My Lawn Has Never Looked This Bad!
Tony Koski, Extension Turf Specialist

Winter desiccation (aka "freeze-drying); made worse because the thatch layer was a little
thick? Probably some rabbit activity, and maybe some cranberry girdler as well? That 
combination will kill grass in the best of lawns during a severe winter.

It seems like nearly every lawn up and down the Front Range has experienced some level of turf injury this spring – more than I can remember in my 30+ years at CSU. Many have been cared for by avowed lawn geeks (like Alison’s lawn, pictured here!). These folks are used to turf perfection, so are especially shocked, dismayed and embarrassed by the spots and patches that have appeared in their normally picture-perfect lawn. What has caused so many beautiful (in 2021, anyway) lawns to become so bad this spring that owners are reluctant to send me pictures of them? Pinning down the exact cause of the turf damage without visiting the lawn can be difficult, but if you are seeing dead patches in your lawn this spring it’s almost certainly one of the following problems. Lawns that were seeded or sodded in 2021 (especially later in the year) were more likely to be injured. If the lawn hasn’t greened up by this point in time – especially after the recent rain – then it’s almost certainly dead, with the solution being new sod or seeding (go here

for some videos on seeding and sodding lawns https://planttalk.colostate.edu/youtube-videos/lawn-videos/#reseed)

Winter Desiccation (freeze-drying)
This is probably the most common cause of lawn damage this spring, most likely to occur on areas of the lawn that were drought-stressed going into winter last fall.  Turf stressed by poor irrigation coverage in 2021 (broken/plugged/low/crooked heads, low pressure, bad spacing) was more susceptible to being damaged by the dry, cold, sunny, windy winter conditions we experienced this year. Lawns with thick layers of thatch also appear to be more likely to have been injured. Check spots that are dead now for irrigation coverage deficiencies – before re-seeding or sodding. You rarely can detect non-uniform water application by simply watching your sprinkler system (“It looks like water is going everywhere” you say…but it’s not going everywhere uniformly). Don’t blindly trust your “irrigation guy”/sprinkler company when they tell you that everything “looks fine”. To be certain about uniformity of water application, it has to be measured by a formal or informal irrigation audit (here’s a DIY method to help you identify dry spots in your lawn).

This turf died from winter desiccation. When you can see where the
irrigation heads are, you know there are irrigation coverage problems. The
dead areas in this lawn were drought-stressed LAST FALL - which resulted
in the turf succumbing to the severely dry and cold winter. The turf also 
survived around the young tree - because of winter watering of the tree.

Insect Feeding Damage

Feeding by cranberry girdler (https://csuhort.blogspot.com/2020/10/cranberry-

This lawn was weakened by cranberry girdler feeding
last fall (2021); the cold, dry, windy winter resulted in
the death of the stressed turf

girdler-rears-its-ugly-head.html) or white grubs (https://extension.colostate.edu/topic-areas/insects/billbugs-and-white-grubs-5-516/) last fall could have gone undetected and so weakened turf root systems that the turf more easily succumbed to winter desiccation. Dead turf that peels up easily from the soil surface was likely fed upon by these insects. If the lawn hasn’t greened up by now, it’s dead and the only alternatives are to seed or sod the affected areas.

Turfgrass mites damaged this lawn. Notice the
lack of mite injury in the neighboring lawn (top
of photo) which received winter watering.

Mite Feeding

Winter mite activity can kill large areas of turf, usually on lawns facing south or west. The damage caused by winter mites can look identical to winter desiccation injury: orange or brown grass (early death), changing to grey/silvery grass (dead for awhile). Mite-damaged turf will still be strongly rooted, distinguishing it from damage caused by root-feeding insects. Even when mites are actively feeding in lawns, they can be difficult to detect – so mite injury is often confused with other types of winter damage. The best control for mites is late winter/early spring irrigation, or a few good snowfalls or rainy spring weather. Since they aren’t insects, insecticides don’t provide great control of turfgrass mites.

