CO-Horts Blog

Wednesday, June 29, 2022

Host an Aphid Watch Party This Summer and Look for Biodiversity

Posted by: Lisa Mason, Arapahoe County Extension

Yes, you read that right! Get excited about watching aphids on your plants this summer just as you get excited about your favorite TV show or a new moving coming out! You’re probably asking, “Why would I watch aphids on my plants? Aren’t they a nuisance pest?”

The definition of a nuisance pest depends on who is asking. For instance, if you are a hungry lady beetle, aphids are a feast waiting to be had!

Except for a few species, most aphids cause very little plant damage. Aphids are host-specific meaning that each of Colorado’s 350 aphid species will only feed on certain plants.

Aphids are also one of the insects that excrete honeydew, which is a sweet, sticky substance that coats the plants and anything underneath the plant. 

So, why would you watch aphids on your plants? Aphids attract a wide variety of beneficial insects to our gardens. An aphid infestation can be a hotspot to observe biodiversity in your garden or landscape. For instance, while I was writing this article, I found aphids in my backyard on a sand cherry! So far, I’ve seen lacewing eggs, lady beetle pupa, a katydid nymph, syrphid fly smears, and other insects feeding on the honeydew.

Aphids (Aphis nerii) on a milkweed plant. Photo: Lisa Mason

Here are some fun observations you may witness while you are watching aphids:

Predators Hunting Aphids

Lady beetles (Family: Coccinellidae), also known as lady bugs, are a common insect you’ll find preying on aphids and other soft-bodied arthropods. We have approximately 80 different lady beetle species in Colorado. Lady beetle larvae have a completely different appearance than the adult beetles because they complete a full metamorphosis (egg, larva, pupa, and adult). The larvae look similar to little dragons or alligators, and they are ferocious predators! Their goal is to eat as much as possible! Convergent lady beetle larvae can devour up to 50 aphids a day, often consuming their weight in aphids (Hoffman and Frodsham, 1993). Other species such as the seven-spotted lady beetle may feed on higher numbers of aphids.

Lady beetle larvae. Photo: Melissa Schreiner

Lady beetles are a natural control option for aphids found in their environment. They are available for purchase at garden centers, but keep in mind that lady beetles can fly away. Since they are so mobile, lady beetles for purchase may not be too effective. However, purchasing and releasing lady beetles can be a great activity for children to help inspire an appreciation for insects and their role in our environment. The lady beetles for purchase are the convergent lady beetle, a native species.

Female lady beetles often lay eggs near an aphid infestation, so look for groups of dark yellow or orange-colored eggs that are oval-shaped and approximately 1 mm long. 

A lady beetle larva preying on an aphid. Photo: Melissa Schreiner

Lacewings (Family: Chrysopidae) are another common predator seen feeding on aphids. Just like lady beetles, the larvae of lacewings are ferocious predators! They earn the nickname “aphid lion” for a reason. In addition to eating up to 200 aphids per week, they can also feed on caterpillars by capturing them with their pair of hooked jaws.

Both green and brown lacewings can be found in Colorado. The adults have long, skinny bodies with membranous wings that that extend over the body forming a triangular or tent-shape.

Lacewings are also available for purchase as a biocontrol for the home garden. They can be more a more effective biocontrol option because they are available as eggs. When they hatch, the larvae will stay in the same place to feed until they reach adulthood.

Lacewing eggs. Photo: Lisa Mason

 Lacewing larva. Photo: Lisa Mason

Syrphid flies are another insect that feed on aphids as larvae, but they are quite elusive. Larvae can feed on 100-400 aphids. They are nondescript, grub-like larvae that vary in color. They leave behind excrement in their path that looks like a black, shiny streak known as a “syrphid smear.”

The adult form of syrphid flies is commonly seen visiting flowers with nectar. They often look like wasps and bees because they exhibit Bastian mimicry i.e., predators may avoid these syrphid flies because they look like stinging insects, though the syrphid flies are harmless. You can differentiate them from wasps and bees by looking for their giant eyes that extend almost to the top of their heads, only one pair of wings, and short antennae.

Syrphid fly. Photo: Lisa Mason

Tiny, parasitoid wasps will prey on aphids by laying eggs inside the aphid. The wasp larvae feed on the aphid. Parasitoid wasps cannot sting people, but they are deadly to aphids! The wasps are so small that they may be hard to observe, but you might see the remnants of them when you see dead aphids on the plant. 

