When to Plant Horseradish in Kenai Peninsula Borough, AK
What to do in May
Each item below is timed to Kenai Peninsula Borough, Alaska's frost dates and soil temperatures. Skip nothing, stress about nothing.
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Set out horseradish seedlings
Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.
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.
Kenai Peninsula Borough, Alaska is in USDA Zone 5a. The average last spring frost is May 17 and the first fall frost is September 25, giving you a growing season of approximately 131 days.
At an elevation of 1,824 feet, Kenai Peninsula Borough receives approximately 55.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 60°F, so choose short-season varieties of Horseradish to ensure they mature before fall. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Horseradish root diseases.
Kenai Peninsula Borough Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-6.8
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 Kenai Peninsula Borough
How your county's soil matches Horseradish's growing requirements.
Soil pH
Your soil pH (5.2–6.8) overlaps with Horseradish's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Kenai Peninsula Borough is excellent for Horseradish — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (6.6%) — 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 | — | 3.2" | 0" | ❄️ Dormant |
| Feb | — | 2.4" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | — | 1.5" | 0" | ❄️ Dormant |
| May | 4.3" | 2.3" | 2" | 💧 Light watering |
| Jun | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Jul | 4.3" | 7.6" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.3" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 10.1" | 0" | ✅ Rainfall sufficient |
| Oct | — | 7" | 0" | ❄️ Dormant |
| Nov | — | 4.3" | 0" | ❄️ Dormant |
| Dec | — | 3.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Kenai Peninsula Borough). 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 — Kenai Peninsula Borough, AK
Horseradish Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 31 | May 31 – Jun 14 |
| Harvest | October 4 | Oct 4 – Nov 15 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | — |
| August | — |
| September | — |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
120–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
131 days in Kenai Peninsula Borough
Growing Tips for Horseradish in Kenai Peninsula Borough
Direct sow Horseradish outdoors after May 17 in Kenai Peninsula Borough when soil has warmed and frost danger has passed.
Your 131.0-day growing season in Kenai Peninsula Borough 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.
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 Kenai Peninsula Borough, AK?
Kenai Peninsula Borough is in Zone 5a with an average last frost of May 17. Plan your Horseradish planting based on this frost date — see the calendar above for exact timing.
What planting zone is Kenai Peninsula Borough, AK?
Kenai Peninsula Borough, Alaska is in USDA Hardiness Zone 5a. The average last spring frost is May 17 and first fall frost is September 25.
Your Kenai Peninsula Borough Garden Planner — Free
A 24-page printable planner built for Kenai Peninsula Borough (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.