Thank you Purdue and MSU for this explanation, which I think is pretty good:
What is a Growing Degree Day (GDD)?A growing degree day (GDD) is a method to track the heat units that have accumulated and are needed for plant growth and development. The formula for calculating GDD is: GDD = ((max temperature °F + min temperature °F) ÷ 2) - base temperature °F, where the base temperature is normally either 22, 32 or 50 °F but varies based on the model.
For example, if the high today was 74°F and the low was 52°F and we used a base temperature of 50°F, our calculation would be, GDD= ((74°F + 52°F) ÷ 2) - 50°F = 13
Models that help us predict plant development use accumulated GDD which is simply adding the GDD calculated each day and determining how many GDD units have accumulated thus far.
In some cases accumulated GDD can be used to monitor when weeds might germinate or flower or when grasses might produce a seedhead while in other cases accumulated GDD can be used to help optimize application timing such as with preemergence crabgrass applications or the selection of amines or esters for spring broadleaf applications. Research into plant development and optimal herbicide application timing has determined a window of accumulated GDD needed to best predict when to time these applications or when these events might occur.
The North Course aerification of greens, tees and fairways went great! Perfect weather - dry, low humidity and 65 deg - helped make this process flow perfectly. Thanks to the staff for the long hours and attention to details.
CORE AERATION is one of the “dirty” words of golf course maintenance. With a golf season of seven months, many would question the necessity of disrupting play each spring and fall.
An important purpose behind core aerification is the removal of unwanted organic matter, allowing roots to grow. With a healthier root system heading into the golf season, the grass plant is better able to withstand the stress of traffic. Aeration also relieves compaction, promotes air exchange and helps with water infiltration.
How much aerification is enough?
There is no rule of thumb for what percentage of surface area should be impacted each year. It would be safe to say however that it is difficult to “over aerify”. The USGA suggests that 15-20% of the surface should be aerified each year. This would dictate a larger hole size – and closer spacing between holes during the aerification process – both spring and fall. Changing from a 1/4” tine to a 1/2” tine increases the surface area impacted by four times. Using a 5/8” tine versus a 1/2” tine increases the surface area impacted by approximately 50%.
How long after aerification before the greens are back to normal?
With cooperative weather, the healing process will take 10 - 14 days. Extra fertilizer and water are applied at this time to expedite recovery.
WHY CAN'T WE HAVE CARTS ON THE NORTH COURSE EARLIER IN THE SPRING? Turfgrass still in winter dormancy has difficulty recovering from mechanical damage like cart traffic. Until the turf is showing signs of growth - and thus the ability to recover - we prefer to keep carts off the golf courses.
Our opportunity to provide excellent conditions later in the season will be enhanced if we limit the traffic damage incurred in the spring. We will allow carts as soon as possible. We are all anxious to get outside and enjoy the weather.