When to plant Irises in Sullivan County, MO
Sullivan County's 183-day season only supports one Irises planting per year. Sow between April 24 and May 8 for the best chance at full maturity before October 17.
When to Plant Irises in Sullivan County, MO
Bearded Iris (Iris germanica) are among the most regal flowers of the late-spring garden, producing elegantly ruffled blooms in virtually every color of the rainbow — often in spectacular bicolor combinations. Named for the fuzzy "beard" on the lower falls (petals), bearded irises grow from thick horizontal rhizomes that spread to form dense clumps over time. Individual blooms last only a few days, but a well-established clump produces successive flowers over 3–4 weeks. Many are intensely fragrant. Native iris species including blue flag iris (I. versicolor) and Virginia iris (I. virginica) are excellent choices for wet or native garden settings.
Sullivan County, Missouri is in USDA Zone 6a. The average last spring frost is April 17 and the first fall frost is October 17, giving you a growing season of approximately 183 days.
At an elevation of 1,019 feet, Sullivan County receives approximately 34.5 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Irises to ensure they mature before fall.
Sullivan County Soil Profile
Soil Type
Silt Loam
Soil pH
5.5-6.8
Drainage
Well Drained
Monthly Watering Guide for Irises
Irises needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Irises Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.6" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| May | 4.3" | 4" | 0.3" | 💧 Light watering |
| Jun | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jul | 4.3" | 3.9" | 0.4" | 💧 Light watering |
| Aug | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| Sep | 4.3" | 3.3" | 1" | 💧 Light watering |
| Oct | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2" | 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.
Irises Planting Timeline — Sullivan County, MO
Irises Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 24 | Apr 24 – May 8 |
| Bloom | June 19 | Jun 19 – Jul 17 |
Plant 0.5" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | Bloom |
| July | Bloom |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
📅 Days to Maturity
60–100 days
🧪 Soil pH
Needs 6.8–7 · Your soil: N/A
🗺️ USDA Zone
Zone 6a
📆 Growing Season
183 days in Sullivan County
Growing Tips for Sullivan County
Plant rhizomes in late summer to early fall (July–September) after bloom season, setting them horizontally with the top of the rhizome at or just slightly below soil surface — never deeply buried. Full sun is essential for best bloom; at least 6 hours. Well-drained soil is critical; wet rhizomes rot in winter. After bloom, remove flower stalks but leave foliage until it browns in fall. Divide every 3–5 years in late summer when clumps become congested (crowded rhizomes stop blooming). Iris borer is the primary pest — remove and destroy affected fans. Year 2+ after division delivers the most bloom; freshly divided rhizomes may have limited or no bloom in their first season.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Irises in Other Locations
Frequently Asked Questions
When should I plant Irises in Sullivan County, MO?
Sullivan County is in Zone 6a with an average last frost of April 17. Plan your Irises planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sullivan County, MO?
Sullivan County, Missouri is in USDA Hardiness Zone 6a. The average last spring frost is April 17 and first fall frost is October 17.
When should I plant Irises in Sullivan County, MO?
In Sullivan County, MO, plant Irises after the last frost (around April 17) and before the first frost (around October 17). Best results when soil holds above 50°F.
What growing zone is Sullivan County, MO for Irises?
Sullivan County sits in USDA Zone 6a. Irises grows reliably in zones 3a through 9b, so it's a good fit here.
Can Irises grow in Sullivan County's climate?
Yes — Irises grows well in Sullivan County's temperate climate. Sullivan County averages a 183-day frost-free season, with last frost around April 17 and first frost around October 17.
Your Sullivan County Garden Planner — Free
A 22-page printable planner built for Sullivan County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.