When to plant Irises in Jerome County, ID
Plant Irises in Jerome County, between May 17 and May 31 — the only viable window. Zone 6b's short season (147 frost-free days) rules out a fall crop.
When to Plant Irises in Jerome County, ID
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.
Jerome County, Idaho is in USDA Zone 6b. The average last spring frost is May 10 and the first fall frost is October 4, giving you a growing season of approximately 147 days.
At an elevation of 6,306 feet, Jerome County receives approximately 13.5 inches of rainfall annually with predominantly loam soil. Summer highs average 85°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.
Jerome County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Irises Planting Timeline — Jerome County, ID
Irises Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Bloom | July 12 | Jul 12 – Aug 9 |
Plant 0.5" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | Bloom |
| August | Bloom |
| 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 6b
📆 Growing Season
147 days in Jerome County
Growing Tips for Jerome 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 Jerome County, ID?
Jerome County is in Zone 6b with an average last frost of May 10. Plan your Irises planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jerome County, ID?
Jerome County, Idaho is in USDA Hardiness Zone 6b. The average last spring frost is May 10 and first fall frost is October 4.
When should I plant Irises in Jerome County, ID?
In Jerome County, ID, plant Irises after the last frost (around May 10) and before the first frost (around October 4). Best results when soil holds above 50°F.
What growing zone is Jerome County, ID for Irises?
Jerome County sits in USDA Zone 6b. Irises grows reliably in zones 3a through 9b, so it's a good fit here.
Can Irises grow in Jerome County's climate?
Yes — Irises grows well in Jerome County's temperate climate. Jerome County averages a 147-day frost-free season, with last frost around May 10 and first frost around October 4.
Your Jerome County Garden Planner — Free
A 22-page printable planner built for Jerome 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.