What to plant in March in Idaho
In Idaho (ID), March sits about 8 weeks before the average last frost (May 10). The state averages 138 frost-free days a year (last frost May 10, first frost September 25; USDA zones 3b, 4b, 5b, 6a, 6b, 7a).
40 crops have a sowing or planting window this month, including mache (corn salad), pea, spinach - and 5 of those windows close during March.
Dates here come from Idaho frost dates (last frost May 10, first frost Sep 25). For one crop in detail, see when to plant pea, spinach or onion in Idaho.
Idaho covers a very wide range of climates, so dates near you can be two weeks or more either side of these. Enter your ZIP code in the planting calendar for dates tuned to your town.
Idaho: planting activity through the year
Last chance in March
Celeriac (start seeds indoors, by Mar 1) · Celery (start seeds indoors, by Mar 8) · Leek (start seeds indoors, by Mar 8) · Onion (start seeds indoors, by Mar 8) · Rosemary (start seeds indoors, by Mar 8)
Sow or plant outdoors in March (3)
Direct sowing and transplanting windows that fall in March, most urgent first. Windows are one-to-two-week bands around the ideal date.
| Crop | What to do | Window | This month |
|---|---|---|---|
| Mache (Corn Salad) | Direct sow (spring) | Mar 31 – Apr 19 | Opens Mar 31 |
| Pea | Direct sow (spring) | Mar 31 – Apr 19 | Opens Mar 31 |
| Spinach | Direct sow (spring) | Mar 31 – Apr 19 | Opens Mar 31 |
Start seeds indoors in March (37)
Indoor sowings for transplants later. Six to eight weeks under lights is typical for tomatoes and peppers; onions and leeks need longer.
| Crop | What to do | Window | This month |
|---|---|---|---|
| Celeriac | Start seeds indoors | Feb 15 – Mar 1 | Last chance - ends Mar 1 |
| Celery | Start seeds indoors | Feb 22 – Mar 8 | Last chance - ends Mar 8 |
| Leek | Start seeds indoors | Feb 22 – Mar 8 | Last chance - ends Mar 8 |
| Onion | Start seeds indoors | Feb 22 – Mar 8 | Last chance - ends Mar 8 |
| Rosemary | Start seeds indoors | Feb 22 – Mar 8 | Last chance - ends Mar 8 |
| Eggplant | Start seeds indoors | Mar 1 – Mar 15 | Mar 1 – Mar 15 |
| Parsley | Start seeds indoors | Mar 1 – Mar 15 | Mar 1 – Mar 15 |
| Shallot | Start seeds indoors | Mar 1 – Mar 15 | Mar 1 – Mar 15 |
| Bell Pepper | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Chili Pepper | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Ginger | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Green Onion / Scallion | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Mint | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Oregano | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Sage | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Tarragon | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Thyme | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Turmeric | Start seeds indoors | Mar 8 – Mar 22 | Mar 8 – Mar 22 |
| Ground Cherry | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Lemon Balm | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Shiso (Perilla) | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Sweet Marjoram | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Tomatillo | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Tomato | Start seeds indoors | Mar 15 – Mar 29 | Mar 15 – Mar 29 |
| Broccoli | Start seeds indoors | Mar 22 – Apr 5 | Opens Mar 22 |
| Brussels Sprouts | Start seeds indoors | Mar 22 – Apr 5 | Opens Mar 22 |
| Cabbage | Start seeds indoors | Mar 22 – Apr 5 | Opens Mar 22 |
| Cauliflower | Start seeds indoors | Mar 22 – Apr 5 | Opens Mar 22 |
| Kale | Start seeds indoors | Mar 22 – Apr 5 | Opens Mar 22 |
| Basil | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Collard Greens | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Endive & Escarole | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Kohlrabi | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Malabar Spinach | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Okra | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Radicchio | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
| Summer Savory | Start seeds indoors | Mar 29 – Apr 12 | Opens Mar 29 |
Planting dates for popular crops in Idaho
Every crop has its own full-year dates for Idaho: indoor start, transplant or direct sowing, and harvest.
Seed-starting season: March garden jobs in Idaho
- Start 37 crops indoors this month, including celeriac, celery, leek, onion. Use a sterile mix and good light - see starting seeds indoors.
- 8 weeks until the average last frost (May 10). The seed-starting calculator works out each crop's exact sowing date from it.
- Keep seedlings from stretching: lights 2-3 inches above the leaves for 14-16 hours a day, and a fan or a daily brush of the hand across the tops.
- Prepare beds as soon as the soil crumbles instead of smearing when squeezed - working wet soil ruins its structure for the season.
USDA zone chart for Idaho
Idaho spans USDA zones 3b, 4b, 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average.
Questions gardeners ask
What vegetables can I plant in Idaho in March?
40 crops have a window in March: mache (corn salad), pea, spinach, celeriac, celery, leek, onion, rosemary, eggplant, parsley and more. The tables above give the exact dates for each.
Is it too late to plant tomatoes in Idaho in March?
No - start seeds indoors runs Mar 15 – Mar 29 in Idaho, so do it before March 29.
Is it too late to plant lettuce in Idaho in March?
Not too late - it's actually a little early. In Idaho the next lettuce window opens around April 5: start seeds indoors.
When is the first frost in Idaho?
The statewide average first fall frost is around September 25 and the last spring frost around May 10. Idaho covers a wide range of climates, so local dates can differ by two weeks or more - look yours up by ZIP code.
What should I start indoors in March in Idaho?
Celeriac (Feb 15 – Mar 1), Celery (Feb 22 – Mar 8), Leek (Feb 22 – Mar 8), Onion (Feb 22 – Mar 8), Rosemary (Feb 22 – Mar 8), Eggplant (Mar 1 – Mar 15), Parsley (Mar 1 – Mar 15), Shallot (Mar 1 – Mar 15), Bell Pepper (Mar 8 – Mar 22), Chili Pepper (Mar 8 – Mar 22), Ginger (Mar 8 – Mar 22), Green Onion / Scallion (Mar 8 – Mar 22), Mint (Mar 8 – Mar 22), Oregano (Mar 8 – Mar 22), Sage (Mar 8 – Mar 22), Tarragon (Mar 8 – Mar 22), Thyme (Mar 8 – Mar 22), Turmeric (Mar 8 – Mar 22), Ground Cherry (Mar 15 – Mar 29), Lemon Balm (Mar 15 – Mar 29), Shiso (Perilla) (Mar 15 – Mar 29), Sweet Marjoram (Mar 15 – Mar 29), Tomatillo (Mar 15 – Mar 29), Tomato (Mar 15 – Mar 29), Broccoli (Mar 22 – Apr 5), Brussels Sprouts (Mar 22 – Apr 5), Cabbage (Mar 22 – Apr 5), Cauliflower (Mar 22 – Apr 5), Kale (Mar 22 – Apr 5), Basil (Mar 29 – Apr 12), Collard Greens (Mar 29 – Apr 12), Endive & Escarole (Mar 29 – Apr 12), Kohlrabi (Mar 29 – Apr 12), Malabar Spinach (Mar 29 – Apr 12), Okra (Mar 29 – Apr 12), Radicchio (Mar 29 – Apr 12), Summer Savory (Mar 29 – Apr 12).
What to plant in March in other states
Dates are computed from Idaho’s statewide average frost dates (from NOAA/NCEI climate normals) and each crop’s timing in our crop database. Your garden may be a week or two either side - for dates tuned to your ZIP code, use the planting calendar.