When to Plant Vinca (Annual) in Kittitas County, WA
Your June gardening checklist
If you only do a handful of things in the garden this June, make it these. They're sequenced around your zone's frost timing.
Coming up in July — start thinking about
- Starting indoors: vinca (annual)
- First harvests: vinca (annual)
Annual vinca (Catharanthus roseus), also called Madagascar periwinkle, is one of the most heat- and drought-tolerant bedding plants available. Glossy foliage stays attractive all season while cheerful pinwheel blooms continue without deadheading. A top performer in hot, humid Southern summers where impatiens and begonias struggle. Self-cleaning; requires little maintenance once established.
Kittitas County, Washington is in USDA Zone 7a. The average last spring frost is May 7 and the first fall frost is October 2, giving you a growing season of approximately 148 days.
At an elevation of 2,468 feet, Kittitas County receives approximately 18.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Vinca (Annual) during the growing season. With low rainfall, drip irrigation is essential for growing Vinca (Annual) successfully. Mulch heavily to conserve soil moisture.
Kittitas County Soil Profile
Soil Type
Silt Loam
Soil pH
5.5-6.7
Drainage
Well Drained
Vinca (Annual) 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 Kittitas County
How your county's soil matches Vinca (Annual)'s growing requirements.
Soil pH
Your soil pH (5.5–6.7) overlaps with Vinca (Annual)'s range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Kittitas County is excellent for Vinca (Annual) — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.4%) — Vinca (Annual) will thrive.
How to Plant Vinca (Annual)
Succession Planting Vinca (Annual)
Sow every 8 weeks. Last sowing by Jul 04 to harvest before frost.
Vinca (Annual) Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Vinca (Annual)
Vinca (Annual) 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 | Vinca (Annual) Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.9" | 0" | ❄️ Dormant |
| Feb | — | 2" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 2.2" | 1.2" | 1" | 💧 Light watering |
| Jun | 2.2" | 0.8" | 1.4" | 🚿 Regular watering |
| Jul | 2.2" | 0.3" | 1.9" | 🚿 Regular watering |
| Aug | 2.2" | 0.4" | 1.8" | 🚿 Regular watering |
| Sep | 2.2" | 0.8" | 1.4" | 🚿 Regular watering |
| Oct | 2.2" | 1.7" | 0.5" | 💧 Light watering |
| Nov | — | 2.8" | 0" | ❄️ Dormant |
| Dec | — | 2.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Kittitas County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Vinca (Annual) 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.
Vinca (Annual) Planting Timeline — Kittitas County, WA
Vinca (Annual) Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 26 | Feb 26 – Mar 12 |
| Transplant Outdoors | May 7 | May 7 – May 21 |
| Bloom | July 16 | Jul 16 – Nov 5 |
Plant 0.1" deep · 10" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | Bloom |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–90 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
148 days in Kittitas County
Growing Tips for Vinca (Annual) in Kittitas County
Direct sow Vinca (Annual) outdoors after May 07 in Kittitas County when soil has warmed and frost danger has passed.
Kittitas County receives only 19" of rain annually. Vinca (Annual) needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 10–12 weeks before last frost — germination requires warm soil (75–80°F) and darkness. Do not cover seeds deeply; they need just a light dusting. Direct sowing is rarely practiced due to slow seedling establishment. Transplant after soil warms and frost danger has passed. Excellent drought tolerance once established; avoid overwatering. Performs best in well-drained beds or containers in full sun.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Vinca (Annual) in Other Locations
Frequently Asked Questions
When should I plant Vinca (Annual) in Kittitas County, WA?
Kittitas County is in Zone 7a with an average last frost of May 7. Plan your Vinca (Annual) planting based on this frost date — see the calendar above for exact timing.
What planting zone is Kittitas County, WA?
Kittitas County, Washington is in USDA Hardiness Zone 7a. The average last spring frost is May 7 and first fall frost is October 2.
Your Kittitas County Garden Planner — Free
A 22-page printable planner built for Kittitas 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.