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February/March 2024 Gardening Solutions

By Noelle Johnson | Illustration by Gary Hovland

Hello Friends,

Gardening in Arizona is different from other regions and can be overwhelming unless you learn how to succeed in a hot, dry climate. For more than 25 years, I’ve been helping people create, grow and maintain beautiful landscapes that thrive in the desert.

My journey began three decades ago when I killed all my plants in my Phoenix yard. I felt like a failure but was determined to figure out how to garden successfully in my new desert home. I Iearned a lot and was hooked. I went on to obtain my degree in plant biology, with a concentration in urban horticulture from ASU and  have never looked back.

I am known by many as “AZ Plant Lady” and have authored a book on gardening in the Southwest. I also work as a landscape consultant and speaker. I enjoy teaching classes at the Desert Botanical Garden and Tucson Botanical Gardens, along with online courses on desert gardening. I do this all to help Southwest dwellers realize the potential of their landscapes. 

You will notice some changes to our garden checklist as we refocus our content on issues relevant to this region, such as responding to the challenges of an increasingly hot climate and ensuring water efficiency. I want to help you in your garden journey, so please send me your questions (and there are no “dumb” questions) to mail@azplantlady.com. 

Noelle Johnson, Horticulturist
“AZ Plant Lady,” azplantlady.com

Noelle Johnson, Horticulturist “AZ Plant Lady,” azplantlady.com

Don’t prune shrubs or groundcovers too early. 

Are your plants looking brown and crispy from frost damage? Or are you anxious to give a bit of a trim? While it’s tempting to remove damaged foliage, wait until the threat of frost has passed in your region. Spring is the ideal time to prune—however, we don’t want to do so too early, which could cause damage to frost-tender plants if another freeze occurs. Many plants in the desert landscape, including bougainvillea, hibiscus, lantana and yellow bells, are susceptible to cold damage.  

In low- to mid-altitude desert areas, March or April are usually safe for trimming. In my low-desert garden, I sometimes cheat and cut back my plants early by looking at the long-range weather forecast until around mid-February. If there is no projection for 10-14 days of temps dipping into the 30s, I know I can safely prune. In mid- to high-altitude elevations, look at the forecast two weeks before your average last frost date to see if you can safely shear a little early. 

Spring is our busiest pruning season, and in our April/May issue, we will discuss what and how much to prune for the health and beauty of your plants.

Pink blossoms on a peach tree add beauty to the early spring garden.

Monthly Garden Tasks

Prune back rose bushes to 1 to 2 feet from the ground by the end of February. Roses bloom on new wood, so winter maintenance will keep them healthy and productive. Remove any brown dead wood, along with any thin branches that are less than the width of a pencil. Prune to an outward-facing bud, which is a small bump where new growth will occur, to create an open shape. Pull off all remaining leaves to get rid of hiding pests and diseased foliage. Fertilize existing roses in March using a rose fertilizer.

Plant fruit trees such as apple, peach and plum in February. Due to our short winters, look for varieties that do well with low-
chilling hour requirements (the amount of time temperatures are below 45 degrees)that are needed for fruit production. March is a great time to add citrus trees. Look for ‘Arizona Sweet’ varieties of oranges, which are excellent for juicing and peeling. Avoid planting fruit trees in reflected heat areas near walls or pavement, which can stress them during summer. Fertilize citrus trees in February with a fertilizer formulated specifically for citrus.

Add compost and aged manure to the vegetable garden. Apply 2 inches of compost and 1 inch of aged manure on top of the soil—there is no need to mix it into the soil layer underneath in existing vegetable gardens. Plant cucumber, eggplant, melons, peppers and tomatoes once the threat of frost
has passed. 

My winter garden is “blah” and colorless. I want to add lower-water-use plants that will provide much-needed cold-weather color instead of thirsty flowering annuals. Is that even possible?

You can have beautiful color through winter in the low- and mid-altitude desert elevations. Some cool-season favorites that add welcome color through the winter into spring: Valentine bush (Eremophila maculata, ‘Valentine’) blooms and lasts through April. I love its reddish-pink flowers. Another prized choice is chuparosa (Justicia californica), which adds a lovely red-orange splashes and is a massive favorite of hummingbirds. Finally, the flowering spikes of firecracker penstemon (Penstemon eatonii) are my top choice for winter and spring color.

