Back East, people plant trees in the spring. Here, that’s a tough time to do it. A tree that goes in the ground in late April has a few weeks to settle in before it faces 110-degree days with a root system the size of its nursery pot.
So when should you plant in Gilbert and the rest of the East Valley? And once you’ve picked the day, how do you avoid the mistakes that kill most new trees? Here’s what Arizona water and forestry experts recommend.
The best time to plant: fall
Water Use It Wisely, the Arizona water conservation program, puts the ideal planting window at September through April. For most desert-adapted trees, fall is the sweet spot. The soil is still warm, so roots keep growing, while the air is cooling off, so the tree isn’t losing as much water through its leaves. By the time summer rolls back around, a fall-planted tree has had months to push roots out into the yard.
The exception is frost-sensitive trees. Citrus and other tender species are better planted in spring, after the last frost, so a cold January night doesn’t catch them before they’re established.
Before you dig
- Call 811. Arizona 811 will mark underground utility lines before you dig. SRP reminds everyone in its shade tree program to call first, and you should too.
- Think about the mature size. That five-gallon mesquite can end up 30 feet wide. Make sure it won’t grow into the roof, the power lines or the pool.
- Check the drainage. Fill the hole with water and see how long it takes to drain. If it’s still sitting there the next day, you probably have caliche or compacted soil to deal with first.
Still deciding what to plant? Our guide to where to plant a shade tree covers placement and good desert trees for the Valley.
How to plant it
1. Dig wide, not deep
Make the hole about twice as wide as the root ball, but only as deep. Water Use It Wisely suggests loosening the soil out to four or five times the root ball’s width so roots can spread easily. A hole that’s too deep is a problem: the tree settles, and the trunk ends up buried.
2. Find the root flare
Nursery trees often have extra soil piled on top of the root ball. Brush it away until you can see where the trunk flares out into roots. That flare should sit level with, or a little above, the surrounding ground.
3. Backfill with the soil you dug out
This one surprises people. The Arizona Tree Planting Guide recommends backfilling with native soil and skipping the compost and other amendments. Studies it cites found no benefit from mixing them in. Break up the clods, fill gently, and don’t stomp it down hard.
4. Build a watering basin
Make a ridge of soil two to three inches high around the planting area so water soaks in instead of running off. Then water deeply right away.
5. Mulch, but keep it off the trunk
Spread two to four inches of organic mulch over the planting area. It keeps the soil cooler and holds in moisture. Pull it back a few inches from the trunk.
6. Stake only if you have to
Take off the nursery stake. If the tree can’t stand on its own or you’re in a windy spot, use two stakes outside the root ball with loose, soft ties, and remove them after the first year. A tree that can sway a little grows a stronger trunk.
Watering the first year
This is where most new trees are lost. The Arizona Tree Planting Guide suggests watering as often as every five to seven days the first year, deep enough to soak the root zone, then stretching out the schedule as the tree settles in. Start with water right around the trunk. Over the next six to twelve months, as roots spread, move your emitters outward toward the edge of the canopy.
Hold off on fertilizer, too. A new tree needs roots, not a push of new leaves. More on that in our post on whether desert trees need fertilizer.
Want some help?
Heartwood offers tree planting in Gilbert, Chandler, Queen Creek, Mesa and throughout our service area. We can help you pick the right tree, put it in the right spot and get it in the ground correctly. If you’re not sure where to start, a tree consultation is a good first step. Browse all of our tree care services, request a free estimate, or call (480) 269-5636.
Sources
- Water Use It Wisely, Planting Trees & Shrubs
- Arizona Department of Forestry and Fire Management, Arizona Tree Planting Guide (PDF)
- SRP, Free trees to shade your home
