Green Horizons

The Right Tree in the Right Place

By KIM YOUNG | Forrest Keeling Nursery
WAYNE LOVELACE | Forrest Keeling Nursery

Differences in leaf emergence due to provenance. Photos taken April 15, 2015 in Elsberry, Mo., which is, on average, the last date for frost in mid-Missouri. Left image, pin oak from seed of Southern origin; at right, pin oak from seed of local origin.

You can take a seed out of the south, but can you take the south out of the seed? To trees, there is something to that old saying "There is no place like home". Within a seed is a plant's "internal clock," or provenance. Provenance is the origin or the original source of the seed. Provenance is coded by a plant's cycles of growth and reproduction, which are influenced by climatic zones, temperature and moisture zones.

This genetic coding dictates time of flowering, leafing, fruiting and dormancy for the seedlings that will germinate from its seeds. When planted outside of the mother plant's climatic zone, offspring may not perform to full potential. Trees grown from seed collected from Southern sources will inherit the clock of the parent tree, which bud and leaf earlier than their Northern counter parts (see photos). Trees grown from seed collected outside of a geographic area may perform fine for many years, but when we experience an extreme weather event (e.g., late spring frost, extreme low winter temperatures), these trees are at high risk for damage and may not survive.

Trees in nature adapt to their specific climate and growing conditions. Provenance is a long- term genetic code passed from parents to offspring that is developed through generations of natural selection. Critical traits such as plant hardiness, drought resistance, and flood tolerance are all inherited from parent trees. The gradual process of natural selection also encourages disease and pest resistance in future generations of plants. Successful establishment and development of healthy trees is dependent on a tree's innate ability to adapt to environmental fluctuations and extremes.

We have observed an increase in the number of planting projects requiring native plants grown from local seed sources. Most projects request plants grown within a geographic area of approximately 150 miles. Foresters prefer that seedlings for reforestation not be moved more than one hardiness zone north or south of the native stand where seed originated. It is also of importance to track seed from flood plains and seed from upland sites. We recently observed seed collected from two trees of Diospyros virginiana (Persimmon). The seed collected from an upland area germinated three weeks earlier than seed collected just one half mile away from a wetland area. Was the wetland source waiting for likely spring floods to recede? As a general rule, a wetland source will perform in an upland planting, but an upland source may struggle in a flood plain planting.

Currently, there are few nurseries that consider provenance when marketing trees. It is both time consuming and complicates inventory. Tracking trees to their parent seed source is a common practice at Forrest Keeling Nursery. Established seed orchards, which consist of trees from numerous geographic areas, as well as upland and wetland sources enable the nursery to provide trees with appropriate provenance to their customers. Street trees, trees in parks and landscapes are typically from unknown seed sources. It is important to obtain seed from native stands to ensure its true geographic provenance. Selecting the right tree will help ensure the long-term success of your planting and investment.