CO-Horts Blog

Monday, February 22, 2021

Five helpful tips for planning a vegetable garden

By John Stolzle, Jefferson County Extension 

If 2020 was any indication, this will be another busy year for gardening. A recent Co-Horts blog post presented some information from two seed suppliers; the gears are turning and companies are stocking up. With the upcoming year in mind, I have laid out five topic areas and include relevant resources from CSU Extension to help gardeners prep for a successful year
1) It’s never too early to plan. 

Having a plan in place for a garden can prevent many problems from ever occurring. Before starting a new garden, it is important to give some time and thought towards site selection and ask questions such as: will this area receive full sun, how was the land previously used, how much produce do I want? The layout and form of a garden (for example, in-ground or raised bed) can also play a significant role in its productivity. Raised beds with a block style layout can save space, drain faster, heat up earlier in the spring, and save water by keeping it where the plants are grown. 

More information to help you select a site and layout can be found in the following links: 

In our dry climate, it is especially important to consider whether a source of water is near to where you are planning to garden. Irrigation systems and mulch are two tools that we can use to help conserve water. On the topic of mulch, it is important to note that mulching too early in the season can actually reduce a garden’s productivity!

Here is some additional information on the topics of irrigation and mulch for vegetables gardens: 

3) Soil matters

One common question I often receive is about best practices for amending soil. From my perspective, it can sometimes be a challenge to make suggestions for fertilizing or adding amendments without first knowing more about a soil’s composition. A soil test can provide baseline information from which recommendations can be made. The CSU soil testing lab in Fort Collins can receive soil samples through the mail. They will analyze a sample’s composition and provide recommendations if they discover any deficiencies. At the time of posting this, the lab is expecting a 2-3 week turnaround time.

Additional information:

 4) Take care when determining your start time to avoid starting seeds too early.

Starting seeds indoors, before the weather warms allows us to get a jump start on the growing season. One challenge that comes with starting seeds early is that larger plants are often more sensitive to the stress that comes with transplanting. For this reason, it can be important to not start seeds too early and to have an idea for when you might plant them in the ground. Frost dates are often used to help determine when to plant outside and when to start seeds; these dates differ between elevations and regions in Colorado. Certain cool season crops do better in cooler temperatures and can resist a light frost (for example, Spinach, lettuce, and broccoli), whereas other warm season crops do much better in the heat of summer after the threat of frosts and freezes has passed (for example, tomatoes, squash, and watermelon). 

5) Plan with a full year in mind

One of the most important tips I can provide is to plan your garden with a full year in mind. Are you interested in donating extra produce to neighbors, or friends, or family? If so, consider planting a few extra vegetables. To receive more information about growing produce and sharing the harvest, you can sign up for the Grow&Give newsletter on the Grow&Give website:

Lastly, I want to include a few additional links to more information which you may find helpful:

As always,
Best of luck in your gardening endeavors! 

Thursday, February 18, 2021

Privacy screens for the garden

 By Irene Shonle, CSU Extension El Paso County

Do you have a view from your yard that you’d rather not see?  Would you like to have more privacy from your neighbors?  Privacy screening is frequently on a gardener’s wish list, and can make your yard feel much more like a place where you want to hang out.

Some questions you need to figure before deciding on plants for a privacy screen include:

1.      1.        How much space do you have?  A very narrow space will dramatically limit your options.
2.      What kind of sun exposure does the area you want to screen have? Full sun will give you the most options, and increasing levels of shade will again limit your options.
3.      Do you need the privacy screen year round, or will a deciduous plant (that loses leaves work)?
4.      How tall do you need it to be? Often for sitting areas, plants don’t need to be taller than 4-6 feet.
5.      Does it need to be drought-tolerant, or can you give it extra water?

If you have both a very narrow space and a mostly shaded area, I would suggest that you will be better off with going with a hardscape option such as a fence.  Boring, I know, but sometimes, that is really the best solution. Another option would be to create a trellis and plant a shade-loving vine such as Virginia creeper or English ivy.  Beware that both of these vines can be quite aggressive, and the Virginia Creeper frequently attracts Japanese beetle.

