Monday, January 5, 2009

Improve plant health with winter pruning

Burrrr… who in their right mind would venture into the cold and snowy weather this time of year to work in their yard? The brave souls that don their long johns, scarves and parkas to do some dormant pruning will be rewarded with healthier landscape plants and less work in the long run.

Many people fear damaging plants and avoid pruning all together. Being a bit leery is wise, but with a little knowledge and practice, anyone can prune properly and should look forward to positive results. Pruning is the removal of plant parts to improve plant health. Do remove dead, diseased or damaged plant material at any time – there is no time like the present to remove damaged plant parts which may only cause long term problems.

Starting with the basics - there are three main types of pruning. Corrective pruning redirects growth to achieve a desired shape and a more natural looking plant. Preventative pruning removes dead, diseased or damaged plant material, as well as problematic branches such as those overhanging walkways or growing into buildings and homes. Rejuvenating pruning is done by heading back heavy growth and thinning crowded older plants to encourage new growth.

Specifically, dormant pruning benefits ornamental plants and trees by removing unhealthy or excessive growth and deadwood, and by improving the natural branching characteristic of the plant. It is a combination of the different types of pruning listed above. The best timing for structural, rejuvenating, or corrective pruning is late January through early March when the plant is inactive. So grab your hat, gloves and tools and let’s get busy.

Proper Pruning Tools & Tips

  • Use bypass pruners and loppers (Use anvil style pruners only on dead wood)
  • Use the proper sized tool for the job – pruners for small finger sized branches, loppers for thumb sized and larger branches and saws for bigger branches and limbs
  • Keep equipment clean, sharp and rust free
  • Get a holster to store tools so they don’t get lost and avoid contact with the wet groun

Dormant pruning helps to maintain a plant’s size in a limited space, and it revitalizes older, woody plants. Plants pruned during dormancy become healthier in spring as the plants energy is directed to fewer remaining branches which is supported by the same root mass. The increased energy transferred to healthier remaining stems and branches grows a more prolific and healthy plant.

Dormant pruning reduces headaches during summer pruning work. Keep in mind that pruning actually encourages growth. For those plants that are sheared in summer months like the common privet hedge, new growth rapidly appears with twice the growth output. This is what causes the outer portion of the plant to become so woody – and darn tough to cut back after years of shearing. Selectively removing some of the excessive woodiness will help to redirect plant growth helping the plant to fill in thin and bare areas.

Before starting, have a vision for what your pruning will accomplish so you are careful to prune the correct way to achieve your goals. When pruning, follow these steps in order: 1) Remove dead, diseased and damaged wood from the plant. 2) Clear building structures, paths and driveways of obstructing plants 3) Remove any crossing or rubbing branches that might cause future injury. 4) Thin and head back according to the plant’s natural growing characteristics. Thinning prevents ornamentals from becoming top heavy and more susceptible to winter snow damage and it encourages the plant to fill in the lower areas with new growth.

Before pruning, determine what the plant can handle – which requires knowing what plant you’re working on and its growing habit. Some plants need to be pruned gingerly, while others benefit from a vigorous pruning. In general, it is best not to prune more than a third or quarter of any ornamental or tree, and in many cases removing a fifth of the plant is more appropriate. Rejuvenating pruning usually involves a three- to five-year pruning plan.

Pruning in late fall or early winter should be avoided. Soil temperatures are still warm and the plant is still actively transferring its energy stored in the canopy to the root system. Pruning late fall robs the plant of vital stored energy potentially weakening the plant. Heavy fall pruning is not advised because it may encourage new growth that may not have time to harden off before cold weather sets in, potentially causing frost damage to the new growth. One major exception to late winter pruning is spring flowering ornamentals (e.g. lilac, forsythia, viburnum), which are best pruned after they flower and before they form flower buds for the following year.

To learn more about proper pruning techniques – email to receive a free copy of Pruning Landscape Plants - OSU Cooperative Extension Service Bulletin #543