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.

Making Lemons From Lemonade

by Mary Small, CSU Extension

State Master Gardener Coordinator

As you’ve probably guessed, this is not about the cold beverage made from oval yellow fruit. It’s about those not-so-nice things that sometimes happen in the landscape.

I planted a climbing yellow rose (can’t remember the name) in the garden. It performed beautifully for several years. Yes, it had some winter dieback every year as roses do in our climate, but nothing like what happened following the November 2014 polar vortex. That took the whole thing out.

I didn’t get around to digging it up last year and it sprouted from below the graft union.  Since I was going to take the thing out, I just ignored it and I think it ignored me, too!

Unidentified fragrant rose

This spring, before I got around to digging it up, the canes rewarded me with the most beautiful apricot colored, fragrant blossoms! The little garden adjacent to the rose is dreamy with its scent. And to think I almost destroyed it!

Young oak is growing well

We used to have a 10 year old catalpa in our front yard. It looked kind of like a Dr. Seuss tree as the top had been broken out of it. But it provided wonderful, cooling shade. A few years back, an early fall snowstorm broke out so many branches that it finally had to be removed. We replaced it with a small oak tree and complained about the lack of shade.The oak has only been planted for three years, but it has put on more yearly growth than I ever expected. Now that catalpas are blooming, I’m reminded that I don’t have to rake up their flower stalks, leaves and seed pods anymore!

Alison O’Connor, one of our bloggers, lost a large maple in a tornado several years back. But it

gave her the opportunity to plant other trees and plants that she wanted to grow. Just look at the before and after pictures. I think you’ll agree the tree loss was really a net gain.

Spring 2016

Alison also lost her vegetable garden in a severe hail storm. (Are we seeing a pattern here?) She turned the loss into lemonade by planting a cover crop – which improved her soil for the next season.

Smashed tomato after hail

Sometimes those gardening “mishaps” or “missteps” actually turn out better than expected...or planned!

9 weeks later, a cover crop!

Warm Weather and Winter's Return

Posted by Eric Hammond- Colorado State University Extension Adams County

 

“Gosh it’s just so beautiful out today”

“Can you believe the weather?  We are so lucky we live in Colorado!”

“It’s flip-flop weather, I love it!”

These are the kinds of statements I have overheard over the past few weeks while the high temperatures have been in the 60’s and 70’s.  As much as I have enjoyed going jacketless, I have to confess these sorts of comments are starting to make me cringe.   

This heat wave started in early February (yes I used bold, underline and italics).  Sure, it’s not uncommon for us to experience a warm day here or there in the winter.  It’s one of the perks of living in Colorado.   However, this has been two solid weeks of warm weather.  Even the mid-week storms we have had were short lived “warm” storms.   These consistently warm mid-winter temperatures come with significant risk for landscape plants.

Some of the effects of all this abnormally warm weather are easy to see.  For example, many spring bulbs are already coming up.  Daffodils, crocuses and even some tulips are already peaking up, especially on the west sides of structures.  Some cool season weeds like redstem filaree and cheat grass (downy brome) have germinated are actively growing and consuming water and nutrients from the soil.   Beyond landscapes many winter annual crops such as winter wheat, encouraged by the warm weather and warming soil temperatures have been actively growing and may now be at risk if we receive a sudden hard frost.



Many spring bulbs have already sprouted

What worries me more is the changes in plants we can’t see that are brought on by the warm weather, especially in woody plants.  These plants go through a complicated and gradual process to acquire hardiness in the winter.  The main goal of which is to avoid the formation of ice crystals within their cells (this process is fascinating in a science-geek sort of way and more information on it can be found here: http://www.warnell.uga.edu/outreach/pubs/pdf/forestry/cold%20tolerance%20pub11-12.pdf).    This process is reversed by consistent warm temperatures leaving woody plants at risk if temperatures suddenly drop again.   

If woody plants have lost of some hardiness during the last couple weeks we might see several things if temperatures should suddenly drop:



·         The death of small outer branches of trees.  These branches are more exposed to cold air and do not have the thermal mass of larger branches to buffer them against temperature changes.

·         Frost cracks in trunks and larger branches.  Cambial tissues which have lost hardiness or which have damaged tissues from a previous cold event (like the early November freeze we had last year) are prone to frost cracking.



Arborvitae damaged by sudden cold temperatures last November.  Many woody plants were damaged by this event

So what can we do as gardeners and landscape managers to deal with fluctuating temperatures?



·         Use organic mulches such as woods chips or straw.  Organic mulch acts as an isolator which helps to mediate soil temperatures.   During the day, soil under an organic mulch does not get as hot (it’s insulated from solar radiation) and during the night the soil may not get as cold (it’s insulated from cold air).  Keeping the soil cooler during the day may help prevent bulbs from prematurely sprouting and help trees maintain cold hardiness.

