Perennials bought at retail outlets, such as garden centers and hardware stores, as well as many plants purchased through mail-order companies, are usually packed in pots or cell packs. (Some mail-order plants are shipped bare-root.)
Potted perennials are described and priced by their pot diameter. Smaller containers (cell packs) are usually made of plastic and joined together in groups of four or six with each cell containing an individual plant. Sometimes cell packs consist of biodegradable material. That means you can set the plant undisturbed directly into the soil.
Perennials are also sold in undivided flats that are the size of six-cell packs. They generally contain many seedlings, which must be pulled apart before they can be planted; roots are often broken in the process. Unless you have no other choice, avoid buying perennials that are packaged in this manner.
Obviously, when you buy nursery plants through the mail you incur shipping costs. These costs are lower if the plant and the container are small; this is one of the reasons why most mail-order nursery plants are sold in cell packs rather than pots.
Continued on page 2: How to Plant