Water is essential for plant growth. Too little water (or too much), and your plants won’t make it. In hot, arid climates, sunken beds are a preventative measure against warmer weather (catch the rhyme there?).

By sinking the bed below ground level, you take advantage of naturally cooler soil, improved moisture retention, and better wind protection. Sunken beds can be a game-changer for gardeners in dry regions, making it easier to keep plants thriving with less water.

In this guide, we’ll cover what they are, why they work, and how you can create one in your garden. Let’s dig in!

What is a Sunken Bed?

A sunken garden bed is exactly as it sounds. Compared to a raised bed, which is elevated above ground level, a sunken garden bed is below ground level. They’re created by digging out an area and primarily using the existing soil for planting.

Sunken beds are well-suited for most plants and can be better than raised beds for many. Deep-rooted plants love the freedom of sunken beds, and there’s less concern with planting right next to the edge of the bed; the plants have the space to extend their roots beyond the sunken area if necessary. Additionally, trailing plants such as squash and watermelon that can overwhelm small raised beds thrive in sunken beds.

Benefits of a Sunken Bed.

Sunken gardens offer a range of benefits in the desert, making them a smart choice for water-wise landscaping. Here are some of the most compelling reasons to try this method:

• Reduces water loss. The deeper you go, the cooler and wetter the soil naturally is. Plus, the surrounding berms help minimize evaporation by shielding the bed from wind and direct sun while channeling water into the bed.
• Keeps temperatures down. During the hottest part of the day, the raised berms around the edges provide shade for some plants, while the lower elevation helps insulate them from extreme heat.
• Improves soil health. Water that would otherwise run off has a chance to sink in, delivering moisture and nutrients more effectively to plant roots. Over time, this helps build healthier, more resilient soil.
• Protects plants from wind. Strong winds can dry out plants and damage delicate stems in open desert landscapes. A sunken bed offers a natural windbreak, creating a more sheltered growing environment.
• Manages soil salinity. In dry climates, salt buildup in the soil can be a problem. Raised beds tend to pull salts toward the surface, which harms plants. Sunken beds, on the other hand, help draw salts deeper into the ground, keeping them away from plants and their roots.

Considerations for a Sunken Bed

Before you start digging, consider your bed’s size and location. Shelter from the intense afternoon sun is essential. If no natural (trees, shrubs) or structural shade (buildings, walls) exists, you may need to add shade fabric alongside the west and south-west sides of the bed.

Because you can walk through a sunken bed, there’s more flexibility in sizing. Larger beds also allow for companion planting and layering plants for shade (see our Tips for Growing in the Southwest Desert). A standard 4’ x 8’ size (1.25m x 2.5 m) is a good starting point for maintenance, and it’s easy to plan with the Planter app.

Drainage is also important. A slight slope toward one side of the bed can reduce pooling during heavy rain. Additionally, placing a terracotta pot in the soil at the lowest point of the bed can catch excess water during monsoon-like rains. The rim should sit just below the soil level, allowing water to collect and slowly soak in.

Building the Bed

1. Mark out the area with string and stakes to visualize the space. Sunken beds don’t have to be rectangular—you can shape them to fit your garden layout. If doing more than one bed, leave a 3-4 foot (around 1-1.5 meter) walkway between the beds to pile the dirt for the berms and move around the garden.
2. Dig down between 9 and 12 inches (23-30 cm). Pile the excavated soil around the edges to form berms. These raised dirt walls provide shade and block wind. Compact the berms with a shovel or walk on them to slow erosion.
3. Remove large rocks and debris as you dig. Any stones you find can reinforce the berms. You may also line the edge of the sunken bed with bricks or larger rocks for a more formal look.
4. Amend the soil. The top layer of desert soil is often nutrient-poor. Mix in compost to improve moisture retention. A 20% compost to 80% native soil mix maintains well-draining conditions while boosting nutrient supply.

Maintaining the Bed

Caring for a sunken garden bed is much like any other part of the garden; regular watering, weeding, and pest control are necessary. To reduce the spread of weeds, disturb the soil around your plants as little as possible.

Mulch is an excellent addition for water retention and weed suppression, although you should avoid geotextiles and bark mulches as much as possible. If you’re willing to collect it, the leaf litter from your yard (or your neighbor’s) is an excellent, nutrient-rich mulch, as are shredded tree trimmings.

Wrapping Up

Sunken beds offer a lower-cost, water-efficient way to garden. Once the hard work of digging is out of the way, they are relatively self-sustaining. They need less additional compost than raised beds, are suited for a wider variety of plants, and can simply be buried once you’re done—unlike raised beds, which are more permanent.

No matter what you grow, if you’re growing where it’s hot, sunken beds are an attractive and cost-effective way to garden.