Insects Feeding on Honeydew

Aphid infestations also attract a wide diversity of beneficial insects that feed on the sweet honeydew. You might observe a variety of wasps, ants, flies, and beetles all feeding on honeydew.

Ants and aphids often have a mutually beneficial relationship. Honeydew can be a major food source for ants, and the ants want to protect that food source. Since aphids are easy prey, ants will protect aphids from prey, and in some cases, protect them from fungal pathogens (Nielsen et al., 2009; Rathcke et al., 1967).

Aphid Reproduction and Life Cycle

Most aphids are wingless in a colony. You may observe winged aphids when they need to seek out new plants. Aphids reproduce at an astounding rate because reproduce both sexually and asexually. During the summer, you are likely to see aphids produced by females in asexual process called parthenogenesis. The female aphids give birth to aphids without fertilization. These aphids share the exact same genetics. Later in the season, the colony will produce male aphids to mate with female aphids that are able to reproduce sexually. The female will lay fertilized eggs that overwinter. Many aphid species will complete their life cycle on one plant host. Other species will overwinter on one species of host plant, and after hatching the spring, they will fly to another species of host plant. See Table 2 of the Aphids on Shade Trees and Ornamentals fact sheet for a list of aphids that have two host plants.

Rose aphids (Macrosiphum rosae) on a rose bush. Photo: Melissa Schreiner

Benefits of Attracting Insects in Your Landscape

Aphids and other pest insects serve an important role in the food web in our garden ecosystems. Just like predatory insects, birds can help keep the pest populations down. Most terrestrial birds rely on insects for a major component of their diet. Hummingbirds will catch up to 2,000 insects per day! They feed on aphids, mosquitos, and a variety of other insects. Consider supporting insects and birds in your landscape by planting a diversity of flowers with nectar and native plants, providing habitat spaces and water sources, and minimizing or eliminating the use of pesticides in the landscape.

Aphid Control Options

Beneficial insects are a great control option for aphids! A few other options are available if additional control is desired. Using a hose with a strong jet of water on the plant will knock aphids down. Since they are a soft-bodied insect, the impact from the water will kill many of them. Horticultural oils are effective at killing overwintering eggs. A variety of insecticide products are available, but use caution because many will kill the beneficial insect predators in your garden. Look for non-persistent contact products like insecticidal soaps that are safer for beneficial insects. As always, follow the label explicitly so that the product is applied effectively and safely. For more information, check out the CSU Extension fact sheet, Aphids on Shade Trees and Ornamentals.

Enjoy Your Backyard Biodiversity!

Have fun making observations this summer. Share photos on social media! Use the hashtag #AphidWatchParty


Hoffmann, M.P. and Frodsham, A.C. (1993) Natural Enemies of Vegetable Insect Pests. Cooperative Extension, Cornell University, Ithaca, NY. 63 pp.

Marvin, D. E. (2018) Hummingbirds as Pest Management Partners? New York State Integrated Pest Management, Cornell University.

Nielsen, C., Agrawal, A. A., and Hajek, A. E. (2009) Ants defend aphids against lethal defense. Biology Letters 6: 205-208.

Rathcke, B., Hamrum, C., and Glass, A. W. (1967) Observations on the interrelationships among ants, aphids, and aphid predators. The Michigan Entomologist, 1(5), 169-173.

Schuh, M. 2022. Lacewing. University of Minnesota Extension.

Statewide Integrated Pest Management Program. (2002) Syrphids (Flower Flies, or Hover Flies). University of California Agriculture and Natural Sciences.

Warner, G. (1993) Syrphid Flies (hover flies, flower flies). Washington State University.

Thursday, June 23, 2022

Keeping cats out of your garden

By Rhiannon Rowe, Eagle County CMG 


As a lifelong cat lover, I hate hearing about how much of a nuisance they can be to gardens and yards. Not to mention the stress they can put on the local bird population! Before I jump on my soapbox about keeping your cats indoors, I know that many cats prefer to be outdoors and are not suited for an indoor lifestyle. With that being said, the best we can do is find ways to deter our feline friends from wreaking havoc on our plants. Cats can smell 14 times better than humans so the best place to start would be planting or placing scents around the yard that cats do not prefer. Citronella, lavender, peppermint, rosemary and chives are all common plants that cats are not fond of. Added bonus is that many of them attract bees and smell great to us! Coffee grounds and citrus peels are also a good idea, plan to replace them often to keep the effect going.

