Page 6, The PALMETTO, Summer 1994 How Old is a Silver Palm? by Daniel B. Ward and Robert T. Ing

Formula: To estimate age of Coccothrinax argentata, multiply 6.5 by the height in feet.

useful. Measurements are needed over a span that is a significant pro• portion of the tree's age. And such data are scarce. Data useful in estimating tree growth are beginning to accumulate from the Division of Forestry's Flori• da Champion Tree Project. Since 1967 this project has encouraged the gath• ering of measurements from through• out the state on many of its native and introduced tree species. As the (\J plants of the Florida Keys, measured a large silver palm in the newly formed Bahia Honda State Park, Monroe County, and recorded its data for the Champion Tree Project. They found the tree to have a trunk Silver palm (Coccothrinax argentata diameter. Palms do, of course, grow circumference at breast height of 22 [Jacq.] Bailey) is a small tree native to in height, and each year produce a inches, a height of 22 feet, and an southeastern Florida and the Bahama new crop of leaves. The number of average crown spread of six feet. By Islands. While it once formed appre• these leaves may be counted, and the the formula used by the American ciable stands in coastal Dade and vertical distance occupied by the leaf Forestry Association (now American Broward counties and on the Florida scars that mark the stem when the Forests), Washington, D.C., for deter• Keys, it has now been reduced to a leaves have fallen may be used to mining comparative tree size, these few protected populations and scat• estimate the year's growth in height. dimensions merited a ranking of 46 tered individuals preserved as speci• If one wishes, the growth in height points. In the absence of any other men trees in residential develop• during a single year may be divided nominee, the Shaw-Avery tree was ments. In 1979 it was designated as a into the tree's total height, to yield an declared the "national champion." "threatened" species by the Florida estimate of the tree's age. In some Shortly thereafter John A. Baust, Committee on Rare and Endangered genera, as in Phoenix, where the leaf then superintendent of Bahia Honda Plants and Animals, and in 1993 it scars remain clear and are not cov• State Park, found a nearby silver was classified as "endangered" by the ered by persistent leaf bases, a patient palm that appeared larger than the Florida Department of Agriculture. observer may count leaf scars over one nominated by Shaw and Avery. The increasing rarity of this small the entire trunk and perhaps gain In March, 1979, Baust measured the palm has begun to bring it to the some additional accuracy. But fluctu• new tree as having a circumference of attention of those who would under• ations in the number of leaves pro• 19 inches, a height of 27 feet, and a stand its biology. But, as is equally duced and the inherent difficulty of crown spread of six feet; these di• true of the vast majority of Florida's counting their scars makes leaf• mensions yield a ranking of 48 native plants, little information about number estimates of age of palms points. Because the two trees were so its life history has been recorded. tedious and erratic. close in overall size, each became a Among the unknown parameters of An obvious approach to the prob• "national co-champion." the silver palm is its longevity. Un• lem of estimating age of palms is to Recently, these two trees have been like typical dicotyledonous woody monitor their height at different remeasured. Though trunk circumfer• plants in which age may be deter• dates; then from the observed rate of ence and crown spread have not mined by counting the concentric growth, extrapolate to the full height appreciably changed, height has in• layers of xylem laid down annually of the tree. But, given the imprecision creased. The Shaw-Avery tree has by a vascular cambium, palms have of measuring tree height, measure• grown three feet in 18 years, while no meristematic tissues in their ma• ments over a single year or a short the Baust tree has grown two feet in ture stems and thus cannot grow in ~ span of years are only marginally 14 years. These height measurements The PALMETTO, Summer 1994, Page 7 thus show an average growth of 6.5 East Coast Railway; these palms even years per foot (or, in reciprocal, 1.85 then would have been between 12 inches per year). and 16 feet tall. In 1846, construction The growth of many species of tree of Fort Jefferson was begun on Gar• slows with age, but in a palm with den Key; these palms were then of a no growth in diameter and thus no size to grace the commandant's door• exponential increase in the vascular yard. In 1823, Key West became an cambium that must be supported by English possession, the beginning of the foliage, growth may indeed be permanent European settlement on linear in rate as well as in direction. the keys; the taller of these palms The determinant for longevity in a was then a healthy two-foot seedling. palm in some cases is known to be It would seem that the older silver the progressive death of the phloem palms of Bahia Honda, modest in the vascular bundles of the trunk, though they may be in absolute size, which - unlike angiosperms in have survived from an era when their which the phloem is renewed each only human associates were the na• tive Caloosas and the transient bucca• season - is laid down when the Silver palm inflorescence trunk is first formed. In other cases neers. longevity is determined simply by We are grateful to John Baust for wind shear, as with Hurricane An• a seedling is always slow to become searching his memory for the infor• drew, which snapped the trunk of the established, one may be justified in mation without which we would national champion buccaneer palm adding a few years to these numbers. have been unable to relocate these (Pseudophoenix sargentii) on Elliott Perhaps a reasonable estimate for the two trees, and to Monay Markey, Key. age that a silver palm may reach in Bahia Honda ranger, for her skill in One may thus now make an esti• the Florida Keys is approximately 200 remeasuring these trees and in sub• mate of the longevity of silver palms. years. mitting detailed nomination docu• The Baust tree, the largest for which The age these Bahia Honda palms mentation. a record is available, at its present have reached may best be appreciated Dr. Daniel B. Ward is Professor of height of 29 feet, and assuming a by placing their years in the context Botany at the University of Florida. Dr. constant rate of growth, would have of South Florida human history. Ac• Robert lng, is a Ph.D. in ent0111010glj attained its present height in 188 cess to Bahia Honda by a means who holds an "Adjunct Assistant in years, while the Shaw-Avery tree other than boat was attained only in Botany" position with the Department of would have required 162 years. Since 1912 with completion of the Florida Botany, University of Florida.

DEMAND creates SUPPLY creates INTEREST creates USAGE creates KNOWLEDGE & ENTHUSIASM create DEMAND creates SUPPLY •••

IT ALL BEGINS WITH YOU.

Ask your retail nursery to stock Florida native plants. Support Florida's native plant growers and wholesalers.

30 acre nursery (Wholesale only) Quality native trees, shrubs, wildflowers & aquatics from 1 to 65 gallons CeJ4.tlLCl~Sto/lida Statewide delivery available Landscape installation and consulting WINNER, 1992 FLORIDA XERISCAP£TM LANDSCAPE ){atiO'e StoILCl GRAND A WARD

P.O. Box 1045 (Kiefer Road), San Antonio, FL 33576 (25 miles north ofTampa) (904) 588-3687 FAX (904) 588-4552