Harvest fruit from citrus trees once they ripen to deter roof rats who like to eat the sweet pulp. These unwelcome pests can cause damage around your house by chewing on drip irrigation tubing and electrical wires. Check underneath your trees every few days and pick up any fallen grapefruit, oranges, lemons or limes from the ground that attract insects such as ants and fruit flies. If you have an excessive harvest, offer some to your neighbors or contact your local food bank to see if they are accepting donations.

My houseplants have a fungus gnat problem. I tried Neem oil and insecticidal soap to no avail. Finally, I gave up and changed out the dirt. Things were fine for a month, but the bugs are back. They get into my coffee, water and wine glasses—I’m ready to replace this with a fake plant. 

Fungus gnats are an unwelcome sight for houseplant owners. These tiny insects eat the organic matter in your potting mix and lay their eggs on the surface. While the adults are the most noticeable, the larvae of fungus gnats cause the most damage by feeding on the plant’s roots. To kill the adults and larvae, trap the adults. Pour 2 inches of apple cider vinegar into a bowl. Cover the bowl with clear plastic wrap and poke small holes in it with a toothpick. The adult gnats will fly through the holes but won’t be able to get out. To kill the larvae on the soil, mix one part hydrogen peroxide with four parts water, and drench the soil surface. To prevent future infestations, water plants less often, allowing the soil to dry out a bit before watering again. Make sure your pot drains well and isn’t sitting in standing water. Finally, add a 1-inch layer of pebbles or pea gravel around your plant, covering the soil surface. The pebbles help prevent the pests from reaching the soil to lay their eggs. Using both of these approaches will help deter fungus gnats without using pesticides.

When is it time to say goodbye?

People often experience reluctance to get rid of plants in their landscape. Perhaps you hesitate to pull out a plant because you feel bad or wasteful removing one that is perfectly healthy. It could be that something existing has failed to flourish, or you moved into a house that has flora you don’t care for. So what should you do—live with a plant you don’t like or replace it with one you will enjoy?

I encourage you to remove plants you don’t want. If this is hard for you, remember that the role of your garden is to bring you joy with its appearance or function, such as shade, privacy, attracting pollinators, etc. If something no longer serves those needs, consider replacing it with another one that will. Use your precious garden space on plants that you will enjoy instead of those you don’t.

A rock penstemon (Penstemon baccharifolius) struggles to survive during record-breaking summer heat.

Plant earlier to beat the summer heat. With hotter summers, it’s time to rethink the ideal time to add to our gardens. To survive the summer heat, a plant must have a healthy root system, which is critical for absorbing water and nutrients. Without a sufficient root system, plants struggle to survive—especially in our summer heat. New plantings undergo stress as they adjust to a new location and different soil and sun exposure, all while concentrating their energy on growing new roots. 

Past recommendations focused on fall and spring as ideal times to add plants. Fall is still the best time as it gives new additions three seasons to grow a large root system before the heat of summer arrives. However, with increasingly hot summers, plants are added in mid- to late spring may not have enough time for sufficient root growth before hot temperatures arrive. Adding new plants in fall, winter and early spring is best. Avoid planting in summer or late spring to increase the plant’s chances of surviving an extra-hot summer.

Many of my plants struggled in the heat last summer, especially my cape honeysuckle. Now that the weather has cooled off, it is looking much better. I’m worried about how it will fare if we have another summer of intense heat. Should I get rid of it?

Last summer was one for the record books, and I lost some plants in my own garden, while others struggled. In the future, we are likely to experience hotter-than-average summers. Cape honeysuckle (Tecoma capensis) does best in filtered sunlight exposures but may still struggle in high-heat conditions. If you keep your cape honeysuckle, cover it in summer with 50% shade cloth if it shows signs of heat stress, such as browning leaves and sparse foliage. Keep the shade cloth on until mid-September, once temperatures have begun to cool. Ultimately, I would consider replacing it with a more heat-tolerant shrub with a similar appearance, such as ‘Crimson Flare’ (Tecoma × ‘Crimson Flare’) or ‘Bells of Fire’ tecoma (Tecoma × ‘Bells of Fire’), both of which are more tolerant of hot temperatures and full sun exposure.

Cape honeysuckle shrubs do best in filtered shade to help them cope with hot summer temperatures.

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