Gardening in the Southwest
Gardening in the dry desert climates of the Southwest can be a challenge, but with planning and extra considerations, gardeners can grow and save seeds in this region.
Gardening in the Southwest
The Southwest region of the United States presents some challenges to gardeners. Low-altitude desert areas have hot summers, low rainfall, and sandy soils. On the other hand, high-altitude desert areas have cooler temperatures and vary widely in the length of their season.
Locations
The Southwest growing region includes Arizona, New Mexico, parts of Texas, the Oklahoma Panhandle, parts of Nevada, and Southern California in the Imperial Valley.
Characteristics
Southwest gardeners experience low rainfall and abundant sunlight. Soil conditions vary, but many areas have sandy, clay, or arid soils.
In low-altitude regions, the summer heat extremes from July through September often surpass 104 degrees F (40 degrees C). Higher-altitude areas of the Southwest can vary widely in the intensity and duration of summer heat as well as the length of the growing season. Winters in the Southwest are mild.
Growing Zones
Growing zones in the Southwest can range from 5B and 6A in some of the higher altitude mountains to 10A in some of the hottest lowland deserts.
The USDA’s Plant Hardiness Zone Map divides the United States into zones according to the “average annual extreme minimal temperature.” Knowing your plant hardiness zone will help you choose crops that will thrive in your location. Your growing zone is especially helpful when growing and saving seeds from biennials (more on that later).
You can find out which plant hardiness zone you garden in here.
Growing Zone Maps
First and Last Frost Dates
Your first and last frost dates help determine the length of your gardening season. These dates are especially helpful when growing and saving seeds from annuals. Use your last frost date to determine when to start seeds and plant out transplants. Use your first frost date to determine the length of your growing season and which crops will have the time necessary to fully mature in your region. The hottest regions may not experience a frost at all.
Click here to find your first and last frost dates by city/state or by zip code.
Another cool tool is this interactive map of last spring frost dates across the United States.
Growing Window
There are generally two gardening seasons in the hottest parts of the Southwest, with planting times in early spring (February-April) and fall (September-October). Splitting the traditional gardening season in two helps avoid the disruptive high summer heat.
Follow these tips to time sowings to avoid the hottest part of the summer.
- Know your first and last frost dates.
- Start seeds indoors during the winter and summer off-seasons for a head start when temperatures mellow.
- Transplant or direct-sow outdoors right after the danger of frost has passed in the late winter or early spring.
- Plant late-summer/fall crops with enough time to mature before the first frost.
Tip: Plant quick-maturing crops
Tips for Gardening in the Southwest
Challenge: Poor Soil
The Southwest has a lot of dry, sandy soil with low fertility, which can make growing vegetables difficult. Sand is a very large particle, and makes soil porous, which means water moves very quickly through the soil. While this helps prevent flooding after heavy rain, it also means a gardener may need to water plants more often as water drains from the root zone too quickly for plants to adequately absorb all of the moisture they need.
These strategies will help you improve the quality of your soil to provide more nutrients to crops:
- Do a soil test and address deficiencies
- Incorporate organic matter
- Cover the soil with landscape fabric or mulch to reduce evaporation and erosion
- Reduce tillage
Note: If growing native plants, do not amend the soil. These plants are already adapted to thrive in the soil in your region.
Tip: Plant crops that like sandy soil
Challenge: Low Rainfall
Whether in the high mountains or lowlands, the Southwest experiences low rainfall. These strategies will help lower your water usage in the garden:
- Water plants deeply and infrequently to encourage deep root systems
- Incorporate organic matter into your soil
- Mulch heavily
- Install a drip irrigation system
- Install a rain barrel
To reduce your household water use, use greywater in the garden. Greywater is relatively clean wastewater from sinks, baths, and showers. Try placing a gallon bucket under the faucet while waiting for your shower to heat up. Collect the water used to rinse produce, dishes, and your hands. Make sure that any soaps and solutions collected in this wastewater are biodegradable, such as castile soap.
Read this article to learn more about strategies for gardening in a drought.
