When to Plant Petunia in Stevens County, WA
June to-do list for Stevens County, Washington
Each item below is timed to Stevens County, Washington's frost dates and soil temperatures. Skip nothing, stress about nothing.
Coming up in July — start thinking about
- Starting indoors: petunia
- 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.
Stevens County, Washington is in USDA Zone 6b. The average last spring frost is May 10 and the first fall frost is September 24, giving you a growing season of approximately 137 days.
At an elevation of 1,751 feet, Stevens County receives approximately 24.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Petunia to ensure they mature before fall.
Stevens County Soil Profile
Soil Type
Silt Loam
Soil pH
5.3-6.3
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 Stevens County
How your county's soil matches Petunia's growing requirements.
Soil pH
Your soil pH (5.3–6.3) is more acidic than Petunia prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Stevens County is excellent for Petunia — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.3%) — Petunia will thrive.
How to Plant Petunia
Succession Planting Petunia
Sow every 8 weeks. Last sowing by Jun 26 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 | — | 3.2" | 0" | ❄️ Dormant |
| Feb | — | 2.5" | 0" | ❄️ Dormant |
| Mar | — | 2.7" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Jun | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Jul | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Aug | 4.3" | 0.4" | 3.9" | 🚿 Regular watering |
| Sep | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Oct | — | 2.3" | 0" | ❄️ Dormant |
| Nov | — | 4.2" | 0" | ❄️ Dormant |
| Dec | — | 3.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Stevens 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 — Stevens County, WA
Petunia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 15 | Mar 15 – Mar 29 |
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Bloom | July 26 | Jul 26 – Nov 8 |
· 12" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | Bloom |
| 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: too_acidic
🗺️ USDA Zone
Zone 6b
📆 Growing Season
137 days in Stevens County
Growing Tips for Petunia in Stevens County
Direct sow Petunia outdoors after May 10 in Stevens 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.
Stevens County receives only 24" of rain annually. Petunia needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
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 Stevens County, WA?
Stevens County is in Zone 6b with an average last frost of May 10. Plan your Petunia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Stevens County, WA?
Stevens County, Washington is in USDA Hardiness Zone 6b. The average last spring frost is May 10 and first fall frost is September 24.
Your Stevens County Garden Planner — Free
A 22-page printable planner built for Stevens 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.