Volume 15, Issue 7 ~ February 15 - February 21, 2007

The Bay Gardener

By Dr. Frank Gouin

Trees to Avoid — and Choose —
in Chesapeake Country

Cold-climate trees find Southern Maryland too warm

When selecting trees for your landscape, consider Maryland’s climate. The mountain ash and the white birch — both European and American varieties — are native to climates colder than Southern Maryland.

Beware of These Lovely Birches

The canoe, or paper bark, birch you see growing in New England, upstate New York and Pennsylvania, requires long periods of cold during the winter months before resuming normal growth in the spring. So does the European weeping white birch. The buds of these species must accumulate over 1,000 hours of temperatures between 45 and 32 degrees during the winter months. Only then will the chemicals within degrade so growth can begin in the spring. Temperatures below 32 degrees do not count in the total amount of cold accumulated.

When we have a mild fall and winter like this year, these species will often delay growth until late May or June. This late start makes them more susceptible to insects and disease. Growth is often abnormal, with smaller leaves.

Another strike against planting both white birch and mountain ash is short lifespan, usually 20 to 30 years.

The farther inland you live from the Bay, the more problems you’ll face in trying to grow species native to New England, upstate New York, Pennsylvania and Ohio. For example, sugar maples appear to survive well in close proximity to the Bay. Places farther west from the Bay — such as Prince George’s County, Charles County and into central Calvert and St. Mary’s counties — tend not to support these species.

Maryland’s climate poses similar problems for species that can’t tolerate heat. Like the white birch and mountain ash, sugar maples have a relatively long dormancy and are less heat tolerant than their cousin, the red maple.

Heartset on these cold-climate trees?

Local Alternatives

Pick a Southern Maryland alternative for better results. If you desire is grow a birch with white bark, select the Heritage birch, which is a river birch with nearly white exfoliating bark. If you desire to grow a small tree with bright berries, in place of mountain ash select the Paul Scarlet hawthorn — but make sure there are no red cedar trees within eyesight. The two trees can’t stand one another.

Ask Dr. Gouin your questions at frgouin@erols.com. All questions will appear in Bay Weekly. Please include your name and address.

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