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When to Plant Lobelia in Crook County, WY

Crook County, Wyoming Zone 4b June

What to do in June

June is a pivotal month for Crook County, Wyoming gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost May 14
Avg. first frost October 1
Soil temp (4") 39°F
Watering High
Pest pressure High
Daylight 15.4 hrs
Coming up in July — start thinking about
  • Starting indoors: lobelia
  • First harvests: lobelia

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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.

Crook County, Wyoming is in USDA Zone 4b. The average last spring frost is May 14 and the first fall frost is October 1, giving you a growing season of approximately 140 days.

At an elevation of 8,060 feet, Crook County receives approximately 24.8 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Lobelia to ensure they mature before fall.

Annual Blooms in Spring Pollinator-friendly
Crook County, WY (Zone 4b) Short season
140 days
Last Spring Frost May 14
140 growing days
First Fall Frost October 1

Crook County Soil Profile

Soil Type

Loam

Soil pH

6.3-7.9

Drainage

Well Drained

Lobelia Planting Risk Windows

Early Start (70% safe) ✓ Fits season (14 days to spare)
Start indoors: Feb 28 Transplant: May 9 🌸 Bloom: Jul 4 – Sep 5
Recommended (50%) ✓ Fits season (21 days to spare)
Start indoors: Mar 5 Transplant: May 14 🌸 Bloom: Jul 9 – Sep 10
Safe Start (90%) ✓ Fits season (20 days to spare)
Start indoors: Mar 20 Transplant: May 29 🌸 Bloom: Jul 24 – Sep 25

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 Crook County

How your county's soil matches Lobelia's growing requirements.

Soil pH

Your soil pH (6.3–7.9) is more alkaline than Lobelia prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Crook County is excellent for Lobelia — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.4%). Annual compost additions will help Lobelia.

How to Plant Lobelia

6"
Between Plants
8"
Between Rows

Succession Planting Lobelia

2
successive plantings in your 140-day season

Sow every 8 weeks. Last sowing by Jul 13 to harvest before frost.

Lobelia Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.3″/week
Watering frequency 1-2 times/week
Season total 383 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — 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 1.5" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 2.9" 0" ❄️ Dormant
May 4.3" 3.1" 1.2" 💧 Light watering
Jun 4.3" 1.6" 2.7" 🚿 Regular watering
Jul 4.3" 2.1" 2.2" 🚿 Regular watering
Aug 4.3" 2.5" 1.8" 💧 Light watering
Sep 4.3" 2.2" 2.1" 💧 Light watering
Oct 4.3" 2.3" 2" 💧 Light watering
Nov 1.6" 0" ❄️ Dormant
Dec 1.5" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Crook 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 needs ~862 GDD — county provides 1,610 GDD Excellent fit

Lobelia Planting Timeline — Crook County, WY

Lobelia Planting Calendar

Activity When Date Range
Start Indoors March 5 Mar 5 – Mar 19
Transplant Outdoors May 14 May 14 – May 28
Bloom July 9 Jul 9 – Sep 10

· 6" apart · Rows 8" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April
May Transplant Outdoors
June
July Bloom
August Bloom
September Bloom
October
November
December

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

70–80 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 4b

📆 Growing Season

140 days in Crook County

Growing Tips for Lobelia in Crook County

Direct sow Lobelia outdoors after May 14 in Crook County when soil has warmed and frost danger has passed.

Crook County receives only 25" of rain annually. Lobelia 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 — 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 →

Frequently Asked Questions

When should I plant Lobelia in Crook County, WY?

Crook County is in Zone 4b with an average last frost of May 14. Plan your Lobelia planting based on this frost date — see the calendar above for exact timing.

What planting zone is Crook County, WY?

Crook County, Wyoming is in USDA Hardiness Zone 4b. The average last spring frost is May 14 and first fall frost is October 1.

🌱

Your Crook County Garden Planner — Free

A 22-page printable planner built for Crook County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Crook County, WY. Local conditions may vary. Last updated: June 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.