When to Plant Sunflower in Harford County, MD
May in Harford County, Maryland — your action list
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Harford County, Maryland.
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Time to start sunflower inside
You're about 25 weeks out from your last frost — the perfect window to get these germinating indoors.
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.
Harford County, Maryland is in USDA Zone 7b. The average last spring frost is April 8 and the first fall frost is November 2, giving you a growing season of approximately 208 days.
At an elevation of 277 feet, Harford County receives approximately 38.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 91°F, providing good warmth for Sunflower during the growing season.
Harford County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-7.1
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 Harford County
How your county's soil matches Sunflower's growing requirements.
Soil pH
Your soil pH (5.7–7.1) overlaps with Sunflower's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Harford 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 Jul 25 to harvest before frost.
Plant Water Budget
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 | — | 3" | 0" | ❄️ Dormant |
| Feb | — | 2.8" | 0" | ❄️ Dormant |
| Mar | — | 3.1" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.8" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.2" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 3.1" | 0" | ✅ Rainfall sufficient |
| Dec | — | 2.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Harford 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 — Harford County, MD
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 18 | Feb 18 – Mar 4 |
| Transplant Outdoors | April 22 | Apr 22 – May 6 |
| Direct Sow | April 15 | Apr 15 – May 6 |
| Harvest | July 1 | Jul 1 – Aug 19 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Harvest |
| September | — |
| 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 7b
📆 Growing Season
208 days in Harford County
Growing Tips for Sunflower in Harford County
Direct sow Sunflower outdoors after April 08 in Harford 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.
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 Harford County, MD?
Harford County is in Zone 7b with an average last frost of April 8. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Harford County, MD?
Harford County, Maryland is in USDA Hardiness Zone 7b. The average last spring frost is April 8 and first fall frost is November 2.
Your Harford County Garden Planner — Free
A 24-page printable planner built for Harford County (Zone 7b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.