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Looks Like Grass… But It Isn’t

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Other than today and yesterday, soil temperatures in New Brunswick have been reaching into the lower 50s °F during the last week or so. And you see the effects, some plants are finally awakening from winter slumber. Cool-season turfgrasses are slowly greening up. Tree buds are swelling, some are flowering. Forsythia is just starting to bloom. And prostrate knotweed, one of the earliest germinating summer annual weeds, is emerging.

Prostrate knotweed is frequently found invading [Read more…] about Looks Like Grass… But It Isn’t

Winterkill on Annual Bluegrass: Don’t Skip the K

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We lost the ice cover on our Poa annua trials two weekends ago (March 7-8th) and initially the turf looked okay. But now… it doesn’t. And it will probably get worse, if we are reading the symptoms correctly.

Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Photo taken 15 March 2015. Healthier looking turf has received K fertilization; dying turf has not.
Blotchy, tan-colored plots and borders around this potassium trial are suffering from winterkill. Green, healthier looking turf received K fertilization; dying turf did not. (15 March 2015)

Last Friday (March 13), my graduate student, Chas Schmid, informed me that I needed to look at his potassium trial on our Poa annua turf. There was a huge difference between no-K and K fertilized plots. The no-K plots have steadily lost green color and become very blotchy. Plants taken from those plots are water-soaked and feel mushy when squeezed (How is that for a scientific description?). Dr. Lindsey Hoffman has a lot of experience with winterkill on Poa annua in Massachusetts and she is convinced that many of the plants are dead. And it smells like it – silage on a dairy farm!

Take home for me – don’t let your Poa annua turf become potassium deficient! Chas’ data for suppressing anthracnose severity indicates that a soil test (Mehlich 3) ≥50 ppm K and a tissue level of ≥2% K in the clippings are indicators that the K level is good. And winterkill in March 2015 hasn’t changed my mind about that data!

Looks like this might be the end of this Poa annua field. Dr. William Meyer said, “Good riddance.”

Traffic Alert: Damage Threat is High

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Damage to landscapes from traffic can be severe during winter and especially now during the thaw. Soil conditions currently range from being frozen to partially thawed/frozen to thawed.

Partially frozen soil will be thawed and very wet at the surface while being frozen at some depth below. Under this condition, soil and turf will be extremely vulnerable to shearing and rutting damage. Traffic, even light foot traffic, must be withheld when this condition exists otherwise severe rutting (soil displacement) will occur.

Severe rut in partially thawed soil.
Severe rut caused by a wheeled vehicle driving on partially thawed soil.

Soil temperature has been “stuck” at freezing for some time now. Today is the first time this year that I have noticed the 2-inch deep bare soil temperature was above 33 °F (> 35 °F at the time of writing this post) at the New Brunswick Rutgers Gardens weather station. Interestingly, the 2-inch soil temperature under sod at this station remains only tenths of a degree above 32 °F, illustrating the insulating effect that vegetative cover has on soil.

Keep in mind that just because a soil has thawed doesn’t mean it is out of danger from traffic. At this time of year, soil will be very loose from frost heaving and very wet or saturated. Soil on very well drained sites will firm up sooner than poorly drained sites but all sites will be very susceptible to damage from traffic for some time after a thaw. Care should be taken to avoid traffic of any kind when the soil and turf is vulnerable.

Allow soil to thaw completely and drain to at least field capacity (preferably drier) before allowing traffic on the landscape. Draining and drying will help to re-settle areas that frost heaved. Light-weight rolling may be need on soil that experienced extensive frost heaving and remains too loose after draining and drying.

Localized Drought Stress is Here

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As stated in an early post, summer stress is developing throughout the state. Summer stress isn’t widespread or severe but it is developing, particularly wilt stress, within very localized areas of many landscapes. Landscapes that receive little to no irrigation are especially prone to wilt and drought stress right now.

It is important to scout and assess the severity of any wilt stress in moderate-to-high value areas of the landscape. Hours are important, don’t put off the scouting of wilt stress. Assuming the grass or other plants will tolerate wilt stress without confirming the severity of the situation can lead to severe drought stress and stand loss at this time of year.

Symptoms of subtle wilt stress.
Symptoms of subtle wilt stress on June 22. Healthy turf will likely to tolerate this level of wilt stress.

