My Planting Calendar

What to plant in March in Colorado

In Colorado (CO), March sits about 7 weeks before the average last frost (May 5). The state averages 149 frost-free days a year (last frost May 5, first frost October 1; USDA zones 3b, 4b, 5a, 5b, 6a, 7a).

50 crops have a sowing or planting window this month, including mache (corn salad), pea, spinach, green onion / scallion - and 7 of those windows close during March.

Dates here come from Colorado frost dates (last frost May 5, first frost Oct 1). For one crop in detail, see when to plant pea, spinach or onion in Colorado.

Seed-starting seasonSow or plant: 50Start indoors: 47Harvesting: 0

Colorado 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.

Colorado: planting activity through the year

0
8
50
70
84
45
34
22
1
2
0
0
JanFebMarAprMayJunJulAugSepOctNovDec
Frost riskFrost-free: May 5 – Oct 1
Bars count the vegetables, herbs and fruit with a sowing or planting window in each month, from the state’s average frost dates. 50 have one in March; the busiest month is May (84).

Last chance in March

Celery (start seeds indoors, by Mar 3) · Leek (start seeds indoors, by Mar 3) · Onion (start seeds indoors, by Mar 3) · Rosemary (start seeds indoors, by Mar 3) · Eggplant (start seeds indoors, by Mar 10) · Parsley (start seeds indoors, by Mar 10) · Shallot (start seeds indoors, by Mar 10)

Sow or plant outdoors in March (4)

Direct sowing and transplanting windows that fall in March, most urgent first. Windows are one-to-two-week bands around the ideal date.

CropWhat to doWindowThis month
Mache (Corn Salad)Direct sow (spring)Mar 26 – Apr 14Opens Mar 26
PeaDirect sow (spring)Mar 26 – Apr 14Opens Mar 26
SpinachDirect sow (spring)Mar 26 – Apr 14Opens Mar 26
Green Onion / ScallionTransplant outdoorsMar 31 – Apr 17Opens Mar 31

Start seeds indoors in March (47)

Indoor sowings for transplants later. Six to eight weeks under lights is typical for tomatoes and peppers; onions and leeks need longer.

CropWhat to doWindowThis month
CeleryStart seeds indoorsFeb 17 – Mar 3Last chance - ends Mar 3
LeekStart seeds indoorsFeb 17 – Mar 3Last chance - ends Mar 3
OnionStart seeds indoorsFeb 17 – Mar 3Last chance - ends Mar 3
RosemaryStart seeds indoorsFeb 17 – Mar 3Last chance - ends Mar 3
EggplantStart seeds indoorsFeb 24 – Mar 10Last chance - ends Mar 10
ParsleyStart seeds indoorsFeb 24 – Mar 10Last chance - ends Mar 10
ShallotStart seeds indoorsFeb 24 – Mar 10Last chance - ends Mar 10
Bell PepperStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
Chili PepperStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
GingerStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
Green Onion / ScallionStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
MintStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
OreganoStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
SageStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
TarragonStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
ThymeStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
TurmericStart seeds indoorsMar 3 – Mar 17Mar 3 – Mar 17
Ground CherryStart seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
Lemon BalmStart seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
Shiso (Perilla)Start seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
Sweet MarjoramStart seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
TomatilloStart seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
TomatoStart seeds indoorsMar 10 – Mar 24Mar 10 – Mar 24
BroccoliStart seeds indoorsMar 17 – Mar 31Mar 17 – Mar 31
Brussels SproutsStart seeds indoorsMar 17 – Mar 31Mar 17 – Mar 31
CabbageStart seeds indoorsMar 17 – Mar 31Mar 17 – Mar 31
CauliflowerStart seeds indoorsMar 17 – Mar 31Mar 17 – Mar 31
KaleStart seeds indoorsMar 17 – Mar 31Mar 17 – Mar 31
BasilStart seeds indoorsMar 24 – Apr 7Opens Mar 24
Collard GreensStart seeds indoorsMar 24 – Apr 7Opens Mar 24
Endive & EscaroleStart seeds indoorsMar 24 – Apr 7Opens Mar 24
KohlrabiStart seeds indoorsMar 24 – Apr 7Opens Mar 24
Malabar SpinachStart seeds indoorsMar 24 – Apr 7Opens Mar 24
OkraStart seeds indoorsMar 24 – Apr 7Opens Mar 24
RadicchioStart seeds indoorsMar 24 – Apr 7Opens Mar 24
Summer SavoryStart seeds indoorsMar 24 – Apr 7Opens Mar 24
Bitter MelonStart seeds indoorsMar 31 – Apr 14Opens Mar 31
Bok Choy / Pak ChoiStart seeds indoorsMar 31 – Apr 14Opens Mar 31
CucamelonStart seeds indoorsMar 31 – Apr 14Opens Mar 31
Fennel (Bulb)Start seeds indoorsMar 31 – Apr 14Opens Mar 31
LettuceStart seeds indoorsMar 31 – Apr 14Opens Mar 31
Luffa (Loofah Gourd)Start seeds indoorsMar 31 – Apr 14Opens Mar 31
Napa CabbageStart seeds indoorsMar 31 – Apr 14Opens Mar 31
New Zealand SpinachStart seeds indoorsMar 31 – Apr 14Opens Mar 31
PeanutStart seeds indoorsMar 31 – Apr 14Opens Mar 31
Swiss ChardStart seeds indoorsMar 31 – Apr 14Opens Mar 31
WatercressStart seeds indoorsMar 31 – Apr 14Opens Mar 31

