[Arid_gardener] Ficus nitida frost damage

[Linda Drew]

Here is information from a certified arborist:

Phoenix got frosted! Yes, the last round of cold temperatures really 
devastated our landscapes. Many frost-sensitive trees and shrubs can survive 
freezing temperatures for a night or two, but several nights in the low to 
mid-twenties are deadly for many desert-adapted flora. And some of you got 
down into the teens! That is a recipe for widespread frost damage in the 
Valley of the Sun. Unfortunately, frost covers or Christmas lights don’t 
help much when temps drop that low.

Shrubs, Groundcovers:
Well, what do you do now with your plants? Here are some tips. First, you 
should wait until after February 15th to trim back dead leaves or branches. 
This is the average last day of frost each year. Some small shrubs and 
ground cover can be radically pruned back to stubs at this time. You can 
also try to cut them back selectively, trying to retain as many live 
branches as possible. A suggestion: If they can stand to be cut back 
further, they will often re-grow more uniformly and the pruning is simpler 
and faster. How you trim them depends on the type of plant and the extent of 
damage. Some plants can sustain heavy pruning. Others are more sensitive. 
Call us or consult your local nursery for guidance on plants that can 
sustain radical pruning.

Trees:
With trees it is even more important to know how far you can trim them back. 
To determine the extent of damage, you can do two things: Investigate on 
your own after February 15th or wait a few more weeks until the tree 
re-foliates. If you don’t want to wait or can’t because you need your 
landscape back to normal sooner, this is an easy way to find out how far the 
freeze affected your plants. Starting at the smallest dead branch tips, use 
your thumbnail or a small knife to scratch the bark to determine the color 
of the underlying tissue. If the cambium below the bark remains green, the 
tissue is alive; if brown or black, it likely is dead. Some tree and shrub 
branches are hard to tell. If in doubt, consider them alive. You can always 
prune them out later. Continue on to larger twigs, stems and branches until 
you find green cambium. When you find the green tissue, you can safely 
remove the damaged foliage outside that area. Remember to check all sides of 
the plant. Some can be more damaged than other protected areas.

The other option for determining extent of damage is to wait until bud 
break. For some plants this may be right around February 15th. For other 
plants it may be several weeks later. At bud break, trees and shrubs 
re-foliate and let you know exactly how deeply they were damaged. The 
branches that are dead will not re-foliate and you can simply cut back just 
above where new growth emerges. On some trees you may be surprised that just 
leaves and small stems were damaged. If this is the case, those leaves will 
dry out and drop, the tree will re-foliate and you may not need to trim at 
all. Other times there may be slightly more damage and longer dead leafless 
branch tips. You will need to decide to cut them or leave them. If you can 
stand to live with dead branch tips for a year or more, new growth can 
eventually grow past the dead ends. This usually is best for larger trees 
that are difficult to reach and with less than 12 inches of dead tips. If 
your damage is deeper than a foot into the tree’s interior, it may be best 
to go ahead and prune the dead branches. Also, you should prune them if you 
don’t want to look at dead branches all year.

A warning: While trimming out dead branches dramatically helps improve the 
appearance of frost-damaged trees and shrubs, be aware that your plants will 
now be more exposed to sun without the normal protection provided by their 
foliage, even dead foliage. The shade provided by dead branches and leaves 
may give needed protection to a plant while the new foliage gets 
established. Especially keep this is mind with sun-sensitive plants like 
citrus. Maybe you should live with the deadwood until the re-growth is 
healthy. Then remove it incrementally as new foliage grows up and into the 
deadwood. Plants with south or west exposures are most vulnerable to 
sunscald.

The aim is to protect the sensitive bark and other interior parts of the 
plant before hot temperatures arrive. Whether you provide that protection by 
live branches or dead, try to encourage healthy re-growth by irrigating 
carefully. A Spring fertilizer application with nitrogen is always helpful, 
never more so than now when lush and vigorous re-foliation is so needed.

John Eisenhower

ISA Certified Arborist WC-5213

Member American Society of Consulting Arborists



>From: r_farley16 at yahoo.com
>To: <arid_gardener at Ag.arizona.edu>
>Subject: [Arid_gardener] Question from Home-Hort WWW page
>Date: Sun, 11 Mar 2007 14:00:24 -0700 (MST)
>
>Rachel
>85022
>r_farley16 at yahoo.com
>
>I had large 10" diameter trunk ficus trees in my back yard.  They provided 
>marvelous dense, cool, shade.  After the freeze this winter, all the leaves 
>are brown and look dead.  I see one new bud developing on a lower branch.  
>These trees are more than 20 feet tall.  Does the tree need to be trimmed 
>back to help it recover from the frost damage? or can I wait to see how 
>much of the tree comes back?
>
>
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>Arid_gardener mailing list
>Arid_gardener at CALS.arizona.edu
>http://CALS.arizona.edu/mailman2/listinfo/arid_gardener

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