Annual bluegrass (Poa annua L.) is a prolific annual grassy weed that can be found worldwide in most landscapes. Known for its ability to produce seedhead at low heights (0.32 cm), thrive in over-maintained areas, and germinate anywhere, annual bluegrass is a highly invasive weed. Due to annual bluegrass’ persistence, those managing this weed have noticed several populations resistant to an array of commonly used herbicides. As herbicide resistant bluegrass becomes a nation-wide problem, researchers are seeking non-chemical means for annual bluegrass management.
A greenhouse nutrient management study sought to determine the effects of phosphorus (P) fertilization on annual bluegrass growth and development in a mixed stand with perennial ryegrass (Lolium perenne L.), at two different seeding timings (annual bluegrass seeded at the same time as the perennial ryegrass, or annual bluegrass inter-seeded into a 45 day-old stand of perennial ryegrass). This study determined that increasing P fertilization also increased percent annual bluegrass when bluegrass was seeded at the same time at the perennial ryegrass. However, when the annual bluegrass was inter-seeded into a 45 day-old stand of perennial ryegrass, percent annual bluegrass establishment decreased when P fertilization increased. In both experiments, clipping dry weight used to quantify P uptake showed that no P resulted in the fewest clippings while the addition of P significantly increased clipping yield. Perennial ryegrass cultivar played an inconsistent role in annual bluegrass establishment or clipping yield.
The objective of the second study, conducted in a growth chamber, was to assess the effect of Kentucky bluegrass (Poa pratensis L.) clipping extract (5.0 g of powdered field clippings + 175 ml deionized water) versus deionized water (175 ml deionized water) on the germination, shoot length and radicle length of three common turfgrass weeds: annual bluegrass, large crabgrass (Digitaria sanguinalis L.), and common dandelion (Taraxacum officinale spp. Vulgare (Lam.) Schinz and R. Keller). The Kentucky bluegrass leaf extract decreased weed germination and radicle lengths compared to the DI water treatment, but had no effect on the shoot length of the weeds. These projects seek to reduce annual bluegrass populations using non-chemical means such as allelopathy and nutrient management and suggest these concepts have potential use in weed management.