Unit 1 (001)

1. Dutch Elm Disease

Dutch Elm Disease was introduced in the late 1920's on burled elm logs from Europe.

It has killed over 70 million landscape elms throughout the United States. In the past,

city streets were lined with beautiful rows of elms with their graceful arching branches.

There are still many elms around, but the street trees are gone. The disease was

spread by bark beetles and through natural root grafts.

There have been a number of dutch elm disease resitstant cultivars developed, but

none will ever replace the former elms.

2. Parthenocissus

Virginia creeper (Parthenocissus quinquefolia) and boston ivy (Parthenocissus

tricuspidata) climb and adhere to walls and trees by small suction cups or disks.

They both have beautiful red to maroon fall color. Virginia creeper is native and

boston ivy was introduced from Asia. Both these vines make beautiful patterns on

building walls.