We just moved to a home in SW PA Z6a/5b that has a large, overgrown Weigela in the yard. (At least I am relatively certain from the Plant Files that it is Weigela.) It has bloomed beautifully, but it is definitely scraggly looking. The bottom three feet of the shrub is just old wood and is unattractive. Is this the kind of shrub that can be cut back to nothing and allowed to regrow or one that should be more carefully pruned? Any advice is appreciated!
Sort of inbetween. It won't grow back like a willow or honeysuckle if you whack it way down, but you can encourage it a little to produce new growth. I would prune out 25% of the old canes and then once you get some new suckers in following years do the same.
Best time to prune any flowering shrub is after the flowering. If you care more about size control than the flower show, then go nuts. Best plan of action is to remove any dead growth right down to the furthest point. If you want to cut it back severely , you can, as long as there are leaves left below your cut. If there are no leaves below your cuts, it will probably croak. You must have some buds left on the branches. It may not look too good when you are done, but it will put out new growth to hide your cuts.
Some shrubs don't respond well to severe pruning, I'd stick with what bigcityal recommended.
