CO-Horts Blog

Thursday, July 29, 2021

Music for a Summer Evening


Posted by John Murgel, Douglas County Extension

The “dog days” of summer bring with them some of the most noticeable insect activity of the year—the sounds of insect calls.  Step outside during the afternoon or evening and you’re likely to hear a raucous mix of invertebrate “vocalizing”.  Here are three of the most common.

1. Crickets.  You’re probably familiar with the black, ground-dwelling Field Cricket.  And yes, they chirp.  But in areas with trees and shrubs (like most neighborhoods!) one of the most audibly noticeable crickets is the tree cricket.  They are green and slender and smaller than field crickets, and spend most of their lives in trees and shrubs.  Last year one of these managed to find its way into my house, and I can attest that they are loud.  Shockingly so.

     Primarily carnivorous (preying on other insects), the only plant damage that they cause is during egg-laying, when females make small wounds in twigs in which to oviposit.  These wounds can be unsightly as the plant grows over them, and may become entry sites for fungi.  The Showy Tree Cricket is famous for chirping in correlation with temperature.  Count the number of chirps you hear in 15 seconds and add 40—you should have the temperature in Fahrenheit!  Good luck doing this when it's hot.  

Tree cricket on pink flowers
A tree cricket 

2. Cicadas.  Colorado is home to several species of cicada, though the famous “periodical cicadas” are not among them (they occur mostly east of the Mississippi).  The largest and loudest cicadas we have get going in late summer.  The “Plains Harvest-fly” (Megatbicen dealbatus) and “Giant Grasslands Cicada” (M. dorsatus) are most common.  In order to attract females, males “sing” by using tymbal organs on their abdomen, producing sounds that are amplified by resonating throughout the insect’s body (much like the resonator on a musical instrument).  Adult cicadas usually live a month or two, but their juvenile phase, which takes place underground, can last several years.

close up of cicada face.
Dog-day cicada, head on!

3. Katydids.  In Colorado, the most common katydid is the Broadwinged Katydid, Microcentrum rhombifolium.  They mature in late summer, and are quite large—up to two inches from head to wing-tips.  They are well camouflaged, being green with very leaf-like venation on their wings.  Unlike their eastern relative, the “true” Katydid, Broadwinged Katydids do not make a “katy-did” call, rather they click and hiss softly by using specialized structures on their wings.  You might find katydid egg masses on twigs in your trees or shrubs; they are flat, tan, and laid in a double-row often resembling shingles or scales.  They are laid in late summer and fall and won’t hatch until the following spring—keep an eye out for them while you’re doing your wintertime pruning!

broadwinged katydid adult
An adult broadwinged katydid. 

If you can’t get enough bugs, or just wonder what insects and other arthropods you  might see out and about in our state, check out the Arthropods of Colorado site, developed by CSU Extension’s entomology program.

Saturday, July 24, 2021

Prostrate Weeds


Posted by: Kara Harders CSUE and NRCS

[Dictionary definition for prostrate: BOTANY- growing along the ground.]

Common Purslane, Spotted Spurge, Prostrate knotweed and Puncturevine . Can you tell them apart? These four have much in common, but where they differ is very important.

All four are annual weedy forbs (non-grasses). They enjoy many of the same conditions, such as hanging out in lawns, gardens, and sides of roads/paths. You may wonder “If they are so similar does it matter if I can tell them apart?” Read on to learn why!

Prostrate spurge - C. maculata L.

Prostrate spurge is the only toxic plant of the four, its stems produce a milky latex juice when broken, and it is the only plant of the four which is native to North America. This plant has a slight variant within the species, Spotted Spurge, which looks the same but with a small purple spot on each leaf. Leaves are ovate, slightly hairy, and generally dark green. The flowers are tiny and pinkish, which will go unnoticed to an untrained eye. Seedpods are 1/16 inch or less long and the oblong seeds are about 1/25-inch-long. Be sure to wear gloves when hand weeding this plant! See picture below, and notice the milky sap!


