When to plant Alliums in Henry County County,
Plant Alliums in Henry County County from mid-spring to late spring in spring. Henry County County sits in USDA Zone 5b, with last frost around April 16 and first frost on October 16. A second sowing from September 4 to September 18 extends the harvest into fall.
When to Plant Alliums in Henry County, IL
June in the garden — Henry County, Illinois
Each item below is timed to Henry County, Illinois's frost dates and soil temperatures. Skip nothing, stress about nothing.
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.
Henry County, Illinois is in USDA Zone 5b. The average last spring frost is April 16 and the first fall frost is October 16, giving you a growing season of approximately 183 days.
At an elevation of 593 feet, Henry County receives approximately 31.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Alliums during the growing season.
Henry County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-7.2
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 Henry County
How your county's soil matches Alliums's growing requirements.
Soil pH
Your soil pH (6.3–7.2) is within Alliums's preferred range (5.5–7.5).
Soil Texture
The silt loam soil in Henry County is excellent for Alliums — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.3%) — 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 | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4.6" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.4" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 2.4" | 0" | ✅ Rainfall sufficient |
| Nov | — | 1.9" | 0" | ❄️ Dormant |
| Dec | — | 1.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Henry 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 — Henry County, IL
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
183 days in Henry County
Growing Tips for Alliums in Henry County
Direct sow Alliums outdoors after April 16 in Henry County when soil has warmed and frost danger has passed.
Your generous 183.0-day season in Henry 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 Henry County, IL?
Henry County is in Zone 5b with an average last frost of April 16. Plan your Alliums planting based on this frost date — see the calendar above for exact timing.
What planting zone is Henry County, IL?
Henry County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 16 and first fall frost is October 16.
When should I plant Alliums in Henry County, ?
In Henry County, , plant Alliums after the last frost (around April 16) and before the first frost (around October 16). Best results when soil holds above 50°F.
What growing zone is Henry County, for Alliums?
Henry 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 Henry County's climate?
Yes — Alliums grows well in Henry County's temperate climate. Henry County averages a 183-day frost-free season, with last frost around April 16 and first frost around October 16.
Your Henry County Garden Planner — Free
A 22-page printable planner built for Henry 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.