Maybe Spring will show up in much of the northern US states? Still, well before many are mowing north of the Mason-Dixon line, the annual bluegrass seedhead suppression discussion is underway; "What combination of products do you use?, What growing degree day (GDD) timing model do you look at?, Do you use phenological (plant) indicators?" All good questions but....

Why not use soil moisture?

In other parts of the world where chemical technology is more restricted and less available, you become more in-tune with the way annual bluegrass flowers. You have to understand the ambiguity in the triggers such as light, temperature and moisture for timing the flush. This information then allows better timing of cultural approaches such as brushing and grooming programs employed to "harvest" the seedhead.

So why in our part of the world do we focus almost exclusively on temperature via GDD models? Especially now that most facilities can reliably measure soil moisture?

There is a ton of ecological research on this issue regarding the prominent influence MOISTURE has on annual bluegrass adaptation and phenology (the appearance and development). Much of this work comes from the west Youngner and Gibbeault, as well as more recent work by Paul Johnson and my old pal Tom Cook! In all these cases there are distinct adaptations and phenological responses to moisture.

Professor Bill Johnston of Washington State University published a paper in 2005 on the influence of climatic region in the Pacific Northwest on greens-type annual bluegrass adaptation. They found clearly that the best turfgrass quality and fewest seedheads were found on plants that came from cool moist climates. Now what does this tell us about seedhead production. To me it confirms what I often see, dry Spring's result in the most defined and prolific seedhead flush.

So why not consider looking at your temperature models AND take soil moisture measures? How often do you spray all the greens within two hours of each other and see the dramatic difference in seedhead suppression? This could be light and moisture in addition to temperature. But now that you have a reliable method for measuring soil moisture, WHY NOT track that as well.