Comparative Morphological Development of Divergent Flowering Types of Annual Bluegrass and Tillering Types of Creeping Bentgrass

Annual bluegrass (AB; Poa annua L.) competition in creeping bentgrass [CB; Agrostis palustris Huds. = A stolonifera var. palustris (Huds.) Farw.] turf under short mowing management is of a primary concern for golf superintendents in the Atlantic region of Canada. The objectives of this study were to (i) characterize relative timing of occurrence of key events in development, and (ii) leaf and internode growth and development of two divergent flowering biotypes of annual bluegrass and two divergent tillering types of creeping bentgrass. Two AB germplasms, early (PAE11) and late (PAL11), and two CB germplasms, UM67-10 (high tillering) and ‘Emerald’ (low tillering), were examined. Leaf appearance, first tiller appearance, leaf stage (Haun scale), internode elongation, inflorescence appearance, and internode number were monitored throughout the study. Haun scale provided a good baseline for determination of developmental stage, whereas West scale better defined comparative timing for tiller initiation, internode elongation, heading, and flowering. PAE11 produced an inflorescence following the seventh or eighth leaf on the main stem [≈25 d after transplanting (DAT)], with anthesis by 35 DAT. Tiller initiation was earlier for PAL11 and UM67-10 compared with Emerald. Internode elongation was at least 4 d earlier for CB than for AB. Emerald and UM67-10 usually elongated above the third node on the main stem compared with the sixth node for PAL11. At 35 DAT, UM67-10 had reached the greatest leaf stage. PAE11 was highest on the West scale. West scale limitations resulted from lack of reproductive initiation by CB and PAL11. PAL11 had significantly higher root and shoot dry weights, root:shoot ratio, and more adventitious root growth than CB. Earlier internode elongation in CB may have diverted carbohydrates from root and leaf production. Internode lengths were greatest for Emerald, then UM67-10, followed by PAL11. Blade length was least for UM67-10. Sheath length increased with successive leaves. PAL11 had a quicker leaf appearance rate at earlier growth stages than CB. Delayed internode elongation in AB may provide an advantage in establishment from seed in an existing stand.