There are a few commercial deterrent sprays you can find in pet stores or online. Just make sure they are safe to use around plants before you start spraying. Barriers can also be effective by physically keeping the cat away from your garden although they can make it tough to reach your plants. Netting can help protect your younger plants as well as putting a ring of pine cones or anything prickly around the plant as cats don’t like to walk on surfaces that aren’t soft. A friend of mine likes to put plastic cutlery around her garden and swears it helps!

Water can be used in a few different ways. Motion activated sprinkler systems can work as well as posting up with a SuperSoaker to catch the cat in the act. Cats aren’t fans of water and it shouldn’t take more than a few times for them to realize that they aren’t welcome! Using water to wash away an intact male cat’s urine scent can also help as well as removing anything that a cat is using to mark his territory.

There are several other ways to deter cats from a garden but these are my favorites! If these ideas aren’t helping, it may be time to speak to your neighbors about their cat’s behavior and try to come to an understanding. If you aren’t sure who the cat belongs to or if it is a feral cat, contact your local shelter. They can pick up the cat and check for a microchip. If the cat is feral, they can help you set a humane trap to try and remove the cat from your premises. 

Finally, cats are conditioned to stay in an area that is comfortable and welcoming to them. If there is food present, their hunger is taken care of. If there is loose dirt, they have found a litter box! If there are fun things to chase such as mice and birds, they have plenty of entertainment! Finding ways to take these luxuries away will help the cat realize that they need to move on and find a new place to enjoy.

Thursday, June 16, 2022

Hoppin' to it with grasshopper control


Posted by Todd Hagenbuch, Routt County CSU Extension

You’re wondering why an Extension blogger from Routt County, of all places, is submitting a piece on grasshoppers, right? Surely our area, home to amazing snows, Ski Town USA, and pristine, green hay meadows doesn’t worry about hoppers, right? Wrong. Look at this map of the state and you’ll see that our gardeners, ranchers, and wildlife managers all have to deal with the impacts of grasshoppers and the damage they cause more than most of the state.

2021 USDA Colorado Grasshopper Count
You might also be wondering where the data on the map came from. Did you know that the USDA counts grasshoppers on range and cropland to figure out how many there are in areas of the state? In NW Colorado, that job has been done for years by two people who are also Colorado Master Gardeners. As people who understand plants and insects, the two different CMGs who have done this job have been key to the Routt County Extension Office helping local landowners decide if and when they should apply control measures.

Control measures are generally recommended in crops and in range if numbers exceed 15 grasshoppers per square yard. Today my CMG friend and USDA grasshopper counted 43 hopper nymphs per square yard (!) at one site, and another intrepid CMG shared the photo below of hoppers in a dog park in Steamboat Springs. How many nymphs can you count in this area, which is just over a square yard?!?

How many nymphs can you count in this square yard?
Photo Courtesy CMG Donna Segale
As a gardener, you know that just a few hoppers can cause a lot of damage, especially after they’ve molted several times and have become ravenous adults. Large-scale spraying efforts, like I’m recommending for rural landowners and ag producers in Routt County, isn’t as desirable for garden situations, especially if you’re growing veggies. That begs the question: what can I do as a gardener when the swarm is heading my way?

Granular baits laced with insecticides are one way to help control grasshoppers. When the insect eats the bait, they die and become part of the organic matter of your garden. As there is still insecticide involved, however, some folks would like another option. Covering your garden, or at least the rows in it with a lightweight, floating row cover is an excellent measure, making sure hoppers can’t get in but light and air can.

One of the most unusual but coolest control measures I’ve seen involved a two-fence approach, where the garden was located inside a fenced area with another fence located about 15’ outside the inner fence. Each fence was about 6’ tall and not only kept elk and deer out of the garden, but the area between the fences housed about 50 hens who patrolled the area. As hoppers flew in, they were immediately gobbled up by the chickens and rarely got as far as the garden. The ‘chicken moat,’ as the owner called it, was a creative, useful idea that brings me a smile every time I think about it.

If you have grasshoppers, think about creative ways you can limit the damage they do to your yard, garden, or property because they can be a formidable enemy. Also, for more information on grasshopper control, hop on over to CSU Fact Sheets 5.536 and 5.535 to learn more ways to keep this insect at bay.

