When to cut back ornamental grasses

First, are your ornamental grasses cool-season or warm-season?

The best time to cut back ornamental grasses depends on the type of grass you have but in general cut back warm=season grasses in Fall or by mid to late Spring, and cut back cool-season grasses in very early Spring.

Leaving some grasses through the winter provides visual interest and ecological benefits for birds and insects. 

However, there are some specific circumstances when a Fall cut is preferable in our specific area:

• We live in an area prone to wildfires.
• Our grasses tend to flop over and look messy due to heavy snow.
• If your grass has a foliar disease that you want to remove.
• You simply prefer a tidy winter landscape

Warm-season grasses to cut back in Fall
These grasses turn brown in the colder weather and can be cut down to 4-6 inches tall anytime from late Fall to mid-Spring. Examples include: 

• Feather reed grass (e.g., 'Karl Foerster')
  
• Switchgrass
• Big bluestem
• Little bluestem
• Maiden grass and Zebra grass (types of Miscanthus)
• Fountain grass 
  
• Blonde Ambition
• Shenandoah (type of switchgrass)
• 
  

Cool-season grasses to NOT cut in Fall 
These grasses often remain attractive through the winter and should not be cut back hard in the Fall. Wait until late Winter or very early Spring (February or March) and only remove about two-thirds of the height. Examples include: 

• Blue fescue
  
• Mexican feather grass
• Sedges
  
• Tufted Hairgrass
• Blue Oat Grass
• Feather Reed Grass
  

CSU Extension provides an excellent chart of grasses, classified by cool or warm.

The dried foliage of ornamental grasses helps insulate the plants' roots, provides winter interest, and offers habitat for overwintering pollinators.