Rabbit Injury

Look for rabbit pellets (aka "poop") in the brown spots
in your lawn as a sign of rabbit activity.

Rabbits feeding is often concentrated in small areas of the lawn. The persistent feeding and deposition of urine can kill small to large areas (depends on how many rabbits are in the yard) over the winter. Rabbits can be trapped and relocated (where legal; check with local animal control for the laws that apply where you live); applying the fertilizer Milorganite to your landscape (lawn and garden beds) can repel rabbits - if they have somewhere else to feed and live.

Rabbit activity can result in the death of large areas in the home lawn.

While it’s good to know what may have killed parts of your lawn – so that you can take measures to prevent the same thing from happening in the future – the “fix” is generally the same: repairing the dead areas by seeding or sodding (here and here, for how to do this).

Lawn Winterkill: Lessons from 2016-'17

Tony Koski' Extension Turf Specialist

It’s been a dry fall and early winter throughout most of Colorado – in spite of the recent snow (that’s rapidly disappearing as I write this today). Little precipitation, combined with windy, sunny, and warm days, is a pretty good recipe for some winter turf injury (aka “winterkill”). Throw in some alternating extreme cold with the warm days and things get potentially worse for turf, trees, and shrubs in our landscapes. But not all “winterkill” is the same when it comes to turf. Here are some examples from the spring of 2017 (these were all in April/May) to illustrate that point.

Winter injury from drought – enhanced by VERY thick thatch in this bluegrass lawn. Note that the green turf is where water was supplied by a gutter downspout, runoff from the driveway (plus the concrete acts as a “mulch” for turf growing alongside it), and runoff from the neighbor’s gravel-covered plastic.

This lawn had been sodded in early 2016 and was perfectly green and healthy going into the winter of

Dead area is where home construction had been "staged",
resulting in extreme soil compaction before sodding.

2016. It had been handwatered religiously throughout 2016, was mowed the correct height, and was otherwise perfectly cared for. The problem was the soil under the sod. The dead area was where home construction was “staged”: lumber, roofing, tile, other building supplies were dropped off – along with concentrated, heavy, constant traffic. The soil was not tilled sufficiently prior to sodding, so almost no rooting occurred following sodding. The constant handwatering in 2016 kept it alive and looking perfect, but the lack of rooting during the winter resulted in winter desiccation and sod death in spring 2017.

Sod had not rooted into the compacted soil, which
lead to winter kill in spring 2017.

Winter mite injury

This lawn suffered from turfgrass mite feeding in the late winter and early spring. Mite feeding and reproduction is favored by dry conditions. Drought-stressed turf is often killed by mite feeding in the spring if numbers are high enough and no snowcover or spring rains occur – and if winter watering isn’t performed at least a few times during the winter.

The common thread here? Water! Turf, trees, shrubs, and other landscape plants may not be growing and thus USING much water during the winter. But when it’s dry, windy, sunny, and humidity is low, our landscape plants are LOSING water. When we don’t receive enough snow to provide periods of snow cover during the winter, and plants aren’t mulched (like turf!), are young and not fully established, or have poorly developed root systems, winter watering can be essential for preventing winter injury or death.

When weather allows (above freezing for a day or two), run a hose and sprinkler out to the drier parts of your landscape (especially south- and west-facing parts of your landscape), to new sod, trees, and shrubs, and to areas where you have experienced winter injury in the past (perhaps from turf mites). Apply enough water to moisten the crowns of the turf plants and to get some water into the root zone of new trees and shrubs. The goal isn’t deep watering, but rather to prevent desiccation of crowns and young root systems.

Winter Water or Re-Sod, Your Choice

Posted by: Curtis Utley, Jefferson County Extension

Unless you have been living under a rock you will have noticed that

 we have been experiencing abnormally warm and dry weather

 this fall, and the long-range forecast looks to promise more

 of the same. In fact, NOAA reported: 

 
Native rocks which one could be proud to live under

...NOVEMBER 2017...DRIER AND MUCH WARMER THAN NORMAL...

