THE ECOLOGY AND BIOLOGY OF PANAX-QUINQUEFOLIUM-L (ARALIACEAE) IN ILLINOIS

A statewide study of Panax quinquefolium L. (American ginseng), a herb commonly collected for commercial sale, was conducted on 33 protected and unprotected forested sites in the northern, central and southern sections of Illinois. Within these sites, data on the tree, sapling, seedling, shrub and herbaceous strata, and on soil texture and nutrients were collected from a 0.05-ha circular plot in each site. Additional recorded site data included aspect, slope position, steepness and exposure, and disturbance from grazing or timber harvesting. Populations of Panax quinquefolium were found in stands dominated by Acer saccharum, Quercus alba or Q. rubra and with a variety of other herbaceous species common to cool, moist site conditions; 84% of the sites were located on NW-, N- and NE-facing slopes and 80% were in mid- to low-slope positions. Phenological events began in early May and progressed from S-N; plants were dormant by mid-October. Seeds from individuals growing on several sites within each region were planted at the time of leaf senescence. Seedlings did not appear until the 2nd spring; 66% of the seeds produced seedlings. An anatomical and morphological study of 30 whole field-collected plants indicated that plant age could be accurately determined by counting bud scale scars on the rhizome. These data were used to develop a multiple regression model to predict rhizome age from stern height and number of leaflets. For 30 field-collected and 65 forest-cultivated roots, average weight increased linearly up to age 20, the age of the oldest roots. Population age structure and fruit production on protected sites were compared with that of sites where roots had been removed by collectors. We found fewer plants of all ages on unprotected sites. Fruit production was lower on unprotected sites because fewer 5- to 11-yr-old plants limit fruit production and rate of population recovery after harvesting.