Clematis are hard to know when to prune because it depends on when the plant blooms. By watching you clematis you should be able to determine what type it is by watching for the flowering cycle. The earliest flowering clematis bloom on old wood, while later flowering types bloom on old and new growth or just new growth. A partical list of clematis types are listed at the bottom.

Plants in this group bloom in early spring, usually in May, from buds produced the previous season. Prune these plants immediately after flowering, but no later than the end of July. This allows time for new growth to produce flower buds before winter sets in. When trimming you may remove the shoots that have flowered and trim back the vines but do not cut the woody stems.

Large-flowered hybrids bloom in mid-June on short stems from the previous season's growth and often repeating in late summer on new growth. The second flowering usually produces smaller flowers, this is common. A lot of plants that flower twice in a season have smaller or less flowers the second time. There is nothing wrong with these plants. Prune B type in February or March by removing dead and weak stems, then cut back the remaining stems to the topmost pair of large, plump green buds. This cut should be 6 to 18 inches from the stem tip. Plants in this group have the tendency to become leafless at the base as they mature, this also is normal. You may be able to force a flush of new growth from the base by cutting the vine back to 18 inches immediately after the first flowering in June. Planting something around the base of the plant will cover the bare spots.

Plants in this group flower on the last 24-36 inches of the current season's growth. Some begin blooming in mid-June and continue into the fall. This is the easiest group since they flower only on new growth. In February or March cut to a height of about 24-36 inches. Don’t worry that you are cutting off healthy looking vines. As the vine matures you can leave the base longer.

C. alpina, C. macropetala, C. armandii, C. montana and C. chrysocoma.