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February/March 2023 Garden Checklist and Solutions

All Elevations

Late winter to early spring is a good time to plant woody shrubs and trees. They are typically in a slow growing phase this time of year and do best when given some time to reestablish root systems that are sacrificed in the planting process before the summer heat stress begins. Planning for the mature size of trees and shrubs is vitally important to their and your success. Too often we are tempted to fill in all the space in our landscapes with new plants instead of allowing enough space for them to grow. At maturity they should be no closer than touching leaf tips. Patience in the early stages of landscape planting will pay off with less maintenance issues as the plants grow to their full potential.

Irrigation As temperatures begin to warm and frozen things thaw out, irrigation systems begin to show the damage from cold weather by leaking. Late winter and early spring are good times to check your lines to make sure things are working as expected and to give you time to locate and replace any damaged parts before the summer heat makes it painfully obvious where the gaps are located.

Low Elevations

Growing plants from seed, such as perennial wildflowers, can begin with taking advantage of late winter rains. If the rains don’t fall as needed, light hand watering will suffice to ensure seeds do not wash away. There are many choices of which flowers to plant, so it is wise to see what is available at your local nursery, garden center or seed library before making decisions. Be careful about ordering things online, especially if they are grown in a vastly different environment. Also, be sure that plants you desire are not invasive or too aggressive for your ability to care for them. For example, Ruellia brittoniana is a common and hardy purple or pink flowered shrub that does very well in Arizona. In fact, you might plant it in one place and a couple months later find it popping up in other locations. These are invasive in places where irrigation and good soil are found and thus may require more upkeep than desired. Vegetable planting at this time of year includes hardy plants such as lima beans, sweet corn, eggplant, potatoes, summer squash, tomatoes and watermelon.

Fertilize Citrus For optimal health and productivity, citrus trees require annual fertilizer. The recommended amount to apply varies based on the type, age and size of the tree. Typically, we fertilize three times each year, splitting the recommended nitrogen fertilizer application into thirds. In general, oranges, tangerines and grapefruit should receive fertilizer in January-February, March-April, and May-June. For lemons and limes, shift the timing of the third application to August-September. For specific amounts based on your tree’s particulars, consult the University of Arizona publication, “Citrus Fertilization Chart for Arizona” at

Spring Planting Often there will be a bit of warm weather during the late winter months. Don’t be tempted to gamble by planting tender vegetables and annuals before the last frost date—you never know when a frost could wipe out your efforts. Most record late frost dates across Arizona’s lower elevations are in May, but more often the last occurrence is in April. To be safe, use Mother’s Day as a guide, but if you live in the lower desert, you could roll the dice on April 15.

I am composting my yard and kitchen waste in a backyard bin. When I turn it occasionally, I find white grubs living in the composted material. Should I worry about putting these grubs on my garden beds?

White grubs are often found in compost because their parents seek out good soil and lay eggs where their offspring may find a nice space to grow with plenty of food to eat. They are part of the food web that helps break down what you put into the compost, so you might consider them free help. There may be multiple species found but the ones that seem to cause the most alarm—but still are not harmful—are the soldier fly maggots and the fig beetle grubs. They are alarming because they are relatively large and easy to see against a darker soil. In the garden, grubs could potentially feed on plant roots, so if you found a large number of them, pick some out and feed them to your chickens, flycatchers or other insectivores in your landscape. Often the act of digging and turning soil will kill or injure these insects and it will also expose them to the birds that would like to eat them. In the end, some will survive, and that is okay. Fig beetles are a source of entertainment as well.

Illustration by Gary Hovland

Middle Elevations

Many of the same plants that grow at low elevations will also be suitable in places a little higher, such as Tucson, Sells and Superior. You might just wait until March instead of planting in February to be sure you are past the last frost date. Some vegetables that can be planted in February include Irish potatoes, spring peas, spinach, kale, endive and garlic.

High Elevations

In very high places, such as Flagstaff and Show Low, it is probably still too cold to plant vegetables outdoors, but starting seed indoors is an option for planting in April and May. If you are itching to get out there, roses, vines and other woody plants can be planted now. There are many options— to find what is suitable for your landscape, it is best to visit local nurseries where you can see what does well in your area and seek advice on selection from local growers.

