DEGREE DAYS, WHAT ARE THOSE? – Homeowner Rx

Last year in April my article gave you some lawn maintenance 101 basics in my “Here Come the Dandelions!” article. This year we’re moving up to a 201 level class… Degree Days.

Most of my lawn care customers know that you have to put down your crabgrass preventer early, and that you better be ready for the attack of the dandelions following right behind. Well that’s a good rule of thumb to get you going, but have you ever heard of Growing Degree Days (GDD)? If you farm for a living, you got this already. If your job is keeping a golf course proper for an entire year, you know all this by heart too. Now let’s apply this knowledge to your front yard!

Growing Degree Days (GDD) is a mathematical equation that will actually calculate when your crabgrass seeds will germinate, or your dandelions will bloom. Seriously, you can figure it out! It might be hard to convince Mother Nature to bring us warm spring days, but it’s really not hard to figure when the dandelions will bloom. She has a rule that even if the daytime high is warm but the nights are still cold, she just doesn’t let the growing begin. So, a combination of the warmer highs and warmer lows have to be at a certain point to get things going.

To start the figuring, take your high temperature of the day, add to it the low temperature of the day, and divide that total by 2. That gives you your base # for the day. If the high is 66 and the low 40, your formula will be: 66 + 40 = 106 / 2 = 53 degrees. Do this computing for every day of the year starting January 1st.

Anytime your daily computing comes up with a number over 50, the closer to spring blooms we get. With the formula we used above, we are 3 degree days above 50, so you add 3 to your total for the year. You only count degree days above 50.  If the day produces a total below 50, nothing is added.

66 + 40 = 53 – 50 = 3 degree days accumulated that day.

Everyday you add or don’t add to the total. And here is the kicker, all weeds, flowers, trees, produce, grass, etc. do their different seasonal things once the GDD# gets to a certain point. A certain GDD level.

Crabgrass Seed Germinates at a GDD level of about 200. Dandelions at 140. I have Zimmerman Pine Borers after my pine trees. I spray them when the GDD gets to 100. And on average, adult mosquitos will make their appearance once the GDD reaches the 230 range. And on, and on. Pretty cool, huh?

When you get good at this, not only can you pick just the right time to battle the lawn weeds in your yard, but also some other intriguing things like when to plant vegetables, attack certain insects, and I even saw an article that set the proper degree day to tell you when turtles come out of hibernation!

The best website I have found to track our GDD is from Michigan State University.  www.gddtracker.net  You plug in your zip code and it will chart out exactly where we are currently at, and whatever the target # is for whatever weed you want to chase.

It looks like right now in Fort Wayne we are at about 60 Degree Days. Last year at the end of April we were over 240! So, get ready to battle and maybe this year with a little GDD knowledge under your belt, your success rate might just be a little higher!

Would love to talk to you about GDD! Got questions, come see me!

Dave Umber
Dave Umber

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