Pruning at the right time of year is essential to plant health

"When to prune?" is a question gardeners have been asking lately. So I thought I would put together a primer on pruning the most common plant groups that I have been asked about.

Most gardeners like to cut ornamental grasses to the ground sometime in the late fall after the stems have turned brown. If they don't prune at that time, the brown stems will often break off during the winter, which results in the need to clean up the mess.

On the other hand, pruning ornamental grasses in the fall leaves a hollow stem that will hold water from rain all winter long. This could result in rotting of portions of the grass crown. Over several years, this could result in loss of plant vigor.

Therefore, my suggestion is to prune ornamental grasses when you want to, but just be aware of the advantage and disadvantage of pruning in the fall or in the spring.

Spring blooming shrubs such as forsythia, viburnum and azalea set their flower buds in the fall, otherwise referred to as on last year's wood. Then in the early spring, those buds open to a plethora of beautiful colors.

Pruning paint for tree wound dressing. (Laura Simon)

Prune these shrubs in the late spring after petal fall. Pruning at this time makes sure that your shrubs will have ample time after pruning to set buds for the next spring flush of color.

You can prune in the fall without hurting the spring blooming shrub, but you will remove the bloom buds and there will be no flowers opening in the spring.

Summer blooming shrubs such as roses, crapemyrtle and abelia can be pruned either in the fall or in the early spring. They bloom on this year's wood.

If pruning is done in the fall, and we experience a hard winter, some of the twigs may have dieback. If this occurs, then another pruning will be needed in the spring to remove the damaged tissue. if you want to prune only once a year, do it in the early spring.

Most deciduous trees (they lose their leaves in the winter) should be pruned in the winter when they are dormant. This includes flowering trees such as dogwoods, redbuds and cherries. Whole branches usually are removed at this time. If you are going to just prune off ends of branches, then dogwoods, redbuds and cherries should be pruned just like spring blooming shrubs in the spring after petal fall.

Pruning paint for tree wound dressing. (Laura Simon)

An exception to dormant pruning are maples. They should be pruned in late August. Maples bleed very badly after pruning. Bleeding -- sap loss -- is reduced at this time of the season.

If you are removing large branches from pines, cedars and cypress, I would do this in the winter when the trees are dormant. If you are pruning the ends of branches, do this in either winter or early spring. The flush of spring growth will hide all of the pruning cuts.

I prefer to prune evergreen shrubs such as boxwood, euonymus and yew in early spring. As above the spring growth will hide all of the pruning cuts.

If you are making large pruning cuts, spray or paint pruning sealer on the cut. The sealer reduces the amount of moisture lost from the cut and will protect the wound from the introduction of bacteria, fungi and insects.