Keep mulch about four or five inches away from the trunk. You want to see the root flare — the spot where the base broadens, just above the soil line. A maximum of three or four inches depth, using a medium-textured mulch, is recommended.
A living mulch layer — rather than rings of lifeless, bagged stuff — adds diversity to a garden, but digging beneath an established tree is tricky and potentially damaging, Ms. Janoski said. When you’re attempting to add ground cover, stick to small herbaceous plants (like landscape plugs or very small divisions) and use a trowel or soil knife, not a shovel. Planting shrubs beneath established trees is not recommended.
Trees Need Watering, Too
We water the tomatoes, and the pots on the patio, but when was the last time we watered our trees?
The northern Midwest had a 12-week drought this spring, and the clinic staff worked to spread an urgent message: “We remind people constantly that when it’s hot and dry for 10 days or so, even mature trees need water,” Ms. Janoski said. “Your lawn will come back, but trees may have long-term damage.”
She can’t give customers a precise prescription for how long to water, because water pressure varies, but except with small trees (or abundant patience), this is not a job for a hand-held wand. Instead, she suggested, set out sprinklers in the root zone, and use rain gauges or makeshift tools — repurposed tuna or coffee cans will do, as will any flat-bottomed pan — to measure rainfall. Your goal should be to provide the tree with at least one inch of water a week, unless nature does it for you.
More plant questions? Ms. Janoski and the Plant Clinic staff welcome them at plantclinic@mortonarb.org or 630-719-2424.
Margaret Roach is the creator of the website and podcast A Way to Garden, and a book of the same name.
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