The poa versus Bentgrass debate is always a contested one. Most say that you cannot grow Bentgrass in Southern California and that poa will out compete Bentgrass in the long run. "It is only a matter of time...." they say. We disagree.
For those of you that remember the tense summers at ACC in years past when the poa would struggle mightily or perish in the heat, I pose the question to you, "Which would you rather have, Bentgrass or poa?" Bentgrass can establish itself and be dominant in Southern California given that the correct management practices are being implemented.
One of the major benefits of Bentgrass is that it is more tolerant of abiotic (non-living) stresses on the extreme levels. I will focus on temperature for this post. The photos below illustrate the difference in root depth between a poa green and a Bentgrass green here in Southern California this summer. The poa root depth may be an inch. The Bentgrass, seven inches.
Root depth and mass are very critical to surviving the summer heat. When soil temperatures reach 80 degree Fahrenheit, new root growth ceases and the aging process begins. At above the mid 90 degree mark Fahrenheit, root hairs dye back and fail to function properly. When the air temperature exceeds 90 degrees fahrenheit, the soil temperature in the upper 1/2" can reach reach upwards of 100 degrees on a bright sunny day. When looking at the illustration below of the shallow poa roots, that can be deadly.
We have had a very mild summer to date and our soil temperatures remain in the upper 60's F in the early part of the morning. Those temperatures creep into the mid to upper 70's F in the afternoon.
Poa Green roots in July:
Bentgrass green roots in July:
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