Managing Perennials
Managing perennials in today’s mixed landscape designs can be challenging for homeowners and landscape professionals. With layered plantings and diverse materials, the goal is to maintain the garden without losing the intent of the original design.
The best starting point is communication with the designer. Strong designs are often orchestrated with near-choreographic precision—balancing structure, texture, and seasonal color so the garden has interest throughout all four seasons.
Most perennials benefit from being cut back after bloom to remove spent flowers and tidy the plant—but how much and when depends on the plant’s growth habit and the effect you want.
A simple way to think about perennials
Perennials generally live longer than annuals, but they’re not as woody or permanent as shrubs. For maintenance, it helps to group perennials by how they grow. Below are three broad (and admittedly imperfect) categories that make seasonal clean-up decisions easier.
Crown types
Examples: Phygelius, Echinacea, Verbascum, and rosette-form salvias (like Mexican bush sage).
Late summer is often the best time to clean up crown-type perennials. Cutting them back in August–September promotes stronger stems and healthy basal foliage through winter.
Some plants (like Verbascum and Echinacea) benefit from winter chill on developing growth points, which can support good bud development for the next season.
Herbaceous types
Examples: Campanula, Coreopsis, Ajuga, Stachys (lamb’s ears), and similar soft-stem perennials.
Herbaceous perennials—deciduous or evergreen—are usually best tidied for winter in early fall. Their stems are generally soft and may be creeping (lamb’s ears), tufting (agapanthus), or bushy (coreopsis).
Early fall clean-up removes spent leaves, pests, diseases, and built-up residue. It also gives plants time to refresh and look presentable going into winter (especially evergreen types that continue to grow).
Root types
Examples: Hemerocallis (daylilies), dahlias, alstroemerias, and oenothera.
Take extra care cleaning old foliage and flower stems from root-type perennials. Their fragile growing points near the soil surface can be damaged easily.
Many root types also have specialized care needs. For example, bearded iris should be cleaned and divided (if needed) in late summer to fall.
For deciduous types (like dahlias and some daylilies), allow foliage time to “ripen” and store energy for next year’s bloom. Avoid hard cutbacks until early December.
Putting it all together
There may be no iron-clad rules for every perennial, but every strong maintenance plan starts with understanding each plant—how it grows and what role it plays in the garden as a whole.
Communication with the designer, the guidelines above, and your own observations are a reliable formula for building an optimal, season-by-season perennial maintenance plan.