When to plant Jostaberry in Boulder County, CO
Boulder County sits in cold Zone 6a. Plant Jostaberry June 4–June 18 for the single annual harvest; the September 26 first frost closes the window.
When to Plant Jostaberry in Boulder County, CO
Your June gardening checklist
A quick June briefing for Boulder County, Colorado gardeners — what's urgent, what's next, and what can wait.
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Get jostaberry in the ground
Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.
Jostaberry is a thornless hybrid of black currant and gooseberry, producing medium-sized, dark berries with a complex, tart-sweet flavor. It is vigorous and disease-resistant.
Boulder County, Colorado is in USDA Zone 6a. The average last spring frost is May 14 and the first fall frost is September 26, giving you a growing season of approximately 135 days.
At an elevation of 7,657 feet, Boulder County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Jostaberry during the growing season.
Boulder County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
Drainage
Well Drained
Jostaberry 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 Boulder County
How your county's soil matches Jostaberry's growing requirements.
Soil pH
Your soil pH (6.7–8.0) is more alkaline than Jostaberry prefers (6.0–6.5). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Boulder County is excellent for Jostaberry — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Jostaberry.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Jostaberry.
How to Plant Jostaberry
Jostaberry Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Jostaberry
Jostaberry needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Jostaberry Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 4.3" | 3" | 1.3" | 💧 Light watering |
| Jun | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Jul | 4.3" | 2" | 2.3" | 🚿 Regular watering |
| Aug | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Sep | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Oct | — | 1.9" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Boulder County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Jostaberry 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.
Jostaberry Planting Timeline — Boulder County, CO
Jostaberry Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | June 4 | Jun 4 – Jun 18 |
· 48" apart · Rows 72" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | — |
| June | Transplant Outdoors |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
730–1095 days
🧪 Soil pH
Needs 6–6.5 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6a
📆 Growing Season
135 days in Boulder County
Growing Tips for Jostaberry in Boulder County
Direct sow Jostaberry outdoors after May 14 in Boulder County when soil has warmed and frost danger has passed.
Your 135.0-day growing season in Boulder County is tight for Jostaberry (730.0-1095.0 days to maturity). Start indoors and choose early-maturing varieties.
Boulder County receives only 22" of rain annually. Jostaberry needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Plant in rich, well-drained soil. No special pruning required beyond removing old wood. Self-fertile but yields improve with a second bush. Berries ripen midsummer.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Jostaberry in Other Locations
Frequently Asked Questions
When should I plant Jostaberry in Boulder County, CO?
Boulder County is in Zone 6a with an average last frost of May 14. Plan your Jostaberry planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boulder County, CO?
Boulder County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 14 and first fall frost is September 26.
When should I plant Jostaberry in Boulder County, CO?
In Boulder County, CO, plant Jostaberry after the last frost (around May 14) and before the first frost (around September 26). Best results when soil holds above 50°F.
What growing zone is Boulder County, CO for Jostaberry?
Boulder County sits in USDA Zone 6a. Jostaberry grows reliably in zones 3a through 8b, so it's a good fit here.
Can Jostaberry grow in Boulder County's climate?
Yes — Jostaberry grows well in Boulder County's temperate climate. Boulder County averages a 135-day frost-free season, with last frost around May 14 and first frost around September 26.
Your Boulder County Garden Planner — Free
A 22-page printable planner built for Boulder County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.