Pruning Group 1 (PG1): Those which flower on old, ripened wood. Pruning Type 2 Clematis Flowers Type 2 clematis are generally larger flowered, spring to early summer blooming varieties that flower from new growth on the stems from the prior years growth. However, if they've outgrown their space, cut back and tidy up after the main flowering period has ended. Clematis Pruning Group 1. For pruning purposes, clematis are placed into three different groups based on their time of bloom. Clematis Pruning Groups. Spring flowering species and their cultivars need little or no pruning. A Quick Guide to Pruning Clematis Groups of Clematis The key to pruning Group 1 is that they don't require any pruning, but if you're going to do it, do it right after bloom. Clematis (pronounced CLEM-ah-tis) can be divided into three groups for pruning purposes. Early-flowering types bloom by early July on stems produced in the previous year, and two types of late-flowering types bloom in mid-summer on current season’s stems. The Ramblers and Early Bloomers. Most will bloom from new stems and older stems, so retaining some of the stems from prior years helps the plant produce the largest and most flowers possible. Group 1 are the Clematis that bloom mostly on old wood (meaning the previous season's growth) and begin their flowering season in mid- to late spring..