Garden Solutions: What to Plant This Fall in Arizona
What to plant, prune and pluck in October and November according to your elevation.
Send your gardening questions to info@azplantlady.com
Hello Friends,
Fall is a favorite time of year for many desert dwellers. We rejoice with the return of cooler temperatures and can enjoy being outdoors again. It is often referred to as our “second spring,” when we can get busy in the landscape again, perhaps adding new plants to replace those struggling to survive summer’s intense heat.
You may be surprised to learn that fall is the optimal period for installing new trees, shrubs and ground covers, as it gives them time to grow a sound root system before next summer. Timing is just one factor in how well a young plant will do—read on for more tips to ensure their success.
If you enjoy the colorful show of wildflowers every spring, now is also the time to sow these seeds, and it’s easier than you may think. In our next issue, we’ll discuss how to punch up the color into your outdoor space to add vibrant interest throughout the winter season.
Questions? Send them to info@azplantlady.com. They may be featured in a future Garden Solutions.
Low to Middle Elevations
Adjust your irrigation schedule once daytime temperatures dip into the low 90s, typically mid to late October. Plants don’t need as much water in fall’s cooler days, and problems with overwatering are common if the schedule isn’t adjusted seasonally. For example, if you water your shrubs, ground covers and vines twice a week in summer, increase that interval to once every five to six days. Trees and succulents can go even longer between watering cycles.
Amend the soil before planting cool-season vegetables this fall. Edible gardens require high levels of nutrients, and over time, their planting bed sinks as organic matter decomposes. To prepare for your new crop, don’t dig or till the soil. Spread compost; aged steer, chicken or rabbit manure; and blood and bone meal over the existing soil, and gently mix them. Don’t dig or till the layer underneath, which can disrupt the structure and beneficial microorganisms within.
Explore new plants to replace those struggling in our hotter summers. Look at options beyond the more commonplace bougainvillea and lantanas expand the variety around your home. There are many different shrubs, perennials and succulents to explore, and Desert Botanical Garden is a great place to get inspired. Most plants there have identifying signage, and you can shop for new additions during their fall plant sale, scheduled for Oct. 17-20. Attendance is free; reservations are required. Learn more at dbg.org.
High Elevations
Bring cold-tender herbs indoors before the first freeze hits. Place them in front of a south- or west-facing window for maximum sunlight. Lightly trim them back and fertilize to encourage a new flush of growth. Sprinkle diatomaceous earth on the soil surface to discourage fungus gnats. Harvest the leaves to flavor your favorite soups or other winter dishes.
Plant spring-flowering bulbs such as daffodils, iris, hyacinths and hybrid tulips. Amend the soil with compost to improve the soil and add nutrients. Plant with the pointy side of the bulb facing upward in staggered rows in beds near structures or in natural groupings in open areas.
After the first hard frost, prune roses back to 18 inches high. Cover them entirely with mulch, such as dried leaves, compost, pine needles or straw. Create an enclosure at least 2 feet tall, made of chicken wire or hardware cloth and stakes, around each shrub to help keep the mulch material from blowing away.
New Plants to Consider
Yellow Bells (Tecoma stans), ‘Sparky’ Tecoma (Tecoma x ‘Sparky’), Texas Sage (Leucophyllum spp.), ‘Outback Sunrise’ Emu (Eremophila glabra ‘Mingenew Gold’), Elephant Food (Portularcaria afra)
We enjoy having a green lawn all year and overseed with perennial ryegrass every October. Last spring, our Bermuda grass didn’t grow back well and is thinning in spots. Should we do something different this fall?
Adding perennial ryegrass seed year after year can harm your warm-season lawn because you have two different grasses competing with each other. Over time, this negatively affects Bermuda, making it more difficult to grow back in late spring, resulting in bare patches where weeds can take root. To help avoid this problem, skip overseeding every three years, beginning now. A bonus is that you will save water and will not need to mow. Next summer, you may want to seed or sod the empty spaces.
Plant for Success
Does your landscape look rather beaten up after our punishing summer? If so, now is the best opportunity to make changes by replacing plants that struggled in the intense heat with more resilient ones. However, other factors must be considered to ensure that new trees, shrubs and ground covers will survive and thrive in your landscape. Yes, the desert is a challenging climate to garden in, but it is possible to have a beautiful outdoor space when you implement these best practices:
- Ensure that any new plants are well-adapted for our hot summers. Look for those native to the Southwest or from regions with a similar climate, which are more likely to thrive here.
- Shop at local nurseries or botanical garden sales, which are more likely to stock those plants proven to do well in the desert. If a big-box store is your preference, beware that not all plants they carry are suitable for a long, hot, dry season.
- Install plants during the cooler months of autumn and winter to allow them time to establish and better enable them to withstand the stress of their first summer.
