When a plant catches your eye in a garden center or nursery, what’s the first thing you should do?

“Read the label,” said Julie Janoski, Plant Clinic manager at The Morton Arboretum in Lisle. “It contains critical information that can tell you whether the plant is likely to work for you.”

The label should tell you the plant’s name, including both a common name and the botanical name, which is more precise and reliable. “Make sure the botanical name is there,” she said. “It’s the key to finding more information about the plant.”

The plant’s light needs should also be stated on the label, often in symbols. They can tell you that the plant needs full sun, meaning six to eight hours of direct sunlight a day; full shade, meaning it can handle a site with two to four hours of sun a day; or part sun or part shade, which are somewhere in between.

You should also find information about how much winter cold the plant can handle. This is usually expressed in terms of the zones on the USDA plant hardiness map. Find the map at planthardiness.ars.usda.gov.

The Chicago region is generally in Zone 5, with a few spots near the lake in Zone 6. You’ll be safe buying plants that are hardy in Zone 5 or the colder Zones 4 and 3. Often the label will show a range, such as Zones 5-9 or Zones 4-7. “As long as the range includes Zone 5, you should be fine,” Janoski said.

Another important fact you can learn from the label is the plant’s mature size. The plant you buy in a garden center will probably be young, with a lot of growing to do. The label should tell you how tall and wide the plant will eventually grow to be.

This is especially critical information if you are shopping for trees or shrubs. “It’s very common for homeowners to buy a tree or shrub without realizing how large it will get to be,” Janoski said. “Just five or 10 years later, that plant can outgrow its site.”

Some labels only give a height. For evergreens, it’s usually the height that the plant is likely to reach in 10 years. “It’s easy to forget that evergreen trees and shrubs will get wider as they grow taller,” she said. “You can plant a row of small arborvitaes, expecting they will grow tall to provide a privacy screen. But they will grow wide, too, and may take up a lot of space in your yard or block the sidewalk.”

There’s a lot that plant labels don’t tell you. “Many labels don’t say much about the soil a plant needs,” she said. “If you have typical Chicago-area soil, which is often dense clay with an alkaline pH, it’s important to buy plants that are suited to those conditions.”

Fortunately, you have a handy tool to learn more before you buy the plant: your phone. A quick search for the plant’s botanical name is likely to bring you a wealth of information beyond the label.

Even if the label is cryptic or sketchy, make sure the plant you choose has one, so you know what you’re buying.

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