Lawn Care Guide for Clarke County
Clarke County, Iowa
USDA SSURGO / PHZMThis week in Clarke County · next up in about 2 weeks (Aug 13)
Get ready to seed cool-season grass — the best fall window is about to open.
Data Story
About Lawn Care in Clarke County, Iowa
Clarke Leads the State in Ease
Clarke County boasts an impressive lawn difficulty score of 83.1, making it one of the easiest places in Iowa to grow grass. This score far exceeds the state average of 77.2 and the national baseline of 50.0. The warmer 5b Hardiness Zone offers a slightly longer window for lawn establishment than northern Iowa.
High Energy and High Heat
The climate produces 3233 growing degree days, signaling a very active growing season that requires frequent mowing. While the 38.7 inches of rain is excellent, the county faces 25 extreme heat days, which is much higher than the state average of 16. Grass here needs extra hydration during July to survive those punishing 90°F afternoons.
Heavy Clay and Poor Drainage
Clarke's silty clay loam soil is characterized by poor drainage and a 28.1% clay content. While this helps keep the 6.24 pH soil moist during heat waves, it can lead to waterlogging and root rot during heavy rains. Incorporating gypsum or organic matter can help break up the heavy clay and improve the soil's structure.
Staying Green Through Dry Spells
Though 100% of the county is currently abnormally dry, it only suffered 2 weeks of drought over the past year. This historical resilience suggests that Clarke County lawns are generally well-hydrated. Keep mower blades sharp and high to shade the soil and reduce water loss during the current dry trend.
Maximize the 5b Growing Season
Heat-tolerant Kentucky Bluegrass cultivars or Turf-Type Tall Fescues are ideal for managing the 25 heat days this county experiences. Start your spring planting after April 29 and wrap up fall chores by October 9. The slightly warmer 5b climate allows for strong root establishment if you seed in early September.
Lawn Difficulty Score
Soil Summary
pH
6.2
Texture
Silty clay loam
Drainage
Poorly drained
Organic Matter
3.0%
Top Grass Fit for Clarke County
Excellent match
Outsidepride Midnight Kentucky Bluegrass Seed
Outsidepride
Top cultivar score: 100/100
Zone 5b vs Kentucky Bluegrass's 3–7 band.
Soil pH 6.23819766673007 vs Kentucky Bluegrass's 6–7 window.
Precipitation 38.74" + soil AWC vs Kentucky Bluegrass's 30–40" need.
Growing-degree-days + frost window vs a advanced-difficulty establishment.
Let's be direct: Outsidepride Midnight Kentucky Bluegrass is one of the best pure KBG seeds you can buy online, and it's not particularly close. Midnight is a specific cultivar — not a generic "Kentucky bluegrass blend" — and that distinction matters enormously.
In Clarke County, USDA zone 5b, soil pH 6.2, silty clay loam, Outsidepride Midnight Kentucky Bluegrass Seed scores 100/100 — a strong zone match, adequate moisture, and a long enough establishment window.
Why we ruled these out
- Scotts Turf Builder Bermudagrass — USDA zone 5b is below Scotts Turf Builder Bermudagrass's effective range (6–11); not recommended for this county.
See our fit-score methodology for how survivability is determined.
Recommended Grasses
Tall Fescue
Festuca arundinacea
Choosing grass in Clarke County
Poor drainage (Poorly drained) is the main thing shaping grass choice in Clarke County. Here's how to work with it — then the specific pick.
- Prepping a poorly drained lawnAeration, grading, and species that tolerate wet feet.
- Kentucky Bluegrass, explainedTraits, care, and where Kentucky Bluegrass wins — the species behind your top match.
Top match for Clarke County: Kentucky Bluegrass
See the full breakdownPremium Grass Seeds is a sister site in our network. We may earn a commission from qualifying purchases made through its retailer links — this never affects your price. Guidance here reflects your county’s climate and soil data, not hands-on testing.
Climate Snapshot
Annual Precip
38.7"
Growing Degree Days
3,233.1
Base 50F
Last Spring Frost
04/29
First Fall Frost
10/09
Days Above 95F
25
Hardiness Zone
5b
Seeding Calendar — Clarke County
Personalized to this county’s frost dates — a 163-day growing season. Windows below are computed from local last-spring and first-fall frost normals, so they differ county-to-county even within USDA Zone 5B.
Plan your seeding — Clarke County
Pick a grass and a goal to get a personalized schedule anchored to this county’s frost dates.
- 1Prepare the seedbedJul 30 – Aug 12
Mow low, dethatch or rake, and loosen the top ½ inch of soil so seed makes good contact.
- 2Sow seedAug 13 – Sep 10
Best window to sow Kentucky Bluegrass in Clarke County, anchored to your local frost dates.
- 3EstablishSep 11 – Oct 8
Protect young seedlings: mow only after they reach ~3 inches and hold off on weed pre-emergents until established.
Loam holds moisture evenly — water about ¼ inch once or twice daily to keep the top inch of the seedbed consistently moist until germination.
Seasonal Lawn Care Checklist
Spring
- Apply pre-emergent herbicide when soil reaches 55F
- Overseed bare spots once frost risk passes
- 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
- Core aerate compacted areas
- Apply fall fertilizer (highest N application for cool-season)
- Continue mowing until growth stops
- Rake or mulch leaves to prevent smothering
Winter
- Avoid walking on frozen turf
- Service mower and sharpen blades
- Plan spring soil amendments based on fall test
- Keep lawn clear of debris
Watering Deficit Calculator
Monthly Deficit
0.6"
inches of water
Monthly Water
1,968
gallons
Estimated Monthly Cost
$15.74
at $0.008/gallon average
Estimates based on 39" annual precipitation and estimated evapotranspiration. Actual costs vary by local water rates.
Lawn Care Advisory: Clarke County
Lawn Verdict
Clarke County sits in USDA hardiness zone 5b, a transitional zone where cool-season grasses dominate but some warm-season varieties can survive. with winter lows reaching around -15.0°F. and 3,233.1 growing degree days, sufficient for most common turfgrasses. Moderate rainfall (38.7 inches) generally supports healthy lawns with minimal supplemental watering.
Seasonal Breakdown
Wait until after April 29 to seed or overseed; soil temperatures should consistently reach 50-55°F. Cool summers (July averages 75.2°F) reduce heat stress — maintain regular mowing and moderate watering. Aerate and overseed cool-season lawns by early fall, well before October 9; this is the best renovation window. Cool winters (January averages 21.8°F) mean slow or dormant growth; keep debris off the lawn.
Watering Guidance
With 38.7 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
Clarke County is close to the Iowa average temperature, USDA zone 5b helps guide grass selection compared to neighboring counties.
Dig deeper into Clarke County
Clarke County is a USDA Zone 5B, loamy-soil, cool-season county. Explore the data that shapes its lawn:
Want detailed soil composition, drainage classes, and soil series data? View soil details on SoilByCounty.com
Frequently Asked Questions
What USDA hardiness zone is Clarke County in?
What is the best grass for Clarke County?
How long is the growing season in Clarke County?
How much rainfall does Clarke County get?
What is the soil pH in Clarke 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 Clarke County