When to Plant Stevia in Columbia County, OR
Your May planting checklist for Columbia County, Oregon
May is a pivotal month for Columbia County, Oregon gardens. Focus on these tasks first and you'll set up the rest of the season for success.
Coming up in June — start thinking about
- Starting indoors: stevia
- First harvests: stevia
Stevia is a subtropical herb whose leaves contain natural sweeteners 200-300 times sweeter than sugar. It is grown as an annual in most climates.
Columbia County, Oregon is in USDA Zone 8b. The average last spring frost is April 14 and the first fall frost is October 29, giving you a growing season of approximately 198 days.
At an elevation of 396 feet, Columbia County receives approximately 46.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Stevia during the growing season.
Columbia County Soil Profile
Soil Type
Silt Loam
Soil pH
5.5-6.6
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 Columbia County
How your county's soil matches Stevia's growing requirements.
Soil pH
Your soil pH (5.5–6.6) is more acidic than Stevia prefers (6.5–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Columbia County is excellent for Stevia — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.6%) — Stevia will thrive.
How to Plant Stevia
Succession Planting Stevia
Sow every 6.9 weeks. Last sowing by Jul 31 to harvest before frost.
Plant Water Budget
Monthly Watering Guide for Stevia
Stevia needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Stevia Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 6.5" | 0" | ❄️ Dormant |
| Feb | — | 4.8" | 0" | ❄️ Dormant |
| Mar | — | 4.9" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.2" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 1.7" | 0.5" | 💧 Light watering |
| Jul | 2.2" | 0.7" | 1.5" | 🚿 Regular watering |
| Aug | 2.2" | 0.8" | 1.4" | 🚿 Regular watering |
| Sep | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Oct | 2.2" | 3.9" | 0" | ✅ Rainfall sufficient |
| Nov | — | 7.6" | 0" | ❄️ Dormant |
| Dec | — | 7.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Columbia County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Stevia 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.
Stevia Planting Timeline — Columbia County, OR
Stevia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 24 | Feb 24 – Mar 10 |
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
| Direct Sow | April 21 | Apr 21 – May 12 |
| Harvest | June 30 | Jun 30 – Sep 8 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 8b
📆 Growing Season
198 days in Columbia County
Growing Tips for Stevia in Columbia County
Direct sow Stevia outdoors after April 14 in Columbia County when soil has warmed and frost danger has passed.
Common pests for Stevia in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors under lights or buy transplants. Pinch flowers to encourage leaf production. Harvest leaves before flowering for maximum sweetness. Dry leaves for year-round use.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Stevia in Other Locations
Frequently Asked Questions
When should I plant Stevia in Columbia County, OR?
Columbia County is in Zone 8b with an average last frost of April 14. Plan your Stevia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Columbia County, OR?
Columbia County, Oregon is in USDA Hardiness Zone 8b. The average last spring frost is April 14 and first fall frost is October 29.
Your Columbia County Garden Planner — Free
A 24-page printable planner built for Columbia County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.