When to Plant Irises in Washington County, UT
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.
Washington County, Utah is in USDA Zone 8b. The average last spring frost is April 6 and the first fall frost is November 1, giving you a growing season of approximately 209 days.
At an elevation of 3,524 feet, Washington County receives approximately 12.7 inches of rainfall annually with predominantly loam soil. Summer highs average 90°F, providing good warmth for Irises during the growing season. With low rainfall, drip irrigation is essential for growing Irises successfully. Mulch heavily to conserve soil moisture.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
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" | 0" | ❄️ Dormant |
| Feb | — | 0.6" | 0" | ❄️ Dormant |
| Mar | — | 1.1" | 0" | ❄️ Dormant |
| Apr | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| May | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Jun | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Jul | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Aug | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Sep | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Oct | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Nov | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Dec | — | 0.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Washington County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Irises Planting Timeline — Washington County, UT
Irises Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | March 30 | Mar 30 – Apr 13 |
| Bloom | May 18 | May 18 – Jun 22 |
Plant 0.5" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Transplant Outdoors |
| April | Transplant Outdoors |
| May | Bloom |
| June | Bloom |
| July | — |
| 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 8b
📆 Growing Season
209 days in Washington County
Growing Tips for Washington 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 Washington County, UT?
Washington County is in Zone 8b with an average last frost of April 6. Plan your Irises planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, UT?
Washington County, Utah is in USDA Hardiness Zone 8b. The average last spring frost is April 6 and first fall frost is November 1.
Your Washington County Garden Planner — Free
A 22-page printable planner built for Washington County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.