Tuesday, June 7, 2022

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

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 (

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

) or white grubs ( 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).

Monday, June 6, 2022

Is It Too Late to Plant A Veggie Garden?


By Yvette Henson, San Miguel Basin Extension

Timing is critical when planting a vegetable garden, especially in the short-season areas of our state where every day counts to get a harvest.  But what if you missed the recommended planting dates for your area?  Is all hope lost for you to have a garden this year?  The answer is: “It depends”.  It depends on how short your season is, your average summer temperature range and what types of crops you plant.

Correct timing for planting a veggie garden matters- the late planted newly sprouted peas in the background didn't produce by the time hard frost arrived.
 (photo by Yvette Henson)

To make this article easier to understand I want to first define some terms: 

  • “warm-season crops” are crops that need warmer temperatures for seeds to germinate (50-90 degrees F) and for the plants to grow to maturity (around 90 degree days and at least 50 degree nights).  Warm-season crops will not tolerate frost.  
  • “Cool- season crops” need a cooler temperature range for seeds to germinate (40 - 80 degrees F) and will not grow well with extended temperatures above 80 degrees during the day (60-65 degrees F is best).  Temperatures above this may result in the plants bolting (forming a flower stalk and eventually seeds) or in the plants having a bitter taste. They will tolerate frost and in fact, develop better flavor with cold night temperatures.  
  • In general, “short-season varieties” will reach maturity in 80 days or less. 
  • Choose varieties based on the average frost-free growing period for your area as well as your average day time and night time temperatures of your location.  You can find this information at

Now, back to the question at hand “Is it too late to plant a garden and get a harvest this year?”

It is likely too late to plant and get a harvest of warm-season crops like corn, peppers, eggplants, melons (particularly watermelons).  These also require a long season to mature. Let’s use winter squash as an example.  Winter squash require warm temperatures around 90 degrees during the day and at minimum 50 degrees at night.  They also require around 90-120 days to mature.  Although there are short-season, somewhat cold-tolerant varieties of most warm-season crops that will improve the odds to get a harvest in short-season areas with cool night temperatures, these varieties still need the basic conditions for good growth of warm-season crops.  

A selection of winter squash, both a warm-season and a long-season crop         
(photo by Yvette Henson)

If you have a longish, frost-free growing season with warm summer temperatures, you could still plant and get a harvest of warm-season crops like bush green beans or summer squash.  Most varieties mature anywhere from 45- 65 days. 

These warm-season bush beans mature in about 50-55 days
(photo by Yvette Henson)

If you live in a location with summer day-time temperatures that reach or exceed 90 degrees then is too late to plant and get a good harvest of cool-season crops like lettuce, arugula, spinach, mustard greens, summer radishes, etc.  These are all cool-season crops that may bolt and/or develop a bitter taste in the heat of summer.  You could wait until July or early August to plant quick- maturing, cool-season crops like peas, lettuce, fall radishes, etc.  These will be ready once the cooler temperatures of fall arrive.  

Beaujolais spinach does well planted late to mature in cool fall weather
(photo from Fedco Seeds)

If you live in an area of the state with a short frost-free growing season and cool nights, you may still be able to plant and harvest crops like cabbage, broccoli, turnips, rutabagas, beets, carrots.  Just be sure to check the days to maturity on the packet of seeds, keeping in mind that cool temperatures increase the actual days to maturity.  I have a 100 day growing season and cool night temperatures, so I prefer to plant peas the first of July.  They will be ready to harvest in the cool of fall and will be sweeter.

This 'Early Jersey Wakefield' cabbage is easy to grow and is ready to harvest in 70+ days
(photo by Yvette Henson)

Also, keep in mind that some crops grow best with certain day lengths.  See my previous article titled: "Day Length and Plants". 

This isn’t an exhaustive list for sure and I would love to get the input of experienced gardeners.  In the comments give your growing conditions and crops that you can plant later than the recommended planting times for that crop.

Thursday, May 26, 2022

The Great Escape! Noxious Weeds Edition

Denyse Schrenker, CSU Extension in Eagle County 

Did you know that the majority of plants used in agriculture, the landscape industry, and forestry in North America are not native to the continent? We introduce non-native plants for a variety of useful reasons and most of the plants introduced do not cause ecological harm. However, there are some that escape our care and cultivation and go on to wreak havoc on our landscapes. 

