When to Plant Asparagus in Clackamas County, OR
Your May planting checklist for Clackamas County, Oregon
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Clackamas County, Oregon.
Asparagus is a long-lived perennial vegetable that produces tender spears each spring for 15-20 years once established. It requires patience but rewards with reliable harvests.
Clackamas County, Oregon is in USDA Zone 9a. The average last spring frost is April 14 and the first fall frost is October 28, giving you a growing season of approximately 197 days.
At an elevation of 199 feet, Clackamas County receives approximately 53.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Asparagus during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Asparagus root diseases.
Clackamas County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.3
Drainage
Well Drained
Plant 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 Clackamas County
How your county's soil matches Asparagus's growing requirements.
Soil pH
Your soil pH (5.7–6.3) is more acidic than Asparagus prefers (6.5–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Clackamas County is excellent for Asparagus — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.7%) — Asparagus will thrive.
How to Plant Asparagus
Plant Water Budget
Monthly Watering Guide for Asparagus
Asparagus needs approximately 0.8 inches of water per week (3.5" per month). Here's how your county's rainfall compares month by month.
| Month | Asparagus Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 8.3" | 0" | ❄️ Dormant |
| Feb | — | 5.3" | 0" | ❄️ Dormant |
| Mar | — | 4.8" | 0" | ❄️ Dormant |
| Apr | 3.5" | 4" | 0" | ✅ Rainfall sufficient |
| May | 3.5" | 3.3" | 0.2" | 💧 Light watering |
| Jun | 3.5" | 2.1" | 1.4" | 💧 Light watering |
| Jul | 3.5" | 0.8" | 2.7" | 🚿 Regular watering |
| Aug | 3.5" | 1" | 2.5" | 🚿 Regular watering |
| Sep | 3.5" | 2.2" | 1.3" | 💧 Light watering |
| Oct | 3.5" | 4.7" | 0" | ✅ Rainfall sufficient |
| Nov | — | 8.2" | 0" | ❄️ Dormant |
| Dec | — | 8.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Clackamas County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Asparagus 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.
Asparagus Planting Timeline — Clackamas County, OR
Asparagus Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.8"/week · Natural rainfall sufficient
📅 Days to Maturity
730–1095 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 9a
📆 Growing Season
197 days in Clackamas County
Growing Tips for Asparagus in Clackamas County
Direct sow Asparagus outdoors after April 14 in Clackamas County when soil has warmed and frost danger has passed.
Your 197.0-day growing season in Clackamas County is tight for Asparagus (730.0-1095.0 days to maturity). Start indoors and choose early-maturing varieties.
General growing tips
Plant crowns in deep trenches with compost. Do not harvest spears for the first two years to allow root establishment. Mulch heavily to suppress weeds and retain moisture.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Asparagus in Other Locations
Frequently Asked Questions
When should I plant Asparagus in Clackamas County, OR?
Clackamas County is in Zone 9a with an average last frost of April 14. Plan your Asparagus planting based on this frost date — see the calendar above for exact timing.
What planting zone is Clackamas County, OR?
Clackamas County, Oregon is in USDA Hardiness Zone 9a. The average last spring frost is April 14 and first fall frost is October 28.
Your Clackamas County Garden Planner — Free
A 24-page printable planner built for Clackamas County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.