As soon as March rolls around, it’s natural to start eyeing shrubs and grasses and wondering if it’s time to cut everything back. The real answer depends on how each plant grows—and especially when it forms its flower buds. Knowing whether something blooms on new growth or old growth is the key to pruning at the right moment.
Shrubs that bloom on new wood set their buds during the growing season. Since they haven’t formed those buds yet, early spring is the perfect time to prune. Rose of Sharon, butterfly bush, crape myrtle, dogwood shrubs, summer‑blooming hydrangeas, and summer‑blooming spirea all fall into this group. Cutting them back now encourages strong new growth without sacrificing blooms.
Shrubs that bloom on old wood formed their buds last summer. Pruning too early removes the flowers you’ve been waiting for. Forsythia, lilac, azalea, spring‑blooming hydrangeas, and spring‑blooming spirea should only be pruned after they finish blooming—usually four to six weeks later—so they have time to set next year’s buds.
Some shrubs don’t bloom much at all, and those can be treated like new‑wood bloomers and pruned in early spring.
Ornamental grasses have their own timing.
Warm‑season grasses (switchgrass, little bluestem, big bluestem, miscanthus, fountain grass) stay dormant through winter and should be cut back now, before new shoots appear.
Cool‑season grasses wake up early and often stay partly green, so they only need a light trim to remove winter damage.
So, should you prune now?
If your plant blooms on new wood, doesn’t bloom, or is a warm‑season grass, early spring is the right time. If it blooms on old wood or is a cool‑season grass, it’s better to wait. A little timing goes a long way toward healthier plants and better blooms each spring.
Check out this link for more information:
A Guide to Successful Shrub Pruning
https://www.johnson.k-state.edu/programs/lawn-garden/agent-articles-fact-sheets-and-more/agent-articles/trees-shrubs/Guide%20to%20Successful%20Shrub%20Pruning.pdf