The USDA National arboretum’s New breeding Program:

The National Arboretum has developed a new focus on breeding trees specifically for street and utility line applications. The available palette of urban tolerant, small trees with compact habit for planting under utility lines is extremely limited. Those species of trees that are of suitable height (e.g. flowering dogwood, Cornus florida) are often intolerant of urban edaphic conditions (e.g. soils compacted and anoxic, high soluble salts, fluctuating moisture and temperature), while traditional tree species utilized in urban tree plantings are either too large (e.g. London plane, Platanus ×acerifolia) or too invasive (e.g. Norway maple, Acer platanoides) for modern cityscapes.

Initiation of a breeding program for small trees requires the acquisition of new germplasm and evaluation and testing to identify clones as parental breeding stock.

New germplasm are acquired through:

1. Exchange from other botanical gardens, arboreta, and institutions,

2. Targeted collection trips in conjunction with the Woody Landscape Plant Germplasm Repository in the U.S. and abroad

3. Purchase of cultivated species and varieties from nurseries in the U.S. and abroad. Target genera and species are listed in the accompanying table.

Goals of the Breeding Program:

Short-term:

• Evaluations for pest and disease resistance, valuable selections are propagated for on-street plantings and preliminary release to the nursery industry for further evaluation and production.

• Parental breeding lines will be identified and breeding programs tailored for developing superior cultivars within a given genus and species-group.

Long-term

• Release of urban, pest, and disease tolerant trees of compact habit suitable for utility line plantings.