Howdy, future tree-growers! Tim Burr here. Planting a tree is one of the best things you can do for a Phoenix yard — shade, value, beauty, the works. But there's a hidden villain lurking under a lot of Valley soil that quietly kills new trees: caliche. Get the planting right and your tree thrives for decades. Get it wrong and it slowly drowns. Let me walk you through doing it right, step by step.
First, what is caliche?
Caliche is a hardened layer of calcium-carbonate-cemented soil — basically natural concrete — found beneath much of the desert Southwest. It can be a thin crust or several feet thick, and it ranges from "tough to dig" to "needs a pickaxe." The real problem isn't digging, though: it's that caliche doesn't let water drain through it. Dig a normal hole in caliche, and it becomes a bathtub. You water your new tree, the water fills the hole, has nowhere to go, and the roots sit in stagnant water until they rot. That's why so many new desert trees mysteriously decline a few months after planting.
Step 1: Test for caliche and drainage before you plant
Before anything, do a simple percolation test. Dig your planting hole, then fill it with water and let it drain completely. Fill it again and watch: if the water drains within a few hours, you're fine. If it's still sitting there after 12–24 hours, you've got a drainage problem (often caliche) and you need to fix it before the tree goes in. This five-minute test saves trees.
Step 2: Dig the hole correctly
- Dig wide, not deep. The hole should be 2–3 times as wide as the root ball but only as deep as the root ball is tall. Roots spread out, not down — a wide hole encourages healthy lateral roots.
- Don't glaze the walls. In clay or caliche, a shovel can smear the sides into a slick barrier roots can't penetrate. Rough up the sides with your shovel or a fork so roots can grow outward.
- Find and breach the caliche. If you hit a caliche layer at the bottom, you must punch through it so water can escape. Use a digging bar, pickaxe, or auger to drill a "chimney" or drainage hole through the caliche layer to looser soil below. This vertical escape route is the single most important step.
Step 3: Handle stubborn drainage
If the caliche is too thick to breach reasonably, you have two good options: relocate the tree to a spot with better drainage, or plant high on a mound. Building the tree up in a raised mound of native soil 12–18 inches above grade lets excess water drain away laterally instead of pooling at the roots. Mounding is a proven desert technique and beats fighting an impenetrable caliche shelf.
Step 4: Plant the tree
- Set the depth right. The root flare (where the trunk widens into roots) should sit at or slightly above grade. Planting too deep is the #1 tree killer — never bury the trunk.
- Backfill with native soil. Resist the urge to fill the hole with rich potting mix or heavy amendments. In our soils, a hole full of fluffy amended soil surrounded by hard native soil becomes another bathtub, and roots circle in the "nice" soil instead of venturing out. Backfill mostly with the native soil you dug out; a light amount of compost mixed in is fine, but native is best.
- Remove stakes/ties from the root ball and gently loosen any circling roots so they grow outward.
- Water in as you backfill to settle soil and eliminate air pockets.
Step 5: Build a basin, mulch, and stake only if needed
- Form a watering basin (a soil berm) around the edge of the root zone to hold water so it soaks straight down to the roots.
- Mulch 2–3 inches deep over the root zone, kept a few inches off the trunk, to hold moisture and cool the soil.
- Stake only if the tree can't stand on its own, using loose ties that allow some trunk movement (movement builds trunk strength), and remove stakes after the first year.
Step 6: Water for strong establishment
For the first growing season, water deeply and regularly: roughly every 2–3 days in summer right after planting, gradually stretching the interval as the tree roots in. Always water deep and wide — a slow soak that wets the soil 2–3 feet down at the edge of the root ball, pulling roots outward and down. After the first year, taper to deep, infrequent soaks; established desert trees need surprisingly little. The deep-watering habit you build now creates a deeply anchored, drought-tough, wind-firm tree for life.
The payoff
It's a little more work than dropping a tree in a quick hole — but breaching that caliche and planting at the right depth is the difference between a tree that struggles and one that shades your home for 30 years. Do it once, do it right, and enjoy the canopy.
Ready to plant? Browse our Shade Trees, Flowering & Accent Trees, and Native & Desert-Adapted Trees. We deliver healthy, established trees to your door and back every one with our survival guarantee — and if you'd rather skip the pickaxe entirely, our team can plant it for you, caliche and all.
🌵 Tim's Tip: Do the five-minute percolation test before you ever buy the tree. Dig your hole, fill it with water, and see how long it takes to drain. If water's still sitting there after 12 to 24 hours, you've got a drainage problem to solve first. That quick test has saved more desert trees than any fertilizer or fancy product ever will.
Frequently Asked Questions
What is caliche and why does it kill trees?
Caliche is a hardened, cement-like layer of calcium-carbonate soil found under much of the desert Southwest. The problem isn't digging through it — it's that water can't drain through it. A normal hole dug into caliche becomes a bathtub: you water the tree, the water has nowhere to go, and the roots sit in standing water and rot.
How do I plant a tree if I hit caliche?
Punch through it. Use a digging bar, pickaxe, or auger to drill a "chimney" or drainage hole through the caliche layer down to looser soil below, so water can escape. If the caliche is too thick to breach reasonably, plant high on a raised mound (12 to 18 inches above grade) so excess water drains away laterally instead of pooling at the roots.
Why shouldn't I fill the hole with rich potting soil?
Because in our soils a hole full of fluffy amended soil surrounded by hard native soil becomes another bathtub, and roots circle in the "nice" soil instead of venturing out to anchor the tree. Backfill mostly with the native soil you dug out — a little compost mixed in is fine, but native is best.
How deep should I plant a tree?
The root flare — where the trunk widens into roots — should sit at or slightly above grade. Planting too deep is the single most common tree killer in the desert. Never bury the trunk, and dig the hole wide (2 to 3 times the root ball) but no deeper than the root ball is tall.
How often should I water a newly planted tree?
For the first growing season, water deeply about every 2 to 3 days in summer, gradually stretching the interval as the tree roots in. Always water deep and wide — a slow soak that wets the soil 2 to 3 feet down at the edge of the root ball — to pull roots outward and down. After the first year, taper to deep, infrequent soaks.
Plant a tree the right way today, and your future self will thank you every summer afternoon. — Tim 🌵
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