If your perennial plants are starting to look crowded, overgrown, are not flowering as well as they used to, or you would like to propagate a favorite perennial–it might be time to divide. Many perennial plants benefit from being divided every two to five years. Most perennials can be divided any time of the year. However, you will have the best success in spring or fall for summer-flowering plants, or in late summer for spring-flowering plants. Basically divide the plant after it has flowered. Try to avoid dividing during the hottest part of the summer, and also no less than 6 weeks before the first frost, so that your divisions are not stressed by extreme temperatures while they re-establish their roots. You can water them in with a little dilute mixture of Kelp or Thrive Alive to help offset the stress. How you dig them will depend on how they multiply–either clumping crowns, rhizomes, tubers or tuberous roots, corms, offsets, bulbils or bulbets. Watch our video on dividing perennials or our article on Dividing Perennials to Keep Them Healthy.