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K-State Turfgrass

Month: January 2020

Ice, Ice Baby.

By Dr. Jack Fry

Ice can cause many problems for turf, in various forms.

Ice Inside the Plant

Ice routinely forms inside plants when temperatures drop below freezing. Where the ice forms is important – when it’s outside the plant cells, it’s usually not an issue. This is called extracellular freezing.  However, no plant cell will survive when ice forms inside it.

The most important part of the turfgrass plant regarding survival is the crown, or growing point. Again, ice forming outside cells inside the crown is common and usually not harmful. It can become an issue, primarily in warm-season grasses, like bermudagrass, when temperatures are very cold for extended periods of time. This forces water inside cells to exit toward the ice (a matter of physics), and too much water leaving the cells will cause dehydration, which can cause the crown to die.

Freezing injury on bermuda is caused by ice forming outside cells within the crown of the plant that causes dehydration.

Ice formation inside cells of the crown commonly causes the death of grasses in the northern U.S, and it’s called intracellular freezing or crown hydration injury.  Usually, grasses that succumb to this type of injury become well hydrated in early spring, often growing in low areas that don’t drain well. Hydrated crowns that are then subjected to extremely low temperatures often suffer from ice formation inside cells of the crown;  when this occurs, they don’t survive. This is common in the northern U.S. on annual bluegrass on golf greens. It could also occur here, but would be most likely on warm-season grasses lying in low areas.

Ice Covering the Plant

Fortunately, in the central U.S., we don’t deal with extended periods of ice cover on turf. Ice cover can result from sleet, freezing rain, or snow melting and refreezing. Turf managers in the northern U.S. begin to worry about ice cover when it remains in place for about 60 days. That’s usually the limit for annual bluegrass – being under ice cover more than that can cause issues with lack of oxygen and/or accumulation of toxic gases under the ice

Ice on the Leaf Surface – Frost!

In a humid environment, when the leaf surfaces cool to temperatures below freezing, ice will form as frost on the leaves. Leaves of cool-season grasses tolerate frost on leaves just fine. Leaves of warm-season grasses don’t like frost, and we often see them go dormant shortly after the first hard frost in the fall.

Frost on the leaf surface can damage when foot or vehicle traffic causes the crystals to puncture the leaf cells (photo courtesy of Dr. Hoyle).

Frost is primarily a problem for turf managers in spring and fall on cool-season grasses. Foot or vehicle traffic pushes the ice crystals through the leaf surface and punctures cells, causing them to collapse. The result is that there is often brown turf where traffic was present. Honestly, I don’t think we know enough about the physics of ice that comprises frost, and I suspect that frost differs a lot – some ice forming on leaves may be more damaging than other ice.

Following are a few articles related to frost on turf.

For golfers:

https://www.usga.org/content/usga/home-page/articles/2018/01/5-things-to-know–frost-delays.html

For superintendents managing golf courses:

https://www.golfcourseindustry.com/article/golf-frost-delay

Apparently, in Japan, golfers play year-round regardless of temperature.  Some courses ignore frost to sustain income and have had less damage than expected:

https://www.blog.asianturfgrass.com/2016/12/how-to-lose-120-million-yen-with-frost-delays.html

 

Seeding Tall Fescue in January? Sure!

By Dr. Jack Fry

Identifying seeding windows for cool-season grasses,  like tall fescue, in our region is often difficult because weather is so different year to year.  For example, for autumn seeding, October 15 is often suggested as the deadline for seeding in northeast Kansas.  Seeding after that date doesn’t mean that there won’t be success – some years there may be, others year not.  The concern is that germination and emergence may still occur after mid-October.  However, the seedling that emerges may not mature to a point where it can survive the cold, dry conditions common during Midwest winters.

Following the mid October deadline, the next window for seeding opens around Thanksgiving and continues into March.  We call it “dormant” seeding.  Dormant seeding means that the grasses out in the lawn now are dormant and not growing.  In addition, the seed you scatter in mid-winter will also remain “dormant” until warmer conditions and moisture return in the spring.  Unfortunately, some of us remain dormant until spring as well – outdoor work in midwinter may not sound attractive.  Tall fescue germination is optimized between soil temperatures of 59 and 72 F, so seed applied in winter will remain inactive in the soil until it warms to near 60 F, and it will then begin to germinate.  Other grasses are also candidates for dormant seeding as well, including other species of cool-season grasses, buffalograss, and bermudagrass.

Seed-to-soil contact is critical.  If conditions are dry, vertical mowing or slit seeding may be possible.  In addition, a light topdressing of soil applied over seed can also maximize seed-to-soil contact.  Seeding on frozen soil is also possible, and seed-to-soil contact is improved as the soil thaws and freezes, which creates cracks in the surface in which seed can lie.  Covering or mixing seed with the soil, where it will likely remain for a number of weeks before germination, also prevents it from being a source of food for birds and rodents.

Twenty years ago, Ward Upham, Extension Associate in Horticulture and Natural Resources, did a study to evaluate dormant seeding month effects on tall fescue cover in May.  He seeded plots on the 15th of each month from December through March onto bare soil that had been tilled and raked.  On May 18, plots seeded in February and March each had an average of 80% coverage.  December and January seedings were each at about 60% coverage.  Ward suspected that having seed out in the environmental longer made in subject to erosion and consumption by animals.

Advantages to Dormant Seeding:

  • Sometimes it is drier in mid-winter than early spring, which allows outside work to be done. Seeding in April and May can be difficult months for seeding during frequent rainfall.
  • Spring emergence will occur at the earliest possible date.
  • There may be more time and labor available now that’s not available in the spring.

Disadvantages to Dormant Seeding:

  • Weather doesn’t always cooperate, and midwinter may be too wet to get it done. However, if just small areas are needing seed, that can be done by hand.
  • Stand establishment may not be as successful as seen with autumn seeding, the preferred time. And, just like spring seeding, weed competition will be greater as the stand matures.
  • Preemergence herbicides applied in late fall or in spring may inhibit germination and growth of the seedlings. Preemergence herbicides that can be used in the tall fescue seedbed include siduron (Tupersan) and mesotrione (Tenacity).