What to plant in December in the Southwest

Worked out for 8 cities from their own weather and frost dates, by zone.

What to sow and plant in December in the Southwest, by zone: frost-free, highs of 61–72 °F (Yuma): broad bean, peas, onion, lettuce, carrot and 35 more; frost possible, highs of 61–72 °F (Phoenix and Tucson): broad bean, peas, onion, spinach, lettuce and 22 more; frost possible, highs of 50–61 °F (Las Vegas, Albuquerque and 1 more): garlic, broad bean, peas, onion, spinach and 23 more; frost possible, highs below 50 °F (Santa Fe (United States) and Flagstaff): garlic, broad bean, spinach, cabbage, broccoli and 1 more.

In the Southwest, December is winter.

Frost-free, highs of 61–72 °F: Yuma

In December, on average, Yuma has highs of 71 °F and lows of 48 °F, 0.6 in of rain on 2 days; the day lasts 10 h 01 min (on the 15th). A dry month: whatever is sown needs watering.

No frost in December in 10 years of data: frost-tender crops can go in too, if it is warm enough for them.

How	What	Where
sow direct	Broad bean, peas, lettuce, carrot, cabbage, broccoli, Swiss chard, beet, parsley, cilantro, arugula, chamomile, chickpea, dill, kale, kohlrabi, mustard greens, parsnip	Yuma
plant sets	Onion, shallot	Yuma
start indoors, plant out in February	Tomato, bell pepper, eggplant, chili pepper, Florence fennel, moringa	Yuma
start indoors, plant out in January	Zucchini, cucumber, melon, watermelon, pumpkin, sweet corn, basil, achocha, bok choy, kiwano, luffa, Napa cabbage, okra, peanut	Yuma

Compared with November: new — carrot, broccoli, cucumber, melon, achocha, luffa, okra and parsnip; no longer sown — cauliflower, green beans, borage, celeriac, celery, chayote, corn and soybean.

Not starting in December: green beans (February, sown direct) and spinach (no month outdoors by these rules) — dates for Yuma.

Ready to harvest in December in Yuma, if sown in the right month: zucchini (October), green beans (October), basil (October), arugula (November), bok choy (October), borage (October), dill (November) and moringa (October).

Frost dates in Yuma

Frost possible, highs of 61–72 °F: Phoenix and Tucson

In December, on average, these cities have highs of 67 to 68 °F and lows of 43 to 45 °F, 1.3 to 1.4 in of rain on 4 days; the day lasts 9 h 57 min to 10 h 03 min (on the 15th).

December falls in the frost season: frost-tender crops wait. Average first frost: Phoenix (December 29) and Tucson (December 18).

How	What	Where
sow direct	Broad bean, peas, spinach, lettuce, radish, carrot, cabbage, broccoli, Swiss chard, beet, parsley, cilantro, arugula, chamomile, daikon, dill, kale, kohlrabi, mustard greens, parsnip	all
plant sets	Onion, shallot	all
start indoors, plant out in January	Cauliflower	all
start indoors, plant out in March	Celeriac, celery, chayote	all
sow direct	Chickpea	Phoenix

Compared with November: new — radish, carrot, broccoli, celeriac, celery, chayote, daikon and parsnip; no longer sown — Brussels sprouts.

Not starting in December: tomato (January, started indoors), bell pepper (January, started indoors), zucchini (February, started indoors) and green beans (March, sown direct) — dates for Tucson.

Ready to harvest in December in Tucson, if sown in the right month: zucchini (October), green beans (October), watermelon (September), sweet corn (September), basil (October), arugula (November), bok choy (October) and borage (October).

Frost possible, highs of 50–61 °F: Las Vegas, Albuquerque and Las Cruces

In December, on average, these cities have highs of 50 to 60 °F and lows of 29 to 41 °F, 0.6 to 0.7 in of rain on 3 to 4 days; the day lasts 9 h 43 min to 10 h 03 min (on the 15th). A dry month: whatever is sown needs watering.

