CO-Horts Blog

Monday, June 14, 2021

Garden for Pollinators, the choice is clear! Or is it?

 Posted by John Murgel, Douglas County Extension

If you have not yet noticed, June is Colorado Pollinator Month!  National Pollinator week kicks off next Monday.  During this month and beyond, you may find yourself the recipient of a lot of different advice on how to best support pollinators in your garden.  I think all of it is given with the best of intentions; differences, sometimes strong differences, exist.  Truth be told, pollinator (and broader ecosystem) support by human activities is an area of active research and practical conclusions are difficult to draw.  To quote Dave Armstrong, professor emeritus at CU-Boulder, “Ecology is not rocket science, it’s harder.” 


Mason bee close-up
Native Bees are cuter than you think!

Here’s a conundrum perhaps not unfamiliar to many Colorado gardeners:  should I plant only natives, from local seed sources? I hear this recommendation (sometimes presented as an imperative!) frequently.  Most of my garden is a mix of non-native and “native” plants.  I put native in quotations because I have collected exactly ZERO of my plants from wild seed.  I stand by this decision—having thousands of gardeners added to the list of seed predators seems like a great way to drive wild populations of native plants to extinction.  So out the window goes “local population source” for my natives.  That will lead a conscientious gardener to the risk of genetic material from my "cultivated natives" getting into the wild populations nearby, at the risk of reducing the wild population’s fitness with “weak” domesticated genes.  At least there’s little risk of a non-native plant doing that!

 Perhaps I shouldn’t worry too much about gene flow.  After all, the “natives” I’m growing aren’t all native to my zip code, or even to my county.  Many are “Colorado natives,” or natives from the Western US, chosen more for drought tolerance than for their geopolitical pedigree.  Many true natives from undisturbed places around my home would shrivel on a day like today with the reflected heat and other challenges associated with highly modified, man-made landscapes. At least my questionable natives and non-natives have flowers to visit!

A mixed native and non-native planting
A mixed native and non-native planting

 Maybe I should plant a tree to help shade that hot landscape.  A little cooling provided by all that transpiration wouldn’t hurt either to mitigate the urban heat island effect!  Trees don’t naturally grow in my neck of the woods, so “native” goes out the window immediately.  I’ll have to water a tree, too.  But if the house is cooler naturally, the carbon-cost of cooling it with electricity on a day like today will be less.  Mitigating climate change would help pollinators, right?  What’s the “greenest” choice?  Decision paralysis seems inevitable—how to make the right choice!?

A native bumble bee visits a non-native plant
Native bee and non-native plant

 Some decisions you might make in the garden are obviously bad for pollinators—putting up butterfly houses, growing sterile, non-pollen producing plants, or liberally using insecticides come to mind.  Many other decisions, though, are good, or at least less clear.  Take the decision to plant flowers.  Should I only grow native plants for the native bees?  Plants with which they’ve co-existed for millennia?  In my garden, all the bees like all the plants—I see non-native honeybees on native plants, and native, wild bees foraging on my non-native drought adapted plants like Eremurus and Salvia.  Bumblebees really seem to like Salvia, with Echium close behind.  Should I remove the non-natives?  I have mixed feelings about honeybees, so where would that leave me?  Which suite of plants is “best”—for pollinators, for water, for climate change?  We may never know.  But don’t let the perfect get in the way of the good.  Grow some flowers, pick plants that grow where you live, and watch the invertebrates!   

Monday, June 7, 2021

June is Colorado Pollinator Month

Posted by: Jan Behler, Douglas County Colorado Master Gardener

When people hear the word “pollinators” they usually think of bees, but ants, beetles, butterflies, flies, hummingbirds, and moths are also primary pollinators in our state. Pollination is the transfer of pollen to stigma, within or between flowers and plants. A plant’s flowers need to be pollinated to complete their life cycle of producing fruit and seeds that make more plants.

