It's always useful to know what a plant looks like in its first stages so that you can either pull it out before it gets established or leave it to flourish your garden. Though the typical clues to its identity---flowers and fruit---will be missing, you can often make a good guess at identification if you pay attention to the more subtle details of texture, shape and color.
One of the first things you'll notice about a small plant is the shape of its leaves. Although plants may have similar leaves and not be related at all, leaf shape is a good clue to the identity of your plant. Take the time to examine them closely, noticing whether they have protrusions at the bottom, whether they're oblong, sword-shaped, divided into finger-like protrusions or finely cut like fern fronds. If a leaf is divided into separate leaflets, it is said to be compound. Conifer needles are present as soon as a seed sprouts, though much smaller. Broad-leaf plants have seed leaves called cotyledons that are not similar to the mature leaves. Wait until a plant has four to eight leaves before attempting to name it.
Many plants have smooth margins to the leaves, but some are wavy, finely toothed or coarsely lobed. There may be hair along the edge or even spines, as in the holly shrub or the Oregon grape. Lobes may, in turn, be lobed themselves.
Leaf Textures and Colors
The surface of a leaf may feel waxy, such as those of camellias, or rough, perhaps even ridged. It may have hair on the top or the underside, sometimes as soft and dense as velvet, sometimes stiff. Rhododendrons, for instance, often have a felt-like covering on the back called "indumentum." The veins of the leaf may be almost invisible, or large and prominent, such as those of the dogwood.
Each of these characteristics is typical of a particular plant, but to the practiced eye, the exact shade of green is the best clue, even from a distance. Deciduous leaves change their shade as the seasons progress, but if you know the leaves of a tree, shrub or flower as an adult, you'll have a good chance of recognizing its seedlings.
Stems and Branches
Note how the leaves are attached to the stem, whether they are arranged alternately or oppositely, or even in whorls. Note also the shape of the buds at the base of each leaf and at the tip of a branch.
Some stem characteristics are typical of certain plants. Square stems indicate a plant in the mint family, and triangular stems mean you have a sedge. The stems may be hairy, as with the black-eyed Susan, or they can be smooth, ridged or speckled. Alder seedlings, for instance, have a speckled, warm brown bark. Close examination will give you many clues to the identity of your plant.
Don't overlook the location of your plant. Similar looking flowers may have different preferences for sun and shade. If you have a seedling in a moist, shady area, you can ignore other, similar plants that are usually found in dry, sunny spaces. For example, a seedling with narrow, upright leaves in full sun could be a bearded iris, but a similar plant in shade would be a Siberian iris or other species, but never a bearded iris.
For Further Assistance
For help in identifying seedlings, you can bring leaves and stems or a potted plant to a nearby nursery or to one of the clinics sponsored by your local cooperative extension service. Staffed by volunteers, these Master Gardener clinics are held all over the United States and in three Canadian provinces.