Overseeding is the process of changing turf from a summer Bermuda grass to a winter rye grass (there are various variations of each grass). Essentially, the Bermuda grass doesn’t like to grow much when temperatures get below 80 degrees and it actually turns yellow from frost when the temperatures go below freezing. Rye grass prefers the temperatures to be in the 80’s or below and handles the frost just fine (as long as you don’t walk on it while frosty – thus the reason for frost delays).
Without being too technical, the overseeding process in the Phoenix area usually starts somewhere between mid-September and late October and lasts from 12-21 days depending on the course (another 7-10 days if you count discontinuing the water prior to starting).
The first step is to mow the Bermuda grass down as low as possible which turns it yellow. After cleaning up the clippings, Rye grass seed is spread throughout the course. The greens use a special blend of seed developed just for the low mowing heights. Once the course starts watering the seed, it usually takes 5-7 days to “pop” and begin to root into the soil as it grows. The course is watered several times per day as the seed must remain hydrated for optimal growth. Many courses will allow play to begin on the newly growing grass within a week of it “popping.”
Mowing heights are kept higher than normal upon opening to help keep the new turf healthy and the heights are slowly lowered every few days or per week. This is why putts on newly overseeded greens will usually roll much slower than normal. They will also break less on most putts.
Most public courses are closed for as little as 12 days which allow for the extreme mowing, seeding and seed growth. Private courses and courses with 36 holes will often keep the course closed for 19 – 26 days. Normally, a course will look great upon opening but the grass is still a little thin and will take a few to several more weeks to get dense.
It might be good to note that some high end courses – usually private courses – have Bent grass greens in the valley so they don’t have to overseed the greens (only the fairways, roughs and tees). These courses are great options to play when most courses are just opening up from the overseeding process and have slower greens.
If you have a choice, it is usually better to play a course that has been open a few weeks after overseeding compared to a course that just opened but that doesn’t mean you can’t have an enjoyable round on opening day. The weather is usually ideal in October so just enjoy the day and hit your putts a little harder than usual. *Please note all dates are subject to change due to weather or other factors – please contact each course directly for the most up to date information.