Tuesday, January 10, 2017

Wait to Prune

This was a post on the Aransas/San Patricio Master Gardeners FB page.

AFTER THE FREEZE—WAIT TO PRUNE - By Ginger Easton Smith, Extension Agent

The recent frigid weather injured countless plants, and killed many others.  Cold temperatures can damage the entire plant, or parts such as leaves, buds, flowers, trunks, stems or roots.

People may be anxious to get outside and prune off the now unattractive parts of plants, but be patient!  It is better to wait until the weather warms up and all chance of a freeze is past for the season.

The exception to this is plants that are not woody and have tissue that has turned mushy.  It can, and should, be removed within a couple of weeks.  This would prevent any pathogens that might have entered through the damaged tissue from moving toward the center of the plant.  Cut off anything that’s mushy and be sure to dip your pruners in rubbing alcohol for 30 seconds between cuts to keep from spreading potential pathogens to other plants or plant parts.

There are several reasons for waiting to prune anything woody; pruning now may stimulate new growth which would be very susceptible to damage if we get some more cold weather, another reason is that it is difficult to tell right now whether branches are dead or have just lost leaves; many may surprise you by pushing out some new shoots.  Often the tip of a branch is killed but the rest is alright.  You wouldn’t want to cut off live branches or twigs.  Also, outer branches, even if they are dead, may provide some wind protection or insulation to inner branches.

There’s no reason to rush anyway as it doesn’t help the plant to prune off dead wood at this point.  When things warm up and new buds form and develop into leaves, it will become obvious where to make pruning cuts to remove dead sections.  Keep in mind that some plants will die back to the ground but will put out new shoots in the spring, so be patient.

The other, unfortunate, side of this is that some damage will be internal and not be visible or cause any problems for several months.  Injury to roots, which have little ability to develop cold tolerance and are particularly susceptible if the plant is growing in a pot, also often won’t show up until a very warm day when the reduced root system just can’t provide enough water to the plant.

Freezing temperatures can also damage the water moving system inside tree trunks, limiting the water that can be moved up the trunk to the leaves. Many broadleaf trees can grow new conducting tissue, but due to their very different structure, palms cannot.  Again, the problem may not be visible until the first hot day when the fronds all wilt severely.

Palm leaf buds deep in the plant may have been damaged by the frigid weather but the signs won’t show up until the bud develops and emerges brown, partially brown or deformed.  Fortunately, the leaves will often grow out of the injury.

Grass that hadn’t turned brown before the storm, is probably brown now.  But don’t worry, most of it will green up nicely when it gets a bit warmer.  Give it a light application of fertilizer in March and water deeply about once a week.

Unfortunately, there will be plants that don’t make it through the freeze.  Look at the bright side. This will give you a chance to try some new plants in your yard.  Watch for the Master Gardeners Spring Plant Sale on March 4 and sales at local nurseries.

Any stress to plants, including freezing temperatures, excessive water, drought, and improper or overly-enthusiastic pruning, weakens plants making them susceptible to diseases and insect infestations that wouldn’t harm a healthy plant.
Any damage, which could include pruning cuts, provides an entry point to pathogens that might not normally bother the plant.

Keep an eye on your plants as the weather warms up, watching for any signs of disease.   If something develops on a few leaves or twigs, you can probably just prune it off.  Be sure to disinfect your clippers after making each cut.

A healthy plant is always best defense against any challenge.  It will be more resistant to damage, and recover from it more easily.  Try to keep your plants supplied with adequate, but not excessive, water and nutrients; and prune as needed.

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