AFTER AN OCTOBER WHICH EXPERIENCED A WIDE TEMPERATURE RANGE WITHIN

THE MONTH, NOVEMBER 2017 RECORDED A FAIRLY NARROW RANGE IN

TEMPERATURE DUE TO LACK OF EXTREME COLD. TWO DAILY HIGH TEMPERATURE

RECORDS WERE SET IN NOVEMBER. THE HIGH ON THE 26TH REACHED A RECORD

SETTING 74 DEGREES WITH 81 DEGREES REACHED ON THE 27TH. THE HIGH OF

81 DEGREES ON THE 27TH ALSO ESTABLISHED AN ALL TIME MONTHLY HIGH

TEMPERATURE RECORD FOR NOVEMBER. THE HIGH OF 81 DEGREES ON THE 27TH

EXCEED THE PREVIOUS MONTHLY HIGH TEMPERATURE OF 80 SET ON BOTH THE

6TH OF THE MONTH IN 2006 AND THE 16TH OF THE MONTH IN 2016.

AS FOR PRECIPITATION, NOVEMBER 2017 LANDED SHORT OF THE MONTHLY

AVERAGE AS PREDOMINANT STRONG WEST TO NORTHWESTERLY FLOW ALOFT

PROVIDED FOR FREQUENT BOUTS OF DRY DOWNSLOPE FLOW ALONG THE NORTHERN

FRONT RANGE. A FEW WEAK COLD FRONTS PUSHED THEIR WAY INTO NORTHEAST

COLORADO DURING THE MONTH, HOWEVER WITH LIMITED MOISTURE ASSOCIATED

WITH EACH ONE, ONLY LIGHT PRECIPITATION AMOUNTS WERE RECORDED. A

STRONG AND FAST-MOVING DISTURBANCE, WHICH PASSED ACROSS SOUTHERN

WYOMING AND NORTHERN COLORADO LATE IN THE DAY OF THE 17TH, PUSHED

RAIN SHOWERS ONTO THE LOWER ELEVATIONS AND GAVE DENVER THE HIGHEST

PRECIPITATION FOR THE MONTH WITH 0.23 ON THE 17TH.

AS THE THANKSGIVING HOLIDAY APPROACHED, A LARGE RIDGE OF STABLE HIGH

PRESSURE BEGAN TO DEVELOP OVER THE SOUTHWEST UNITED STATES ON THE

21ST. THIS STABLE RIDGE PERSISTED ACROSS THANKSGIVING AND INTO THE

NEXT WEEK WHILE KEEPING THE REGION AND DRY WITH WELL ABOVE AVERAGE

AND EVEN RECORD SETTING TEMPERATURES.

TEMPERATURES:

THE AVERAGE TEMPERATURE AT DENVER INTERNATIONAL AIRPORT FOR THE

MONTH WAS 45.3 DEGREES F, WHICH IS 7.0 DEGREES ABOVE NORMAL. THIS

NOW RANKS AS 10TH WARMEST NOVEMBER`S SINCE TEMPERATURES RECORDS

BEGAN IN 2017 1872. THE WARMEST NOVEMBER ON RECORD OCCURRED IN 1949

WITH AN AVERAGE MONTHLY TEMPERATURE OF 50.9 DEGREES F. THE COLDEST

NOVEMBER ON RECORD WAS OCCURRED IN 1880 WITH A MONTHLY AVERGAE OF

22.0 DEGREES.

TEN WARMEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

50.9 1950

47.2 1999

46.2 1933, 1914

45.9 1981, 1927

45.6 1910, 1917

45.5 1917

45.3 2017

TEN COLDEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

22.0 1880

28.9 2000

29.7 1985

31.5 1929

32.3 1952

32.5 1889

32.8 1972

33.0 1886

33.1 1872

33.3 1979

PRECIPITATION:

PRECIPITATION FOR THE MONTH OF NOVEMBER AT DENVER INTERNATIONAL

AIRPORT WAS 0.29 INCHES, WHICH IS 0.32 INCHES BELOW THE NORMAL OF

0.61 INCHES. THERE WERE 3 DAYS WITH MEASURABLE PRECIPITATION DURING

THE MONTH. 0.23 INCHES OF PRECIPITATION FELL ON THE 17TH, WHICH IS

THE GREATEST DAILY AMOUNT FOR THE MONTH.