Prostrate spurge

Prostrate knotweed - Polygonum aviculare L.

Also a non-native annual, growing 1 to 3 feet tall, with wiry corrugated stems. The leaves of this weed are hairless, alternate, and lance-shaped to oval, 1/2 to 2 1/2 inches long and 1/8 to 1/3 inch wide. Flowers are small and pink, occurring in clusters along the flower stems at leaf axils. Flowering stems compose about half of the height of a mature plant. It was likely introduced to North America with the first colonists and was first collected in Canada in 1821.

See picture below.

Prostrate knotweed

Common purslane - Portulaca oleracea

A non-native, fleshy weed with succulent like leaves, this prostrate annual was introduced in the Americas as early as the 16th century and has made its way around the world. A possible reason for its wide distribution is its historic role as a medicinal plant and edible plant, meaning it was likely, at times, spread intentionally. High in a variety of nutrients, this plant in grown intentionally in some places, but its ability to easily reproduce and visual similarity to the toxic Prostrate Spurge has made it undesirable in many lawns, gardens, and fields. Small yellow flowers will produce many small black to brown seeds within a brown seed pod.

*Please note that this article does not contain enough information to teach or instruct people to consume weeds or other herbs for culinary purposes, please do additional research if that is something you are interested in. 

See picture below.

Common purslane


Puncturevine - Tribulus terrestris


Another non-native annual, Puncturevine is mat forming, with trailing stems, each can be 1/2 to 5 feet long. With small, hairy, oval leaves, it can look similar to the prostrate spurge. A key identifying figure are its flowers, which are yellow, 1/3 to 1/2 inch wide with 5 petals, And of course, its seed pods. These seed pods develop as a larger pod of 5 sections that break at maturity into tack-like structures with sharp, sometimes curving spines. These seeds will remain dormant in the soil for 4 to 5 years, so even when they appear controlled one year, they may come back the next. This is one of the later flowering weeds, with blooms not coming on until July to October. See picture below.


These four plants do not make up all of the prostrate weeds we have here in Colorado but they should help you distinguish between the most common problematic ones.

When you are trying to identify a weed and are unsure of what you have, try to identify what time of year it grows, the flower size, structure, and color, and other factors so you are better able to research it, or present your problem weed to another person to try to get an ID.

Remember, you can’t properly control a weed until you know what kind it is!


Wednesday, July 21, 2021

Hardiness Zones: A Cautionary Tale

Posted by Todd Hagenbuch, Routt County Extension

As I closed my website search engine the other day, a pop-up read, “Click Here to see what you can grow in your area!” It came from a reputable, long-time purveyor of seeds and plants so I thought, “I wonder what they think I can grow in Routt County?” I clicked on the link and was fascinated by the results.

Immediately I was taken to a site that said, “Top plants for your zone” and “Phippsburg, Colorado is in zone 5a.” 5a is a USDA hardiness zone.  Hmmm…my faith in the company was fading.

As a brief reminder, USDA hardiness zones are based on the average extreme minimum temperature an area will see in the winter months. The numbers are designed to help gardeners determine what perennials will survive the winter, which is not necessarily the same as what will grow in the summer in your neighborhood.

Another concern is the zone it had us pegged for. Zone 5a has an average extreme minimum temperature range of -20 to -15. While some areas of Routt County are in this zone, Phippsburg is in zone 4b. But I went on, wanting to see what plants the company recommended.

Some of the items recommended for Phippsburg
(identifying characteristics removed to protect the guilty)
Many of the plants recommended for zone 5a were appealing. Spinach and summer squash are great choices. But the next items, including popping corn and Fuji apples? We simply don’t get enough growing degree units (or heat) to grow them well here.