Planting dates for popular crops in Colorado

Every crop has its own full-year dates for Colorado: indoor start, transplant or direct sowing, and harvest.

When to plant pea in Colorado →When to plant spinach in Colorado →When to plant onion in Colorado →When to plant eggplant in Colorado →When to plant bell pepper in Colorado →When to plant chili pepper in Colorado →When to plant tomato in Colorado →When to plant broccoli in Colorado →Colorado frost dates by zone →

Seed-starting season: March garden jobs in Colorado

  1. Start 47 crops indoors this month, including celery, leek, onion, rosemary. Use a sterile mix and good light - see starting seeds indoors.
  2. 7 weeks until the average last frost (May 5). The seed-starting calculator works out each crop's exact sowing date from it.
  3. 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.
  4. 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 Colorado

Colorado spans USDA zones 3b, 4b, 5a, 5b, 6a, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average.

ZoneLast frostFirst frostSeason
Zone 3May 15Sep 15120 days
Zone 4May 10Sep 25135 days
Zone 5Apr 30Oct 5160 days
Zone 6Apr 15Oct 15185 days
Zone 7Apr 5Oct 25200 days

Questions gardeners ask

What vegetables can I plant in Colorado in March?

50 crops have a window in March: mache (corn salad), pea, spinach, green onion / scallion, 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 Colorado in March?

No - start seeds indoors runs Mar 10 – Mar 24 in Colorado, so do it before March 24.

Is it too late to plant lettuce in Colorado in March?

No - start seeds indoors runs Mar 31 – Apr 14 in Colorado.

When is the first frost in Colorado?

The statewide average first fall frost is around October 1 and the last spring frost around May 5. Colorado 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 Colorado?

Celery (Feb 17 – Mar 3), Leek (Feb 17 – Mar 3), Onion (Feb 17 – Mar 3), Rosemary (Feb 17 – Mar 3), Eggplant (Feb 24 – Mar 10), Parsley (Feb 24 – Mar 10), Shallot (Feb 24 – Mar 10), Bell Pepper (Mar 3 – Mar 17), Chili Pepper (Mar 3 – Mar 17), Ginger (Mar 3 – Mar 17), Green Onion / Scallion (Mar 3 – Mar 17), Mint (Mar 3 – Mar 17), Oregano (Mar 3 – Mar 17), Sage (Mar 3 – Mar 17), Tarragon (Mar 3 – Mar 17), Thyme (Mar 3 – Mar 17), Turmeric (Mar 3 – Mar 17), Ground Cherry (Mar 10 – Mar 24), Lemon Balm (Mar 10 – Mar 24), Shiso (Perilla) (Mar 10 – Mar 24), Sweet Marjoram (Mar 10 – Mar 24), Tomatillo (Mar 10 – Mar 24), Tomato (Mar 10 – Mar 24), Broccoli (Mar 17 – Mar 31), Brussels Sprouts (Mar 17 – Mar 31), Cabbage (Mar 17 – Mar 31), Cauliflower (Mar 17 – Mar 31), Kale (Mar 17 – Mar 31), Basil (Mar 24 – Apr 7), Collard Greens (Mar 24 – Apr 7), Endive & Escarole (Mar 24 – Apr 7), Kohlrabi (Mar 24 – Apr 7), Malabar Spinach (Mar 24 – Apr 7), Okra (Mar 24 – Apr 7), Radicchio (Mar 24 – Apr 7), Summer Savory (Mar 24 – Apr 7), Bitter Melon (Mar 31 – Apr 14), Bok Choy / Pak Choi (Mar 31 – Apr 14), Cucamelon (Mar 31 – Apr 14), Fennel (Bulb) (Mar 31 – Apr 14), Lettuce (Mar 31 – Apr 14), Luffa (Loofah Gourd) (Mar 31 – Apr 14), Napa Cabbage (Mar 31 – Apr 14), New Zealand Spinach (Mar 31 – Apr 14), Peanut (Mar 31 – Apr 14), Swiss Chard (Mar 31 – Apr 14), Watercress (Mar 31 – Apr 14).

← February in ColoradoApril in Colorado →Full-year Colorado planting calendar →Colorado frost dates →

What to plant in March in other states

IdahoMontanaNevadaUtahWyomingAlabamaAlaskaArizonaAll states →

Dates are computed from Colorado’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.