Photo Credit: John Murgel
Photo Credit: John Murgel, Douglas County Horticulture Agent

Pollinators are nearly as important as sun, soil, and water in the production of most fruits and vegetables. According to the U.S. Department of Agriculture, over three-quarters of the staple crops that feed the world rely on animal pollination. On a small scale, a lack of pollination results in a fruitless tree. However, since many of the foods we eat require pollination on a larger scale that could mean a shortage to our food supply. So, the month of June has been officially designated as pollinator month to help bring awareness to the importance of pollinators.

Photo Credit: John Murgel, Douglas County Horticulture Agent

Here are a few action items to protect these important contributors to food production and beauty in our world:

  • Plant flowers in groups. Groupings or clumps of plants will attract more pollinators than single plants scattered. A bee or butterfly will feed more if they don’t have to travel too far between plants.
  • Think of providing flowers throughout the season. Plant a variety of plants that flower at different times to offer continuous pollen and nectar sources. A few examples of spring plants could include blue flax, allium, crocus, and serviceberries. For summer you might try blanket flower, bee balm, lavender, and sage.  For fall, hyssop, coreopsis, common sunflower, and golden rod.
  • Use insecticides carefully, if at all. This is self-explanatory!
  • Grow native flowering plants which are adapted to local soil and climate. Plant Select has many great plant recommendations that are suited to Colorado and known for their hardiness and low water consumption. For a good list of native plants, check out the CSU Extension Website for the fact sheets: NativeHerbaceous Perennials for Colorado Landscapes – 7.242 and CreatingPollinator Habitat – 5.616
Photo Credit: John Murgel, Douglas County Horticulture Agent

It is quite amazing but there are over 950 species of bees in Colorado alone. Did you know that hummingbirds can fly backwards and upside down? Also, t
he average lifespan of those beautiful adult butterflies is roughly three to four weeks so take a moment to look around in your yard and notice the pollinators and be kind to them this June and always!

Friday, June 4, 2021

UnBEElievable: The Benefits of Pollinators in Our World

Posted by: Lisa Mason, Arapahoe County Extension

Let’s celebrate pollinators! June is Colorado Pollinator month and June 21-27th is National Pollinator Week!

Pollinators provide so many benefits to humans and ecosystems that they deserve more recognition than just one month out of the year! Education and awareness is critical because pollinators are declining all over the world for a variety of reasons including habitat loss, pesticides, parasites, diseases, climate change, etc.

Pollinators around the world include bees, bats, flies, beetles, wasps, ants, butterflies, moths, and some species of reptiles and small mammals. Bees are among the most efficient pollinators because the pollen sticks to the hairs on a bee.

Why should we care about pollinators?

Pollinators provide valuable ecosystems services. They transfer pollen grains from one flower to another which enables the plants to reproduce. Here is a closer look at the value pollinators have to humans and ecosystems:

  • 75% of more than 240,000 plant species rely on pollinators for reproduction.
  • The global production of crops that depend on pollinators is an industry worth up to US $577 billion annually.
  • Bees help to pollinate 1/3rd of the human diet including the most nutritious part of our diet—fruits, vegetables and nuts.
  • In addition to crops, they pollinate the food for livestock that contributes to the meat and dairy industry.

In addition to providing nutritious food, pollinators offer a variety of other ecosystem services that are less known. Think of all the benefits that plants provide us. We can thank pollinators for facilitating plant reproduction for many of those plants. Examples of ecosystem services include:

  • Raw material production
  • Recreation
  • Climate regulation
  • Erosion control
  • Nutrient cycling
  • Clean air
  • Cultural value
  • Medicinal plants
  • Plant-based dyes
  • And more!

