When to Plant Lobelia in USDA Zone 3a
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.
In Zone 3a, the average last spring frost is around May 15 and the first fall frost is around September 15, giving you a growing season of approximately 123 days.
Lobelia Planting Timeline — Zone 3a
Where Is USDA Zone 3a?
The map below highlights the states that contain Zone 3a. Click any state to see the Lobelia planting schedule for that location.
Lobelia Planting Calendar — Zone 3a
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 6 | Mar 6 – Mar 20 |
| Transplant Outdoors | May 22 | May 22 – Jun 5 |
| Bloom | July 17 | Jul 17 – Aug 28 |
· 6" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | Bloom |
| August | Bloom |
| September | — |
| October | — |
| November | — |
| December | — |
Free Zone 3a Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 3a with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Partial Shade (3-6 hours)
💧 Water
Moderate — regular watering
Days to Maturity
70–80 days
Soil pH
6 – 7
Zone Temperature Range
-40°F to -35°F average annual minimum
Growing Season
123 days (Zone 3a average)
Planting Specifications
| Plant Spacing | 6 inches apart |
| Row Spacing | 8 inches between rows |
Growing Tips for Lobelia in Zone 3a
Zone 3a has a short growing season (~123 days). Start Lobelia indoors early and use season-extension techniques like row covers and cold frames.
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
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Warm soil for faster germination of heat-loving crops like tomatoes and peppers.
Protect plants from frost, wind, and pests while letting light and water through.
Related Plants
Lobelia in Other Zones
Lobelia by State
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- Rhode Island
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
Frequently Asked Questions
When should I plant Lobelia in Zone 3a?
In Zone 3a, plan your Lobelia planting around the average last frost date of May 15. Start seeds indoors around March 6. Transplant seedlings around May 22.
Can Lobelia grow in Zone 3a?
Yes, Lobelia can grow well in Zone 3a, hardy in USDA zones 3a through 9b. Zone 3a has a growing season of approximately 123 days, which is sufficient for Lobelia (70-80 days to maturity).
When can I harvest Lobelia in Zone 3a?
In Zone 3a, expect to harvest Lobelia from July 17 – August 28. Lobelia takes 70-80 days from planting to harvest.
What is the last frost date for Zone 3a?
The average last spring frost in Zone 3a is around May 15, and the first fall frost is around September 15. This gives a growing season of approximately 123 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Lobelia?
Good companion plants for Lobelia include Petunias, Sweet Alyssum, Begonias, Impatiens. These companions can help with pest control, pollination, and nutrient sharing.
Your Zone 3a Garden Planner — Free
A 22-page printable planner tailored to Zone 3a. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.