Tip: Plant crops that, once established, can handle a drought
Challenge: Extreme Heat
The Southwest faces some of the hottest summers in North America, with temperatures surpassing 104 degrees F (40 degrees C)! Extremely high temperatures can seriously affect the growth of crops (even those of heat-loving crops), especially during flowering and seed development.
These strategies will help you manage the high summer heat of the Southwest:
- Water plants in the early morning to reduce evaporation
- Mulch heavily
- Provide afternoon shade (with shade cloth or intercropping), especially for tender greens
- Time your plantings carefully to make sure vegetables mature before the summer heat or in the fall before the first frost.
Tip: Plant heat-loving crops
Seed Saving in the Southwest
Annuals
Heat presents the biggest challenge to saving seeds in the Southwest. Extreme heat can affect crop seed development in annuals, so a little careful timing is needed to save seeds. Sow crops for seed so that their period of flowering does not coincide with the hottest time of the year.
Some annual crops, such as tomatoes and winter squash, reach market maturity (ready for eating) and seed maturity at the same time. However, many other annuals reach seed maturity long after they’re ready to eat, such as cucumbers, eggplants, and green beans. When planning for seed saving, be sure to start the crops early enough for the plants to reach seed maturity before the hottest part of the summer.
Biennials
Biennials are crops that require two seasons of growth to produce seeds. Typically, gardeners plant biennial crops, such as carrots, beets, and cabbage, in late summer and allow them to overwinter until spring, when they resume growth and flower.
To produce seeds, biennials must undergo vernalization, a prolonged exposure to colder temperatures. In general, biennial crops need 10-12 weeks of exposure to temperatures around 50 degrees F, without regular temperatures below 35 degrees F.
Because of these temperature requirements, many Southwest gardeners are unable to save seeds from biennials. However, if you garden in a higher-altitude region with a cooler climate, you might be able to have success with biennials.
Gardening at High Altitude
Many gardeners in the Southwest live in high-altitude locations. High altitude presents its own gardening and seed saving challenges and opportunities.
Challenges
- Temperature swings: High-altitude gardeners experience a high variance in temperature from day to night, sometimes as much as 40 degrees F or more.
- Late killing frosts: Late frosts can occur in May or June. These frosts pose a danger to warm-season crops, such as tomatoes.
- Poor soil: The soil is very rocky and lacks nutrients.
- Short frost-free growing season: The frost-free growing season is often less than 100 days.
- Intense sunlight: High altitude=closer to the sun, which leads to drier, crispier plants.
Benefits
- Cooler summers: Cooler summers can make saving seeds a little easier.
- Cool season crops: Cool season crops won’t bolt as quickly in the warm season.
- Biennials: Cooler winter temperatures allows for biennial seed saving.
- Adapted varieties: Tough conditions quickly adapt plants to the region increase their resilience through seed saving.
Tips and Tricks
Season extenders: Use season extending methods to mitigate temperature swings, late or early frosts, and a short growing season.
- Cold frames and green houses
- Row covers
- Cloches on young seedlings and transplants — A cloche is a covering placed over a young seedling for protection from late frosts. You can buy cloches from gardening supply stores or create your own using a jar or milk jug.
- Wall O’ Water — A Wall O’ Water is an insulator filled with water that is placed around a young plant. The water absorbs heat during the day and distributes it at night. You can find this at gardening supply stores.
Learn more about extending the gardening season.
Use passive heat sources: Try painting an empty milk just black, then filling with water. Put the jug right next to warm-season plants. During the day, the jug will absorb heat from the sun, then distribute it at night.
Save your seeds: Save seeds from the best plants you grow. Select plants for desirable traits such as earliness, frost tolerance, drought tolerance, etc. Over time, the variety will become adapted to your regional microclimate and more resilient.
Save seeds from biennials: Due to the cooler winters, high altitude gardeners in the Southwest are able to save seeds from biennials by overwintering in the field. To protect biennial crops over the winter, mulch heavily or use low tunnels.
Choosing varieties: Look for varieties that are
- Short season or early maturing
- Cold tolerant
- Drought tolerant
Recommended Varieties
