Annual bluegrass ( Poa annua)

Annual bluegrass (Poa annua) has been very difficult to control ever since maintenance and weed control use on desirable turf grass began. Despite the industries technological advancements with weed control products, annual bluegrass continues to be problematic in most turf grasses. One of the main reasons is that annual bluegrass has become highly adapted to turf grass environments over time. Maintenance practices which include mowing, irrigation and weed control are also factors. Weather patterns are a large factor as well as turf grass type, drainage, soil type, soil pH and soil compaction. Another factor is that poa annua has both annual and perennial biotypes. Poa annua can tolerate being mowed at 1/8 of an inch and still produce seed. It’s a very prolific seeding plant and one plant can produce over 2000 seeds and create many different generations over changing seasons. New research has shown that it can germinate year round even though most germinate during early fall and the following spring. The available preemergent herbicides do a good job controlling poa annua  most of the time when all the factors are in favor but it only takes one factor to affect good results. The preemergent herbicdes help keep the germinating poa annua seeds from establishing a root system and therefore the seed cannot survive to become a mature plant. These herbicides are designed to bind to the soil where they are applied and provide a layer that is present in the top few inches of the soil. However poa annua has adapted itself to be able to have the seeds survive high in the soil line and in the layer of dead material just above the soil line during the summer months. Most visible poa annua in March is due to this adaptation. The seed is able to germinate above the preemergent line and develop a shallow root system that has been stunted when it hits the preemergent line. Unfortunately there is no available preemergent that can stay up high in the soil near the surface.  The available post emergent weed controls do well but most take several (6-9) weeks for results and new generations of poa annua can appear depending on certain factors. Fortunately this winter annual does not survive the summer heat in our area and will begin to die out naturally as the temperatures warm into  the mid 80’s consistently. Be aware that treating poa annua post emergently during the spring transition may cause a delay in the green up of your turf. 

Even under the best lawn maintenance program, concerns or issues may arise between treatments due to seasonal, weather, or any number of causes or conditions. The annual treatment program includes three free service calls to address any concerns. Contact our office at 770-632-7288 or www.aabbylawncare@bellsouth.net to request a service call and to schedule any beneficial service.