The Spring Freeze: Impact of the Drought
Plants have developed a strategy for survival over millions of years of evolution, but every once in a while the forces of nature offers up a new challenge. This year's mid-spring freeze has challenged many of our plants and has tested their adaptability to an ever-changing set of conditions. This event gives us a rare chance to be witness to the interplay between plants and the forces of nature.
At the UT Arboretum we are documenting the effects of "the freeze" on a variety of plant species. A click on the timeline at right leads to our documentation of the effects of the freeze at the various stages of plant re-growth. The article below outlines the lastest observations after three months.
"Effects of the drought... three months after the freeze."
The saga of the 2007 Spring Freeze keeps building, as an early summer drought compounds our woes. By this time most folks feel like they have waited long enough to prune-out the dead twigs and stems caused by the freeze. However, we are now seeing some additional "dieback" that might not be directly associated with the freeze, but by the lack of rain. At the Arboretum we are seeing several trees and shrubs that are obviously being stressed from the lack of water - even on some well established trees, some of the leaves have taken on slight hues of fall color. These weather related conditions caution us to keep-up the "watering" of all plants that were planted within the last couple of years, whether they were damaged by the freeze, or not.
In the article below, Dr. Alan Windham, UT Extension Plant Pathologist, highlights some of the lingering and progressive effects of the freeze and things you might look for as you examine your own landscape.
Japanese pine showing signs of damage after the freeze.
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Japanese pine freeze damage confirmed at the three month mark.
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Dieback of Yew, Cryptomeria, Arborvitae and assorted conifers
This has been a trying year so far for the Tenn Green Industry. Winter months were drier than normal in most locations. The dry weather continued into Spring as evidenced by NOAA (see "The Freeze"), and coincided with the Easter freeze which was unprecedented in recent history. This combination of a drought, warm weather, a freeze that was followed by severe drought, is causing widespread damage in nurseries and landscapes.
While damage to evergreen conifer trees and shrubs was not visible at first, it is currently quite visible in many landscape locations throughout the state. In Middle Tennessee, dieback on yew is quite common. On a three mile drive along Old Hickory Blvd in South Nashville on Friday afternoon, almost every subdivision entrance had yew showing moderate to severe dieback.
Several of the plantings that I stopped by to photograph had several things in common. First, there was no irrigation at most of the plantings showing severe damage. Second, there was no bark splitting on branches or main stems as I have observed in other plant species.
Third, the damage was randomly scattered throughout the canopy of most plants. Fourth, I could see no correlation between sheared or pruned and unpruned plants. Fifth, some of the plants were mulched, others were not. Sixth, no fungal fruiting bodies or wood boring insects were observed on any of the damaged plants.
Dieback on other plant genera has been observed. Home owners, grounds managers and nursery producers have noted dieback on arborvitae, cryptomeria and other species. I have noticed dieback on cryptomeria before, but have never associated a fungal pathogen with this problem. Dirr in his Manual of Woody Landscape Plants notes this dieback as a problem of cryptomeria in the Southeast.
So what is to be done at this point? In some cases I have seen, landscape plants are totaled and should be removed and replaced when conditions are more favorable for planting. In other cases, dead shoots can be removed and with a year or two of corrective pruning, things could be back to normal. Nursery producers will prune out damaged parts, cutting into live tissue; if the damage does not go to the ground.
If possible, plants need to be irrigated when dry conditions occur. Here's hoping that the rest of 2007 and 2008 is more normal on the climatological front.
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