"Whether the bedding plant you are considering is a six-pack of petunias or a five-gallon Fountain Grass, don't forget the roots," she said. "The roots take up water, nutrients and keep the plant anchored. Without a vigorous root system the plant will not establish quickly and it will be less prepared to deal with the change in environment that goes along with transplanting."
Bates noted that healthy roots appear pale or white at the tips. This indicates the roots are actively growing. The roots should be reaching out the drainage holes in the bottom of the pot or package, or at least peeking out.
"Be sure you are paying for a plant--not for soil," she said. "If the bottom one-third or more of the pot has few or no roots in it, the product may be overpriced. If you pay the price for a gallon of plant, you should be getting close to a gallon of good, healthy roots."
Plants whose roots have become tightly packed in the pot can perform poorly unless an extra step is taken at planting.
"It is important to loosen, sometimes even cut the roots during planting so they will spread out in the soil," said Bates. "Think of it as root pruning to create more branching and fibrous roots.
"Loosen roots with your fingers or a three-prong hand cultivation tool. An old kitchen fork works well, too. Spread the roots out as you plant and untangle any that may have started to grow in a circle due to the pot. If cutting the roots is required to get them apart, butterfly the roots with a knife or sharp trowel."
When examining bedding plants for purchase, the buyer should look above ground as well.
"Look for new growth, normal-sized leaves, and proper stem structure and shape," Bates said. "Leaves and buds should be free of blemishes and deformation. This is even more important regarding the stem. The stem supports and holds the vascular system that moves nutrients and water throughout the plant. If the stem is damaged, it could mean trouble for this growing season, and possibly even next year if a disease caused the damage."
With herbaceous perennials, the only part of the plant that will come back next year is the roots.
"With this in mind, lanky, overgrown perennials can be a bargain for the future if the root system is in good shape," she said.
Bates encouraged consumers to also check the undersides of leaves and growing points for insects. Even the most reputable nurseries can get an infestation of highly mobile insects if plants are kept outdoors. Try to avoid bringing such pests home with you.
"For recommendations on plants best suited to Illinois, check out U of I Extension's Urban Extension Program Resources site at: http://www.urbanext.uiuc.edu ," she said.