CO-Horts Blog

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.

Monday, May 9, 2022

Wait…What? Beans Don’t Come from a Can?

Posted by: Chelsea Didinger, PhD Candidate and Horticulture Program Outreach Assistant, CSU Extension

You may have seen snap bean and sugar snap pea plants in your garden, but raise your hand if you have ever seen a pinto bean plant in real life. If your answer is no, we have good news for you – Colorado is sixth in the nation in terms of bean production, and approximately 75% of our dry bean production is pinto beans. So, keep your eyes open this summer and you may be able to spot your first Phaseolus vulgaris from the pinto group!

A pinto bean field in northern Colorado in August 2021

Beans in Colorado

Colorado produces numerous market classes of beans. Pinto, light red kidney, and Mayocoba (aka yellow) beans are our three main types, and we also grow great northern beans, black-eyed peas, and others. The Colorado Dry Bean Committee and other organizations work to support bean growers in our state, and Colorado State University researches diverse aspects of beans, ranging from nutritional and health benefits to bean breeding. As gardeners know all too well, growing in Colorado can be challenging (albeit rewarding). So, what does it look like growing beans here?

Generally, growers plant beans sometime in mid-May through early-June. Last year (2021) we had a very wet year in northern Colorado, so some of the farmers I spoke with had to delay planting, or sometimes even plant less acres. Want to see what a pinto bean planting looks like? Check out this video taken in Wellington, Colorado.

A pinto plant approximately 60 days after planting

Depending on the variety of bean, harvest occurs about 85-100 days from planting. Beans are left to dry in their pods in the field. Then, they need to be harvested and cleaned of dirt and debris before being bagged and sold to consumers. It is a very labor-intensive process when done by hand and processing equipment can be quite expensive, so often beans are sent to a facility to be cleaned. Want to see what that all looks like? Check out this video!

This field of pinto beans in Longmont, Colorado was almost ready for harvest in mid-September 2021. At this stage, the beans have a lower moisture content and their beautiful pinto coloration.

Beans are essential to Colorado agriculture for a whole host of reasons, including:

  • Soil health – Beans are a type of legume and can form a symbiotic relationship with bacteria in the soil to fix nitrogen.
  • Crop rotation – Partially due to their nitrogen fixation ability, beans are critical in rotation with crops like corn, wheat, and sugar beets.
  • Sustainable food systems – Beans are more water-efficient than many other crops and can help reduce greenhouse gas emissions.

Fun Facts About Beans

Beans are a hot topic, especially with all the interest in sustainability and plant-based proteins. If you are searching for ways to impress your friends, look no further!

  • Black-eyed peas are generating much interest among researchers right now because they are known for their drought and heat tolerance, factors which are becoming increasingly important with our dry and hot summers.
  • Beans are a type of pulse. ‘Pulses’ are the dried, edible seeds of non-oilseed legumes and include chickpeas, cowpeas (like black-eyed peas), lentils, dry peas, and dry beans (e.g., pinto, red kidney, Mayocoba, black, etc.). Conversely, oilseed legumes include peanuts and soybeans.
  • Not all pintos are the same! This may be obvious to gardeners, but people may not always think about the incredible diversity in beans. There are numerous varieties of pinto beans, and the same goes for other types of beans. Some varieties of pinto bean include Cowboy, Windbreaker (we’re not kidding), and Othello.
  • Beans are one of the richest natural sources of fiber. Looking for delicious ways to increase fiber and protein all at once? Beans and other pulses are a great option.

Whipping up bean dip on the blender bike at the Larimer County Farmers’ Market – fiber never tasted so good!

Do you have any bean questions? I’m Chelsea, a PhD student researching beans here at Colorado State University. My research focuses on outreach, so please feel free to reach out!