Trees in a hard climate
Trees in St. George live with heat that tests even desert-adapted species. The cooperative station there read 117°F on July 10, 2021, tying Utah's all-time maximum. Soils add their own problems: the Utah Geological Survey's hazard maps for the St. George–Hurricane area include caliche, collapsible soil and gypsiferous soil. And the City of St. George says most local water is hard. This checklist helps trees through each season.
Spring (February through April)
- Prune before heat arrives. Late winter and early spring are a good time for structural pruning on many species.
- Check irrigation. Make sure drip emitters reach the outer root zone, not just the trunk, and that lines are not clogged with mineral scale.
- Mulch wide and shallow, keeping mulch a few inches away from the trunk.
Summer (May through September)
- Water deeply and less often. Deep watering encourages deep roots, which survive heat better.
- Watch for leaf scorch: browning at leaf edges, which often means the tree cannot move water fast enough.
- Avoid heavy pruning in summer. Removing shade from the trunk can expose bark to sunscald.
- Look for pests. Stressed trees attract borers and other insects.
Fall (October and November)
- Plant new trees in fall, so they can root before summer.
- Adjust irrigation as temperatures fall, but keep watering evergreens.
Winter (December and January)
- Water occasionally during dry spells.
- Inspect structure of deciduous trees while bare.
Soil and water problems
Caliche, a hard calcium carbonate layer, can stop roots and trap water. Ask an arborist whether planting holes need to break through it. Hard water and alkaline soil can lead to yellowing leaves (chlorosis) in some species. Choose species suited to these conditions.
Spraying and pest treatment
In Utah, anyone applying pesticides commercially must hold a Commercial Pesticide Applicator License from the Department of Agriculture and Food and work for a business holding a Commercial Pesticide Business License. If a tree service offers spraying or injections, ask for both and check them.
Hiring a tree service
Ask for a written scope naming each tree, cut and treatment, how debris will be handled and whether stump grinding is included.
Keep notes
Write down species, planting dates, irrigation changes and treatments. In a desert climate, small watering changes often explain a tree's decline.
Roots, walls and slabs
In St. George, many trees grow near block walls, pools and patios. Ask about mature root spread before planting near hardscape, and avoid shallow, frequent watering that keeps roots near the surface where they lift pavers.