Unit 24 (024)
1. Prunus or Cherries
Cyanide poisoning can be a problem in wilted foliage.
The leaves, twigs, and bark of black cherry contain cyanide in bound form as the
cyanogenic glycoside, prunasin. During foliage wilting, cyanide is released and
domestic livestock that eat wilted foliage may get sick or die. Native deer can eat
unwilted foliage without harm.
Most Prunus leaves have glands on the petiole or leaf stalk. Viburnum opulus and
Viburnum trilobum also have glands on the petiole (see Unit 022).
2. Pyrus calleryana or Bradford Pear
Fire blight bacteria disease is an often fatal problem in Pears. The Bradford Pear
Pyrus calleryana cv. Bradford and related cultivars were selected for fire blight
They have been widely used as street trees, but there is one problem. The trees main
branches develop narrow crotch angles and these narrow branch angles split more
easily in storms. The narrow crotch angles contain bark inside the angle instead
of solid wood like in a wide branch angle on an oak tree.