When to Plant Astilbe in Cache County, UT
Astilbe (Astilbe x arendsii) is a premier perennial for shaded, moist gardens, producing feathery plume-like flower spikes in shades of pink, red, white, and lavender above deeply cut, ferny foliage. Originating in Asia and naturalized in shade gardens worldwide, astilbe thrives where many sun-lovers fail: under trees, beside water features, or in persistently moist woodland borders. The dried flower plumes remain attractive through fall and winter. Different cultivars extend the bloom season from early summer through early fall when several varieties are combined.
Cache County, Utah is in USDA Zone 6a. The average last spring frost is June 11 and the first fall frost is September 2, giving you a growing season of approximately 83 days.
At an elevation of 6,265 feet, Cache County receives approximately 15.5 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Astilbe to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Astilbe successfully. Mulch heavily to conserve soil moisture.
Cache County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Astilbe Planting Timeline — Cache County, UT
Astilbe Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 9 | Apr 9 – Apr 23 |
| Transplant Outdoors | June 18 | Jun 18 – Jul 2 |
| Bloom | August 27 | Aug 27 – Nov 5 |
Plant 1.5" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | — |
| June | Transplant Outdoors |
| July | Transplant Outdoors |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | Bloom |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
High — keep soil consistently moist
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–8 · Your soil: N/A
🗺️ USDA Zone
Zone 6a
📆 Growing Season
83 days in Cache County
Growing Tips for Cache County
Plant bare-root crowns in spring as soon as the ground is workable, setting eyes 1–2 inches below soil level. Fall planting (Zones 4+) is equally effective. Consistent moisture is non-negotiable — astilbe will wilt and scorch in drought. Amend with generous compost to improve moisture retention. Partial shade (morning sun, afternoon shade) is ideal; deep shade reduces bloom but foliage remains. Fertilize lightly in spring with a balanced slow-release granular. Divide every 3–5 years in early spring as clumps become congested. Leave plumes standing through winter for ornamental interest and wildlife value. Year 2+ plants produce the fullest bloom spikes; first-year crowns may flower lightly or not at all.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Astilbe in Other Locations
Frequently Asked Questions
When should I plant Astilbe in Cache County, UT?
Cache County is in Zone 6a with an average last frost of June 11. Plan your Astilbe planting based on this frost date — see the calendar above for exact timing.
What planting zone is Cache County, UT?
Cache County, Utah is in USDA Hardiness Zone 6a. The average last spring frost is June 11 and first fall frost is September 2.
Your Cache County Garden Planner — Free
A 22-page printable planner built for Cache 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.