Many of these introduced species that become invasive were brought here as ornamental plants. Several plants on the Colorado Department of Agriculture noxious weeds list were originally brought to the United States to decorate our landscapes but have since escaped our yards and become pests of our natural areas. These plants are quite attractive and you might think, “oh but I love that flower!” Despite their beauty, they are listed as noxious weeds for a reason and can disrupt native ecosystems. 

Dalmatian toadflax (Linaria dalmatica) is one of these notorious plants. Native to the Mediterranean region, Dalmatian toadflax was introduced as an ornamental in the western U.S. in 1874. Dalmatian toadflax is able to monopolize landscapes because it spreads by creeping roots known as rhizomes, and produces vast amounts of seed. A single plant can produce 500,000 seeds which remain viable for up to 10 years! Early identification is key to preventing a Dalmatian toadflax invasion. This perennial plant has thick, waxy, often bluish tinted, heart-shaped leaves that wrap the stem and bright yellow, snapdragon-like flowers. Dalmatian toadflax’s sibling, yellow toadflax (Linaria vulgaris) is also a listed noxious weed in Colorado. Yellow toadflax is native to south-central Eurasia and was brought to North America in the late 1600s for fabric dyes, medicinal purposes, and ornamental purposes. It is still occasionally sold in nurseries in states where it is not listed as noxious under the name “butter and eggs” or “wild snapdragon”. Like its relative, yellow toadflax develops an extensive root system and can reproduce through creeping roots. Yellow toadflax is distinguished from Dalmatian toadflax by its very narrow, linear leaves, and its flower is lighter yellow with a dark yellow to orange center (hence the nick-name butter and eggs!). Although these perennial toadflax are in the Snapdragon family, the ornamental snapdragons found in planters and landscaped areas throughout the county are not invasive. Ornamental snapdragons are annuals and not well equipped to survive without the help of human cultivation which sets them apart from toadflax.
Dalmatian Toadflax (CSU Factsheet 3.114)
Yellow Toadflax: CSU Factsheet 3.114
Oxeye daisy (Leucanthemum vulgare) was introduced as an ornamental to North America by Pilgrim settlers in the 1700s. Oxeye daisy is also commonly included in wildflower mixes so it is important to read the label, check the scientific names, and make sure you know what you are planting. Oxeye daisy spreads by seed and creeping roots. The seed can remain viable for up to 40 years! This weedy daisy is a fierce competitor and can form dense stands that choke out native plant diversity. Management of oxeye daisy is often thwarted by its good looks. However, do not be deceived, oxeye daisy is no friend to our landscapes. Wildlife and livestock alike do not feed on the lousy tasting daisy and even avoid walking through oxeye daisy infested fields because it irritates their faces and legs so this weed directly reduces wildlife habitat. Oxeye daisy is detrimental to soil health because organic matter does not build up like it does under our native plant communities due to its shallow root system. The shallow root system and its formation of dense stands can also lead to areas of bare soil which causes soil erosion. Oxeye daisy carries several plant diseases such as aster yellows and harbors several detrimental nematode species. Shasta daisy, native daisies and asters are good alternatives to oxeye daisy.
Oxeye Daisy

The last ornamental escapee we are going to discuss today is poison hemlock (Conium maculatum). Poison hemlock is a native of Europe, western Asia, and north Africa. It was imported from Europe in the 1800s as a garden plant and is now found in almost every state in the U.S. As its name suggests, poison hemlock is extremely toxic and has been used as a source of poison throughout history. The ancient Greek used it to poison political prisoners. The famous Greek philosopher Socrates suffered this fate in 339 B.C. in Athens. In the past, Indigenous Americans used it to make poisoned arrows. Today, human deaths most often occur due to confusing poison hemlock with edible relatives such as wild carrots or parsnips. Poison hemlock is a biennial meaning that it forms a rosette in its first year and then sends up a large stem which flowers and then dies. Preventing poison hemlock from setting seed is vital to controlling this species. Poison hemlock has lacy, fern-like leaves that resemble parsley and clusters of tiny white flowers. Crucial to identifying poison hemlock are the purple spots found on its stem.
Poison Hemlock: CSU Guide to Poisonous Plants

The key to controlling all noxious weeds is prevention and early identification. Weeds tend to invade bare and disturbed ground so maintaining a healthy landscape full of non-invasive species is the best thing you can do to avoid a weed infestation. Information about controlling these species is available through the Colorado Department of Agriculture at

Tuesday, May 24, 2022

Converting to Xeriscape, with some help!

