When to plant Phlox in Roseau County, MN
Roseau County's short 124-day growing season means one Phlox planting between June 4 and June 25. No fall crop in Zone 3b.
When to Plant Phlox in Roseau County, MN
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.
Roseau County, Minnesota is in USDA Zone 3b. The average last spring frost is May 21 and the first fall frost is September 22, giving you a growing season of approximately 124 days.
At an elevation of 655 feet, Roseau County receives approximately 32 inches of rainfall annually with predominantly silt loam soil. Summer highs average 79°F, so choose short-season varieties of Phlox to ensure they mature before fall.
Roseau County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Phlox Planting Timeline — Roseau County, MN
Phlox Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 12 | Mar 12 – Mar 26 |
| Transplant Outdoors | June 4 | Jun 4 – Jun 18 |
| Direct Sow | June 4 | Jun 4 – Jun 25 |
| Bloom | August 27 | Aug 27 – Oct 22 |
Plant 0.3" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | — |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
80–110 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 3b
📆 Growing Season
124 days in Roseau County
Growing Tips for Roseau County
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
Frequently Asked Questions
When should I plant Phlox in Roseau County, MN?
Roseau County is in Zone 3b with an average last frost of May 21. Plan your Phlox planting based on this frost date — see the calendar above for exact timing.
What planting zone is Roseau County, MN?
Roseau County, Minnesota is in USDA Hardiness Zone 3b. The average last spring frost is May 21 and first fall frost is September 22.
When should I plant Phlox in Roseau County, MN?
In Roseau County, MN, plant Phlox after the last frost (around May 21) and before the first frost (around September 22). Best results when soil holds above 50°F.
What growing zone is Roseau County, MN for Phlox?
Roseau County sits in USDA Zone 3b. Phlox grows reliably in zones 3a through 9a, so it's a good fit here.
Can Phlox grow in Roseau County's climate?
Yes — Phlox grows well in Roseau County's temperate climate. Roseau County averages a 124-day frost-free season, with last frost around May 21 and first frost around September 22.
Your Roseau County Garden Planner — Free
A 22-page printable planner built for Roseau County (Zone 3b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.