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How to care for your ornamental grasses

  • James Campbell
  • When I was a kid, grass meant a lawn, and grass-care meant dragging the lawn mower out every other week. In today’s gardens, ornamental grasses are becoming increasingly popular for their deer resistance and water-wise qualities, as well as for creating movement with a strong visual impact. Ornamental grasses require far less care than a lawn, and no mower is required. The two main ways to care for ornamental grasses are periodic combing and, depending on the variety, an annual prune.

    Ornamental grasses can be broken down into cool season or warm season plants depending on if they bloom in the summer or fall. You can also differentiate a cool season grass from a warm season grass by the time of year it does most of its growing. If you’re like me, you probably aren’t paying close enough attention or might not be certain of the grass variety. I use this simple shortcut to figure out my grass care: Does the grass go brown and dormant or does it stay evergreen. Yup, it is that simple.

    If your grasses are small and go dormant in the fall, they are warm season and deciduous, so you have a choice. You can prune them after they go brown in late fall or you can prune them in early spring before new growth starts to appear. If you leave them through the winter, they provide seed for birds to feed upon. In areas of high fire danger, it is more sensible to prune them after they go brown. When you decide it is time, use pruners or hedging shears to cut the grasses down to a height of 3 inches if the grass stays under 3 feet tall. Trim to a height of 6 inches for varieties that grow above 3 feet tall.

    Pruning large dormant grasses is a similar process to the smaller deciduous grasses. You can choose to enjoy the winter interest of the dried foliage but be sure to prune before the new growth starts to avoid cutting new fresh growth tips. You may also choose to prune in late fall if you live in an area of high fire danger.  Big grasses make a big mess and they also have sharp leaves so be sure to wear long sleeves and gloves when pruning. Wrap a rope, bungee cord or even masking tape around the outside of the grass to form a tight bundle, this will not only help with cleanup, but will also make the job of pruning easier. Use hedging shears to cut grass to a height of 10 inches.

    Evergreen grasses are cool season plants and will look good throughout the year. After their growing season, brown foliage can pile up inside these plants, so this is when these ornamental grasses could use a combing. The simplest way to do this is to get a pair of rubber gloves (dishwashing gloves work great) and then run your fingers through the grass like you are combing hair. The brown blades with cling to the gloves and come out easily. You may not get all the spent foliage removed, but what you do remove will trigger the plant to refresh itself.

    Every two or three years evergreen grasses benefit from a rejuvenation pruning. Use pruning shears or hedge trimmers to remove no more than two-thirds of the plant. Cutting these grasses back too much might allow moisture to gather on the crown, which causes rot.

    It is also important to bear in mind that evergreen cool season grasses are not as vigorous as warm season grasses that go dormant; if you cut too much off the leaves it does not have the energy necessary to put in to produce new growth.

    For more gardening tips and techniques please go to marinmg.ucanr.edu.