December falls in the frost season: frost-tender crops wait. Average first frost: Las Vegas (December 12).

How	What	Where
plant cloves	Garlic	all
sow direct or start indoors, plant out in January	Broad bean, spinach	all
sow direct	Peas, radish	all
plant sets	Onion, shallot	Las Vegas and Las Cruces
sow direct	Lettuce, carrot, Swiss chard, beet, arugula, chamomile, daikon, dill, kale, mustard greens, parsnip, turnip	Las Vegas and Las Cruces
sow direct or start indoors, plant out in February	Cabbage, broccoli	all
start indoors, plant out in January	Cauliflower	Las Vegas and Las Cruces
start indoors, plant out in February	Parsley	all
start indoors, plant out in January	Kohlrabi	all
start indoors, plant out in February	Brussels Sprouts	Las Vegas and Albuquerque
start indoors, plant out in March	Celeriac, celery, chayote	Las Vegas and Las Cruces
plant bulbs	Crocus, daffodil, hyacinth, tulip	Albuquerque

Compared with November: new — celeriac, celery and chayote; no longer sown — leek, cilantro and chicory.

Not starting in December: tomato (January, started indoors), bell pepper (January, started indoors), zucchini (February, started indoors) and green beans (April, sown direct) — dates for Las Vegas.

Ready to harvest in December in Las Vegas, if sown in the right month: radish (November), watermelon (September), sweet corn (September), arugula (November), corn (September), dill (November), Florence fennel (September) and kiwano (September).

Frost possible, highs below 50 °F: Santa Fe (United States) and Flagstaff

In December, on average, these cities have highs of 42 to 45 °F and lows of 25 to 28 °F, 0.9 to 1.0 in of rain on 4 days; the day lasts 9 h 46 min to 9 h 48 min (on the 15th). A dry month: whatever is sown needs watering.

December falls in the frost season: frost-tender crops wait.

How	What	Where
plant cloves	Garlic	all
start indoors, plant out in January	Broad bean, spinach	Flagstaff
start indoors, plant out in February	Cabbage, broccoli	all
plant bulbs	Crocus, daffodil, hyacinth, tulip	all

Compared with November: no longer sown — peas, onion, radish, arugula and turnip.

Not starting in December: tomato (March, started indoors), bell pepper (March, started indoors), zucchini (April, started indoors), green beans (June, sown direct), lettuce (February, started indoors) and peas (March, sown direct) — dates for Santa Fe (United States).

Ready to harvest in December in Santa Fe (United States), if sown in the right month: broad bean (September), peas (October), spinach (October), lettuce (October), radish (November), Swiss chard (October), beet (October) and parsley (October).

How we work it out

For each city we use its average weather in December and the months after (highs, lows and rain for 2016–2025, ERA5 reanalysis via Open-Meteo) and its average frost dates. A crop starts in December if the month's mean temperature reaches the minimum soil temperature for germination on its card (we use the mean air temperature as a stand-in for the soil's) and if, over its first months (up to three), the average highs stay within its group's range, with no frost for crops that cannot take it. Crops started indoors count from the month they are planted out.

Temperature groups from Colorado State University Extension: cool-season crops prefer 60–80 °F and lose quality in heat; hardy ones grow in days as cool as 40 °F, semi-hardy ones from 40–50 °F (we use 50 °F); warm-season crops need days above 55 °F, and the most tender (tomato, pepper, eggplant, melon, watermelon, squash) above 60 °F, up to 95 °F. Crops the guide does not name go into the stricter group by their frost hardiness. Fava (broad) beans, which the guide does not name, count as hardy: hardy varieties are sown in fall and overwinter (RHS). Garlic and bulbs: a month before the first frost, and later only while the ground is not frozen (as on each city's page).

This is a general rule from averages: your garden can be a week or two earlier or later, and a greenhouse or a cold frame brings the season forward. Greenly works out the dates for your location.