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How to Care for Aspen Trees

Aspen trees (Populus spp.) grow as deciduous hardwood trees throughout North America. Aspen trees can reach heights of 60 feet, but usually don’t survive for more than 25 years in an urban or home landscape. Controlling pests and treating fungal diseases will take up the majority of your time when caring for aspen trees.

Water aspen trees deeply to thoroughly moisten the soil in the entire root zone once every one or two weeks to supplement rainfall. Allow the top 2 inches of soil around the trees to become slightly dry before watering again.

Feed aspen trees a balanced, slow-release granular tree fertilizer once each year in the spring. Spread the fertilizer granules on the ground around the tree, covering the entire canopy area and following the dosage instructions on the label.

Prune aspen trees in the winter to thin out the branches, as well as to remove any dead, diseased or damaged limbs. Never remove more than one-third of the tree in a single year.

Treat aspen trees for poplar borer infestations by injecting an insecticide into the bored holes in the trunk.

Watch for tent caterpillars in aspen trees, which create large webs around the leaves, stems and branches when they pupate. Remove the webs and spray your aspen trees with dormant horticultural oil in late winter or early spring.

Treat aspen trees for the fungal disease leaf spot if you see premature leaf drop and black blotches on the leaves. Rake away and destroy all the fallen leaves and spray the tree with a fungicide in early spring.

Control aphid infestations in aspen trees by spraying them thoroughly with a high-pressure hose and insecticidal soap.

Tip

If you see rough areas developing on the aspen tree’s bark along with tiny black lines, you likely have a scale infestation. Rake away and destroy any fallen leaves and spray your aspen tree with dormant horticultural oil in the winter. Spray the aspen tree with an approved insecticide in June.

Warning

Watch out for cytospora canker infecting aspen trees. Look for orange dots and callused canker growths on the bark to spot this fungal disease. Prune away and discard all infected branches. Always disinfect your pruning tools when cutting away diseased wood to prevent spreading the disease to other trees. Dip your pruning tools into a mixture of three parts denatured alcohol and one part water for about 30 seconds.

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