TEN WETTEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

3.21 INCHES 1946

2.67 INCHES 1991

2.63 INCHES 1983

2.13 INCHES 2015

1.95 INCHES 1922

1.93 INCHES 1886

1.88 INCHES 1975

1.74 INCHES 1908

1.69 INCHES 1972

1.68 INCHES 1881

TEN DRIEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

TRACE 1949, 1901, 1889

0.01 INCHES 1939

0.03 INCHES 1917

0.04 INCHES 1905, 1904

0.05 INCHES 2003

0.07 INCHES 1903

0.08 INCHES 1920, 1874

NO THUNDER WAS OBSERVED AT DENVER INTERNATIONAL AIRPORT AND

4 DAYS WITH DENSE FOG WITH A VISIBILITY AT OR BELOW 1/4 MILE DURING

THE MONTH. THE PEAK WIND GUST OF 52 MPH FROM THE NORTHWEST OCCURRED

ON THE 1ST.

While attending the Rocky Mountain Regional Turfgrass Association Conference and Trade Show last week my colleague, Carol O’Meara and I were lamenting the fact that landscapes along the Front Range are going to suffer if the dry warm weather continues through the winter. Both of us planned on watering our landscapes a little, over the weekend, to prevent winter-kill from desiccation.

I also received a few calls last week from landscape maintenance companies concerned about protecting customer’s lawns from turfgrass mites which can kill drought-stressed turf in the winter months. This morning I decided to inspect the turfgrass outside of my office for mite activity and sure enough, I found clover mites actively feeding on the turf close to a south-facing retaining wall. Without natural winter precipitation or winter watering it is likely the clover mite population will explode and cause enough feeding damage to the quasi dormant turf to kill it out right.

Southwest facing retaining wall

Active Clover mites

Clover mites and Bank’s grass mites are cool-season pests of turfgrass along the Front Range and have caused economic damage to landscapes in the past and will kill turf this year too unless susceptible aspects of lawns receive irrigation or natural precipitation. To learn more about turf mites, check out the factsheet http://extension.colostate.edu/docs/pubs/insect/05505.pdf   

What does that mean? Damage caused by these cool-season mites is always most severe on south or west facing slopes (aspects) or on the South or West sides of evergreen trees, shrubs, buildings, walls, and fences, so focus your winter watering efforts on those areas of your lawn specifically. To learn more about winter watering, check out the factsheet  http://extension.colostate.edu/docs/pubs/garden/07211.pdf

South facing slope with mite damage

South facing side of a blue spruce

West facing slope with mite damage

Check for mite activity in your lawn by swiping a white sheet of paper over the lawn. Turn the paper over and examine it for small red streaks; the streaks represent crushed mites. If found, know that your lawn at that specific location is in peril and you should water. If the paper has lots of streaks, consider spraying that aspect with an insecticidal soap to knock back the population of mites then begin watering. To learn how to check for mites, watch this video

Next spring, if you notice the south and west aspects of your lawn are not greening-up with the rest of your lawn, check the margins of the damage with a clean sheet of white paper. If you find streaks, begin watering.The areas of turf that have not greened up by April are probably dead and should be re--sodded, reseeded or, consider mulching those areas and planting western natives in those locations. To learn more, check out this factsheet http://extension.colostate.edu/docs/pubs/garden/07241.pdf  or this Plantalk script http://planttalk.colostate.edu/topics/lawns/1517-sodding-lawn/ . A little water now may save you the cost of replanting, and a lot of water next spring to re-establish your turf.

Small red streaks are crushed mite bodies and indicate activity