When to plant Astilbe in Fillmore County, MN
Plant Astilbe in Fillmore County during the brief May 17–May 31 window. With 156 frost-free days, fall plantings can't mature before October 6.
When to Plant Astilbe in Fillmore County, MN
August to-do list for Fillmore County, Minnesota
August rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Fillmore County, Minnesota.
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Harvest astilbe as they ripen
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
A few tasks this August that'll pay off in September
- First harvests: astilbe
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.
Fillmore County, Minnesota is in USDA Zone 4b. The average last spring frost is May 3 and the first fall frost is October 6, giving you a growing season of approximately 156 days.
At an elevation of 870 feet, Fillmore County receives approximately 37.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 81°F, so choose short-season varieties of Astilbe to ensure they mature before fall.
Fillmore County Soil Profile
Soil Type
Silt Loam
Soil pH
6-7.3
Drainage
Well Drained
Astilbe Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Fillmore County
How your county's soil matches Astilbe's growing requirements.
Soil pH
Your soil pH (6.0–7.3) is within Astilbe's preferred range (6.0–8.0).
Soil Texture
The silt loam soil in Fillmore County is excellent for Astilbe — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.3%) — Astilbe will thrive.
How to Plant Astilbe
Succession Planting Astilbe
Sow every 8 weeks. Last sowing by Jun 28 to harvest before frost.
Astilbe Water Budget
Monthly Watering Guide for Astilbe
Astilbe needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Astilbe Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.8" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | — | 3.6" | 0" | ❄️ Dormant |
| May | 6.5" | 4" | 2.5" | 💧 Light watering |
| Jun | 6.5" | 5.1" | 1.4" | 💧 Light watering |
| Jul | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| Aug | 6.5" | 3.6" | 2.9" | 💧 Light watering |
| Sep | 6.5" | 3.3" | 3.2" | 💧 Light watering |
| Oct | 6.5" | 3" | 3.5" | 🚿 Regular watering |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Fillmore County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Astilbe Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Astilbe Planting Timeline — Fillmore County, MN
Astilbe Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 22 | Feb 22 – Mar 8 |
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Bloom | August 9 | Aug 9 – Oct 4 |
Plant 1.5" deep · 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1.5"/week · 1-2 times/week
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 4b
📆 Growing Season
156 days in Fillmore County
Growing Tips for Astilbe in Fillmore County
Direct sow Astilbe outdoors after May 03 in Fillmore County when soil has warmed and frost danger has passed.
General growing tips
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 Fillmore County, MN?
Fillmore County is in Zone 4b with an average last frost of May 3. Plan your Astilbe planting based on this frost date — see the calendar above for exact timing.
What planting zone is Fillmore County, MN?
Fillmore County, Minnesota is in USDA Hardiness Zone 4b. The average last spring frost is May 3 and first fall frost is October 6.
When should I plant Astilbe in Fillmore County, MN?
In Fillmore County, MN, plant Astilbe after the last frost (around May 3) and before the first frost (around October 6). Best results when soil holds above 50°F.
What growing zone is Fillmore County, MN for Astilbe?
Fillmore County sits in USDA Zone 4b. Astilbe grows reliably in zones 3a through 8b, so it's a good fit here.
Can Astilbe grow in Fillmore County's climate?
Yes — Astilbe grows well in Fillmore County's temperate climate. Fillmore County averages a 156-day frost-free season, with last frost around May 3 and first frost around October 6.
Your Fillmore County Garden Planner — Free
A 22-page printable planner built for Fillmore County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.