About the second week in March, there was some alarm over mild winter weather followed by a prediction of several hard freezes. Indeed, the National Phenology Network showed that our spring was about 20 days ahead of schedule, and the National Weather Service was predicting lows in the 20s and teens.
Daffodils and saucer magnolias were blooming, which the experienced and the cynical take as a frost warning in any year! Early flowers are always at risk for spring frost damage, so that goes with the territory. Frost on tender plant parts may limit flowering or fruiting, but is rarely a threat to the whole plant.
While we don’t have much control over spring frosts, there are risks to trees and other landscape plants over which we do have control. Are you ready? Many have become common, but deadly just the same.
Planting too deeply
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Trees that are machine-dug in the nursery often come with soil piled over the lower trunk, called the root flare, which must be exposed when the tree is set. If the root flare is buried, it begins to rot – interrupting the tree’s vascular system. This is enough to kill the tree, but there’s more!
The feeder roots that eventually encircle the trunk below grade will strangle it. Once a tree has been in the ground like this for a few years, there aren’t any options for saving it, so plant well.
Volcano mulching
Over-mulching is the dreadful cousin of planting-too-deeply, causing many of the same deadly issues. While a well-constructed mulch ring around a young tree offers many benefits, too much mulch kills.
Consider a depth of 2-3 inches to be quite enough at the outer edges, tapering to no mulch at the root flare – which is above ground, right? Otherwise, you get the rotting trunk and feeder roots that strangle once they grow into the mulch.
Tree-topping
With the advent of standards in tree care, topping has become less common, but it’s a threat to human safety and tree health just the same.
Topping is the practice of removing large limbs and leaving stubs, which eventually resprout. However, it leads to widespread decay and poor attachment of the new limbs.
Trees at close quarters offer both risks and benefits, and topping increases risk. Better to follow the best practices described in the American National Standards for Tree Care Operations, which a certified arborist will know well.
Too much fertilizer
As humans, we often want to act when something in our care — trees, in this case — are ailing. Fertilizer often comes to mind, but it can make things worse.
We know that a stiff dose of nitrogen can actually invite the pests and fungal diseases, which is the last thing a sick tree needs. While a healthy tree needs little or no fertilizer. Any fertilizer going on trees should be slow-release and low in nitrogen, applied according to the label.
If those spring frosts cause you worry, you may want to avoid the early bloomers: star and saucer magnolias, early cherries and spring bulbs. Avoid the flowering pears too, as they have become invasive. And do make sure that you aren’t allowing any of these tree-killing practices on your watch.
Kris Medic is Bartholomew County’s Purdue Extension educator for agriculture, natural resources and community development. She also is a boardcertified master arborist. She can be reached at [email protected] and 812-379-1665.