Every plant needs a certain amount of Growing Degree Units to move from one phenological stage to the next. As you can imagine, our mountain valley does not accumulate many growing degree units in our short season. Plants like spinach don’t need many units, and does well here; popping corn, however, needs heat and would not produce well here at all. In fact, the notes about it on the site indicate it needs a minimum of 105 days to mature, many more than our average 59-day growing season.

My biggest concern about this list is that most of the plants listed as ‘popular’ in my area were annuals. Since USDA Hardiness Zones are all about how likely perennials are to survive the winter, there was no connection between the annuals the site is selling and USDA zones. More than that, it confuses the issue of winter hardiness vs. growing season.

Sites like these are why I regularly get calls from people wanting to know what variety of apples, apricots or even peaches will grow here. Even if the plants are going to survive the winter months, that does not mean they will produce here. You can probably plant a zone 4 apple tree and expect it to live here; just don’t expect it to be a big fruit producer.

As for garden company catalogs and websites, use them as a guide but do your research before you order.  Know what will thrive in your location, not just survive. You’ll be a happier gardener and save a lot of money in the long-run, too.

Sunday, July 18, 2021

CSI: Jeffco

Mari Hackbarth, Jefferson County Plant Diagnostic Clinic

This summer, the Jeffco PlantDiagnostic Clinic in Golden has had a rash of strangely similar cases.  Here are descriptions of three plant crime scenes with eerily similar “MO’s”.  Can you solve them?

Crime Scene 1

Where:  Denver, Colorado; residential                                         When:  Late June 2021

Case Summary:  three plants submitted to find out what was infecting them.



Possible Causes


  • New leaves distorted and thickened with strap-like edges
  • Fruit shrunken and shriveled
  • Older leaves appear normal
  • Lab results:  no insects, mites or pathogens observed.


  • Leaves distorted, fiddle-necked, strapping
  • Lab results:  no insects, mites or pathogens observed.



  • Leaves mottled with splotches of green to gray; appeared necrotic under 40X magnification
  • Lab results:  no insects, mites found.  No pathogens isolated from culture.


                   Grape, 40X      

                      Boxwood 40X


The homeowner reported in the cultural history of the samples that the damage pattern had been observed beginning in 2020.  The history also listed that a 3-in-1 (insect, mite, disease) pesticide had been applied in 2020 and 2021 to treat for mites, based on a recommendation from a local nursery.  The cultural history indicated that no herbicides had been applied in the yard.  With no leads on biotic (living) causes of the plant deformation, and no history of herbicide use, we evaluated the 3-in-1 pesticide.  It contained 3 active ingredients:  Imidacloprid (insecticide), Tau-Fluvalinate (miticide), and Tebuconazole (fungicide).  Of the three, Tebuconazole has been reported to cause phytotoxicity in some studies.  The grape Eutypa dieback is rare in Colorado.  Boxwood blight has not yet been detected in Colorado, so is very unlikely.

Verdict:  no verdict reached.  It’s possible that the phytotoxicity/deformation was caused by Tebuconazole, but it was just as likely due to herbicide drift or vaporization from a neighboring yard.  To prove the Tebuconazole was the culprit, the plants would have to be tested for the chemical, a pricey investment.

Crime Scene 2

Where:  Burns, WY; hobby ranch/farm surrounded by grassland                                         When:  Early July 2021

Case summary:  the clients worried because their tomato plants were not thriving.  Their plants were much smaller than the ‘sister’ plants that were growing in Greeley, CO at a family member’s farm.  They were concerned that they were over- or under-watering.



Possible Causes

Tomato plants, various varieties

                      Burns, WY


                              Damaged tomato leaves on top, normal below    


While walking the property, we found multiple other species of plants showing distortion and strapping of new growth:  grape, chokecherry, Blue-mist Spirea.

                           Leaf Strapping on Grape                                          
Vein Clearing on Grape

                     Chokecherry, normal leaves are 'entire'                            

 Blue Mist Spirea

The client had sprayed a 2,4-D-based broadleaf herbicide with a backpack sprayer on weeds in the grassland adjacent to the house, but felt that the herbicide had been sprayed within the temperature and wind-speed limits.  There are corn and wheat fields within 5 miles of the damage where herbicides may have been used.

