When to plant Petunia in Sullivan County, IN
Sullivan County sits in cold Zone 6b. Plant Petunia April 25–May 9 for the single annual harvest; the October 17 first frost closes the window.
When to Plant Petunia in Sullivan County, IN
What to do in July
Here's what deserves your attention in Sullivan County, Indiana this month. Everything below is tailored to Zone 6b and timed around your local frost dates.
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Pick petunia
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
Looking ahead to 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.
Sullivan County, Indiana is in USDA Zone 6b. The average last spring frost is April 18 and the first fall frost is October 17, giving you a growing season of approximately 182 days.
At an elevation of 914 feet, Sullivan County receives approximately 34.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Petunia during the growing season.
Sullivan County Soil Profile
Soil Type
Silt Loam
Soil pH
6-7
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 Sullivan County
How your county's soil matches Petunia's growing requirements.
Soil pH
Your soil pH (6.0–7.0) is within Petunia's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Sullivan County is excellent for Petunia — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.5%) — Petunia will thrive.
How to Plant Petunia
Succession Planting Petunia
Sow every 8 weeks. Last sowing by Jul 19 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 | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.6" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| May | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| Jun | 4.3" | 4.9" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Aug | 4.3" | 4" | 0.3" | 💧 Light watering |
| Sep | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| Oct | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Nov | — | 2.2" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Sullivan 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 — Sullivan County, IN
Petunia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 21 | Feb 21 – Mar 7 |
| Transplant Outdoors | April 25 | Apr 25 – May 9 |
| Bloom | July 4 | Jul 4 – Oct 17 |
· 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: ideal
🗺️ USDA Zone
Zone 6b
📆 Growing Season
182 days in Sullivan County
Growing Tips for Petunia in Sullivan County
Direct sow Petunia outdoors after April 18 in Sullivan 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 Sullivan County, IN?
Sullivan County is in Zone 6b with an average last frost of April 18. Plan your Petunia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sullivan County, IN?
Sullivan County, Indiana is in USDA Hardiness Zone 6b. The average last spring frost is April 18 and first fall frost is October 17.
When should I plant Petunia in Sullivan County, IN?
In Sullivan County, IN, plant Petunia after the last frost (around April 18) and before the first frost (around October 17). Best results when soil holds above 50°F.
What growing zone is Sullivan County, IN for Petunia?
Sullivan County sits in USDA Zone 6b. Petunia grows reliably in zones 2a through 11b, so it's a good fit here.
Can Petunia grow in Sullivan County's climate?
Yes — Petunia grows well in Sullivan County's temperate climate. Sullivan County averages a 182-day frost-free season, with last frost around April 18 and first frost around October 17.
Your Sullivan County Garden Planner — Free
A 22-page printable planner built for Sullivan County (Zone 6b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.