By Laurie Casey, Special to Tribune Newspapers
4:29 PM CDT, July 12, 2012
Your mature tree needs some TLC … or rather, "PWM" — that's pruning, watering and mulching, according to Sharon Yiesla, Plant Clinic assistant at The Morton Arboretum in Lisle.
"People assume that when trees get older they take care of themselves. But trees living in our communities undergo a lot of stress," Yiesla said. "We can help them have healthy lives by properly pruning, watering and mulching them."
When a tree is younger and growing faster, it may need substantial pruning to train it into a healthy shape. "But when trees are older and maturing, they might just need a nip and tuck approach, taking off a dead or diseased branch here and there," said Yiesla.
Some people worry that their tree has become too tall, and they "top" or cut off the uppermost branches.
"Never top a tree," Yiesla cautioned. "Removing large limbs and lots of leaves stresses the tree.
"If the tree is healthy, height isn't necessarily bad, unless it's in a confined place, such as under power lines."
Watering is the second technique. Give an older tree long, deep waterings during extended warm, dry weather. Water its roots, which range widely under branches and beyond.
"A lot of people think older trees never need water because they imagine their root systems reach down to the center of the earth. But in our region, most roots are in the top 2 feet of soil," said Yiesla.
Mulching is the final key. Spread a 3- to 4-inch layer of organic mulch over the roots, out to the branch tips, if possible. Don't let mulch rest against the bark.
"As mulch decomposes, nutrients improve soil. It also helps conserve soil moisture," said Yiesla.
For free advice about caring for your mature tree, contact The Morton Arboretum Plant Clinic at firstname.lastname@example.org, 630-719-2424, or mortonarb.org/plantadvice. Laurie Casey writes for The Morton Arboretum in Lisle.