What happens if I do NOT prune certain plants?

Those plants whose whole infloresences do not develop into seed pods, such as Hydrangeas, for example. Would the flower heads simply fade and decompose/ What if one were to leave a Buddleja davidii un-pruned/ Presumably the plant would grow straggly and diseased, but would the new buds grow exactly where the old ones were, or would the lack of pruning limit the production of new vegetative or flowering buds?

 

Pruning dead flowers encourages further flowering,after flowering a plant produces seeds if you cut the flower off the plant has not completed its life cycle and will try to flower again, the case of hydrangeas some leave the flowers on over winter as they can look quite attractive they are trimmed off in spring to allow new growth if left on new growth would still occur but the old flower would drop off by trimming them off you stop the possibility of "die back".A buddleia left un-pruned will grow straggly the flowers would be much smaller the plant would not necessarily be diseased pruning makes for stronger growth and bigger flowers,new flowers would not grow exactly were the old flowers were the old flowers would die away new shoots would form.

 

Very good advice Walnut.:thumb:Hel.xxx.

 

thank you.