The Buzz with Bees

All bees should be celebrated! Our planet has an incredible amount of bee diversity! We have approximately 20,000 species of bees worldwide. We have over 900 species in Colorado! Most of us are familiar with the honey bee (Apis mellifera), a non-native bee species to the United States. The honey bee was brought over from Europe in the 1600’s and is a domesticated species. While they are not at risk of going extinct, they do face a variety of challenges like varroa mites. Honey bees are an important species economically and for pollinating food crops. They also provide us with honey, wax, and other products. Native bees provide an incredible amount of biodiversity and many native bees have specialist relationships with the plants they pollinate meaning other bees are unable to pollinate those specific plants. A couple of examples include squash bees that are very efficient at pollinating pumpkins and squash, and bumble bees that “buzz pollinate” plants. Buzz pollination occurs when a bee has a strong vibration frequency that allows the plant to release the pollen. Plants that need buzz pollination include tomatoes and peppers.

While writing this blog post, I took a break to water flowers in my yard. I came across this little bee who landed on my hand. This bee was less than a quarter of an inch, but she was working hard a pollinating the catmint (Nepeta spp.). She is closely related to Mason bees (Osmiini Tribe). We need a microscope to determine the exact genus, but she is likely a Hoplitis spp. or Heriades spp. bee. She has special pollen-collecting hairs on the underside of her abdomen. She is also a cavity-nesting bee.

How are you going to celebrate Colorado Pollinator Month?

Here are some ideas:

  • Observe pollinators in your backyard, parks, or open spaces. Look for visiting insects and birds that might be pollinating blooming flowers. Notice the diversity of flower visitors, and how hard they work at collecting pollen and nectar. If you take photos, you can upload them to iNaturalist, a biodiversity science database of observations. You can also explore iNaturalist to see what others are observing. 
  • Plant flowers and provide pollinator habitat in your landscape. No landscape is too small or too big. Planting some pollinator-friendly flowers or providing some habitat space will benefit the pollinators that visit. How can you provide habitat space? Keep in mind that approximately 90% of bees are solitary which means they mostly do not interact with other bees with the exception of mating.  Of the solitary bees, about 70% live underground and the other 30% are cavity nesters.  Here are some resources:
  • Join the Native Bee Watch Community Science program! All training free and provided. You can watch bees in your landscape and collect data on your observations. Register here by June 13th. Learn more about the program at Check out the CSU Source Story on Native Bee Watch.
  • Attend a virtual class during National Pollinator Week! Register here to take a one-hour class on June 25th at 12pm on who the pollinators are and how to support them. 
  • Spread the word! Check out the resources for National Pollinator Week and share with your friends, families, and neighbors. Share your photos on social media and use the hashtags: #ColoradoPollinators #PollinateCO #NativeBeeWatch #CSUExtension 

Tuesday, June 1, 2021

Be Gone, Grass (in landscape beds)!

 Posted by: Alison O'Connor, Larimer County Extension

Do you battle grass creeping into your landscape beds? Me too. And it isn't fun dealing with it. I've tried all the recommendations--pulling, mowing, digging, and herbicides. Now, before you label me as a "spray head", I'm not. I pull a lot of weeds in my landscape, mostly because I find it therapeutic. I love listening to music, filling up a bucket of weeds, and appreciating my landscape on a micro-level. However, I also have my limits, and trying to dig out bluegrass around my delicate plants isn't fun.

Kentucky bluegrass creeping in my Heuchera (coral bells).

Fortunately, the herbicides available for this problem are extremely effective and readily available. If you choose not to use herbicides, then keep on keepin' on with pulling, digging, and using mulch. These efforts can be successful, but persistence is key. Do it regularly.

If you want to consider herbicides, then look for products that contain either fluazifop or sethoxydim. There's a third, clethodim, but it tends to be more expensive. These herbicides are sold in products like Ortho Grass B Gon, Fertilome Over the Top II, Bonide Grass Beater, Monterey Grass Getter, etc.  

One of many options you can use to selectively remove grass from landscape beds.
This is not an endorsement of any particular product.

[Side note: I absolutely LOVE saying "fluazifop" and find it to be the most fun chemical name to use in everyday conversation. Flew-as-uh-fop. Fabulous.]

