Annual and Biennial Flowering Habit of Kentucky Bluegrass Tillers

Abstract

A stand of Kentucky bluegrass (Poa pratensis L.) consists of a collection of leafy tillers at various stages of development. Tiller morphology over 2 yr of growth was studied by sampling 3‐yr‐old dryland fields to determine tiller ages and to test whether burned and nonburned fields show different proportions of tiller types. Three classes of tillers were identified and named (i) small newly emerging nonleafy D tillers, (ii) leafy F tillers that grow directly from D tillers, and (6) leafy C tillers that have persisted for at least a year before flowering. On the basis of measurable floral features, C tillers are larger, more robust, can be induced sooner in the fall, and produce panicles of greater production potential than F tillers. Our results show that bluegrass tillers can be annual or biennial in flowering habit. Dense populations in burned fields produce higher proportions of D tillers in mid‐fall than non‐burned fields, but similar proportions of C and F tillers throughout the growing season. Fall regrowth may thus influence stand composition over a 2‐yr growth cycle. Assessment of tiller density should be a useful tool for grass seed growers when they are designing new management strategies, since annual F and biennial C tillers are found in all of the cultivars examined. Given pressures to avoid open‐field burning, alternative methods can be tested by determining changing proportions of C to F tillers. Manipulation of the balance between annual and biennial tillers may contribute to improving yield in the absence of open‐field burning.