When to Plant Sunflower in Bennett County, SD
Top priorities for Bennett County, South Dakota gardeners in May
May is a pivotal month for Bennett County, South Dakota gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Move sunflower from tray to bed
Your last frost (May 11) has passed. These warm-season crops can handle outdoor soil now.
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Seed sunflower outdoors
Keep the top inch of soil moist until germination — a gentle morning watering for 5–7 days does the job.
Sunflowers are tall, cheerful annuals grown for their edible seeds and as pollinator magnets. They come in sizes from 2-foot dwarfs to 12-foot giants.
Bennett County, South Dakota is in USDA Zone 5a. The average last spring frost is May 11 and the first fall frost is October 4, giving you a growing season of approximately 146 days.
At an elevation of 1,025 feet, Bennett County receives approximately 24.9 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Sunflower to ensure they mature before fall.
Bennett County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.6
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Bennett County
How your county's soil matches Sunflower's growing requirements.
Soil pH
Your soil pH (6.2–7.6) overlaps with Sunflower's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Bennett County is excellent for Sunflower — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.3%). Annual compost additions will help Sunflower.
How to Plant Sunflower
Succession Planting Sunflower
Sow every 8 weeks. Last sowing by Jun 26 to harvest before frost.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Sunflower
Sunflower needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Sunflower Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | — | 2.9" | 0" | ❄️ Dormant |
| May | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 1.6" | 0.6" | 💧 Light watering |
| Jul | 2.2" | 2.2" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.1" | 0.1" | 💧 Light watering |
| Oct | 2.2" | 2" | 0.2" | 💧 Light watering |
| Nov | — | 1.8" | 0" | ❄️ Dormant |
| Dec | — | 1.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Bennett County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sunflower Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Sunflower Planting Timeline — Bennett County, SD
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 16 | Mar 16 – Mar 30 |
| Transplant Outdoors | May 25 | May 25 – Jun 8 |
| Direct Sow | May 18 | May 18 – Jun 8 |
| Harvest | August 3 | Aug 3 – Sep 21 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
146 days in Bennett County
Growing Tips for Sunflower in Bennett County
Direct sow Sunflower outdoors after May 11 in Bennett County when soil has warmed and frost danger has passed.
Common pests for Sunflower in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
Bennett County receives only 25" of rain annually. Sunflower needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow after last frost. Stake tall varieties in windy areas. Harvest seed heads when the back turns brown and seeds are plump. Dry heads upside down.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Sunflower in Other Locations
Frequently Asked Questions
When should I plant Sunflower in Bennett County, SD?
Bennett County is in Zone 5a with an average last frost of May 11. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Bennett County, SD?
Bennett County, South Dakota is in USDA Hardiness Zone 5a. The average last spring frost is May 11 and first fall frost is October 4.
Your Bennett County Garden Planner — Free
A 24-page printable planner built for Bennett County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.