These are selective herbicides, meaning they will remove grass selectively from other plants. Namely, they will kill grasses, but leave your broadleaf plants unharmed. But they can injure/kill other grasses (ornamental grasses), iris, and other monocots. So read the label and use carefully.

But they do work! And usually in one application.

Use of fluazifop in my front landscape bed on bluegrass;
nearby plants included sedum and spring bulbs.

Don't worry, sedum, help is on the way!

Hang tight, little sedum, you'll be free from that bluegrass soon.

Monday, May 17, 2021

This is Colorado Noxious Weed Awareness week!


Colorado Governor Jared Polis recently designated this week, May 15-22nd, as Noxious Weed Awareness Week in Colorado. For anyone who, like me, considers themselves a Weed Warrior, this proclamation helps highlight the need for everyone in our state to take noxious weed control seriously. And while many landowners are very familiar with the identification of noxious weeds, many home gardeners are not and may inadvertently be harboring these weeds in their gardens.

As a little reminder, noxious weeds aren’t just annoyances in your yard or property: they are non-native, invasive weeds that have a competitive advantage over our vegetation and displace our native plants. Many of them are from other continents entirely and don’t have insects or disease they may have had in their native land that kept them from becoming unruly. Noxious weeds are ones that have been determined by state or local governments to be a threat to local environments and have been placed on a Noxious Weed List. In Colorado, there exist three lists of noxious weeds, and corresponding controls are needed for each.

List A species are weeds that must be eradicated whenever detected in order to protect neighboring communities and the state as a whole. These weeds may or may not be in the state yet, or may be in adjacent states and infestation is probable. Eradicating them as soon as they are found helps keep them from getting a foothold in our state.

A few plants that may be planted in gardens can be found on List A. Myrtle Spurge, Orange Hawkweed, and Purple Loosestrife are all plants that someone thought would make wonderful ornamentals in the yard, but showed quickly that they are aggressive, dominating species that quickly take over our native vegetation when they escape the confines of a garden.

Oxeye Daisies taking over fields
near Steamboat Lake

List B
species are those that are present in the state, but the Colorado Department of Agriculture, in consultation with the Colorado Noxious Weed Advisory Committee, has developed a plan to keep these weeds from spreading. Plants that were once considered ornamentals that have now found themselves on List B due to their aggressive tendencies include Common Tansy, Dalmatian Toadflax, Dames
Rocket, Oxeye Daisy, Russian Olive, and Yellow Toadflax.

List C species are weeds that the CDA will help support efforts by local county and city governments to educate people on their threat and to help use management methods to limit spread. This list includes many common ‘garden weeds,’ like Field Bindweed and Redstem Filaree. List C also includes common mullein, which is spreading along roads, railroads, and trails across the state.

Dalmatian Toadflax on a hillside

Controlling noxious weeds is not only the right thing to do if you’re a gardener or native plant advocate, but also because it is the law. Many of these weeds can be controlled with mechanical, cultural, or chemical means, and using an integrated approach to control using all of these methods is most effective. Of course, keeping the ground covered with healthy vegetation and not giving weeds a place to grow is the best solution, and also gives our native pollinators the best chance at thriving, too.

Wednesday, May 12, 2021

Underused Trees and Shrubs You Can Plant in Your Landscape

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

Planting a new tree is a great thing to do, but planting an underused tree is even better! For one, it increases the biodiversity around us. Having a variety of plant and animal species increases the overall health of an ecosystem.

Another thing to consider, is the positive effects using an underused tree would have if there were a pest outbreak. Right now, we are dealing with the potential of the Emerald Ash Borer coming to Pueblo, and many places around the state are currently dealing with EAB outbreaks. Where the EAB is present, there is a potential to lose a whole lot of Ash trees. Since Ash trees have been widely planted for decades this could cause many of our neighborhood trees to be gone. If we had a greater variety of tree species, one pest could not wipe out such a large number of trees.