Verdict: Sub-lethal Herbicide damage due to herbicide drift, likely from the local spraying, but drift from neighboring properties cannot be ruled out.

Crime Scene 3

Where:  Denver, CO Residence                       When:  Early July 2021

Case Summary:  a client submitted photos of tomatoes and grapes that showed leaf distortion, strapping, and vein clearing.  He wanted to know what disease was causing the problem.



Possible Causes

Grape vine

  • New leaves distorted and thickened with strapping margins, some vein clearing
  • Older leaves appear normal

  • Eutypa dieback (fungus)
  • Grapevine fanleaf virus
  • Herbicide Injury

Tomato plants

  • Older leaves showed curling, distortion, twisting and strapping, and were slightly thickened. 
  • Newer leaves appeared normal. 
  • The were no blooms or fruit. 
  • There were no leaf spots, nor areas of scorch.





During discussion the client reported using 'Weed B Gon' herbicide on lawn weeds, but not near the garden plants.  He also reported using lawn clippings as mulch for both the tomatoes and the grapes.

Verdict: Sub-lethal Herbicide damage very likely

The active ingredients in Weed B Gon are 2,4-D, Dicamba, and MCPP-P.  All three are growth regulator- type broadleaf herbicides that affect plant growth processes, such as cell division, protein production, and respiration.  At a high concentration, they kill the plant; at sub-lethal concentrations they cause plant distortion.  These herbicides can be carried by clippings, as well as compost made with treated plants.  When applied as mulch, they can leach into soil and be taken up through the roots of mulched plants, causing damage from the bottom up.  Grass clippings make great mulch for a vegetable garden, but not when the grass has been treated with growth regulator herbicides!

What is the common MO?   All three of these cases involve similar phytotoxic symptoms on multiple species/families of plants that are consistent with phenoxy- herbicide damage.  Most plant pests and diseases are pretty host specific, causing damage to only one kind of plant or to closely related plants.  Abiotic disorders such as herbicide damage typically cause problems across multiple kinds of plants.  The plant distortion in these three cases is typical of damage caused by the growth regulator herbicides, also known as the ‘phenoxy’ herbicides.  These herbicides can cause off-target damage due to drift, vaporization, overspray, and root uptake when not applied carefully. Grape and tomato plants are very sensitive to even small amounts of phenoxy herbicides -  the ‘canary in the coalmine’ for phenoxy herbicide damage.  

To avoid damage, always follow all label instructions exactly:  the label is the law!  Apply when wind is below the specified speed (drift), temperature is below the specified limit (vaporization), and equipment is working properly (overspray).  Take care not to transfer treated plant material to planting beds.

While Scenes 2 and 3 can be solved based on circumstantial evidence, Scene 1 will remain an ‘unsolved mystery’!

Want more info?  Check out these fact sheets!

Thursday, July 15, 2021

The Benefits of Hail Cloth

Guest Blog by: John Weiss, Master Gardener in Larimer County
Hailstorms are every gardener's fear...and nemesis!

According to the Colorado Climate Center at CSU, hail season runs from April 15 through September 15. Using hail cloth offers the gardener at least two benefits. The first benefit is obvious - to protect your vegetables from unwanted hailstorms and the potential damage they can produce. The second benefit is shade for your vegetables. Studies suggest that a small amount of shade reduces the intensity of the sunlight. Plants appreciate the shade and responses with enhanced performance.

The hail cloth I selected provides 13-15% shade and can be obtained from (but there are other businesses that sell it).  The hail cloth has a somewhat open weave that allows air movement and rain to penetrate it while keeping even small hail out. 

Close-up of the hail cloth available from; this cloth provides 13-15% shade and protects plants from small hailstones

It can be easily cut with scissors and comes in any length.  Keep in mind that the cloth will shrink over the first season so cut large enough in anticipation of the shrinkage.

