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Moment of Nature - March 27, 2015
The beauty and bane of Bradford pear trees
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Spring is here in the City and the Bradford pears look so pretty.

White flowers abound to entice the bees, but they stink so bad, bringing me to my knees.

A canopy so round like a lollipop, looks like someone went chop, chop to the top.

Their autumn color looks great, which is a wonderful trait.

A good urban tree for the first 20 years, but then branches break and the tree disappears.

Ok, so I am not a good poet, but it sums up the essence of my relationship with Bradford pear trees. ‘Bradford’ pear is a specific cultivar of the ornamental Callery pear (Pyrus calleryana), a species native to China and Vietnam. Like many other plants, Callery pear was imported to the United States over a century ago. The first introduction was in 1909 to Harvard University’s prestigious Arnold Arboretum, the oldest public arboretum in North America. The second time was a decade later when the U.S. Dept. of Agriculture (USDA) introduced it for the development of fire blight resistance in the common pear (Pyrus communis). The blight, a potentially fatal bacterial disease spread by pollinators, was devastating the commercial pear industry. Therefore, it was widely planted as the rootstock for the common pear long before it gained interest as an ornamental.

During the early 1950s, the ornamental value and hardiness of Callery pear were recognized, leading to the development of a number of cultivars, including ‘Bradford’, which was named after F.C. Bradford, a horticulturist at the USDA Plant Introduction Station in Glenn Dale, Md., at that time. By 1962, the tree was available commercially. These ‘wonder trees’ were promoted as the next best thing to sliced bread and they eventually became one of the most widely planted trees in urban and suburban areas.

Bradford pear trees usually grow 25-30 feet tall, with a canopy width around 20-25 feet and are noted for their uniformly rounded canopy which lends itself to symmetrical landscape plantings. The tree can tolerate a variety of soil and site conditions, it blooms dependably, displays wonderful fall color and best of all, it has a high resistance to most insect and disease problems. Unfortunately, that’s where the good news about Bradford pears comes to an end.

The same branch structure that makes the rounded canopy shape so pleasing (to some), has major structural flaws. Because there are numerous branches (technically they are co-dominant trunks) attached in one general area, there are narrow crotch angles between the branches. As each branch (or trunk) expands in diameter each year the angle between them becomes narrower. This causes the branch bark to fold in on itself, resulting in a bark to bark union instead of a wood to wood union. This is called bark inclusion and over time, the included area may become weakened by external and internal pressure causing the branch(es) to break off because they are not firmly attached.

This structural weakness makes the trees susceptible to storm damage, whether from wind or ice, and the damage often causes large limbs to rip down one side of the trunk. However, I have seen branches also break off on hot, clear, sunny days as well. In those cases, the wood has dried out and shrunk, causing the bark inclusion to separate and ‘let go’ of the branch. Often times what’s left is a gaping wound and a lopsided tree. Unfortunately, there’s not much to do to repair either consequence. Some folks elect to remove the tree altogether and replant with something different.

Structural weakness is not the only drawback associated with Bradford pears, though. Originally bred to be sterile, this ornamental pear tree was never intended to produce fruit. In reality, though, it is often pollinated by newer Callery pear cultivars (‘Aristocrat’and ‘Redspire’) that were developed to overcome some of Bradford’s structural issues. This cross-pollination can lead to viable seeds and that’s where the real trouble starts. The offspring of those well-mannered ornamental pears are, to put it nicely, aggressive thugs. They spread rapidly with the help of birds dropping their seeds. The resulting plants are thorny invaders that choke out native plants wherever the seedlings take hold. The problem is severe enough that many municipalities discourage planting Bradford pear altogether. Ironically, the USDA, the same federal agency responsible for propagating Callery pear decades ago, listed ‘Bradford’ pear in 2010 as an invasive tree in southern forests.

If this weren’t discouraging enough, Bradford pears just don’t live a long time, as trees go. Starting around the age of 20, the trees simply begin to decline, with few of them living to the age of 30. Consequently, other Callery pear cultivars with improved branching patterns are promoted, such as ‘Aristocrat’ and ‘Chanticleer’. ‘Bradford’, however, is still preferred because it has better resistance to fire blight than the other cultivars.

If you happen to have (or had) a Bradford pear that you’d like to replace, here are some other tree species to consider. Flowering apricot (Prunus mume) -- Small maturing tree. Late winter bloomer with showy flowers. Many cultivars available. Serviceberry (Amelanchier arborea or Amelanchier x grandiflora) -- Small maturing native multi-stem tree up to 25 ft. tall. Delicate spring flowers. Good fall color. Fruit is edible. Fringetree (Chionanthus virginicus or C. retusus) -- Small maturing tree. Showy summer flowers. Saucer magnolia (Magnolia soulangiana) -- Small maturing tree. Early blooming showy flowers. Crape myrtle (Lagerstroemia indica, L. faurei, or hybrids) -- Small maturing tree up to 25 ft. tall. Summer flowers. Many colors available. Amur maple (Acer ginnala) -- Small-maturing tree up to 20 feet high. Shade tolerant and tends to be multi-stemmed. Chinese pistache (Pistacia chinensis) -- Medium maturing tree up to 35 feet high and wide. Fall color is good. Persian parrotia (Parrotia persica) -- Medium maturing tree up to 40 ft. tall. Fall color is excellent.

Keep in mind that just because a tree is small when you plant it, doesn’t mean it will remain that way. It’s best to match the mature height and width of the tree being planted with the long-term space that it will grow into. Narrow or limited growing spaces or areas next to driveways, patios, electric lines, etc. call for small maturing trees. Wide open spaces with no above or below ground conflicts or restrictions call for large maturing shade trees. If you’d like to plant a tree within the street right-of-way, be sure to ask for and submit a Tree Planting Permit from our Public Works Department (only required in the city limits). If you’re not sure what tree to plant, please feel free to contact me and I’d be happy to help you match the right tree to the right spot!