When to plant Lobelia in McHenry County, IL
McHenry County's 185-day season only supports one Lobelia planting per year. Sow between April 11 and April 25 for the best chance at full maturity before October 20.
When to Plant Lobelia in McHenry County, IL
Your June game plan for McHenry County, Illinois
Your McHenry County, Illinois garden is entering a new phase. Here's what's on the schedule for June and why each task matters now.
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Time to start lobelia inside
A seed-starting mix and a sunny window (or a grow light) are all you need. Keep soil warm — around 70°F — for fast germination.
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Harvest lobelia as they ripen
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
Before July arrives, get these ready
- First harvests: lobelia
Lobelia (Lobelia erinus) is a cool-season annual prized for the intense cobalt blue that is rare among bedding flowers. It blooms most prolifically in spring and early summer but stalls or dies back during heat peaks above 90°F. In zones 3–7 it delivers a long display; in zones 8–9 it is best treated as a spring annual that fades by midsummer. Trailing types cascade beautifully from containers and window boxes.
McHenry County, Illinois is in USDA Zone 5b. The average last spring frost is April 18 and the first fall frost is October 20, giving you a growing season of approximately 185 days.
At an elevation of 640 feet, McHenry County receives approximately 39.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Lobelia to ensure they mature before fall.
McHenry County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-6.7
Drainage
Well Drained
Lobelia 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 McHenry County
How your county's soil matches Lobelia's growing requirements.
Soil pH
Your soil pH (5.9–6.7) overlaps with Lobelia's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in McHenry County is excellent for Lobelia — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.1%) — Lobelia will thrive.
How to Plant Lobelia
Succession Planting Lobelia
Sow every 8 weeks. Last sowing by Aug 01 to harvest before frost.
Lobelia Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Lobelia
Lobelia needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Lobelia Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.9" | 0" | ❄️ Dormant |
| Mar | — | 2.5" | 0" | ❄️ Dormant |
| Apr | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| May | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jun | 4.3" | 4.8" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Aug | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 3.3" | 1" | 💧 Light watering |
| Oct | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in McHenry County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Lobelia 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.
Lobelia Planting Timeline — McHenry County, IL
Lobelia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 7 | Feb 7 – Feb 21 |
| Transplant Outdoors | April 11 | Apr 11 – Apr 25 |
| Bloom | June 6 | Jun 6 – Aug 22 |
· 6" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | Transplant Outdoors |
| May | — |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
70–80 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
185 days in McHenry County
Growing Tips for Lobelia in McHenry County
Direct sow Lobelia outdoors after April 18 in McHenry County when soil has warmed and frost danger has passed.
General growing tips
Start seeds indoors 10–12 weeks before last frost — seed is dust-fine and requires light to germinate; surface-sow and press gently. Keep at 65–70°F. Not reliably direct-sown. Transplant in cool weather, 2–4 weeks before last frost date is acceptable in zones 5+. Shear plants by one-third after the first bloom flush to encourage a second flush in fall. Provide afternoon shade in zones 7+ to extend bloom into summer.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Lobelia in Other Locations
Frequently Asked Questions
When should I plant Lobelia in McHenry County, IL?
McHenry County is in Zone 5b with an average last frost of April 18. Plan your Lobelia planting based on this frost date — see the calendar above for exact timing.
What planting zone is McHenry County, IL?
McHenry County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 18 and first fall frost is October 20.
When should I plant Lobelia in McHenry County, IL?
In McHenry County, IL, plant Lobelia after the last frost (around April 18) and before the first frost (around October 20). Best results when soil holds above 50°F.
What growing zone is McHenry County, IL for Lobelia?
McHenry County sits in USDA Zone 5b. Lobelia grows reliably in zones 3a through 9b, so it's a good fit here.
Can Lobelia grow in McHenry County's climate?
Yes — Lobelia grows well in McHenry County's temperate climate. McHenry County averages a 185-day frost-free season, with last frost around April 18 and first frost around October 20.
Your McHenry County Garden Planner — Free
A 22-page printable planner built for McHenry 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.