Warm Fall 2003 Impacts Overseed in Southwest
The moans and groans started when September average air temperatures stayed stuck above 90F (with maximum temperatures hovering over 100F), and escalated to sobbing, kicking and screaming when they stayed high (rarely dipping below an average of 80F) through the first three weeks of October. In short, all of the elements for a difficult overseed were in place during the Fall of 2003. For while the objective of overseeding is to encourage the growth of cool-season turf types such as ryegrass and Poa trivialis, and to discourage the growth of bermudagrass, the weather this autumn conspired to create exactly the opposite effect. The above-average weather this fall has been absolutely ideal for bermudagrass, which flourishes when air temperatures are between 75 and 100F. These same warm temperatures have weakened the growth of ryegrass and Poa trivialis, both of which prefer lower air temperatures between 60 and 75F. When average temperatures climb to above 80F, ryegrass and Poa trivialis take a big dive. The survival of these cool-season turf types is further compromised by the fact that bermudagrass growth escalates rapidly at these temperatures, crowding out the weaker rye and Poa triv stands.
