Tips for finding healthy plants at the garden center

When you’re shopping in the garden center, how do you know you’re getting a healthy plant?

“Don’t just judge by the green part you can see,” said Stephanie Adams, a pathologist in plant health care at The Morton Arboretum in Lisle. “Look at the roots, which are just as important.”

Here are some tips from Adams for choosing good plants:

Read the label. “The first step is to make sure you’re buying the right kind of plant for the place where you’re going to put it,” she said. Consider the amount of sunlight the plant requires, and be sure it is hardy in USDA winter hardiness zone 5, which applies to most of the Chicago area. If the plant is a tree or shrub, find out how tall and wide it will ultimately grow so you know if it will fit in the space you have available. Make sure the plant is a good match for the soil conditions in your garden.

Judge the color. Most plants should be a uniform medium green. If a plant’s leaves are not uniformly green, make sure the white splotches or the purple tinge is the appropriate color for that cultivated variety and doesn’t represent a problem. Some cultivated varieties are bred to have differently colored leaves. For example, a plant with yellowish leaves might have been bred that way, or it might be a naturally green plant that is losing chlorophyll because of a disease. The label should make it clear what the plant is intended to look like.

Look for symmetry. Among perennials and shrubs, choose plants with evenly distributed leaves and stems all the way around.

Check for healthy roots. “Ask permission to gently pull the plant from its pot and examine the roots,” Adams said. “It’s common sense, like looking under the hood before you buy a car.” In annuals, vegetables and most perennials, roots should be white. Roots of trees and shrubs may be yellowish or brown. You should be able to see plenty of roots distributed throughout the soil. The roots and soil should be moist.

Avoid plants with diseased roots. “If you buy a plant with bad roots, you’re set up for failure,” Adams said. A sickly plant will disappoint you, and it also may introduce disease-causing fungus spores or bacteria to your garden soil, where they may infect other plants. “Diseased roots are usually brown, sometimes even black,” she said. “They might look squishy or flat, like a shoelace, because they’ve collapsed.” Avoid dried-out roots too.

Spot-check flats. “When I’m buying a flat of plants, I usually pull up one or two plants from the middle to check the roots,” Adams said. “If any plants in the flat look poor — either the leaves or the roots — I won’t buy it. A disease could be spreading through the whole flat.”

Too many roots? No problem. On a plant that you will transplant, it’s not a problem if it looks pot-bound, with roots that completely fill the pot, or if it has circling roots. “You can correct that at planting,” she said. For pot-bound plants, make cuts around the outside of the root ball and fluff out the fine roots to encourage them to grow out into the soil. For circling roots, cut them or pull them apart to direct their growth outward into the soil. “The main roots should grow out like the spokes of a wheel.”

Avoid pot-bound houseplants and container plants. It is important to avoid buying a that is pot-bound if you will be keeping it in the same container. Or, transplant it to a larger pot so its roots won’t be overcrowded all summer.

Get a guarantee. For major purchases, such as trees and large shrubs, make sure the garden center gives you a written guarantee, and be prepared to do your part. “The guarantee will only protect you if you have correctly planted and cared for the plant,” Adams said. “It won’t cover a plant that dies because you forgot to water it.”

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.