Nursery plants come in a variety of container sizes. Bedding plants and vegetables are usually sold in flats or small cell packs. Larger plants are sold in containers that range from 4-inch pots to large boxed trees.
What Size Container?
Just as with most products you purchase, larger plants cost more than smaller ones. However, the difference in cost between smaller and larger plants is often dramatically greater than for other products. Part of what you are paying for is the nursery’s labor to grow the plant to the size you are buying, and hundreds of hours of labor may have gone into a large boxed tree.
Because all plants will grow to their largest possible size in your garden, why buy larger plants at all? Almost the only reason is to get quicker results. A 10-gallon tree looks like a tree when you plant it in your yard, but the same species in a 1-gallon can might look like a twig. However, in 3 years or 5 years, they will look very much alike. Younger trees, because they are more adaptable than trees that have been in cans for several years, often establish and grow faster, catching up with the larger trees in a few years.
Like trees, shrubs and perennials will catch up to larger sizes in a short time. Very young perennials may not bloom the first year they are planted, but they will the second year, and in their third year will probably reach full size. Shrubs might also take a year or so to establish, but then will grow rapidly to the size you want.
Annuals establish most quickly when planted young. It’s better to select annual vegetables and flowers that have not yet begun to bloom. They will be more satisfactory in a couple of months than if you had planted larger blooming plants.
Is the Plant the Right Size for the Container?
Nurseries propagate plants from seed or as rooted cuttings, often in “liners”—flats or trays full of small pots. Once they have grown to full liner size, they are transplanted into larger pots. They may be offered for sale at this size or grown on, then planted into a yet larger container.
No matter what size container you select, look for plants that have filled the container with roots, but are not root-bound. If you are not sure if the plant is the right size and age for the container, knock it out of the container and examine the roots. Many white root tips should be visible on the outside of the rootball, and the rootball should feel firm in your hand. If few roots are visible and the rootball feels loose, the plant has not been in the container long enough. The rootball may break apart when you try to plant it.
If the outside of the rootball is a hard mass of brown, woody roots, with few white tips visible, the plant may be potbound. It has been in the container too long, and will be slow to grow again when it is planted out. Potbound plants are stunted (bonsai trees are created by purposeful pot-binding). It is often difficult to get them to grow vigorously after being potbound for some time.
Bare-root plants are purchased by garden centers in the late winter or early spring. They are usually stored in beds of damp sawdust until they are sold. However, if they do not sell before warm weather starts them growing, they are potted up, often into 5-gallon cans, and sold as container trees. If you are purchasing a container tree in the spring, either knock it out of the container to check its rootball, or tug lightly at the trunk to be sure is it firmly rooted (it shouldn’t move in the soil). If a bare-root tree has not had sufficient time to establish in its container, the rootball may fall apart when you try to plant it, damaging the tree.