When to plant Petunia in Harrison County, MO
Plant Petunia in Harrison County, between April 26 and May 10 — the only viable window. Zone 5b's short season (179 frost-free days) rules out a fall crop.
When to Plant Petunia in Harrison County, MO
July to-do list for Harrison County, Missouri
Your garden in Harrison County, Missouri is working on a schedule, even when you're not. Here's where you should be this July.
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Bring in the petunia
If you can't use it all right away, check the food-preservation section of your planner.
Get ahead of August
- First harvests: petunia
Petunias (Petunia x hybrida) are warm-season tender annuals prized for their prolific, trumpet-shaped blooms in nearly every color. They perform from hanging baskets to garden borders and bloom continuously from late spring until frost, provided spent flowers are removed regularly.
Harrison County, Missouri is in USDA Zone 5b. The average last spring frost is April 19 and the first fall frost is October 15, giving you a growing season of approximately 179 days.
At an elevation of 1,349 feet, Harrison County receives approximately 37.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Petunia to ensure they mature before fall.
Harrison County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-6.9
Drainage
Well Drained
Petunia 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 Harrison County
How your county's soil matches Petunia's growing requirements.
Soil pH
Your soil pH (5.6–6.9) overlaps with Petunia's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Harrison County is excellent for Petunia — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.8%). Annual compost additions will help Petunia.
How to Plant Petunia
Succession Planting Petunia
Sow every 8 weeks. Last sowing by Jul 17 to harvest before frost.
Petunia Water Budget
Monthly Watering Guide for Petunia
Petunia needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Petunia Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.9" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| May | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Aug | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Sep | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Oct | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Harrison County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Petunia 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.
Petunia Planting Timeline — Harrison County, MO
Petunia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 22 | Feb 22 – Mar 8 |
| Transplant Outdoors | April 26 | Apr 26 – May 10 |
| Bloom | July 5 | Jul 5 – Oct 4 |
· 12" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
70–90 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
179 days in Harrison County
Growing Tips for Petunia in Harrison County
Direct sow Petunia outdoors after April 19 in Harrison County when soil has warmed and frost danger has passed.
Common pests for Petunia in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 8–10 weeks before last frost; seeds need light to germinate — press onto moist mix surface, do not cover. Transplant after last frost once nights stay above 50°F. Pinch back leggy plants mid-summer to encourage bushy re-bloom. Wave/spreading types tolerate light shade but bloom less. Feed every 2 weeks with balanced fertilizer once established.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Petunia in Other Locations
Frequently Asked Questions
When should I plant Petunia in Harrison County, MO?
Harrison County is in Zone 5b with an average last frost of April 19. Plan your Petunia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Harrison County, MO?
Harrison County, Missouri is in USDA Hardiness Zone 5b. The average last spring frost is April 19 and first fall frost is October 15.
When should I plant Petunia in Harrison County, MO?
In Harrison County, MO, plant Petunia after the last frost (around April 19) and before the first frost (around October 15). Best results when soil holds above 50°F.
What growing zone is Harrison County, MO for Petunia?
Harrison County sits in USDA Zone 5b. Petunia grows reliably in zones 2a through 11b, so it's a good fit here.
Can Petunia grow in Harrison County's climate?
Yes — Petunia grows well in Harrison County's temperate climate. Harrison County averages a 179-day frost-free season, with last frost around April 19 and first frost around October 15.
Your Harrison County Garden Planner — Free
A 22-page printable planner built for Harrison County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.