If the space is narrow and sunny, you could grow one of the many honeysuckles (some of which have a sweet fragrance- none of which seem to be invasive in CO), sweet autumn clematis, native Virgin’s bower clematis,  other clematis, or Trumpet vine.  You could also grow a row of tall sunflowers.

If you have a sunny exposure with a bit more room, now you can consider more plants.

For evergreens in not-too-big spaces, consider some of the Rocky Mountain Juniper cultivars such as ‘Medora’, Skyrocket, or ‘Woodward’.  Non-native arborvitae also can work here. If you have more room, a full size evergreen that keeps its branches all the way to the ground such as a Blue Spruce (needs more water) or a Douglas fir (more drought tolerant) becomes an option.

Juniper 'Medora"

Some broad-leafed evergreen options include two native plants: curl-leaf mountain mahogany (Cercocarpus ledifolius)  and Fremont’s mahonia (Mahonia fremontii).  The latter has fragrant yellow flowers in the spring, and red berries in the fall, but it also comes with sharp spines on the leaves – which can be a bonus or a problem, depending on your circumstances. A hardy boxwood or yew would be good non-native options.

Curl-leaf mountain mahogony-

Non-evergreen sun options can include two near-native plants – the spectacular grass, giant Sacaton (Sporobolus wrightii), which keeps flowering stalks throughout the winter, and the fragrant Cheyenne Mock Orange.  If you want a shrub that suckers to help improve the screen and provides great habitat, consider a chokecherry (Prunus virginiana). Lilacs, Rose-of-Sharon, Elderberry,Siberian Pea shrub and Viburnums, and Nanking cherry can also be good choices. 

Giant sacaton in the winter

Finally, for plants that can tolerate some shade, consider the natives red-twig dogwood (would appreciate some extra water) or Boulder raspberry (Rubus deliciosus), with large white flowers in the spring and reddish bark.

Boulder raspberry

For more information:


Native trees:

Native shrubs:


Monday, February 15, 2021

A Wasp-Benefit Analysis

Posted by: Lisa Mason, Arapahoe County Extension

What is the purpose of wasps?

I am asked this question quite often. Why do we have wasps? What is their purpose? Do we need them?

We have a couple of wasp species that can be a nuisance to people. They tend to give wasps a bad reputation. In reality, wasps are a fascinating, diverse group of insects that play a critical role in our ecosystem!

A beneficial sand wasp (Bembix sp.) hunts caterpillars and flies. They can often be seen visiting flowers for nectar in the summer. Photo: Lisa Mason 

Here are some important facts to know:

  • Two species of wasps Colorado are considered a nuisance: The Western yellow jacket (Vespula pensylvanica) and the European paper wasps (Polistes dominula).
  • Besides those two species, wasps are a very diverse group of insects with thousands and thousands of species documented worldwide. How diverse? Current science says that beetles (Coleoptera) are the largest group of organisms on the planet representing about a quarter of all described species. However, some research suggests that parasitoid wasps are actually the largest group of organisms but we haven’t been able to document all the species. Here is a fun NPR article on subject.
  • Many wasps can’t actually sting including parasitoid wasps and other solitary wasps.
  • Most wasp species are solitary insects. Only wasps in the Vespidae family are social and live in colonies. Often, the social wasps are brightly colored to warn predators that they are dangerous. They will defend their nest and sting if needed.
  • Many other insects mimic the bright colors of social wasps to protect them from predators. This phenomenon is known as Batesian mimicry. Common mimics include flies in the Syrphidae family, also known as flower flies or hover flies. You can observe these harmless insects in flowers in the summer time.
  • Wasps provide valuable ecosystems services to humans because they provide pest control in your landscape. Some wasps are predators and others are parasitoids, meaning the wasps will lay eggs in another host insect and consume the host. Our world would be full of pest insects without wasps!
  • You can thank paper wasps for our current paper production industry! In the 1700’s, paper was made from cotton and linen until there was a shortage of those materials. A French naturalist named Antoine Ferchault de Réaumer had observed how paper wasps use wood fibers to make their paper nests, and thought people could do the same thing to create paper. Paper products today are still made out of cellulose fibers from wood (Paulson and Eaton, 2018).
European paper wasp (Polistes dominula). Photo: Lisa Mason

A syrphid fly (Spilomia sp.) that mimics stinging wasps but can't sting. Photo: Lisa Mason 

What about the “murder hornets”?

