With their clusters of smooth foliage, hostas can provide a calming effect in a garden that may be otherwise overcrowded with contrasting plants. Hostas also make great garden plants because of their ability to flourish in nearly all soil types besides pure chalk or bogs, and they are largely disease resistant. Identifying a hosta plant is possible by observing certain characteristics such as leaf size, shape, texture, color and the type of flowers when the plant is in bloom.
Find a book solely on hostas that not only provides written descriptions of different variations, but also many pictures and a section on the botany of hostas. "The Gardener's Guide to Growing Hostas" by Diana Grenfell is an excellent example; it even has diagrams of leaf stalk cross sections of hostas.
Take a picture of the plant you suspect to be a hosta for later reference, or a pad of paper if you prefer to sketch.
Note the overall shape of the plant. Hostas are hardy clump-forming perennials that grow from short rhizomes. According to Grenfell, most hostas develop into dome-shaped mounds, but some grow into flattish mounds.
Observe the leaves of the plant. Hostas have large, mostly basal, stalked, simple leaves. There are four different types of leaf bases found in hostas: truncate (as if cut straight across the base); wedge-shaped; attenuate (with curving and converging sides); and heart-shaped (similar to lily pads). If the leaf of the plant you are looking at doesn't have one of these shapes, you can deduce it is not a hosta.
Check for any flowers that may be blooming on the plant. Hostas have large, tubular, funnel or bell-shaped flowers, usually with six spreading lobes, white to dark purple. The stamens are bent, resting on the tube.
Run your fingers around the edges of the leaves to check the margins. All hostas have entire margins, meaning they are never toothed, cut, serrated or lobed but are smooth. Some may appear slightly crimped from the veins in the leaves. Hostas have typical vein patterns that follow the shape of the leaf and are more prominent on the underside of the leaves.
Look at the surface of the leaves. Hostas have smooth or puckered leaves and are never haired. Their surfaces may be matt, shiny or waxy but are usually satiny. Leaf color is usually green, but some hostas may have lighter green, white or yellow stripes or rims.