Weigela (Weigela florida) confuses well-meaning gardeners who want to keep their plant neatly trimmed: there's a lot of poor horticultural advice out there concerning its care, notes Ron Smith. The shrub benefits from regular pruning, but should not be cut back entirely since it flowers on both new and old wood. Prune weigela after it blooms, then check again after winter if you experience frost conditions. The delicate branches on your shrub are prone to ice and snow damage.
Wait until your weigela finishes flowering to trim it. The time frame varies by cultivar; WSU Whatcom County Extension notes that some varieties flower once, others flower twice and others bloom continuously from summer to early fall.
Clip off broken or damaged branches on your weigela using anvil pruners. Low growing branches may get snapped by critters so check by the base of the shrub. Damaged branches can contract disease if they aren't removed.
Prune old branches back to the ground, removing the entire branch with anvil pruners. Old branches bear fewer flowers and foliage, so you can identify them by their foliage after the blooms pass. Remove up to 1/3 of the old branches in a season.
Leave your weigela plant alone through the fall and winter. When frost danger passes for your area and your plant begins growing again, check on your weigela. Identify winter-damaged branches that aren't growing. Clip these off with anvil pruners. If left on the plant they will be unattractive and may rot.