The Asian giant hornet (Vespa mandarinia), the world’s largest hornet, has received a lot of press recently because a small number of individuals were found in Washington state. While the insect may look intimidating, much of the news media is sensationalized.

I encourage you to read a media interview with Dr. Cranshaw, CSU entomologist. He talks about how calling them “murder hornets” is unnecessary. Many wasps are predators and hunt other insects. The Asian giant hornet is no different. 

Much of the media has focused on how Asian giant hornets preys on honey bees. While they can prey on honey bees if near a hive, Asian giant hornets are generalist predators. They will feed on a variety of insects and will be opportunistic in hunting. They will not specifically target honey bees unless there is a hive nearby. Beekeepers around the country have more important challenges concerning honey bees including the varroa mite.

Will the Asian Giant Hornet come to Colorado?

Short answer: No. We don’t have to worry about the Asian Giant Hornet coming to Colorado for the following reasons:

·       Asian giant hornets thrive in different climate than Colorado. They need low-elevation areas and higher moisture levels.

·       There are many geographic barriers preventing the Asian giant hornet from spreading including the Rocky Mountains.

·       They are unlikely to hitchhike like some other invasive species. 

·       Efforts to eradicate the hornet is Washington are occurring now.

What if I find an Asian Giant Hornet in my backyard?

Colorado has some wasp species that large and may appear to look similar to the Asian giant hornet. These wasps are harmless and common in Colorado landscapes. The two wasps that may look like the hornet include cicada killers and horntails. Both of these wasps cannot sting you. 

Cicada killers target cicadas when hunting and provide the prey to their young.

Horntails appear to have a large “stinger.” This “stinger” can’t sting you at all! It is called an ovipositor, which is adapted to drill into the bark of trees. Female horntails lay their eggs underneath the bark of trees. They don’t harm trees and tend to lay eggs in trees that are already stressed out.

Solitary wasps such as these found in your landscape are not aggressive and should be left alone. 

If you are looking for the identification of a wasp found in your landscape, contact your local Extension office for assistance.

Here is a visual of the Asian giant hornet compared to common, harmless wasps including cicada killers and pigeon tremex horntails. Photo: Texas A&M Extension

Stay tuned for more info on wasps!

Look for future blog posts about wasps! I will discuss the differences between social and solitary wasps, and well as some common and beneficial wasps you might see in your backyard.

Wasps can be scary to people for a variety of reasons, but I hope to article can help instill some appreciation for what all wasps contribute to our ecosystems.

Wednesday, February 10, 2021

Jeffco Clinic’s Top 10 Plant Problems of 2020

Usually, a top ten list highlights the 10 best of something.  Unfortunately, when looking at plant problems, we are looking at the ten problems most frequently seen...the 10 worst!  

Here is a summary of the top 2020 plant problems that were seen on samples submitted to the Jefferson County Extension Plant Diagnostic Clinic in Golden.  Some plant problems are consistently seen in the Jeffco Plant Clinic every year, while others are influenced by factors like weather conditions, and clientele.  For example, freeze damage to plants was everywhere this year; highly managed golf courses will experience different turf diseases than home lawns.  Since we only report on what has been submitted to the clinic, you may have experienced slightly different problems.  

