April: What to Do in the Desert Garden

While there’s beauty to be found all year in the desert, April just may be the most beautiful month. And for gardeners, it’s possibly the busiest, too. Here’s a look at what you can plant, what you should prune, how to adjust your watering schedule, and more.

April is unparalleled when it comes to desert beauty. Plants of all kinds — wildflowers, cactus, shrubs, and trees — are in bloom. It is also one of the busiest months for desert gardeners.

April Weather Outlook

April is a month of change and it can get quite hot or still be chilly. But the average daytime temperatures are typically pleasantly warm, while the nights are pleasantly cool.

For those of us who grew up thinking “April showers bring May flowers,” it can be jarring to learn that spring is the driest season and that April is the first of the desert’s three driest months.

Here’s a look at April weather averages in both Tucson and Phoenix.

April Weather Averages (Tucson)

High temperature	83°F
Low temperature	53°F
Precipitation	.39″
Relative humidity	24%
UV Index	8.5
Wind	15 mph

April Weather Averages (Phoenix)

High temperature	86°F
Low temperature	61°F
Precipitation	.23″
Relative humidity	22%
UV Index	7.6
Wind	8 mph

If you live elsewhere, enter your city or town in the search bar at TimeandDate.com to find your weather averages. And you can find your average UV index at UVIndex.io.

What To Do in the Garden in April

Here’s a snapshot of the tasks you can do this month.

Read on for all the details and exceptions!

What to Prune

It’s time to get out your pruners and loppers. If you didn’t prune cold-damaged plants in March, do it this month.

Plants that die back in the winter — perennials, ground covers, vines, and ornamental grasses — benefit from a hard prune. Some, like ornamental grasses, should be cut to nearly ground level to remove old growth while most perennials should be cut by 1/3.

Hand prune shrubs to shape or control size. Wait to trim spring-flowering shrubs until after they’ve finished blooming.

Prune vines to remove any cold damage. You can prune vines lightly or extensively as needed to control their size. Prune basal sprouts to the ground if you wish to prevent their spread.

You can continue to deadhead annuals to encourage flowering.

What You Can Plant

Some plants should be planted in April. April is an ideal time to plant cactus, agaves, and other succulents since warm soil temperatures encourage their root development.

The exception is aloes, which should be planted in the fall.

It’s also a good time to plant other heat-loving plants. Bougainvillea, hibiscus, lantana, fig trees, citrus trees, and flowering vines such as crossvine and queen’s wreath fall into this category.

Other plants can be planted in April, even though it would be less stressful for them to be planted in the fall.

You can plant nearly all trees, shrubs, perennials, vines, and ornamental grasses in spring. If you’re going to plant in the spring, do it early in the month. This gives your plants the most time to acclimate before it gets really hot, which can be surprisingly early. In 4 of the past 6 years, the first 100-degree day occurred in April!

You can also move plants and divide perennials and clusters of aloe now as well.

Minimize planting stress with
6 Steps for Successful Spring Planting.

While nurseries are well-stocked with summer annuals, resist the urge until the nighttime temperatures stay above 55°F. Here in Tucson that’s usually in late April or even in May. Then you can plant gaillardia, marigold, pentas, moss roses, vinca, zinnia, and other heat-loving annuals.

If you’re eager to freshen up your containers, add a few “shoulder season” plants such as dianthus, gerbera daisies, dusty miller, and African daisies. Move containers as needed to adjust for seasonal changes in the position of the sun.

Watering New Plants

It’s critical that new plants get enough water. Here’s a good rule of thumb for watering.

Weeks 1 & 2	Every 3 – 4 days
Weeks 3 & 4	Every 6 – 7 days
Weeks 5 & 6	Every 7 – 10 days
Weeks 7 & 8	Every 10 – 14 days

Adjust Your Water Schedule

If you didn’t adjust your watering schedule for your existing plants in March, do it now. As the weather gets warmer and drier, plants should be watered more frequently.

Most people water too little too often. Don’t be one of them! Use the University of Arizona’s Recommended Watering Schedule as a simple guide or Landscape Watering by the Numbers flipbook as an in-depth guide.

Not sure how to water your plants in April?
These articles can help:
How to Water Desert Trees: How Often? How Much?
How to Water Desert Shrubs: How Often? How Much?

Check Your Irrigation System

If you have an irrigation system, now is a good time to make sure it’s working properly and that the placement of emitters is keeping up with the growth of your plants. See Check Your Irrigation System for information on what to check and how to get professional help.

