Comparison of the morphology, flowering phenology, and life cycle type in plants of Grindelia lanceolata (asteraceae) from cedar glades in middle Tennessee and northern Alabama: A common garden study

The life cycle type of Grindelia lanceolata Nutt. has been described as biennial, short-lived monocarpic perennial, and (polycarpic) perennial in the taxonomic literature. Plants of this species in middle Tennessee cedar glades clearly are monocarpic. However, field observations suggested that those from glades in northern Alabama are at least dicarpic, and further that they differ morphologically and flower later than those in Tennessee glades. The purpose of this study was to determine if differences in morphology, flowering phenology, and/or life cycle type of Tennessee and Alabama plants are retained when grown from seeds in a "common garden" - i.e., in a nonheated greenhouse in Lexington, Kentucky. Morphological differences (all statistically significant) between G. lanceolata plants from Tennessee and Alabama were measure in the following: (1) size of both rosette and stem leaves; (2) number of secondary basal stems; (3) height of primary stem; (4) number of capitula per plant; (5) number of ray and of disk flowers per capitulum; (6) diameter of capitulum; and (7) length of ray flower corolla. Tennessee plants began flowering about 1 month earlier than Alabama plants, and none of them produced basal rosettes after they flowered once (in their 2^nd year), confirming that they are strictly monocarpic. Alabama plants also flowered first in their 2 ^nd year; however, 66% of them have produced basal rosettes (which bolted and flowered) for five consecutive growing seasons, confirming that they are polycarpic. Also, individual Tennessee plants potentially can produce twice as many seeds as individual Alabama plants during a single flowering/fruiting period. These results strongly suggest genetic differences exist in vegetative and floral morphology, flowering phenology, and life cycle type between Tennessee and Alabama plants of G. lanceolata. We speculate that these differences could be associated with different ancestral geographic origins: Tennessee plants from a monocarpic race in the Ozarks and Alabama plants from a perennial race in the Southwest.