Lawn Care Guide for Sullivan County
Sullivan County, Tennessee
USDA SSURGO / PHZMData Story
About Lawn Care in Sullivan County, Tennessee
Above-Average Lawn Success in Sullivan
Sullivan County boasts a lawn difficulty score of 55.3, indicating it is easier to grow grass here than the national and state averages. Located in Zone 7b, the county offers a favorable environment for many popular turf varieties. You start with a significant advantage compared to neighbors in more difficult Tennessee climates.
Perfect Precipitation for Healthy Roots
Annual precipitation averages 44.5 inches, falling perfectly within the ideal 30-50 inch range for lawn health. The area sees only 26 extreme heat days per year, which is 10 days fewer than the Tennessee state average. This milder summer helps prevent the turf burnout often seen in hotter Southern regions.
Amending Highly Acidic Clay Soil
A low soil pH of 5.17 means your lawn likely needs lime to reach the 6.0 to 7.0 sweet spot for nutrient uptake. The soil is a well-drained silty clay loam with about 16.0% clay and 35.6% sand. While the drainage is excellent, the high sand content may require more frequent light watering during dry periods.
Staying Green Through 24 Weeks of Drought
Sullivan County experienced 24 weeks of drought over the last year, and 100% of the county is currently abnormally dry. Maintaining a higher mowing height during these periods helps shade the soil and retain moisture. Proper irrigation is critical when natural rainfall dips below the 44.5-inch average.
Seeding for Success in Zone 7b
Tall fescue is a top performer for this region, balancing cold hardiness with heat tolerance. Your primary growing window opens after April 16 and closes with the first frost around October 29. Get your soil tested today to address the acidity before your next seeding project.
Lawn Difficulty Score
Top Grass Fit for Sullivan County
Excellent match
Jonathan Green Black Beauty Ultra
Jonathan Green
Top cultivar score: 92/100
Zone 7b vs Tall Fescue's 3–8 band.
Soil pH 5.16567406954617 vs Tall Fescue's 5.5–6.5 window.
Precipitation 44.5" + soil AWC vs Tall Fescue's 20–30" need.
Growing-degree-days + frost window vs a intermediate-difficulty establishment.
If you spend any time on lawn care forums, Reddit's r/lawncare, or YouTube lawn channels, one name comes up more than any other: Jonathan Green Black Beauty Ultra. It's practically a cult favorite, and the label, cultivar story, and long-running owner reports explain why. The secret is in the genetics.
In Sullivan County, USDA zone 7b, soil pH 5.2, silty clay loam, Jonathan Green Black Beauty Ultra scores 92/100 — a strong zone match, adequate moisture, and a long enough establishment window.
Recommended Grasses
Tall Fescue
Festuca arundinacea
Bermudagrass
Cynodon dactylon
Best Grass Seed for Sullivan County
Zone 7b • Cool- and warm-season grasses thrive here.
Find Seeds for Zone 7bClimate Snapshot
Annual Precip
44.5"
Growing Degree Days
4,027.2
Base 50F
Last Spring Frost
04/16
First Fall Frost
10/29
Days Above 95F
26
Hardiness Zone
7b
Seeding Calendar — Zone 7B
Seasonal Lawn Care Checklist
Spring
- Apply pre-emergent herbicide when soil reaches 55F
- Begin mowing when grass reaches 3 inches
- Start irrigation if rainfall is below 1 inch/week
- Soil test every 2-3 years — adjust lime or sulfur as needed
Summer
- Mow at recommended height weekly
- Water deeply 1-2 times per week (1 inch total)
- Avoid fertilizing cool-season grasses in peak heat
- Scout for grubs and treat if >10 per sq ft
Fall
- Overseed warm-season lawns if thinning
- Apply fall fertilizer (highest N application for cool-season)
- Continue mowing until growth stops
- Rake or mulch leaves to prevent smothering
Winter
- Apply pre-emergent for winter weeds
- Service mower and sharpen blades
- Plan spring soil amendments based on fall test
- Keep lawn clear of debris
Watering Deficit Calculator
Monthly Deficit
0.2"
inches of water
Monthly Water
550
gallons
Estimated Monthly Cost
$4.40
at $0.008/gallon average
Estimates based on 45" annual precipitation and estimated evapotranspiration. Actual costs vary by local water rates.
Common Lawn Problems in Sullivan County
Acidic Soil
Soil pH of 5.2 is below the ideal range for most grasses (6.0-7.0). Apply agricultural lime to raise pH gradually.
Persistent Drought Conditions
Sullivan County experienced drought conditions for 24 of the past 52 weeks. Prioritize water-efficient grasses and consider reducing lawn area.
Learn more about regional lawn challenges at The Lawn Report.
Lawn Care Advisory: Sullivan County
Lawn Verdict
Sullivan County falls in USDA hardiness zone 7b, a favorable range for both cool- and warm-season grasses. with winter lows reaching around 5.0°F. and 4,027.2 growing degree days annually, supporting vigorous warm-season lawns. Moderate rainfall (44.5 inches) generally supports healthy lawns with minimal supplemental watering.
Seasonal Breakdown
Wait until after April 16 to seed or overseed; soil temperatures should consistently reach 50-55°F. Cool summers (July averages 76.0°F) reduce heat stress — maintain regular mowing and moderate watering. Aerate and overseed cool-season lawns by early fall, well before October 29; this is the best renovation window. Cool winters (January averages 36.6°F) mean slow or dormant growth; keep debris off the lawn.
Watering Guidance
With 44.5 inches of annual rainfall, established lawns typically need watering only during extended dry spells. Currently, 100.0% of the county is in abnormally dry according to the US Drought Monitor. Standard warm-season watering of 1 inch per week is usually adequate during summer.
Regional Context
Sullivan County is close to the Tennessee average temperature, it is significantly drier than the state average (11.1 inches less), USDA zone 7b helps guide grass selection compared to neighboring counties.
Want detailed soil composition, drainage classes, and soil series data? View soil details on SoilByCounty.com
Frequently Asked Questions
What USDA hardiness zone is Sullivan County in?
What is the best grass for Sullivan County?
How much rainfall does Sullivan County get?
What is the soil pH in Sullivan County?
Data sourced from USDA SSURGO, NOAA Climate Normals (1991-2020), USDA Plant Hardiness Zone Map, and US Drought Monitor. Lawn difficulty scores and grass recommendations are estimates for informational purposes only.
Explore more data for Sullivan County