·         Avoid pruning until early spring.  Pruning cuts can lead to cracking when exposed to extremely cold temperatures or rapid temperature fluctuations.



·         Wrap the trunks of young trees to help insulate them against temperature changes.  Trees should generally be wrapped around Thanksgiving and unwrapped at Easter.  Paper wraps are preferred to plastic.  More information can be found here:  http://www.ext.colostate.edu/ptlk/2111.html and http://www.ext.colostate.edu/pubs/Garden/02932.html

·         Protect spring bulbs which have sprouted with a thick layer of organic mulch (cover the plants).  Mulch can help insulate the tender shoots of bulbs from cold temperatures, to a point.  Be sure to remove the mulch in the spring, as deep mulch can restrict gas exchange and lead to low soil oxygen levels. 

·         Winter water when appropriate.  Plants that are healthy better tolerate most environmental stresses.  More information on winter watering can be found here: http://www.ext.colostate.edu/pubs/Garden/07211.html

Winter watering should be done about once a month if
we don't have significant snowfall

·         Follow other best management practices to improve plant health.  Plants that are healthy and have higher energy reserves are better able acclimate to changing temperatures.

·         Use appropriate plant material and site more tender material in sheltered sites.

·         Don’t panic.  No one can control the weather.

 

It does not look like temperatures are going to drop quite as severely tonight as was forecasted last week (at one point the low for Tuesday morning was forecasted to be just north of 0 degrees Fahrenheit) and I’m not saying that next time your co-worker, significant other or neighbor gushes about the warm weather you should lecture them on cold hardiness in plants, or normal weather for February in Colorado.   However, you might chime in with a word of sympathy for the plants or remind them to winter water.  Colorado is a tough place to be a plant.

When It's Cold Outside...

Posted by: Linda Langelo, Horticulture Agent, Golden Plains Area

....you can always add more layers to your clothing.  But not your plants, they are open to the elements.  When plants are exposed to high winds, fluctuating temperatures from warm to cold, there is water loss within the foliage.  This is called desiccation.  What is the best care for your plants? Here are some tips:

• Knowledge of proper site selection for all your plants reduces stress and helps with winter injury, even with tender evergreens and perennials.
• Providing protection for your plants by appropriately placing them nearby structures and other plantings.
• Watering well before the ground freezes in late autumn hydrates plants giving them a good start.  When the ground freezes, the root system cannot uptake any water.
• Fertilizing plants appropriately will help reduce plant stress.
• Mulching around plants in the fall helps protect the root system by helping to maintain a steady soil temperature.  Do not mulch shallow rooted plants too deeply such as carpet bugle, thyme or blue fescue.  A mulch of about 2 inches will suffice.  Other plants can tolerate mulch up to 4 inches.  Too much mulch mitigates the oxygen in the soil available for the roots.  Shallow roots can get pushed out of the soil during the freezing and thawing of the soil over winter.  When mulching around trees, do not place mulch against the trunk which creates a condition of excess moisture.  This moisture attracts mold, fungus and insects to the bark.
•  Using burlap as screening about 18 inches from the evergreen tree or shrub to help reduce the impact of winter winds.  However, if you live on the plains this option can be helpful for certain plants in your landscape plantings but impossible for any windbreak.  Rather pay attention to the first two tips mentioned above.

  

  Burlap protects evergreen plants from prevailing winds.
  (Photo from "sunny" Ohio; Alison O'Connor)

• Winter mulches such as straw or evergreen boughs are good to use for perennials, bulbs, groundcovers and strawberry plantings.
•  Pray for snow.  Snow provides insulation for plants.

How can you tell if your plants are desiccated?  Damage appears as browning at the tips and margins of needles and leaves of plants.  Some evergreens may exhibit yellowing or bronzing of their needles. The injury will appear on the side exposed to predominant winter winds.  

Browning and bronzing of evergreen needles.
(Photo courtesy of the University of Maryland)

Yellowing needles on evergreens from cold injury.
(Photo courtesy of the University of Maryland)

On some shrubs, freezing and thawing can turn to browning and blighting of the shrub.  Another sign of winter injury is blackened buds or buds that are dry and brown.  In trees, the bark can split due to the fluctuation in winter temperatures.  As in the picture below, courtesy of University of Maryland Extension, de-icing products can cause leaf scorch on plants by the sidewalk or roadway. 

Salt injury to evergreen foliage from de-icing products.
(Photo courtesy of the University of Maryland)

In spring do not rush to prune off those browned or bronzed needles of your evergreen plants.  Wait until the weather warms up which may be the middle of May to early June for some of us.  Don’t let the brown foliage fool you.  Check the stems and look for any new growth.