- Observe how much sunshine the planting location receives. A common mistake is not paying attention to the amount of light a plant can tolerate. Note that “full sun” on a label doesn’t mean it can handle the intensity of the desert sun. To find accurate information, utilize resources such as a certified nursery professional or regional online resources such as amwua.org/plants.
- Before buying, measure the planting area, and research the size plants will reach at maturity. This will allow them to grow to their natural size and shape, which means less pruning to keep them from outgrowing their space.
- Create a hole two to three times wider than the plant’s nursery container. Most roots grow outward, allowing them to grow more quickly, which will help increase the rate of growth. The depth of the hole should be the same or an inch or two shallower than the root ball to allow for settling after planting.
- Studies show that soil amendments can inhibit growth, as roots tend to stay close to the plant where the amended soil is rather than growing outward. The exception is when there is poor drainage. Mixing one part compost with two parts existing dirt can help open up the soil.
- Skip the fertilizer, which stimulates the growth of leaves, stems and branches before the roots have had time to develop enough to support them. Many trees and shrubs such as mesquite (Prosopis spp.), paloverde (Parkinsonia spp.), Baja fairy duster (Calliandra californica), feathery cassia (Senna artemisioides) and red bird of paradise (Caesalpinia pulcherrima) are nitrogen fixers and don’t need fertilizing. Some plants do best when fertilized at the time of planting, including container plants, flowering annuals, herbs and vegetables.
- Irrigate new plants more frequently for the first year, which is vital to survival since they have a smaller root system and can dry out more quickly. For watering guidelines, refer to amwua.org/landscaping-with-style/maintain/watering-schedules.
- Young plants can experience stress in their first winter and summer. Cover those that are cold-sensitive with frost cloth, towels or sheets when temperatures dip below freezing. During intense heat, cover them with shade cloth if they show signs of stress, such as yellow or brown foliage. As plants grow larger, their tolerance to weather extremes will increase.
I’m new to desert gardening and in September, I replaced the annuals in my containers with alyssum, petunias and snapdragons. I watered them daily, but they struggled. Two weeks later, most were dead. Do these types of flowers even grow in our climate?
The good news is you can grow these types of flowers in the desert. However, the timing of when to plant them is likely to be the cause of your troubles. Many nurseries begin to carry these colorful beauties in late summer, tempting shoppers to buy them. These small, blooming plants are raised in greenhouses, where they are protected from weather extremes. Planting them too early in our climate causes them to experience heat stress. Temperatures can still hit triple digits in late summer, which they cannot tolerate. Wait until mid to late October to add annuals for best results.
Create a Wildflower Garden
One of the things we look forward to in spring is colorful wildflower displays along the roadways. The number of blooms is largely dependent on the amount of rainfall received in winter and early spring, which is why the floral display is variable.
Popular native wildflowers that paint the desert in vibrant colors include arroyo lupine (Lupinus succulentus), desert blue bells (Phacelia campanularia), red flax (Linum grandiflorum rubrum) and Mexican gold poppy (Eschscholzia californica ssp. mexicana). If you want to enjoy the beauty of wildflowers in your landscape, they are easy to grow and most of the work is done in fall.
Select a location in full sun that is free of weeds. If landscape rock is present, move it back to expose the bare soil. Lightly rake the top couple of inches of exposed soil to help break it up. You don’t need to add supplements, as our native wildflowers do well in our soil. Water the area to moisten the soil to a depth of approximately 4 to 6 inches to provide the ideal environment for seeds to germinate. Avoid using pre-emergent herbicides, which will prevent them from coming up.
It’s best to use wildflowers native to the Southwest from a local source such as nativeseeds.org. Mix eight parts of sand with one part seeds to help make it easier to spread evenly. Apply the mixture with your hands in an even layer over your prepared soil, or use a handheld broadcast spreader. Afterward, compress the soil by placing a piece of cardboard and walking over it, moving it as needed until finished. If you have moved landscape rock, gently rake it back over to cover the area, and the seeds will grow through it.
Water regularly every three to four days to keep the soil evenly moist but not soaking—a hose-end sprinkler or drip irrigation micro-sprayers is ideal. Once seedlings are 6 inches tall, decrease the frequency to once a week (if there is rain, you can skip a week). Soon, you’ll enjoy a lovely splash of springtime color that is also beneficial to pollinators.
Many of my shrubs and ground covers have unsightly brown leaves and stems after the extra-hot summer. I want to prune them because they are ugly. Can I do this now, or must I wait until spring?
Plants not well-adapted to extreme heat can experience burned foliage at summer’s end. While it is tempting, fall isn’t a good time to do any severe cutting back of shrubs, vines or ground covers, as this stimulates tender growth susceptible to injury from freezing temperatures in winter. Live growth will be flexible. If a stem or branch breaks off when slightly bent, it isn’t alive and can be removed now. Wait until spring to do any major pruning of living parts of plants.