9 ways to kill a plant…or not

Updated May 6, 2019
Roots girdling a red maple. Photo: Randy Cyr, Greentree, Bugwood.org.Roots girdling a red maple.
Photo: Randy Cyr, Greentree, Bugwood.org.

When a plant dies, the landscape looks bad. And so do you.

Maybe Mother Nature is to blame, or any one of a host of factors beyond your control. But dead plants are evidence of wasted time and money and affect your reputation. “Your clients are counting on you,” says Stacey Hirvela, horticulturist with Spring Meadow Nursery. “When a plant dies, no matter what the reason, you appear less professional.”

The school of hard knocks teaches that you’re going to lose a plant occasionally, no matter how much TLC you give it. But learn from experience and avoid these common missteps to give every plant a fighting chance:

Mistake No. 1: Choosing the wrong plant

Plants have needs. Ignore what they want and they’re doomed. “Look at a site’s exposure, soil texture and moisture levels,” says Fred Kapp, education director for the Green Industry Web Portal, a green industry educational site, and program manager for the Alabama Urban Forestry Association. “Then select a plant that fits those criteria. Plants have been adapting to certain conditions for millions of years. You can’t ignore genetics.”

Ditto for plant hardiness. “If a client says they want a plant but you know it’s not going to thrive in that zone, suggest an alternative,” says Kapp. Stick with natives or look for hybrids that are cold and heat tolerant and more resistant to disease and pests. And consider a plant’s mature size. Plants that are sized incorrectly require more maintenance, such as pruning, or eventual removal.

A topmost root planted incorrectly well below grade. Photo: Courtesy of Fred Kapp.A topmost root planted incorrectly well below grade.
Photo: Courtesy of Fred Kapp.

Mistake No. 2: Planting too deep or in a hole too small

For shrubs, it’s generally fine to plant at the level of the container soil. But many container and balled and burlapped (B&B) trees have excess soil piled on top of the root ball. Remove the soil to expose the flare, the area where the trunk widens at the tree’s base. “The flare should be visible after you plant the tree, (either) at or slightly above grade,” says Kapp. “If the tree looks like a telephone pole, straight up and down, you’ve planted too deep.”

Make the hole the right size; dig two to three times wider than the root ball and only as deep as the root ball (you want the plant to sit on solid ground, not on loose soil that may settle). Look for circling (girdling) roots, which are common in container plants, and loosen and spread out as many as possible. Learn more techniques for handling roots here.

Mistake No. 3: Failing to cut away the burlap or planting cage

An incorrectly planted tree with straps, basket and burlap in place. Photo: Courtesy of Fred Kapp.An incorrectly planted tree with straps, basket and burlap in place.
Photo: Courtesy of Fred Kapp.

It’s a misconception that burlap can stay in place because it decomposes. “That doesn’t happen quickly,” says Hirvela. “In the meantime, extra water is needed to saturate the material and get to the root ball.” Don’t just push the burlap down; cut away as much as possible once the plant is in the hole. Remove natural or synthetic twine so it doesn’t strangle the tree.

Cages should be cut off as much as is practical. Set the plant in the hole, snip around the cage on opposite sides at 12 and 6 o’clock and at 3 and 9 o’clock, then gently wriggle the pieces out. Even peat pots should be removed. “Your goal is to encourage fast and healthy root growth. Remove anything that gives the plant an obstacle to growing roots,” says Hirvela.

Mistake No. 4: Building a ‘mulch volcano’

Everybody’s seen it: mulch piled up around the base of a plant to resemble a volcano. “A tree’s roots develop up high under the mulch and these roots eventually girdle and choke the tree,” says Nancy Buley, communications director with J. Frank Schmidt and Son Company. “Piling mulch against the tree also keeps the stem moist and provides entry for disease and pests.” Mulch correctly: Add a maximum of 2-4 inches and keep it away from the plant’s stems.

Mistake No. 5: Not watering adequately 

Many B&B plants leave 75 percent or more of their roots in the nursery, so don’t let them dry out as they establish themselves. According to the Morton Arboretum, new trees and shrubs need about an inch of water through summer and fall or 2 inches in sandy soils. Small amounts of water two to three times per week are recommended over infrequent flooding, says Kapp. Your nursery, grower or extension service can provide advice on a watering plan.

Topping damage on a mimosa. Photo: Randy Cyr, Greentree, Bugwood.org.Topping damage on a mimosa.
Photo: Randy Cyr, Greentree, Bugwood.org.

Mistake No. 6: Topping trees

Say it aloud: Topping trees is never OK. According to the International Society of Arboriculture, cutting off the top branches removes the leafy crown. Leaves make the food, so removing them forces multiple shoots to form below each cut. The new growth is weak and prone to breakage. A stressed tree also is more vulnerable to disease, insects and decay. If a tree needs to be reduced in size, consult an arborist.

Mistake No. 7: Incorrect use of soil amendments

You may think you’re giving plants a head start by adding peat moss or bagged soil to the hole, but it’s not recommended. “A plant is better off acclimating to the soil it will grow in for the rest of its life,” says Hirvela. Furthermore, if you don’t mix in the amendment, you create a “bathtub effect” in which water enters the new material quickly but backs up and rots roots due to the different infiltration rate of the surrounding soil.

If amending, prepare a planting bed, not individual holes. Add compost, and till it into the entire area, mixing the backfill in thoroughly. Avoid using peat moss alone; if exposed, it can dry out and form a crust, causing water to roll off instead of reaching the root ball, says Hirvela.

Mistake No. 8: Having no clue what’s in your soil

Some plants like alkaline soils; some like acidic. Choose the wrong plant for the site and it struggles. “Get a lab soil test for an accurate analysis,” says Vanessa Gardner Nagel, owner of Seasons Garden Design in Portland, Oregon and Vancouver. “Know what micronutrients are missing before you add anything.”

Mistake No. 9: Not staying current

Haven’t heard about the boxwood blight but you just installed 50? Don’t know about rose rosette virus and yours are fading? Haven’t paid attention to impatiens downy mildew? Not educating yourself about new issues costs time, money, your reputation and the plants. Stay informed by reading TLC’s plant articles, attending extension classes and talking to nurseries.

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