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April/May 2023 Garden Checklist and Solutions

All Elevations

Since we are now officially enjoying spring, there is a wide variety of plants to consider based on your wants and needs. It is still not too late to plant shrubs, vines and trees.  Properly planted and maintained, woody plants can still begin to establish roots in a new location and tolerate the warmer temperatures. Anytime past your last frost date is a good time for annuals to go in the ground or in containers. 

A diverse population of insects and spiders is a sign of a healthy ecosystem, and pest management is an important part of garden maintenance. Taking a weekly walk through your landscape is a good idea to catch potential problems before they get out of hand. Small clusters of insect eggs or newly hatched immature insects should be examined to determine their potential cost or benefit to your plant. Most insects are either beneficial or not at all harmful, so don’t reflexively kill everything. We get a lot of free pest management from nature as the bigger bugs eat the smaller ones. And the little bugs have even smaller bugs upon their backs to bite them. 

One pest that does surprisingly well in a drought is mites. These are the only arachnids that actually damage plants. Mites are microscopic, and even the best eyes can benefit from a 10x lens or stronger when inspecting leaves for their evidence. Start looking when leaves are discolored or have fine webbing on them. Evergreens such as arborvitae, pyracantha or cypress are typical victims of these creatures, although some species may be found on aloe and other succulents. If found, a weekly spray from a hose will knock them back. Do not spray with insecticides, as the chemicals are more likely to kill the predators that eat the mites, and since they are not insects, mites can tolerate many insecticides.

One of the most common and difficult garden tasks in spring is keeping weeds from taking over. Persistent attention while they are small and easier to manage is critical to making light work of something that can easily become a big deal. Hula hoes and similar tools can be good at rogueing out young, tender weeds at the surface. As they get older and develop tougher stems, it takes weed whackers and mowers to manage.  Herbicides are much more effective on young weeds, so if that is your preferred method, don’t wait until they are a foot-tall, or you will be wasting time and money. Systemic products that are absorbed through the green parts and travel down to the roots are often more effective than chemicals that simply burn off the tops, allowing the roots to live another day.

Spring is also a time for wildlife to emerge, and newly planted or fresh green shoots may be desirable. If you live in a rural or unprotected space, a wide variety of animals might want to visit and sample your plants. Even in urban areas, there are pack rats, javelina and ground squirrels competing for our produce. Protecting these plants from the start may save a few headaches. Fence out large animals or cage entire plants to protect them from smaller animals that can climb over fencing.  Of course, not all wildlife are pests. Birds will sometimes eat their weight in insects and have superior eyesight, which means they can sometimes find the critters we miss.

In May, the heat will be up and the humidity will be down. Preparing flora for tough times ahead may include shade cloth for very sensitive plants. Adding an inch or so of mulch around the root zone will slow down evaporation and moderate the temperature of the soil around the roots.

I have a desert broom in my yard that has grown quite large. I really like it, but it is now blooming and is sending cottony stuff all over the area. My neighbor said it is a weed and a nuisance and should be cut down. Is there any way I can keep this plant from blooming?
Desert broom (Baccharis sarothroides) is a very common native plant. It is often considered a weed because of its ability to quickly colonize open spaces. As the old saying goes, one person’s weed is another person’s wildflower. There is no way to prevent it from blooming without basal pruning, but you could prune off the flowers before they go to seed and start taking flight. That could be a lot of work if your plant is as large as you say, but that way you can still enjoy the plant to some extent and hopefully appease your neighbor.

Low to Middle Elevations

Early April is a fine time to sow seeds for bush beans, carrots, cucumbers, pumpkins, squashes and radishes. Cucumbers may do better as transplants later in the month, as would eggplant, Jerusalem artichoke, melons, peppers, sweet potato and numerous herbs, including basil, mint, oregano, parsley, sage, rosemary and thyme. You don’t really need an acre of land for herbs.  Most will do fine in containers or a raised-bed garden.

For annuals, consider zinnias, coneflowers or marigolds. Perennials that add some hardy color to the landscape include Justicia, salvia and verbena. Of course, there are new varieties every year, so it is a good idea and often fun to visit local nurseries to see what is available and doing well in your area. Keep an eye out for potentially aggressive or invasive plants that are sometimes for sale. Things such as fountain grass (Pennisetum setaceum) can be spread unintentionally by weather and wildlife but are nonetheless available. If you are not certain which plants are invasive, visit the Arizona Department of Forestry and Fire Management website at

I’ve noticed a few dirt mounds in my lawn that measure about 4 inches in diameter and 2-3 inches high. I suspect ants. What can I do to get rid of them permanently?
I suspect you are correct. Leafcutter ants and harvester ants are two common species you might encounter in this area. Plant damage and a parade of leaf bits between their mandibles would likely alert the presence of leafcutter ants. Harvester ants tend to appear a bit less organized and may be more of a nuisance because they sting. Putting ant bait stations in the midst of their trails or near their mounds is one solution. Gel baits work well because they allow the foragers to bring the toxic food back to the colony, where many ants will get a taste before the poison kicks in. Another option is to drop a more toxic insecticide directly in the holes of the ant hills. These products may work quickly on contact, but they lack the distribution potential of the gels. I also prefer the gel baits because they are less likely to harm other animal species. There is no permanent solution. These ant species were here long before us and will likely be here long after us.


Spring is good time to fertilize. The March/April time frame is when we should be applying the second citrus fertilizer dose. As perennial shrubs and trees spring back to faster growing, pay attention to their health. Leaves can often send a message about their needs for fertilizer and water. When things don’t look as they are supposed to, consider the possibility of a nutrient or water deficiency. Sometimes these needs manifest as yellowing leaves, but there may be other signs, such as the curling of leaves of a plant without sufficient water. There might be a simple fix, such as adjusting your irrigation controller to put out more water, or it might be sign of winter damage to irrigation tubes. In any case, it is important to make sure irrigation is in working order before we reach the hot and dry May/June time frame.

High Elevations

April is a bit early for some vegetable species, but there are plenty you can get started, such as garlic cloves, leeks, mustard, parsnips, radishes, rutabaga and spinach. Once we are into May, squash, peppers, okra, eggplant and cucumbers may be planted outdoors.

Do you have a question about gardening in Arizona? Send your queries to plant and insect specialist Peter L. Warren at

It appears that milkweed bugs have taken over my Tempe garden—even though I don’t have any milkweed plants. I noticed a single bug a few years ago in the bark of one of my Mexican fan palms, and they have now spread to other parts of my yard. Is there a non-chemical way to repel these insects, which have become a huge nuisance?
While it is possible to have milkweed bugs without milkweed plants, what may be invading your gardens is the similar-looking species, the boxelder bug. Both are about the same size and have black and orange-red markings. This is an educated guess, but an online search can often be helpful for diagnosis. Since you have no milkweed, you may have boxelder trees, which boxelder bugs feed on. But that may be only part of the problem. These insects are well-known sun worshipers and seek out spots where the sun and reflected sunlight are abundant, such as a pool or a white house with southern exposure. They are known to gather in large numbers on warm winter days and may seek sunny spots from a distance, such as a neighbor’s tree. Once weather warms up, they will disperse to the food plants nearby. While these pests can be a nuisance, the good news is they don’t damage plants. Some insecticides will work, but it can be like a game of whack-a-mole. While I wouldn’t recommend it, you could consider cutting down any boxelder trees on your property if the bugs are really driving you crazy.

illustration by Gary Hovland


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