When to Plant Sweet Pea in Montana

Sweet peas (Lathyrus odoratus) are beloved cool-season climbing annuals grown primarily for their intensely fragrant, ruffled blooms in shades of pink, purple, red, and white. They thrive in cool spring conditions, climbing trellises to 4–6 feet, and make outstanding cut flowers. Bloom ceases once summer heat arrives, making early sowing critical for a long cutting season.

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 Sweet Pea planting dates based on your local frost dates.

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

Sweet Pea 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 22	Mar 22 – Apr 5
Transplant Outdoors	May 10	May 10 – May 24
Direct Sow	April 12	Apr 12 – May 3
Bloom	August 2	Aug 2 – Sep 13

▸ 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	March 18	Mar 18 – Apr 1
Transplant Outdoors	May 6	May 6 – May 20
Direct Sow	April 1	Apr 1 – Apr 22
Bloom	July 29	Jul 29 – Sep 9

▸ 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	March 20	Mar 20 – Apr 3
Transplant Outdoors	May 1	May 1 – May 15
Direct Sow	March 27	Mar 27 – Apr 17
Bloom	July 24	Jul 24 – Sep 11

▸ 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	March 14	Mar 14 – Mar 28
Transplant Outdoors	April 25	Apr 25 – May 9
Direct Sow	March 21	Mar 21 – Apr 11
Bloom	July 11	Jul 11 – Sep 12

▸ 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	March 7	Mar 7 – Mar 21
Transplant Outdoors	April 18	Apr 18 – May 2
Direct Sow	March 14	Mar 14 – Apr 4
Bloom	July 4	Jul 4 – Sep 5

▸ 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 27	Feb 27 – Mar 13
Transplant Outdoors	April 10	Apr 10 – Apr 24
Direct Sow	March 6	Mar 6 – Mar 27
Bloom	June 26	Jun 26 – Sep 4

Growing Tips for Montana

Soak seeds 24 hours before sowing to soften the hard seed coat; nick the seed coat with a file for the fastest germination. In cold zones (2–6), direct-sow as soon as soil can be worked, 4–6 weeks before last frost; seedlings tolerate light frost but not a hard freeze. In zones 7–9, fall-sow 8–10 weeks before first frost for earlier, stronger spring bloom. Provide a trellis or netting from the start. Feed with low-nitrogen, high-potassium fertilizer once buds form. Pick blooms regularly — even one mature seed pod stops flower production. All plant parts are mildly toxic if eaten.

Sweet Pea in Other States

Frequently Asked Questions

When should I plant Sweet Pea in Montana?

Planting dates for Sweet Pea 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