Trees are easiest to identify by their leaves. Deciduous trees that have shed their leaves for the winter may be identified by the appearance and texture of the bark. The seeds produced by the tree, when used as a sole identifier, require greater expertise and possibly intensive research. Tree identification books should be available at your local library. Private company and government websites also provide identification tools to assist in the process.
Determine whether your seed is housed in a cone, has a winged enclosure, is surrounded by a fleshy fruit, is enclosed in a pod or resembles an acorn or nut. This is easiest if the seed pod is available, but you can also use a photo of the seed's enclosure.
Go to a seed identification website. You could also use a government-sponsored or extension service website that identifies trees that grow in your area. Match your seed or seed picture to its corresponding image on the site.
If you prefer, find a book on identifying trees at your local library. Use the book to narrow your search until your seed is identified.
Measure your cone with a measuring tape if your seed had a conical enclosure. Oblong cones 0.3 to 0.5 inches long are probably northern white cedar, while those measuring 0.5 to 0.8 inches in length could be hemlock. Rounded cones about 1 inch in diameter may be cypress, while the cone of the tamarack is rounded but is longer than it is wide and measures 0.5 to 1 inch in length. Use step 2 to confirm your identification.
Compare winged seeds to the photos or drawings of seeds of trees belonging to the maple family. Match seeds surrounded by fleshy fruit to pictures of various fruit trees and their corresponding seeds until you find a possible match. Use step 2 as required.
Compare seeds enclosed in a pod or resembling an acorn against pictures of seed pods and acorns from hardwood trees such as oak, chestnut, black walnut or butternut to find an exact match. Use step 2 as required.
An "Audubon Field Guide to Trees" is a good book to look for at your local library. Other books on the subject generally can be found in the same area of shelving.