Guest post from Adams County Colorado Master Gardener Heidi Stark. 

Plants laid out after arrival 

I recently helped a relative convert about 200 square feet of turf in her yard to a xeric garden. She had been contemplating it for a while, realizing that the grass in that area was chronically thin with large bare spots. There are organizations like ReSource Central that provide garden kits to help jump start a xeriscape conversion. In early spring, she did some research and decided to purchase a Garden in a Box to replace the existing turf. She settled on the Splendid Seasons box, the largest one offered on the Resource Central website. The kit offered a nice mix of grasses and herbaceous perennials that create interest in her landscape 365 days a year.

Since xeric plants are happier growing in a leaner soil with less water than turf, she added two tons of squeegee, small rock about ¼-inch in size, that increases drainage and reduces the present organic matter to roughly 3% to 4%. She had the squeegee tilled in to a depth of 6 inches.  Then she waited to be contacted by Resource Central that her plants were ready!

Figuring out the best spacing

The Garden in a Box system is a great way to put in a xeric perennial garden without much forethought. The predesigned kits have landscape plans that are simple to comprehend and have a color layout with mature dimensions on the gridded paper that anyone can follow to plant a diverse, colorful, exciting design. There are many options for almost anyone’s desires. You can look up in your area to see if your city, water service or other providers have resources for you to do a similar conversion. 

When the plants arrived, we set a day to plant. First, using the color layout plan, we took each container and set it out on the prepared area with sufficient space between the plants to represent what mature size would be. At first, we thought there would be too many plants for the space. However, once all the pots were placed on the ground, it was evident that they needed to be spaced further apart to make the area symmetrical. So, we inched the pots here and there until the layout looked right. 

Root washing small plants is
easy with a plastic bucket

Since the plants are grown in a nursery under ideal conditions in cushy container soil, we decided to root wash each plant before putting it in the ground. This encourages the roots to spread out into the native soil and avoids circling roots, which can be detrimental.  

The entire planting process took about two hours.  We watered the newly planted perennials and stood back to admire our work. She now plans to convert her existing sprinkler zone to a drip system. She purchased some conversion kits for her pop-up sprinklers that will direct the correct amount of water to each plant. Since she can manually regulate the water to that zone, she will not overwater these plants as she might if they were planted in an area on a schedule that’s programmed for turf. Once established, which can take up to two years, these plants should not need any extra irrigation unless we experience a prolonged hot, dry period. 

The finished result - For this year!

Total cost of the project was roughly $700 between the cost of a landscaper rototilling in the squeegee, the Garden in a Box package, and the sprinkler conversion parts. Some water districts are helping to defray the cost of such a turf conversion to encourage residents in the Denver area to make this change.


As she said to me before I left, “It will be interesting to see how it thrives in year 2.” And how much this change will make a dent in her summer water bill.



Thursday, May 19, 2022

Winter is on it's way back...for a day

Posted by: Deryn Davidson, Boulder County

This blog was originally posted on April 28th, 2017...but here we are again with wintery weather on it's way to the Front Range so I thought it would be a good idea to post again! Yes, this is the second post on the same day, so be sure to check out the previous post, The Role of a Bumble Bee too!!!
For the past several weeks it's seemed that the warm weather was here to stay. But, we all have to remember that we live in Colorado and you NEVER know what Mother Nature has in store for us here. Over the next two days, much of CO is predicted to get below freezing temps overnight and many people are asking if their plants will survive. Well, as usual, it depends...

freeze is when the temps drop low enough to cause the water in plant tissue to turn into tiny ice crystals and the next day your plants turn to mush (destroyed plant tissue). A frost is when there is a lot of water vapor in the air and temps drop low enough to freeze that vapor. The result is frost on top of plants. We can get light frosts, that don't actually freeze plant tissue. The different is based on: how low (below 32F) the temperature get, how long the low temp lasts, what species of plant you have, and where the plant is located (sheltered or out in the open).

There are some plants that will be affected by this cold-snap and there are measures you can take to help protect them:
  • Covering plants is the most common. You can use old sheets, blankets, frost cloth, burlap sacks, etc. Flower pots or large trash cans turned upside down can also be placed over plants. If you use something heavy like a blanket be sure that you have stakes or something else besides the plant to hold up the blanket. You don't want to crush the plant while you're trying to save it from the freeze! Cover the plant in the evening to try to trap some of the heat that has built up during the day, then UN-cover the plants the next morning once the sun is out. 

