When to plant Vinca (Annual) in Cass County, IA
Plant Vinca (Annual) in Cass County, between May 2 and May 16 — the only viable window. Zone 5b's short season (167 frost-free days) rules out a fall crop.
When to Plant Vinca (Annual) in Cass County, IA
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.
Cass County, Iowa is in USDA Zone 5b. The average last spring frost is April 25 and the first fall frost is October 9, giving you a growing season of approximately 167 days.
At an elevation of 1,043 feet, Cass County receives approximately 31.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Vinca (Annual) during the growing season.
Cass County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Vinca (Annual) Planting Timeline — Cass County, IA
Vinca (Annual) Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 7 | Feb 7 – Feb 21 |
| Transplant Outdoors | May 2 | May 2 – May 16 |
| Bloom | July 11 | Jul 11 – Oct 3 |
Plant 0.1" deep · 10" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
📅 Days to Maturity
70–90 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5b
📆 Growing Season
167 days in Cass County
Growing Tips for Cass County
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 Cass County, IA?
Cass County is in Zone 5b with an average last frost of April 25. Plan your Vinca (Annual) planting based on this frost date — see the calendar above for exact timing.
What planting zone is Cass County, IA?
Cass County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 25 and first fall frost is October 9.
When should I plant Vinca (Annual) in Cass County, IA?
In Cass County, IA, plant Vinca (Annual) after the last frost (around April 25) and before the first frost (around October 9). Best results when soil holds above 50°F.
What growing zone is Cass County, IA for Vinca (Annual)?
Cass County sits in USDA Zone 5b. Vinca (Annual) grows reliably in zones 3a through 11b, so it's a good fit here.
Can Vinca (Annual) grow in Cass County's climate?
Yes — Vinca (Annual) grows well in Cass County's temperate climate. Cass County averages a 167-day frost-free season, with last frost around April 25 and first frost around October 9.
Your Cass County Garden Planner — Free
A 22-page printable planner built for Cass County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.