PHOENIX — With scorching summers and a statewide average of just 12.3 inches of rainfall per year, starting a garden in Arizona can be intimidating, especially for those who live in the Valley region.
ABC15 shares the basics of gardening and what people can do to hone their horticultural skills all year round.
What is a climate zone?
When you go to the store to buy plants or seeds, you may see guides that tell you the best time to plant based on your area's USDA-established “hardiness zone.”
USDA plant hardiness zones are determined by the extreme cold that a location may experience throughout the year.
According to the USDA website, the zones “do not reflect the coldest temperatures ever or will ever occur in a particular location, but simply indicate the average minimum winter temperatures in that location for a particular time period. Low temperatures during the winter are an important factor for plant survival in a particular location.”
Arizona's plant hardiness zones range from 4b to 10b. Most of Maricopa County is in zone 9b, where temperatures never get colder than 25 to 30 degrees Fahrenheit.
According to a University of Arizona publication, nurseries, landscapers and gardeners in the Southwest often use “sunset climate zones” when selecting plants.
Sunset climate zones consider overall temperatures and conditions, not just minimum temperatures.
Angelica Elliott, associate director of public horticulture at Desert Botanical Gardens, says if a plant isn't suited to your hardiness zone, there are things you can do to help it thrive.
“In many cases, you can create what are called 'microclimates' around your home,” Elliott says.
Elliott gives the example of yellowbell, or tecoma, which can be damaged by frost, especially when young.
“I often plant them close to walls, south-facing or west-facing walls to prevent frost damage,” Elliott says, “or around swimming pools where they can get reflected heat.”
For plants that thrive in warmer climates, Elliott said they may do well under a canopy of trees that provide shade and cooler temperatures of 4 to 7 degrees.
A University of Arizona publication classifies the various climate zones and provides a list of trees and shrubs that thrive in each.
What can you grow in Arizona?
For those thinking about starting a garden, mid-summer may not be the best time.
Matthew Whitfill of Whitfill Nursery says the best time to plant new plants is in the autumn when it's not as hot outside.
“Whenever the weather breaks,” he said, “it doesn't have to be nice outside. We just want it to be sure it's not 110 degrees outside. That way we can all get through fall, winter and spring before 110 comes along and it gets nasty again.”
Elliott said there are two vegetable growing seasons in the valley: warm season (March through September) and cool season (September through February).
Warm season vegetables include asparagus, cucumbers, eggplant, okra, peppers, tomatoes, squash, and zucchini.
“Okra grows very well here in the Sonoran Desert,” Elliott says, “and it has beautiful yellow flowers, almost like hibiscus, so it could be a beautiful landscape plant. It flowers and produces fruit all summer long and has very few pests.”
Cool season vegetables include artichokes, arugula, broccoli, carrots, cauliflower, garlic, a variety of leafy greens, onions, and Swiss chard.
For a more detailed list of vegetables and specific varieties, click here.
For those looking for landscape plants, both Elliott and Whitfill suggest looking around the valley to find them.
“Plants that are commercially planted in front of commercial buildings, such as lantana, bougainvillea and Texas sage, all do really well in home gardens because they require much less maintenance than plants that need a lot more water, such as roses or hibiscus,” Whitfill says.
The University of Arizona has a guide on when to plant various fruits and vegetables, including seeds, seedlings, and clove plants, and when they should be ready to be harvested.
Identifying and troubleshooting issues
Elliott says most people assume that when they see a wilted plant, it's because they're not getting enough water, but wilting can be a symptom of both overwatering and underwatering.
Before giving your plant more water, check the soil: if the soil is moist and the plant is wilted, the plant is overwatered. If the soil is dry and you haven't watered your plant in a while, the plant is underwatered.
Another sign of lack of water is brown, crispy leaf edges, Whitfill said.
Elliott adds that some plants may simply wilt in an attempt to withstand the heat, especially during the heat of the day, and will likely bounce back once the weather cools.
“Sometimes you just need to get to know your plants really well,” Elliott said.
If your plant is exposed to too much sun, it may become discoloured.
Elliott suggests covering your plants with shade cloth that blocks 30 to 60 percent of the sunlight. Using a cloth that's too dense, blocking more than 60 percent of the sunlight, can block too much sunlight and hinder photosynthesis in your plants.
Whitfill said plants that are already established and have been around for several seasons tend to be more resilient and tolerate the heat better.
During cold weather, plants may suffer from frost damage, which can cause leaves to discolor and even cause parts of the plant to die.
“Believe it or not, we do get cold spells periodically here in the Sonoran Desert,” Elliott said. “They don't last as long as they do in the Midwest or East, but they do come periodically.”
When a freeze warning is issued, be sure to cover your plants. The Desert Botanical Garden recommends using fabrics such as burlap, old sheets, or medium-weight, UV-treated N-Sulate. The garden warns against using plastic, as it can burn plants that come into contact with it.
If you find pests on your plants, you may not need to use large amounts of chemicals.
Elliott said another option is to manage the pests with biological control, meaning introducing another animal or insect to manage the pest.
“Some animals, like hummingbirds, eat aphids, so you want to encourage hummingbirds to come to your garden,” Elliott says, “or if you have lacy wings or ladybugs, you want to encourage hummingbirds to eat those insects.”
Vegetable plants often attract more insects, and one way to control them is to use diatomaceous earth, but be sure to buy a food-grade product if you're using it around vegetables or other edible plants.
Elliott says he has used a small handheld vacuum to get rid of pests, and has even managed to get rid of bugs by simply sucking them up.
Seed Library
Do you want to start a vegetable garden but are on a budget? Many local libraries have seed libraries where cardholders can “borrow” a certain number of seeds at a time. For a list of libraries in Maricopa County that have seed library programs, click here.
Classes around the Valley
Want to learn more? Local community colleges, organizations, libraries, and daycare centers offer classes around the Valley. Some classes may require a fee.
