When to plant Alliums in Davis County, IA
Davis County's spring Alliums window runs mid-spring through late spring. time plantings around the expected last-frost window for best survival. A second sowing from September 4 to September 18 extends the harvest into fall.
When to Plant Alliums in Davis County, IA
What to do in June
Your garden in Davis County, Iowa is working on a schedule, even when you're not. Here's where you should be this June.
Ornamental alliums (Allium spp.) bridge the gap between spring and summer with their striking globe-shaped flower heads in shades of purple, violet, white, and pink. Blooming after tulips have faded, they extend the spring display well into early summer. 'Gladiator', 'Globemaster', and 'Purple Sensation' produce softball-sized heads on 18–36 inch stems, while smaller species create charming accents at border fronts. Deer and rodents shun them completely due to the characteristic onion scent. Dried seed heads provide architectural interest into fall.
Davis County, Iowa is in USDA Zone 5b. The average last spring frost is April 19 and the first fall frost is October 16, giving you a growing season of approximately 180 days.
At an elevation of 859 feet, Davis County receives approximately 30.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Alliums during the growing season.
Davis County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.7
Drainage
Well Drained
Alliums 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 Davis County
How your county's soil matches Alliums's growing requirements.
Soil pH
Your soil pH (6.2–6.7) is within Alliums's preferred range (5.5–7.5).
Soil Texture
The silt loam soil in Davis County is excellent for Alliums — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.7%) — Alliums will thrive.
How to Plant Alliums
Fall planting: Sow 6 weeks before your first frost date for a fall harvest.
Succession Planting Alliums
Sow every 3.1 weeks. Last sowing by Sep 04 to harvest before frost.
For a dedicated fall crop, sow by Sep 04.
Alliums Water Budget
Monthly Watering Guide for Alliums
Alliums 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 | Alliums Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 2.6" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.3" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.2" | 0" | ❄️ Dormant |
| Dec | — | 1.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Davis County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Alliums 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.
Alliums Planting Timeline — Davis County, IA
Alliums Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Bloom | October 9 | Oct 9 – Oct 30 |
| Fall Sowing | September 4 | Sep 4 – Sep 18 |
Plant 5" deep · 7" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | — |
| June | — |
| July | — |
| August | — |
| September | Fall Sowing |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
28–42 days
🧪 Soil pH
Needs 5.5–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
180 days in Davis County
Growing Tips for Alliums in Davis County
Direct sow Alliums outdoors after April 19 in Davis County when soil has warmed and frost danger has passed.
Your generous 180.0-day season in Davis County allows multiple plantings of Alliums. Sow every 14.0 days for continuous harvest.
Common pests for Alliums in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
General growing tips
Plant bulbs in fall, 3–4 times as deep as the bulb diameter (typically 4–6 inches for large types, 3 inches for small species). Space 6–8 inches apart for standard cultivars. Foliage often looks untidy as it dies back before bloom — plant around perennials that will conceal the yellowing leaves. Excellent drainage is essential; alliums rot in wet soils. Leave bulbs in place for naturalization; divide every 3–4 years when clusters become congested. Deadhead spent globes or leave for ornamental seedheads and self-sowing.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Alliums in Other Locations
Frequently Asked Questions
When should I plant Alliums in Davis County, IA?
Davis County is in Zone 5b with an average last frost of April 19. Plan your Alliums planting based on this frost date — see the calendar above for exact timing.
What planting zone is Davis County, IA?
Davis County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 19 and first fall frost is October 16.
When should I plant Alliums in Davis County, IA?
In Davis County, IA, plant Alliums after the last frost (around April 19) and before the first frost (around October 16). Best results when soil holds above 50°F.
What growing zone is Davis County, IA for Alliums?
Davis County sits in USDA Zone 5b. Alliums grows reliably in zones 3a through 9b, so it's a good fit here.
Can Alliums grow in Davis County's climate?
Yes — Alliums grows well in Davis County's temperate climate. Davis County averages a 180-day frost-free season, with last frost around April 19 and first frost around October 16.
Your Davis County Garden Planner — Free
A 22-page printable planner built for Davis 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.