#1 – Winter Damage (22 samples, 9.8%)

Freeze damage on Bosnian pine

In the Jeffco Clinic, the most frequently diagnosed problem in 2020 was plant damage caused by severe winter weather.  With three sudden freezes within a 12 month span across the Front Range, the majority of the plant problems that came into the Clinic were diagnosed as “Winter Desication” or “Freeze Damage”.  With the freezes of October 2019 and September 2020, plants had not yet hardened off for winter, resulting in freeze damage to existing growth.  In the spring freeze of April 2020, many plants had started to come out of dormancy:  tender young buds and leaves were frozen.  The cumulative effect of these 3 freeze events continued to show up all season long as needle browning and branch death. 

#2 – Drought Injury (22 samples, 9.4%)

Drought injury is an environmental disorder that occurs when more water is lost through leaves or needles than can be taken up by the roots, causing plants to become dehydrated.  The cause of drought injury can be due to either cultural (insufficient irrigation) or environmental factors such as prolonged heat, low humidity, drought, wind, and root damage.  

Deciduous trees typically develop leaf scorch.  

Symptoms on conifers include needle discoloration (yellow, red, brown or purple, depending on variety) as well as tip dieback of needles progressing from the top of the tree down.

#3 – Necrotic Ring Spot on Kentucky Bluegrass, 13 samples, 5.5%

Necrotic Ring Spot (NRS), is a perennial disease caused by a fungal pathogen of Kentucky Bluegrass that causes circular (sometimes donut-shaped) patches of dead grass.   It thrives in grasses that have poor drainage, and that are overwatered.  Good turf management practices are the best means of prevention and control.

Necrotic Ring SpotHoward F. Schwartz, 

#4 - Herbicide Injury, 10 samples, 4.3%

 Herbicide injury was diagnosed on vegetables as well as herbaceous and woody plants.  Plant symptoms include deformed leaves and stems, scorch, stunting and dieback, depending on the active ingredient. 

Paul Bachi, University of Kentucky Research and Education Center,

Herbicides can reach non-target plants in several ways:  via vapor movement from nearby properties, drift of sprays, and through manure or straw mulch.  With good cultural care, plants can outgrow sub-lethal doses over one to several seasons.  

For more information see  Vegetable Herbicide Damage and Herbicide Damage to Trees.

#5 - Eriophyid mite damage, 7 samples, 3.0%

Eriophyid mite scabbing on Oak

Eriophyid mites are tiny (microscopic) mites that feed on plant sap, causing plant damage such as leaf galls, scabbing and distortion.  Most years we see finger galls on Linden leaves, but in 2020 we received multiple samples (Maple and Oak) that had these scabbing symptoms due to the mite feeding.

The damage is primarily aesthetic and typically doesn’t warrant control.  


#6 - Planting Issues, 6 samples, 2.6%

The most common planting issue that we see is deep planting of both herbaceous and woody plants, evidenced in trees by lack of trunk flare. When roots are planted too deep in the soil profile, then they don’t get enough oxygen.  Poor growth, or even death, is a result.  Other planting issues can include choosing the wrong plant for your hardiness zone or soil, or planting in the wrong spot.  See Planting Trees and Shrubs.

    Deep planting (above)

Deep planting (no trunk flare) above
 Overwatering (below)

 # 7 – Overwatering, 5 samples, 2.1%

When plants are overwatered, water replaces oxygen in the soil, causing oxygen starvation (aka suffocation).  Plant symptoms can include leaf discoloration and leaf drop from the bottom up, stunting, root rot, and death.  See Environmental Disorders of Woody Plants.

# 8 – Cultural problems, 4 samples, 1.7%

Sprinkler coverage or malfunction

“Cultural problems” is a category that we use to include plant symptoms and diagnoses resulting from sub-optimal cultural care (water, fertilizer, core aeration of turf, etc.).  

The samples with this diagnosis in 2020 were typically lawns that had become thin & weedy due to improper sprinkler coverage, failure to apply sufficient water to the roots, and lack of aeration. See Lawn Care and Waterwise Landscape Design for recommendations.

 #9 - Spider Mites, 4 samples, 1.7%

Spider mites feed on plant sap, causing leaf damage that ranges from stippling/flecking to scorch, leaf drop and plant death.  Providing appropriate water to the plant is the first line of defense.