Grouping of pots at DBG covered for late April freeze

Nursery stock covered in preparation for the April freeze

  • Watering plants can help, but you would have needed to do that a few days ago. Moist soil retains more heat and will raise humidity levels which can help reduce frost damage.
  • Mulch can provide some protection if you have a nice layer down. You can mound it up around plants, but delicate/tender plants won't like to be covered with a thick layer of mulch. 
These precautions can help, but we all have to realize that some plants just won't take the cold well and may be set back by the low temperatures, others will make it through just fine. If you have plants that seem particularly tender, go ahead and give them some extra protection. 

I have to give a nod to Jack Frost and Mother Nature, always keeping us gardeners on our toes here in CO!! Good luck everyone, I hope your gardens come through just fine!!

The Role of A Bumble Bee

The Role of A Bumble Bee
By CSU Horticulture Agent, Linda Langelo

A great northern bumble bee (Bombus fervidus) foraging on catmint (Nepeta spp.) at the Lima Plaza Pollinator Demonstration Garden in Araphoe County, Photo: Lisa Mason

According to the Xerces Society, bumble bees pollinate wild flowering plants and crops. They do not depend on flower type to survive. With some plants, it is not that way. There are some rare plants that depend on a bumble bees such as the native monkshoods and lady's tresses orchids. Bumble bees are the only known pollinator of potatoes worldwide.

Other flowers the bumble bee pollinates are snapdragons, mints, orchid and peas. According to the Brooklyn Botanic Gardens, flowers pollinated by the bumble bee must have a sturdy lip, apron or heel for a landing pad. When the bumble bee lands on monkshood it opens the flower. The petals pop open and the bumble bee clambers over the male and female parts collecting pollen at its feet while reaching with its head to the nectaries in the hood of the monkshood flower. Once it flys to the next monkshood, seeds are pollinated, and the species is ensured continuation. 

One of the most common bumble bees in Colorado, the Hunt's bumble bee (Bombus huntii) forages
on a linden tree (Tilia spp.) in the Araphoe County. Note the ball of pollen and nectar she has collected
in her pollen baskets called corbiculae. Photo: Lisa Mason

What would the world look like without bumble bees as pollinators? There would be several plants missing from the world. However, there is some recent research according to in an article Bumble Bees Have Learned to Hack Plants by Nina Pullano. Pullano is referring to the hacking of a plant when a bumble nibbles on the leaves of a plant that is not producing flowers. This may damage the plant by stimulates flower growth. Plants not in flower can bloom up to a month earlier. This behavior was found in a lab at the University of ETH Zurich by researchers Mark Mescher and Consuelo De Moraes. They found that this also happens in the wild. This is a particular characteristic that only bumble bees possess. Researchers are uncertain if they have in their saliva that causes plants to flower. But it seems we can say that bumble bees are adapting to climate change. But what will they be able to tolerate as the climate continues to change remains to be seen?

Bumble bees still need our help. Creating gardens with diverse flowers and the right habitat for bees is essential. Here is a brief list of the trees that benefit bumble bees:

  • Oak
  • Black Locust
  • Elms
  • Wild Cherry
  • Maples
  • Honey Locust
  • Plum
  • Peach 
  • Apricot
  • Lindens
The following link is a Colorado State University Fact Sheet Attracting Native Bees to the Landscape: Https://

Bumble bees need pollen because it is a great source of protein. They also need nectar which provides carbohydrates. The more diverse type of plants in our landscapes, the more opportunities we give the bumble bees the chance to obtain what they need when they need it. Having plants that bloom early to late season ensures the success of keeping bumble bees going. 

The following link is a Colorado State University Extension Fact Sheet Creating Pollinator Habitat: Https://

A Nevada bumble bee (Bombus nevadensis) foraging on a Rocky Mountain Bee Plant (Cleome serrulata) in Gilpin County. Photo: Lisa Mason

Thursday, May 12, 2022

Top 10 Vegetables to Grow in Colorado


by: Katie Dunker, Statewide Colorado Master Gardener Coordinator and John Murgel, Horticulture Agent; Douglas County, Colorado

It’s May, and that means in much of the state, the official gardening season has begun!  For many people, it wouldn’t be a garden without a few vegetables, and with that in mind, here are ten vegetables we think you have to grow this year!  How did we get to 10, you ask?  We considered general ease of growing, plants that are particularly well suited to one or more climates in Colorado, and veggies that tend to be popular for growing, eating and donating.

