Lawn Care Guide for Union County
Union County, South Dakota
USDA SSURGO / PHZMData Story
About Lawn Care in Union County, South Dakota
Mixed Success for Union County Lawns
Union County scores a 47.1 for lawn difficulty, reflecting a more challenging environment than the state average. This Hardiness Zone 5a area requires specific strategies to overcome local soil and drought issues.
High Rainfall with Mild Summers
At 29.7 inches of annual precipitation, Union County is much wetter than the state average of 22.8 inches. Only 17 extreme heat days occur annually, making the climate relatively friendly for cool-season grasses compared to western neighbors.
Poor Drainage in Silty Clay
The soil is classified as poorly drained and consists of silty clay with nearly 30% clay content. Frequent aeration and the addition of organic matter are necessary to prevent the soil from becoming waterlogged or compacted.
Extensive Drought Despite High Rainfall
Despite having higher annual rain, the county endured 40 weeks of drought over the past year. With 100% of the area currently abnormally dry, managing moisture levels in the heavy silty clay is a delicate balance.
Prepare for Clay-Based Growth
Select grass types that can handle occasionally wet feet due to the poor drainage of the silty clay. Tall fescue is a strong candidate for this Hardiness Zone 5a environment and its varied moisture levels.
Lawn Difficulty Score
Top Grass Fit for Union County
Excellent match
Outsidepride Midnight Kentucky Bluegrass Seed
Outsidepride
Top cultivar score: 89/100
Zone 5a vs Kentucky Bluegrass's 3–7 band.
Soil pH 7.17729575860109 vs Kentucky Bluegrass's 6–7 window.
Precipitation 29.7" + soil AWC vs Kentucky Bluegrass's 30–40" need.
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 Union County, USDA zone 5a, soil pH 7.2, silty clay, Outsidepride Midnight Kentucky Bluegrass Seed scores 89/100 — a strong zone match and adequate moisture.
Why we ruled these out
- Scotts Turf Builder Bermudagrass — USDA zone 5a 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
Buffalograss
Bouteloua dactyloides
Blue Grama
Bouteloua gracilis
Tall Fescue
Festuca arundinacea
Climate Snapshot
Annual Precip
29.7"
Growing Degree Days
N/A
Base 50F
Last Spring Frost
N/A
First Fall Frost
N/A
Days Above 95F
17
Hardiness Zone
5a
Seeding Calendar — Zone 5A
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
1.3"
inches of water
Monthly Water
4,123
gallons
Estimated Monthly Cost
$32.99
at $0.008/gallon average
Estimates based on 30" annual precipitation and estimated evapotranspiration. Actual costs vary by local water rates.
Common Lawn Problems in Union County
Persistent Drought Conditions
Union County experienced drought conditions for 40 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: Union County
Lawn Verdict
Union County sits in USDA hardiness zone 5a, a transitional zone where cool-season grasses dominate but some warm-season varieties can survive. with winter lows reaching around -20.0°F. Moderate rainfall (29.7 inches) generally supports healthy lawns with minimal supplemental watering.
Seasonal Breakdown
Spring seeding is risky here; cool, wet springs favor pre-emergent weed control over renovation. Cool summers (July averages 73.1°F) reduce heat stress — maintain regular mowing and moderate watering. Fall is the prime seeding season here; aerate, overseed, and fertilize cool-season grasses before October. Winters are harsh (January averages 17.3°F); avoid foot traffic on frozen turf and plan snow mold prevention.
Watering Guidance
Moderate rainfall (29.7 inches) means lawns benefit from weekly deep watering during summer stress. Currently, 100.0% of the county is in moderate drought according to the US Drought Monitor. Consider reducing irrigation frequency and allowing cool-season lawns to go semi-dormant during peak heat. Cool summers reduce water demand; overwatering is a bigger risk than drought stress.
Regional Context
Union County is close to the South Dakota average temperature, it is somewhat wetter than the state average, USDA zone 5a 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 Union County in?
What is the best grass for Union County?
How much rainfall does Union County get?
What is the soil pH in Union 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 Union County