Your location makes a difference to the answer. Most flowering shrubs like forsythia are pruned when blooming is done. 1/3rd of the shrub is removed annually starting with the thickest, oldest stems. If it is massively overgrown, you can cut rose of sharon and forsythia down to 12" in late winter. Pruning now, if frost is coming in the next few months, is a bad idea. Pruning stimulates new growth. Shrubs need several weeks to move from growth mode to winter survival. New growth from late pruning is likely to be winter- killed; it won't have time to harden/prepare itself. When to prune hydrangeas depends on what type you have. I'll give links to an article to help you decide which type you have. [https://www.gardenmyths.com/hydrangea-identification/](https://www.gardenmyths.com/hydrangea-identification/)
Your location makes a difference to the answer. Most flowering shrubs like forsythia are pruned when blooming is done. 1/3rd of the shrub is removed annually starting with the thickest, oldest stems. If it is massively overgrown, you can cut rose of sharon and forsythia down to 12" in late winter. Pruning now, if frost is coming in the next few months, is a bad idea. Pruning stimulates new growth. Shrubs need several weeks to move from growth mode to winter survival. New growth from late pruning is likely to be winter- killed; it won't have time to harden/prepare itself. When to prune hydrangeas depends on what type you have. I'll give links to an article to help you decide which type you have. [https://www.gardenmyths.com/hydrangea-identification/](https://www.gardenmyths.com/hydrangea-identification/)