If you are unsure about where to locate local nurseries, ask friends and neighbors. It is easy to find larger garden centers because they tend to advertise widely, but there are many small to medium nurseries that may specialize in cacti, citrus, etc., that may be off the beaten path or not as well advertised. These sometimes have the specialty plants or odd varieties that other places may not sell.

High Elevations

Pruning Fruit Trees Late winter, a few weeks before bud break, is a good time to prune fruit trees such as peach, apple and fig. Certain pruning methods are recommended, depending on the type of tree. Pruning correctly can keep a tree in good health, while incorrect pruning can damage and shorten the life of a tree. Unfortunately, unlike getting a bad haircut, pruning can permanently affect a tree’s structure. It is important to know how and why to make a proper pruning cut using sharp, clean tools. The rule of thumb is not to remove any more than one third of live branches. Damaged limbs may be removed any time but pruning in the cold part of the year is ideal for trees that are about to begin the growing season. If you aren’t sure how to prune, ask a local extension agent or employ a certified arborist, which can be located in your zip code by using the “” website.

Soil Preparation While waiting for the weather to warm up enough to begin planting vegetables or annuals, consider improving the soil in the beds you will be using. Arizona soil is almost devoid of organic matter, so it behooves us to add some before we expect anything to grow well. If you are in the habit of composting, you already have a great source of organic matter to apply. If not, purchased fertilizer, compost or aged manure will work. Don’t use fresh manure, as it will damage plants. Work the amendments into the soil with a shovel or rake so it will be ready for planting. If you are breaking new ground, remove rocks and old plant roots now for easier planting later. If you are uncertain which ratio of fertilizer to buy, a soil test of the garden beds can let you know which parts of the nitrogen, phosphorus, potassium formula you already have and which ones your soil needs. Locate a soil test kit at your favorite garden center, online or ask your local county extension agent. You won’t go too far in the wrong direction by using a general 10-10-10 fertilizer. There are, of course, specific formulations for cactus, citrus, etc., that take some of the guesswork out of the process.

The tips of my agave leaves are turning brown. Any idea what causes this and how I should treat it?

Brown tips on leaves of many plants, including agaves, are often a symptom of drought. If you are already irrigating, make sure there isn’t a problem such as a disconnected or damaged part or a clog in your line. Our water often leaves a residue that over time can clog irrigation systems, especially the smaller diameter lines going to individual plants. Damage can come from pests chewing on the line, accidental cuts from digging and the occasional freezing and thawing that may cause cracks in older tubes. If you’re not irrigating, there needs to be a natural water source available, and that is not always the case with desert plants. You could consider hand watering if you have that kind of spare time, but drip irrigation is usually the best option.

My Mexican sunflower (Tithonia) is about 8 feet tall and still blooming. I feel like I should cut it back before spring, but when?

There are several species and varieties of sunflowers and within the genus Tithonia. If you are still seeing blooms in the cold part of the year, you probably live in the low to mid desert. In the colder places, these plants are considered to be annuals because they are killed by frost, but in places like Phoenix, Tucson and Yuma, they can be perennial plants. Needless to say, the pruning issue is less concerning if your sunflowers die when freezing temperatures arrive. But even in that case, deadheading throughout the growing season is often desirable to keep up appearances and to promote continued blooming. For those tall varieties, such as Tithonia fruticosa, planted in warmer locations, pruning them down to an acceptable size might be an issue.

This plant can grow to be 6 or 7 feet tall, on average, and with good irrigation and soil, possibly as tall as 12 feet. Deadheading won’t solve this problem, but we can prune to a desirable size. Typically, you would want to keep a tall plant like that under a certain height so that it fits your garden design or doesn’t flop over when it becomes top heavy with blooms that overwhelm the stalks. With pruning, the general rule is to take no more than one third of the plant off any one time. Some plants, like this sunflower, can tolerate more harsh treatment in the cold part of the year, which is typically the end of the season. At that time, this plant may be pruned down to 18 to 24 inches above ground, after which it will grow back to bloom again.


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