When to plant Phlox in Sumner, IL
Plant Phlox in Sumner, when soil hits 50°F — usually April 20. Continue planting through May 11 for the spring crop.
When to Plant Phlox in Sumner, IL
Lawrence County, Illinois gardeners: here's your June plan
If you only do a handful of things in the garden this June, make it these. They're sequenced around your zone's frost timing.
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Start phlox under lights
Bottom-water once the first true leaves appear — it keeps stems dry and knocks back damping-off.
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Pick phlox
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
Get ahead of July
- First harvests: phlox
Garden Phlox (Phlox paniculata) is a beloved native perennial of eastern North America, producing large, domed clusters of fragrant flowers atop upright stems from mid-summer into fall. Its sweet honey-like fragrance carries on summer evenings and draws hummingbirds, butterflies, and sphinx moths. Modern cultivars offer colors spanning white, pink, salmon, red, purple, and bicolors. A classic cottage garden stalwart, phlox combines well with black-eyed Susans, echinacea, and ornamental grasses in naturalistic plantings. Select mildew-resistant cultivars for best long-term performance.
Sumner, Illinois is in USDA Zone 6b. The average last spring frost is April 13 and the first fall frost is October 27, giving you a growing season of approximately 197 days.
At an elevation of 969 feet, Lawrence County receives approximately 35.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 88°F, providing good warmth for Phlox during the growing season.
Sumner Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-7.3
Drainage
Well Drained
Phlox 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 Sumner
How your county's soil matches Phlox's growing requirements.
Soil pH
Your soil pH (5.8–7.3) overlaps with Phlox's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Lawrence County is excellent for Phlox — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Phlox.
How to Plant Phlox
Succession Planting Phlox
Sow every 9.1 weeks. Last sowing by Jul 09 to harvest before frost.
Phlox Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Phlox
Phlox needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Phlox Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.7" | 0" | ❄️ Dormant |
| Mar | — | 2.7" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.3" | 1" | 💧 Light watering |
| May | 4.3" | 4" | 0.3" | 💧 Light watering |
| Jun | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Aug | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Sep | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| Oct | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Nov | — | 2.5" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Lawrence County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Phlox 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.
Phlox Planting Timeline — Sumner, IL
Phlox Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 9 | Feb 9 – Feb 23 |
| Transplant Outdoors | April 20 | Apr 20 – May 4 |
| Direct Sow | April 20 | Apr 20 – May 11 |
| Bloom | June 29 | Jun 29 – Sep 21 |
Plant 0.3" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
80–110 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 6b
📆 Growing Season
197 days in Lawrence County
Growing Tips for Phlox in Sumner
Direct sow Phlox outdoors after April 13 in Lawrence County when soil has warmed and frost danger has passed.
General growing tips
Start seeds indoors 8–10 weeks before last frost, or transplant container divisions in spring. Named cultivar seeds may not come true; divisions from named plants are the preferred propagation method. Space generously (18–24 inches) and avoid overhead watering to reduce powdery mildew risk. Good air circulation is critical — thin clumps to the strongest 5–7 stems per plant in spring. Deadhead after the primary bloom flush to encourage secondary flowering. Division every 2–3 years in spring keeps plants vigorous. Fall planting of divisions (Zones 5+) is equally effective. Year 2+ plants develop into full clumps with the most prolific bloom.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Phlox in Other Locations
When should I plant Phlox in Sumner, IL?
In Sumner, IL, plant Phlox after the last frost (around April 13) and before the first frost (around October 27). Best results when soil holds above 50°F.
What growing zone is Sumner, IL for Phlox?
Sumner sits in USDA Zone 6b. Phlox grows reliably in zones 3a through 9a, so it's a good fit here.
Can Phlox grow in Sumner's climate?
Yes — Phlox grows well in Sumner's temperate climate. Sumner averages a 197-day frost-free season, with last frost around April 13 and first frost around October 27.
Your Lawrence County Garden Planner — Free
A 22-page printable planner built for Lawrence 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.