zoysia is its warm-season pick.
- North Carolina: NC State says tall fescue is the most common lawn grass, followed by bermudagrass.
- Illinois: Illinois Extension describes a lawn where newly seeded tall fescue stays green beside brown bermudagrass in fall.
If you live in the transition zone, do not assume your type from your location. Check the grass itself.
How do I tell what kind of grass I have?
Look at the color in late fall and winter
This is the easiest test. Illinois Extension sums it up: green means cool-season, and brown means warm-season. Cool-season grasses keep their chlorophyll through cold weather. Warm-season grasses die back above ground and turn tan or brown.
One caution: clover and creeping Charlie also stay green in winter. They are weeds, not grasses.
Check how it spreads
Pull up a small plug and look at the base and roots. UMD describes three growth habits:
| Growth habit | What it looks like | Examples |
|---|---|---|
| Stolons | Runners on top of the soil | Bermudagrass, zoysia |
| Rhizomes | Runners below the soil surface | Kentucky bluegrass, creeping red fescue, bermudagrass, zoysia |
| Bunch type | Separate clumps, no runners | Tall fescue (sometimes short rhizomes), perennial ryegrass |
Runners above the ground, combined with brown winter color, point strongly to a warm-season grass such as bermudagrass or zoysia. Clumps that stay green in winter point to tall fescue or ryegrass.
For a confident species ID, take a sample to your county Cooperative Extension office.
How does lawn care differ between the two?
The rule of thumb is to do major lawn work when your grass is actively growing. That means spring and fall for cool-season grass and summer for warm-season grass.
- Fertilizing: Timing depends on the grass type. See when to fertilize your lawn.
- Seeding and overseeding: Fall is the main window for cool-season lawns. See how to overseed a lawn in fall, and use the grass seed calculator for amounts.
- Watering: UGA notes cool-season grasses need significantly more water than warm-season grasses, especially in summer.
- Fertilizer needs vary within a group: UMD says Kentucky bluegrass needs more nitrogen than fine fescues. High nitrogen rates stress fine fescue.
Germination speed also differs by cool-season species, per UMD:
| Species | Days to germinate |
|---|---|
| Perennial ryegrass | 5-10 |
| Tall fescue | 7-14 |
| Fine fescue | 7-14 |
| Kentucky bluegrass | 14-21 |
Quick answers
Is my grass cool-season or warm-season? Check it in late fall or winter. A lawn that stays green is cool-season. A lawn that turns brown and dormant is warm-season.
Is tall fescue cool-season or warm-season? Tall fescue is a cool-season grass. It is the most common lawn grass in North Carolina, per NC State.
Is bermudagrass cool-season or warm-season? Bermudagrass is warm-season. It grows best around 80 to 95°F and turns brown in winter.
Is zoysia warm-season grass? Yes. Zoysia is warm-season and spreads by both stolons and rhizomes.
Why does my lawn have brown and green patches in winter? You likely have a mix of warm-season and cool-season grasses. This is common in the transition zone.
Can warm-season grass grow in the North? Warm-season grasses have poor winter tolerance, per UGA. In colder regions, a cool-season grass is generally the safer choice. Ask your local extension office before planting.