Fertilize Citrus

Citrus should receive their second dose of fertilizer this month. The rule of thumb used to be to fertilize three times per year at the holidays — Valentine’s Day, Memorial Day, and Labor Day — but there’s been an update to that.

Here’s University of Arizona’s, latest citrus fertilization calendar. Dates are now a little earlier and have a wider range, rather than being tied to specific holidays.

	Lemons, Limes	Oranges, Grapefruit
1st	Jan. – Feb.	Jan. – Feb.
2nd	March – April	March – April
3rd	Aug. – Sept.	May – June

Figuring out the right amount of fertilizer used to be complicated, but the University of Arizona recently published this handy online citrus fertilizer calculator. To use it you’ll need to enter:

• the type of tree
• your tree’s height (in feet) and the trunk diameter (in inches)
• percentage of nitrogen in your fertilizer

It will then tell you how many pounds of fertilizer you should apply and when to apply it.

Don’t neglect this important step. Properly fed trees are healthier, more resilient, and produce better yields and tastier fruit.

While we’re talking about citrus, don’t fret if your tree loses older yellow leaves or drops premature fruit. Both are perfectly normal. The tree will only keep the amount of fruit that it can comfortably support.

Fertilize Non-Native/Flowering Plants

While most desert landscape plants don’t need fertilizer, you may want to fertilize those that are not southwest desert natives and/or that flower profusely for extended periods.

Examples of plants that can benefit from an application of fertilizer this month include:

• flowering vines (i.e., lilac vine, snail vine, queen’s wreath, crossvine)
• flowering shrubs (i.e., hibiscus, cape honeysuckle, yellow bells)
• flowering perennials (i.e., Gregg’s mist, coral fountain, Jerusalem sage)
• any flowering potted annuals

Don’t fertilize plants immediately after planting or when they are otherwise stressed, such as during an early heat wave.

Harvest Wildflower Seeds

Some wildflowers such as desert bluebells, penstemon, and native poppies may have finished flowering. If you have any growing on your property, you can harvest seeds to sow next fall.

Watch for Insect Pests

With warmer weather comes increased insect activity. Here are two insect pests to watch out for this month.

Agave Weevil

One of the most feared and destructive insects in the desert garden is a small black bug called agave weevil.

They attack agaves and by the time you notice the damage, it’s too late to save the plant.

The first sign an agave is struggling is that it looks droopy, yellow, and the lower leaves look wrinkly but the top remains upright. If you give your plant a gentle rock, it will easily move and even break off at the base if it’s infected.

While it will be too late for that plant, you can learn about the steps you can take to stop its spread and prevent future infestations here.

Genistra Broom Moth

If you grow Texas mountain laurel, look for genista caterpillars, the larval stage of the genista broom moth.

They like to dine on new leaves and young seed pods. Learn how to recognize and deal with an infestation here.

Watch for Weeds

Depending on how much winter rain you’ve had, you’ll almost certainly have some weeds pop up this month. My first-line strategy for keeping weeds at bay is to pull them when they’re young and the ground is wet.

Never let a weed go to seed. One weed today can turn into 100 future weeds. When a weed is left to go to seed, it can produce hundreds of seeds — which become next season’s weeds.

You can keep the number of weeds down dramatically by following this simple rule. Pull your weeds before they seed. When a weed is left to go to seed, it can produce hundreds of seeds — which become next season’s weeds.

If you sowed wildflower seeds in the fall or hope some of your plants will reseed, be sure you aren’t pulling any seedlings of plants you want in your yard. 😉

Stinknet

Stinknet is a weed that’s in a category of its own. It’s bad news even in its native South African habitat. But here it’s an alarmingly aggressive, invasive plant that threatens desert biodiversity, contributes to wildfires, and emits toxic gases when burned.

Every gardener should know how to ID it, what to do if you find any, and how to get rid of it safely. To learn more, watch this video or visit Stinknet.org.

Upcoming Gardening Events in April

There are loads of gardening classes and events throughout April. You’ll find an up-to-date list of gardening-related events in our Tucson Gardening Events Calendar.

Pima County Master Gardener Home Tour will be held early this month. Get your tickets soon because they sometimes sell out.

Semi-annual plant sales to check out include Pima County Master Gardeners and Desert Survivors (native plant nursery).

Don’t live in Tucson? Look for Zoom classes. You can participate in these no matter where you live.

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Image Credits

Nanosancho, CC BY-SA 3.0, Wikimedia Commons