When to Plant Horseradish in Franklin County, WA
This month in Franklin County, Washington
We've pulled the most time-sensitive tasks for Franklin County, Washington this May and put them front and centre. Tackle them in order.
Horseradish is a vigorous perennial grown for its pungent, spicy roots used as a condiment. Once established, it can be difficult to eradicate, so choose its location carefully.
Franklin County, Washington is in USDA Zone 7a. The average last spring frost is April 13 and the first fall frost is October 23, giving you a growing season of approximately 193 days.
At an elevation of 1,556 feet, Franklin County receives approximately 15.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Horseradish during the growing season. With low rainfall, drip irrigation is essential for growing Horseradish successfully. Mulch heavily to conserve soil moisture.
Franklin County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-6.6
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 Franklin County
How your county's soil matches Horseradish's growing requirements.
Soil pH
Your soil pH (5.6–6.6) overlaps with Horseradish's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Franklin County is excellent for Horseradish — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.5%) — Horseradish will thrive.
How to Plant Horseradish
Plant Water Budget
Monthly Watering Guide for Horseradish
Horseradish needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Horseradish Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.5" | 0" | ❄️ Dormant |
| Feb | — | 1.8" | 0" | ❄️ Dormant |
| Mar | — | 1.4" | 0" | ❄️ Dormant |
| Apr | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| May | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Jun | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Jul | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Aug | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Sep | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Oct | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Nov | — | 2.2" | 0" | ❄️ Dormant |
| Dec | — | 2.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Franklin County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Horseradish 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.
Horseradish Planting Timeline — Franklin County, WA
Horseradish Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 27 | Apr 27 – May 11 |
| Harvest | August 31 | Aug 31 – Nov 9 |
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 | Harvest |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
120–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
193 days in Franklin County
Growing Tips for Horseradish in Franklin County
Direct sow Horseradish outdoors after April 13 in Franklin County when soil has warmed and frost danger has passed.
Your 193.0-day growing season in Franklin County is tight for Horseradish (120.0-180.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Horseradish in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
Franklin County receives only 16" of rain annually. Horseradish needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Plant root cuttings at a 45-degree angle in early spring. Harvest roots in late fall for strongest flavor. Contain the plant with barriers or grow in large containers.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Horseradish in Other Locations
Frequently Asked Questions
When should I plant Horseradish in Franklin County, WA?
Franklin County is in Zone 7a with an average last frost of April 13. Plan your Horseradish planting based on this frost date — see the calendar above for exact timing.
What planting zone is Franklin County, WA?
Franklin County, Washington is in USDA Hardiness Zone 7a. The average last spring frost is April 13 and first fall frost is October 23.
Your Franklin County Garden Planner — Free
A 24-page printable planner built for Franklin County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.