Low-Desert Southwest Vegetable Planting Calendar

The seasons are inverted: garden cool, rest in summer

The core idea to unlearn from cold-climate gardening: in the low desert, summer is not the growing season. University of Arizona Extension states the region has two optimal growing and planting seasons — one in spring, the other in fall — with conditions swinging from short, cold winter days to long days and extreme summer temperatures. The extreme heat, not frost, is the season-limiting force here.

So the calendar reads inside-out. In Yuma, University of Arizona describes a cool season running roughly September through February that's ideal for non-fruiting crops, and a warm season from about March through August for fruiting crops that can take spring's rising heat — with high summer being the hardest stretch. You plan around avoiding summer, not surviving winter.

Cool-season crops: plant in fall, grow through winter

The mild desert winter is prime time for leafy and root vegetables. University of Arizona's low-desert guidance puts cool-season crops — lettuce, spinach, broccoli, cauliflower, cabbage, carrots — in the ground in fall and through winter, with Yuma planting windows like broccoli and cauliflower September–December, lettuce September–January, and spinach September–February.

Timing the start matters because early fall is still hot. Arizona suggests that while the calendar allows September planting for some cool-season crops, most gardeners should wait until October when the weather cools; you can start in September only with added shade and careful irrigation to keep seedlings alive through the still-warm days. This is exactly the opposite instinct from a northern gardener racing to plant in spring.

Warm-season crops: plant late winter, beat the heat

Warm-season fruiting crops get a spring window aimed at harvesting before summer becomes unbearable. University of Arizona's low-desert calendars put tomatoes, squash, melons, peppers, eggplant, and okra in around February to March, with Yuma tomatoes planted February–March for a May–July harvest — set to mature before peak summer heat shuts fruit set down.

Use a soil thermometer rather than the calendar alone: Arizona advises aiming for soil temperatures of 65 to 85°F for many commonly grown vegetables. Because the whole system runs on beating the heat, succession planting and knowing your frost-free window help — see our guides to planning a vegetable garden, succession planting, and USDA hardiness zones to place these dates in your own microclimate.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• University of Arizona Cooperative Extension — Vegetable Planting Calendar for Maricopa County (az1005) — The low desert has two optimal growing and planting seasons, one in the spring and the other in the fall, with conditions ranging from short days and cold temperatures in winter to long days and extreme temperatures in summer; cool-season crops such as broccoli, cabbage, and lettuce are planted from late summer through fall for winter harvest while warm-season crops like tomatoes and peppers are planted February through April; use a soil thermometer to aim for optimal soil temperatures in the range of 65 to 85°F for many commonly grown vegetables.
• University of Arizona Cooperative Extension — Planting and Harvesting Calendar for Gardeners in Yuma County (az1615) — There are two distinct growing seasons: a cool season from September through February ideal for non-fruiting crops such as lettuce, spinach, broccoli, cauliflower, and cabbage, and a warm season from March through August ideal for fruiting crops such as tomatoes, squash, melons, and peppers; example planting windows include broccoli and cauliflower September–December, lettuce September–January, spinach September–February, and tomato February–March with a May–July harvest; for most gardeners it is best to wait until October when the weather cools before planting cool-season crops, though those who provide shade and enough irrigation can start in September.

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