Jon's raised bed with hail cloth in place.

Above is my large, raised bed with a frame to hold the hail cloth about 4’ above the center of the bed.  The frame is PVC and each vertical piece fits over rebar imbedded in the raised bed.  A wood strip on each side was added for strength.  To keep the hail cloth from blowing off the frame, PVC pipe (lying on the ground) with a 3-4’ piece of rebar (for weight) sits on the raised bed frame.  Two vertical pieces of wood (on each end) was added to keep the PVC pipe from falling off the frame (see below).

PVC, rebar, and wood hold the hail cloth in place

Hail cloth can be draped over any sort of structure, even tomato cages and will last multiple seasons. If you haven’t tried hail cloth, give it a try as it’s great insurance against unexpected hailstorms.

Don't let this happen to your tomatoes! Get some hail cloth.

Monday, July 5, 2021

So you want to be on a garden tour...

 Guest post by: Khursheed Mama, CSU Extension Master Gardener in Larimer County

Khursheed's landscape in its fully glory the day of the tour.

So you said yes to being on the Junior League of Fort Collins garden tour, got your husband to agree, and even recruited neighbors to do it. After all, it’s a fundraiser for a cause you believe in. You’ve been on the tour before (12 years ago) and it seemed fine, so why not again. Especially this year when the tour had to be cancelled in 2020 because of COVID. It seemed like a good plan in November. Ah, but you forgot what it takes to prepare and how Colorado weather doesn’t always cooperate.

Spring in Colorado is unpredictable!

Now it’s late winter and trees and non-spring flowering shrubs need to be pruned. Some are too tall to do with pole pruners and loppers but you decide it will have to do. You decide to remove an oak that isn’t thriving, but a second one, only slightly healthier, gets to stay. A 15-year-old arborvitae that was impacted in the 2020 freeze event got a breather in the hopes that it would re-vitalize (sadly, it’s not looking promising). Then two feet of snow came, and with it, broken branches, but you told yourself that the moisture is good.

Spring brought life back to the garden with bulbs, early perennials, and shrubs, putting on a beautiful show and you wondered why the tour couldn’t be during their blooms. The copious spring rain resulted in oh-so-many weeds and ‘tree babies’. If you are ever considering a golden raintree—don’t! As pretty as they are, they are also prolific seeders. Then you battle your lawn encroaching your landscape beds, and groundcovers encroaching your lawn. You pull more weeds. Rabbits decide to take up residence in the middle of the lawn. Then you focus on deadheading early perennials and bulb foliage as it fades.

A plant-filled path leading to the shed.

The heat wave hits and now time is devoted to watering the lawn and garden beds, focusing on new and replacement plantings. The garden bursts into bloom with peonies and spirea, and evergreens put out their new growth. If you can look past the chaos, the garden is lovely and it seems birds are enjoying it too. Now we just hope the hail stays away and mother nature does not deal another blow. While the ‘tasks’ vary with the seasons, the focus is on keeping plants healthy and creating a landscape that you can enjoy all year.

Tour-goers enjoying Khursheed's diverse landscape.

Now it’s the week of the tour and weeding, watering, and deadheading continue with record heat, and then…hooray!...rain and cooler temperatures in the forecast. Excitement for the moisture, tempered by fear of hail, the steady rain was so beneficial and freshened things. A mix of sun and clouds was a perfect way to start the day of the tour and around 8:40 a.m., tour-goers were on site enjoying the garden and asking questions. The catalpa, bear's breeches, and alliums seemed to draw the most attention. Luckily, Master Gardeners and Fort Collins Nursery personnel were on hand to help with gardening questions, and the Junior League team helped with logistics. This allowed us to visit with friends and colleagues that stopped by to support this great cause. Yes, in sum total, we would do it again!

Khursheed Mama (right) with Master Gardener Roger Heins,
who helped answer questions the day of the tour.