Friday, January 3, 2014

Coping With Trees and Landscape Winter And Salt Damage

20131223BPWIcyPines4003crop(1)Each year the Northern New York region gets a half-dozen or more freezing rain events, and every few years we might see an actual ice storm (technically at least 0.25 inches ice accumulation). But the storm that froze the North Country in up to two inches of glaze between December 21 and 23, 2013, was exceptional.

It didn’t have quite the punch of “The Great Ice Storm of 1998” in which freezing rain tumbled for 80 solid hours, but in some locations damage was extensive.

Ice storms happen when a warm, moisture-laden front slides up and over a cold air mass, and then lets loose the water works. Cumulus clouds billow up (occasionally spawning winter lightning), and when cloud air temperature is between 25 and 30F, the resulting subcooled rain freezes to cold surfaces. Warmer than 30, it rains; colder than 25, it sleets. If the warm front is slow-moving—or worse yet, stalls—the ice really builds up.

Sadly, this recent storm caused many hardships, from extended power outages to injuries. Coming as it did during the holidays meant some travel plans were canceled; some family connections not made.

While it doesn’t compare to more serious privations, many people are concerned about trees and shrubs that are broken or bent over. I can’t make the lights come on sooner, but I can tell you the best way to deal with iced-over landscapes.

The first order of business is, of course, safety. Broken, hanging limbs and split trunks can pose a risk to you or others. Glazed branches are surprisingly heavy, though, and it’s hard to get good footing on the icy crust. If you don’t feel confident doing the work, then please cajole, coerce, or pay someone to remove hazards.

Avoid trying to shake or break ice from branches, because there’s a good chance of causing further damage. Right now there’s no good way to tell if a bent tree will right itself. Many of them will, though a bit of judicious pruning in early spring can go a long way to assist them. It doesn’t hurt to prop up a bent-over trunk or low-hanging branch with a two-by-four or similar, which can help prevent further damage should we get snow before the ice melts.

Where breakage has left a jagged stub, you can assist the tree by making a clean cut. Final cuts should be close to, but not flush with, the parent stem. Those tar-like wound coatings may help us feel better, but it turns out they work against the tree, and are no longer recommended.

In cases where a tree has lost 30% or more of its crown, it’s a good idea to get a professional’s opinion. Hiring a Certified Arborist is the best way to be sure the person doling out advice has demonstrated basic competence in all aspects of tree care.

If a company has no Certified Arborist on staff, at least see that they belong to one or more professional organizations. Membership in the ISA (International Society of Arboriculture) is most significant, and there’s also the TCIA (Tree Care Industry Association). Get quotes in writing, and get their insurance certificate directly from their insurer.

Coping with Salt Damage

Every winter brings its requisite salt on roads and walkways. In icy conditions, salt can be a good thing, but too much can cause cars and concrete to suffer in obvious ways, while damage to trees and other woody plants is all but invisible. Salt injures trees and shrubs by several means.

When road spray hits twigs, buds and, in the case of evergreens, foliage, such direct contact causes yellowing of needles and death of evergreen twigs and limbs. It also leads to stunted or deformed growth, such as “witches’ brooms,” in hardwoods. Severe or repeated direct exposure, especially for sensitive species like white pine, can kill the whole tree.

Less obvious, but worse by far, is the effect salt has on roots when it gets directly deposited onto a tree’s root zone by plowing or when runoff washes salt into the soil. Enough salt in the soil will kill a tree. But even at lower concentrations it makes water less available to tree roots, producing drought stress in the presence of moisture.

This latter, chronic injury may show up as brown, scorched-looking leaf margins in July, when deicing salt is the last thing on people’s minds. It can also manifest as subtle, cumulative damage that weakens a tree year after year until eventually it succumbs to opportunistic agents such as insects or diseases.

Salt actually damages soil structure, causing what’s known as “sodium compaction.” Roots need to get oxygen through soil pores, and healthy soil forms tiny clumps which form natural channels for air to pass. The chemical bonds holding the clumps together are broken by salt, and as a result the pore spaces collapse, restricting roots’ access to air and further stressing trees. While it was once thought that rain could wash road salt out of the soil each summer, it now appears this is rarely the case, and that salt levels often slowly build over time.

There are many “low-salt recipes” for dealing with this problem. Some tree species — honeylocust, hawthorn and Norway maple, for example — are more salt tolerant and can be used in place of sensitive trees like sugar maple.

Homeowners can reduce salt damage by employing only sand or other mineral abrasives, or by at least switching to a salt/sand mixture. Alternative deicer products like calcium magnesium acetate (CMA)are much less toxic to plants, though they cost more. In addition, constructing barriers to deflect road salt spray and/or divert spring runoff from root areas can also help a great deal.

Photo of recent storm by Brian P. Whattam.

Paul Hetzler

Paul Hetzler is the Horticulture and Natural Resources Educator at Cornell Cooperative Extension of St. Lawrence County.

You can reach Paul at the Cornell Cooperative Extension office in Canton at (315) 379-9192.

5 Responses

  1. A Mr. Lomez says:

    Great article. I hope people won’t plant Norway maple as an alternative, as they are an invasive species.

  2. Paul Hetzler Paul Hetzler says:

    That’s a very good point; thank you! In some places, Norway maple has naturalized and become invasive, and many jurisdictions have banned its sale.
    Currently, Cornell still lists it among recommended street trees. (Perhaps that will change soon, especially since Norway maple has become a problem invasive species in the Ithaca area!) Although I’m no fan of Norway maple, I’m not aware of any instances where it has “escaped” into the wild in St. Lawrence County.
    One thing I’ve noticed is that very few people seem to realize the red-leaf ‘Crimson King’ is a cultivar of Norway maple, with the same potential for naturalization.
    Thanks again.

  3. Jesse B says:

    Paul, any data on the time frame for salt contaminated soil becoming ‘neutral’ again? I imagine that in a region like the Adirondacks that has less topsoil and shorter growing season, the effects of salt would be greater than a warmer region that produces topsoil more rapidly.

  4. Paul Hetzler Paul Hetzler says:

    Soil texture is the most important factor in the speed with which salt leaches out–sandy soils clear faster than clay soils. Precipitation matters, obviously, but there isn’t that much variation throughout northern NYS–basically, we get plenty. If you’re curious about salt concentration in your garden you can get the soil tested for either conductivity or Total Dissolved Solids (TDS). (It would be nice if you have a friend who teaches Biology who could loan you a meter.) Sample depth should be about 6 inches. Values above 1,000 micro-mhos/sq. cm. might raise an eyebrow; above 10,000 is real cause for concern.

  5. Hillel B says:

    ‘Great post!
    ‘Yeh in my neck of the woods (north/central Appalachians), I witnessed in my lifetime, construction of a 4-lane highway (replacing an old 2-lane US route), that now, 30+ years later, you can clearly see the impacts of what I think is salt, where the road cuts through hardwood forest and is at particularly windy locations; what once was nice roadside woods, is largely dead and as you say full of “witches broom”, with younger trees.