Two-spotted spider mites, Frank Peairs, Colorado State University,

# 10 Tomato Spotted Wilt Virus, 3 samples, 1.3%

Tomato Spotted Wilt Virus (TSWV) was reported in both tomato and pepper plant samples.  Symptoms of TSWV include distorted leaves with purplish veins, brown to purple spots on leaves, wilting, and yellow to orange/brown rings on fruit.  

With no treatment available, infected plants should be pulled and discarded.  See also  Recognizing Tomato Problems 


Regardless of what plant disease 2021 sends our way, prevention is the best management tool.  Awareness of what diseases can affect a plant host enables the gardener to monitor and intervene before disease develops.  

Want to know more? To see additional summary data, CLICK HERE.  If you have plant problems, or need help identifying insects or plants, please contact the Jeffco Plant Clinic at 303-271-6627,  We look forward to hearing from you!

Thursday, February 4, 2021

Who’s Awake During Spring and How Do We Help Them?

By Sherie Shaffer, Horticulture Agent, CSU Extension-Pueblo County

If you have looked into having a good pollinator habitat in your yard, then you know it is important to have flowers blooming all year long. Often times people have plenty of things in bloom mid and late season, but are lacking those important early season blooms. Many pollinators are up and at ‘em early in the spring and will be on the hunt for pollen and nectar. It’s important to help these early emerging pollinators out by planting things that bloom early.

So, who’s awake early in the spring anyway?   I was wondering that myself. Luckily for me we have a pollinator prodigy in Extension, Lisa Mason, who sent me this helpful list of pollinators that she has seen early in the spring. See if you can spot them in your yard!

  •     Andrena (mining bees)- look for them in bare, undisturbed soil
  •   Queen bumble bees- they overwinter as adults, and emerge early to find food and start a new colony
  •     Mason bees- these mild mannered bees will appreciate your bee hotel being ready in spring
  •      Leafcutter bees- come out a little later in the spring, cut circles out of the edges of leaves
  •      Honeybees- will leave the hive on any day over 50 degrees
  •     Some species of Syrphid flies (flower flies/hover flies)- easily confused for a bee, but have two wings rather than four
  •      Lithurgus apicalis- a cactus bee that is very common on prickly pear cactus

 Andrena, Whitney Cranshaw, Colorado State University,

Mason bee, Scott Famous, DoD,

Syrphid Fly, Whitney Cranshaw, Colorado State University,

Now that we know who’s around in the spring, let’s talk about what we can plant to support them. It’s so exciting to me when I go on a spring hike and see a pasque flower covered in bees! Anything that’s blooming early is bound to be a hit with the pollinators. Here are some ideas of early blooming plants to try in your yard.

  •    Chokecherry (Prunus virginiana)- This large shrub is very drought tolerant and provides early blooms that pollinators will love. After the blooms fade it will bear fruit that birds as well as humans love
  •     Golden currant (Ribes aureum)- Another fruit bearing shrub who’s flowers are one of the first signs of spring in Colorado. This Colorado native will require periodic irrigation
  •      Pasque flower (Anemone patens var. multifida)- As I mentioned above one of my spring time favorites. All kinds of bees and hoverflies will visit this beautiful spring bloom.
  •      Blue Flax (Linum lewisii)- This is one of the first things that blooms in my yard. It has tons of blue flowers early in the morning and is very low maintenance.
  •      Prickly pear cactus (Opuntia polyacantha)- This is fun one to have in your yard although maybe not pet or kid friendly. Very drought tolerant and likes low fertility. Many bees will love these colorful open flowers
  •     Blanketflower (Gaillardia pinnatifida)- Beautiful and easy, my kind of flower. Starts blooming early and goes all season long. It re-seeds readily so it’s easy to add more to your landscape

Chokecherry flower, Rob Routledge, Sault College,

Blue flax flower, Dave Powell, USDA Forest Service (retired),

Prickly pear flower, Dave Powell, USDA Forest Service (retired),

If you want to have a great pollinator habitat on your property, be sure to consider our early emerging pollinators!