 In no particular order...


Harvested Beets
Photo: Yvette Henson

1. Beets.  Because they are a cool-season, frost tolerant crop, beets can grow just about anywhere in the

state.  They’re colorful, durable, and nutrient-dense.  Start beets from seed and be sure to thin the seedlings as they grow to give ample space for beets to develop underground—be sure to eat those thinned plants, though; beet greens (micro- or full grown) are edible too.

2. Summer Squash.  Everyone knows the zucchini, but dozens of varieties of summer squash in all shapes and sizes are available.  Squash plants enjoy warm temperatures, so they won’t do well in mountain communities with a short growing season without some extra effort—but for those of us on the plains, (regardless of slope direction) they are prolific producers.


3. Tomatoes.  Tomatoes have a reputation among some as being garden divas, but so many varieties are available that there’s a tomato for you (almost) regardless of where you live.  Look for short season, cherry varieties if your growing season is short.  Many cultivars were developed specifically for cooler growing conditions. See some northern Colorado options evaluated at


4. Swiss Chard.  Ok, I admit that we’re kind of cheating here, since chard and beets are really the same plant, Beta vulgaris.  Chard varieties were bred specifically for their tasty leaves, though, rather than for a beefy (earthy?) root.  Coming in a wide color range and virtually “bolt-proof” owing to its biennial nature, chard is a charming ornamental vegetable that looks great in a container or in a garden row.

Swiss chard leaves


5. Potatoes.  Potatoes take all year to grow, but the payoff is worth it.  Start in the spring, a few weeks before last frost, and harvest in the fall just before the first frost.  Similar to tomatoes (and in fact a member of the same genus in the Nightshade family), potatoes come in many varieties including some that are adapted to cooler conditions.  Consider growing colors you don’t see in the store, like purple!


6. Snap Peas.  Peas are another great cool-season treat that can be grown just about anywhere across the state.  Eat the new shoots if you’re impatient, or wait to harvest the bounty of sweet pods, perfect for snacking or stir-fries (and kid snacks!)


 7. Onions. 

Photo: Yvette Henson
 Much of Colorado is a steppe climate, and steppes are where onions call home.  Our bulb-ready climate is favorable to these recipe staples.  Grow “slicing” onions from sets or scallions from seed.  If growing onions for the bulb, be sure to choose long-day or day-neutral varieties.

8. Cucumbers.  For fresh eating or pickling, cucumbers make easy, prolific plants.  A wide range of varieties are available, from pigmy to full-length; from round, lemon-yellow balls to long, fuzzy snakes—there’s a cuke for you! 

Green Pumpkin
9. Pumpkins and Winter Squash.  Many people
 quibble about what qualifies as a pumpkin versus a winter squash—and truth be told, they’re the same thing!  (Not that either is a scientific term, but we tend to call anything orange and round a pumpkin and everything else a squash, even though the same three species of plant produce both forms).  Pick a variety that matches your growing season—many small varieties will mature in August if planted in late May or early June.  Pumpkins and winter squash, when fully ripe and “cured,” can keep for months (I once used the same pumpkin on two consecutive Halloweens—a lovely white Cucurbita maxima).


10.  Your Favorite Vegetable.  We know that growing vegetables in Colorado can be a challenge, but we have the resources to help you succeed.  Call your local Extension office, and check out these free resources from CSU Extension:

Romaine Calm and Grow Veggies Poster

Free Registration for the Summer 2022 Growing Vegetables online course Register between May 12 and 26 and receive100% off!  You can access the course materials for a year from registration, so need to rush your gardening wisdom. 

 The Colorado Vegetable Guide. This 67-page booklet contains a growing summary for a wide range of crops.  Available free online. 

 Grow & Give Colorado.  This “Modern Victory Garden Project” webpage is full of CSU vegetable gardening videos, fact sheets, and recorded lectures.  

Because you’ll have a bountiful harvest, check out the resources for donating your produce too.  Many food banks accept donations of fresh produce, and garden-grown vegetables are typically popular.  Consider including recipes with your donation.