Gardening in the Southwest desert comes with unique challenges, but also the opportunity for near year-round gardening. With the right strategies, you can grow a thriving, productive garden, whatever the weather. By selecting heat-tolerant plants, optimizing shade and soil conditions, and managing water efficiently, you can harvest bumper crops of veg year after year.

When to Start

The vibrant bloom of wildflowers marks the arrival of spring in the Southwest, the warm, sunny season in between the nippy winter and the scorching summer. March is the ideal time in the Southwest to transplant warm-season vegetables or start quick-growing seedlings for a full harvest by June.

What to Plant

Focus on quick-maturing vegetables that can handle high temperatures like those from the nightshade (tomatoes, peppers) and squash families (cucumbers, melons, summer squash) as well as herbs, especially rosemary, oregano, thyme, chives (with some shade), and culinary sage. When sourcing plants, look for desert heirloom varieties, hybrids, or regular cultivars that suit the warm, drier climate. Mediterranean plants generally do well in the Southwest; however, you should always check before you buy.

If you’re looking for a wider variety, you can expand your search to plants that mature quickly. Many plants that mature for harvest between 30-90 days (up to 70 days is optimal) can survive a Southwest spring, particularly if given sufficient shade and water.

Where to Plant

The summer sun is hot, and the high UV index in the desert can do a number on plant tissue. To minimize heat stress, focus on planting in areas that receive shade in the afternoon. Raised beds made from fired adobe bricks are excellent in the desert because of their high thermal capacity (they regulate heat well) and will keep the soil cooler than the dirt around it. 

Another consideration is sunken garden beds, which are as equally effective as raised adobe beds for keeping the soil cool. Look for a future article on this and how to create them.

Take temperature readings in your garden before choosing where to plant and observe where shade falls throughout the day as well. Areas near concrete walls or driveways will typically be hotter than those closer to trees or adobe buildings. Be mindful of planting too close to trees however, as they will compete for water and stunt your vegetable growth.

How to Create Shade

Not every spring is mild, and if you don’t have naturally shaded areas in your garden, you can easily create some. 

First, you’ll need some shade fabric, or shade cloth (the name can vary). A shade rating around 60% is ideal so that the sunlight is reduced but not entirely blocked. Shade fabric often comes pre-sized, and with grommets to attach it easily (we recommend this option for ease) so you may be able to buy one that fits your garden bed perfectly, or you can buy a bulk roll and trim to size as needed.

Installing it is very straightforward. The tunnel method, where the fabric is draped over curved canes, or like a triangular tent is excellent for low growing plants, and the fabric can be attached to the canes or structure using zip ties. Alternatively, you can used tall garden canes or fence posts to elevate the fabric to cover taller plants such as tomatoes. For larger posts, a screw can be drilled into the top or side of the post, and the fabric secured over it. For garden canes, zip ties are very handy once again.

Reducing Water Loss

Mulch is essential in Southwest gardens. A 2–4" (5-10 cm) layer around (but not directly on top of) seedlings and young plants helps trap moisture while maintaining airflow. Mulch can also lower soil temperature significantly during the heat of the day. When using mulch, be mindful of small scorpions that may use it as refuge if it becomes too damp; citrus peel or planting lavender with your veg will help to deter them.

Drip irrigation works well in the Southwest desert. Water early in the morning to reduce evaporation and keep roots healthy. Check plant health regularly and provide supplemental watering, especially on hot days. If needed, water again in the early evening with at least 2 hours of daylight left.

Multi-Story Gardening

Layering plants at different heights helps create a cooler microclimate, reduce water loss, and maximize space. You may have heard of the Three Sisters method—corn, beans, and squash—which works well in hot climates. In this system, tall corn provides shade, beans fix nitrogen in the soil, and squash spreads across the ground to retain moisture and suppress weeds.

You can apply these principles to other plants in a Southwest garden:

• Tall plants (e.g., tomatoes, sunflowers, okra) provide shade for heat-sensitive crops.
• Medium-height plants (e.g., peppers, bush beans, eggplants) benefit from dappled sunlight beneath taller plants.
• Low-growing herbs (e.g., basil, oregano, creeping thyme) help retain soil moisture while deterring pests.
• Vining plants (e.g., cucumbers, melons, pole beans) can be trained to climb, reducing ground heat exposure.

By carefully layering plants, you can create a self-sustaining ecosystem that protects your crops from excessive heat and evaporation while improving soil health.

Choosing the Right Soil

Desert soil is often dry and low in nutrients but drains well. Mix it with compost to improve moisture retention and fertility. A good starting ratio is 2/3 compost to 1/3 native soil. Adding in decomposing mulch such as hay is excellent too.

Wrapping Up

Gardening in the desert Southwest isn’t tricky, but a little planning goes a long way. Choosing the right plants and location will help you enjoy a productive harvest year after year.