When to Plant Lobelia in Montana

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.

Montana spans USDA hardiness zones 3b, 4a, 4b, 5a, 5b, 6a (with planting data available), so planting dates vary by your location within the state. Click your zone below for the most accurate dates.

Find Your County

Click your county for exact Lobelia planting dates based on your local frost dates.

Hover over a county to see details. Click to view planting guide.

Lobelia Planting Calendar for Montana

▸ Zone 3b ~135 day growing season · Full guide →

Last frost: May 10 · First frost: September 22 · 135 day season

Activity	When	Date Range
Start Indoors	March 1	Mar 1 – Mar 15
Transplant Outdoors	May 17	May 17 – May 31
Bloom	July 12	Jul 12 – Aug 30

▸ Zone 4a ~145 day growing season · Full guide →

Last frost: May 6 · First frost: September 28 · 145 day season

Activity	When	Date Range
Start Indoors	February 25	Feb 25 – Mar 11
Transplant Outdoors	May 6	May 6 – May 20
Bloom	July 1	Jul 1 – Aug 26

▸ Zone 4b ~155 day growing season · Full guide →

Last frost: May 1 · First frost: October 3 · 155 day season

Activity	When	Date Range
Start Indoors	February 20	Feb 20 – Mar 6
Transplant Outdoors	May 1	May 1 – May 15
Bloom	June 26	Jun 26 – Aug 28

▸ Zone 5a ~166 day growing season · Full guide →

Last frost: April 25 · First frost: October 8 · 166 day season

Activity	When	Date Range
Start Indoors	February 14	Feb 14 – Feb 28
Transplant Outdoors	April 18	Apr 18 – May 2
Bloom	June 13	Jun 13 – Aug 22

▸ Zone 5b ~178 day growing season · Full guide →

Last frost: April 18 · First frost: October 13 · 178 day season

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

▸ Zone 6a ~193 day growing season · Full guide →

Last frost: April 10 · First frost: October 20 · 193 day season

Activity	When	Date Range
Start Indoors	February 6	Feb 6 – Feb 20
Transplant Outdoors	March 27	Mar 27 – Apr 10
Bloom	May 22	May 22 – Aug 14

Growing Tips for Montana

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.

Lobelia in Other States

Frequently Asked Questions

When should I plant Lobelia in Montana?

Planting dates for Lobelia in Montana depend on your USDA zone. Montana spans zones 3b, 4a, 4b, 5a, 5b, 6a. Check the planting calendar above for your specific zone's frost dates and planting windows.

What zone is Montana for planting?

Montana contains USDA hardiness zones 3b, 4a, 4b, 5a, 5b, 6a. Your specific zone depends on your location within the state — northern and higher-elevation areas are in colder zones, while southern and coastal areas are warmer.

Blog