How To

Using RPM's to Rev up Wetland Reforestation
by Tharran Hobson, The Nature Conservancy

Innovation, cutting-edge technology, and accelerated growth—these words are associated with high tech, on-line day trading on the NASDAQ, right? Not necessarily. The same can be said for everyday forrested-wetland restoration thanks to Forrest Keeling Nursery RPM™s (an acronym for the nursery's specialized "root production method" trees) which can speed the slow process of bottomland-hardwood reestablishment.

The new technology enhances a tree's root system capabilities hundreds or possibly thousands of times, giving roots the capacity to better fulfill the demands of the rest of the plant. Forrest Keeling achieves this miracle through a patent-pending, multi-step process that goes something like this:

Nuts or acorns placed in bottomless "oyster flats" for cold stratification until February → flats transferred to greenhouse for germination → seedlings produce tap roots that protrude below the bottom of the flats → air contact causes natural pruning of the tap root → lateral roots produced higher up on the collar → between March 1st and 15th seedlings transplanted to bottomless shallow pots and placed on open benches for air pruning of lateral roots → root mass becomes more dense → after May 1st seedlings placed outdoors to harden stem tissues → plants transferred to 2.5-gallon growing containers → fertilizer and water added.

This system allows Forrest Keeling to finish most native species to a marketable 5-foot height in one growing season, or approximately 210 days from germination. Planting RPM™s in wetland-reforestation situations gives land managers healthier, more vigorous plants with greater tolerance to moisture extremes and accelerated mast production.

A typical problem when using traditional bare-root seedlings in wetland restoration is the soil's high moisture content, which tends to deprive the seedlings of oxygen and causes stunting or mortality. The RPM™'s enhanced root system is better equipped with more tips for oxygen exchange. Also, with the added height, the tree is less likely to be completely inundated and better survive an abbreviated flood event. The size of the tree also makes it less vulnerable to deer-browse damage. Possibly the best benefit is that flowering and fruiting may come as early as 3 years after planting for some species, providing food for wildlife and reseeding.

Anything that speeds the glacially slow process of forest succession is a plus. However, the initial planting process for RPM™s can be a little more tedious than for bare-root trees. The most efficient planting method uses a tractor-mounted posthole auger followed by as many eager school kids and volunteers as one can muster to do the planting. A small crew of four to six can plant over 600 trees a day. Most foresters recommend about 40 RPM™ trees per acre, a rate well below that usually recommended for bare-root seedlings. Higher survivability of the RPM™s allows for a lower planting rate, and overall, the cost per acre is comparable.

Given the complexities of wetland forest restoration and management, RPM™s add another alternative to the list of plant material choices—and choice is good.

For more information, contact Hugh Stevenson, Forrest Keeling Nursery, P.O. Box 135, Elsberry, Missouri 63343, (800) 356-2401, info@fknursery.com, www.fknursery.com.