[header] How to prune weigela [title] Saw 2-3 secondary stems to the ground on mature plants. [step] Cutting secondary stems will give you a fuller weigela plant. Locate 2-3 branches that are growing next to the main stem and use a hand-held pruning saw to cut the stems upward at a 45-degree angle. 
Saw the stems as close to the ground as you can. [substeps] This will divert the plant's energy to the main stem and new growth, which will promote stronger blooms.