Page 45 - Free State Winter 2021

sources that resulted in Callery pears bearing fruit. The
fruit was carried by animals to new sites and hybrid
We cannot easily correct the pears, with many reverting to their thorn-bearing cousin
problems that have developed species, which popped up in places people did not
want them.
with this ornamental pear that The parking lot surrounding the Holiday Inn where the
has now grown into the category MAC-ISA meetings were held, had many plantings of

of invasive species. Pyrus callerayana ‘bradford” . Every tree I examined
had hits of bacterial fireblight on flower spurs but it did
not progress beyond this tip damage. It is not immune
Plant explorers reported that the Pyrus calleryana in but is still resistant to the disease. The interesting thing
Manchuria appeared to be resistant to Fireblight. The is the trees were growing in hot parking lots in poor
intent of plant breeders of fruit was to breed in the quality soil and the trees were growing very slowly.
resistance to bacterial fireblight from this pear species There did not appear to be many trees with any
into cultivated, edible pear species. This was done in indication of large branches breaking off.
the 1950-1960s . During the early years of breeding, it Keep in mind in the Manchurian area where these trees
was noted that the Pyrus callerayana pear was actually grow natively, the trees grow very slowly and do not
a very attractive tree that had beautiful spring flowers, push out large amounts of growth each year. This tree
nice shiny foliage, resistance to fireblight and tolerated species is really adapted for what we would call poor
the poor soils of urban environments. Most importantly, growing conditions. The way the trees are being grown
unlike its wilder cousins, this one didn’t have long in the nursery, and sometimes, in the landscape may be
thorns. After testing them in a D.C. neighborhood, they creating some of the branch breakage problems. The
were released to the nursery trade in 1960 under the pears do respond to watering and fertilization but have
name Bradford Pear. It was planted in large plantings in growth of weak wood that is more susceptible to storm
the College Park area in the early 1970s. It was an easy damage.
leap to popularity and many nurseries started growing
the trees. Callery pears were used extensively in urban We cannot easily correct the problems that have
landscapes. developed with this ornamental pear that has now
grown into the category of invasive species. We can use
In the nursery, growers did what they did best – grow
trees rapidly with generous fertilization and irrigation this as example of what not to do with a new species
creating a saleable tree in 3 – 5 years. A great, rapid of plant brought into the nursery industry. Look at what
turnover of plants in the nursery industry proved very environment it has evolved to grow in and do not over
profitable. By the early 1980 we had several severe stimulate growth in reproducing the plant. Also, be
summer storms which resulted in many of these aware of what happens when you bring in additional
ornamental pears dropping branches. The Callery pear cultivars that can cause heavy fruit and seed set that
can grow to be a problem. A
was declared a weak wood tree; seminars were held on
how to properly prune the trees to create less upward Stanton Gill, Extension Specialist in
branching, to reduce the branch breakage. This helped IPM for Greenhouses and Nurseries,
to a small degree but the trees still tended to break up University of Maryland Extension
in severe storms. And Professor , Montgomery College,
Germantown Campus, Landscape
The original ‘bradford’ was self-sterile, which is Technology Program
common in many cultivated pears. Plant breeders
sgill@umd.edu
made a huge mistake and introduced new cultivars https://go.umd.edu/ipmnet
with better branch structures, but this provided pollen

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