Saturday, August 30, 2008

Landscape - Drought Effects on Landscape Plants

The following are some comments on the current drought effect on landscape plants in the Region from the University of Maryland TPM/IPM weekly report.

We had major droughts in 2006 and 2007. Now we are experiencing a drought again in August. There are parts of the Eastern Shore that are claiming the drought this summer is even worse than last summer’s drought (Delaware is not as bad as last year but we still have a serious drought in most of the state). We are getting reports of Leyland cypress with trunk cracking and oozing from cankers. Leyland cypress commonly shows these problems under severe drought stress. Carroll County and Baltimore County have many red maples that are showing premature red color of foliage. (many trees in Delaware are also starting to go into senescence early this year). This is very common in a lot of neighborhoods. Several sites I have visited showed severe scorching of foliage. I visited a new home community in Carroll County to look at dying maples. The site had a large planting of maples and conifers on embankments. The plants were under severe stress and many of the plants were well on their way to death. The planting was installed over the last 3 years and the plants were not being watered and left to fend for themselves. This is a good way to guarantee the death of the trees. In central Maryland we are seeing many scorched leaves on oaks, zelkova, London plane, red maples, and Japanese maples. Cherry trees have whole trees that are turning pre-maturely yellow and dropping foliage in August from the drought. (Similar comments can be made for Delaware). Plants in parking lot islands are really suffering with a lot of leaf scorch and dieback. Red oaks, white oaks, and pin oaks are showing branch dieback and in some cases death of trees from 3 years of drought stress. We visited a site in Wheaton and viewed large American beeches, red oaks and white oaks with severe branch dieback from drought injury. The impact of the drought can be devastating to large old, mature oaks. It is rather late to start watering at this point in the season but if the drought period continues I would suggest getting water into the root zones of valuable trees using a trickle irrigation system. The long range prediction is for a colder than normal winter and if the plants go into the winter under drought stress we can expect winter injury.

Reprinted with added comments from the August 29, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

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