Grasses such as the fine fescues and annual bluegrass will be

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Crabgrass Emerging

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Crabgrass has been emerging for several weeks now, depending on the exposure. Warmer and more open turfs will likely have more advanced (larger) plants while cooler and denser turfs will have smaller plants.

Relatively small crabgrass plants.
Relatively small crabgrass plants (most pre-tillering stage) emerging from a footpath on June 11th.

Management options for this weed at this point in the season range from doing nothing to

[Read more…] about Crabgrass Emerging

Tis the Season for Summer Stress

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Optimum growth of cool season grasses occurs within the temperature range of 60 to 75 °F. Yesterday, the New Brunswick weather station indicated that soil temperature at 2 inches exceeded 75 °F for more than 12 hours and peaked at 82 °F.

This doesn’t mean that grasses will soon be dead. But it is a signal to be watchful for summer stress problems.

Summer stress is often a combination of multiple stresses. Localized drought, ponding of water, diseases, insect pests, poor culture (mowing, fertilization, and irrigation) and other stresses combined with high temperature stress can challenge the health and persistence of cool season turfs from now through the end of summer. It is important to avoid situations that compound too many stress at the same time.

For example, now is the time [Read more…] about Tis the Season for Summer Stress

Right On Cue: Dollar Spot Disease

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Exactly like Dr. Bruce Clarke teaches, Memorial Day arrives and so does dollar spot disease.

Symptoms appear as round, brown to straw-colored spots approximately the size of a silver dollar. On short cut turf, the spots with advanced damage can become somewhat sunken. At taller cutting heights (greater than 1 inch), the damaged spots are larger and more diffuse.

Highly susceptible grasses will be the first to exhibit symptoms including annual bluegrass, creeping bentgrass (depending on cultivar), and perennial ryegrass. Tall fescue and most Kentucky bluegrasses will be more tolerant of this disease.

Cultural techniques that can suppress dollar spot disease include disruption of dew and guttation water in the morning and increasing N fertility (if it is low). Mowing early in the morning (disruption of dew) should also be helpful.

Creeping bentgrass.
Creeping bentgrass entries in Dr. Stacy Bonos’ evaluation trials that are highly susceptible to dollar spot disease appear in the image foreground.

Drought Ends in New Jersey

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Last autumn I was blogging about the drought conditions that we were experiencing. Thankfully, this winter’s precipitation, albeit lots of snow, has changed our water status in the region. The U.S. Drought Monitor no longer lists New Jersey as having abnormally dry or moderate drought. You can view more details at http://www.nrcc.cornell.edu/page_drought.html

Expect I will have to post about snow mold disease and flooding, once we get a thaw.

A drought monitor map of the Northeast.
The current drought monitor map of the Northeast.

Abnormally Dry to Moderate Drought Condition in Much of NJ

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I mentioned in my previous post that dormancy has been apparent in many non-irrigated turfs. These conditions still persist throughout the central and northern NJ.

You can view the distribution and severity of the dry conditions throughout the northeastern U.S. at http://www.nrcc.cornell.edu/page_drought.htmlThis map shows that southern NJ is not experiencing drought conditions; whereas, central NJ is experiencing abnormally dry conditions, and northern NJ is experiencing moderate drought. This dryness typically doesn’t last through winter but it is something to watch. Moreover, you should assess your landscapes for any potential susceptibility to winter desiccation.

I want to share a some observations and ideas that have  come up while discussing this topic with turf managers.

  1. In those areas experiencing limited rain this fall, there has been very little recovery from summer stresses on non-irrigated turfs (and other plantings). These turfs may benefit from an application of a slow release N source to ensure recovery starts when water levels improve in late winter and early spring. Recall that NJ prohibits N applications to turf by professionals after December 1st (except on golf courses).
  2. While dry soil conditions this fall may have induced dormancy of the grass, the grass may be vulnerable to extended dryness through the winter especially in localized areas of turf that are sloped (water runs off) and exposed. These dry areas could experience desiccation damage if there are cold harsh winds combined with little to no snow or rain. If feasible, some irrigation of these areas before winter sets-in may be helpful in avoiding winter damage.
  3. Localized dry areas may have developed water repellency (become hydrophobic). These areas could benefit from an application of wetting agents to improve infiltration of rain and snow melt into the soil. Even if the soil is not hydrophobic, wetting agents will improve water infiltration of irrigation or winter precipitation.

Let’s hope that precipitation becomes more typical where it is currently dry.

Have a Happy Thanksgiving!