Clematis (Clematis spp.) can be trailing shrubs or herbaceous perennials, but the most familiar clematis are the climbing vines that have large, bright flowers. Clematis grow in U.S. Department of Agriculture plant hardiness zones 3 through 11, but exact zones vary among species. While many clematis grow as perennials and return each year, you can collect the seeds if you want to increase the number of clematis vines in your garden or if you want to replace perennials with short life cycles. Collect the seeds from the seed heads that form just below the flowers.
Look for developing seed pods as the flowers fade at the end of the blooming period. The blooming time varies among the different species and also depends on your climate. Woodbine (Clematis virginiana), a vine for USDA zones 3 through 8, usually blooms from August to October. Sweet autumn clematis (Clematis terniflora) blooms from August to September and grows in USDA zones 5 through 9. "Jackmanii" clematis (Clematis "Jackmanii") grows in USDA zones 4 through 8 and blooms in July.
Leave the seed pods on the vine until the pods swell with seeds and begin to dry out and turn brown. The fine hairs on the seed pods change from flossy to feathery when the seeds dry. Waiting for the right time means the seeds are mature when harvested and dry enough to store without rotting.
Hold a cardboard box or bowl under the seed head to catch seeds. Tap or shake the seed head so some seeds fall out of the head. Gathering seeds from all the pods if most of the seeds are dark brown. Leave the pods on the plant to dry further if the test pod contains green seeds.
Cut the seed pods off the vine when they turn brown and dry, but before they split open and disperse the seeds in the wind. Use bypass pruners, scissors or a sharp knife to cut the pods off the vine.
Lay a piece of white paper on a flat work surface away from winds. Split the seed heads open in your hand and pull them apart along the seams on the heads. Allow the seeds to drop onto the white paper.
Shake the piece of paper over a box or bowl. Allow the seeds to fall into the container while using your finger to prevent chaff and plant pieces from falling into the container.
Put the seeds in an envelope, plastic container or jar with a lid. Label the container with the collection date and clematis species and cultivar name. Store the seeds in a cool, dry place.