If you are thinking of planting a tree, look around and don’t choose a tree species that you see already planted near your home. Here are some ideas, from CSU Extension PlantTalk scripts, for underused trees and shrubs you can plant to increase the tree biodiversity in your neighborhood:

  •         Aesculus flava (octandra) or Yellow Buckeye- Has an oval shape at maturity and can grow up to 50 feet tall. Yellow flowers appear around May. Has a great orange color in the fall. Ideally it would like a moist, well-draining soil, and it can adapt to our alkaline soils.
  •         Quercus muehlenbergii or Chinkapin Oak- Grows up to 45 feet tall and can spread just as wide if not wider. The leaves have a nice rust color in the fall. Being an oak, it will have an acorn that will mature in the first season.
  •         Pyrus calleryana ‘Whitehouse’ or Whitehouse Callery Pear- Has a columnar/pyramidal form. The leaves are glossy green, and long and narrow. Leaves turn reddish-purple earlier in the fall than other clones. The white flowers are a little later than other clones of Callery Pear.
  •         Crataegus x lavallei or Lavalle Hawthorn- It grows 15-20 feet tall and has a round to oval crown. The leaves are glossy green in spring and summer and copper red in the fall. It has white flowers that bloom in May or June and a red fruit that will last through winter.
  •         Maackia amurensis or Amur Maackia- Grows to about 20-25 feet tall and wide and has a round crown. The interesting bark peels when mature. It blooms in June and July with fragrant white flowers.
  •         Lacebark Pine Pinus bungeana- Lacebark pine has attractive exfoliating bark in patches of green and brown which makes it a good single or multi-stem specimen tree.Needles are medium to dark green about 3 inches long. It tolerates moderately alkaline soils and is hardy to zone 4 to 5.  This tree will reach a mature height of about 30, with a 15 foot width.
  •     Harvest Gold® Linden Tilia x ‘Harvest Gold’- This hybrid of littleleaf and Mongolian linden develops reliable yellow/gold fall color and is more resistant to linden aphids. As a younger tree itis less prone Harvest Gold Lindento winter sunscald than other lindens. When mature, the bark becomes mottled. You can expect this linden to reach approximately 35 feet tall and 25 feet wide. It is hardy to zones 3-4.
  •         Crimson SpireTM Oak Quercus x ‘Crimschmidt’- This hybrid of white oak and columnar English oak is a good choice where there is a need for a tall, narrow tree. Crimson Spire™ oak has attractive blue-green leaves that are resistant to powdery mildew. Leaves turn rust-red in October for 2 weeks. The leaves then turn brown and persist into early spring. Hardy to Zone 5, you can expect this oak to reach 35 to 40 feet tall and 12 to 15 feet wide.  It has shown some intolerance to wet soils.

In addition to these great underused trees, native species are always a wise choice. You can find a list of Colorado native trees here:  , and a list of native shrubs here:


Monday, May 10, 2021

Aspen Alternatives for the Front Range

By Amy Lentz, Weld County Extension Horticulture Agent

It's tree planting season which means there are choices to be made in yards all across the state. But which tree should you choose?

Today's tree-in-question - the aspen. So many of us want one in our yard to give us that 'Colorado' feeling. From the beautiful white bark to the perfectly shaped and uniform green leaves, or maybe it's the fall color or rustling sound that you just have to have! Before you go out and buy an aspen to plant in your home landscape, I urge you to reconsider if you live along the Front Range or Eastern Plains. These native trees are only native to the higher elevations of Colorado, the mountains and foothills.

Aspen fall color in mountains

Aspens have a few needs that just can't be met down at lower elevations. For one, the soil is much different than that of the higher elevations - it's higher in clay content, more alkaline and drier. The temperatures get much hotter in the summer at lower elevations than what the aspens prefer which can lead to stress. Once an aspen tree is stressed, it can invite other insect and disease problems like oyster shell scale, Marssonina leaf spot or cytospora canker. See PlantTalk Colorado - Aspen Trees (#1701) for more information.

Finally, aspens want to reproduce via suckers and create groves and many home landscapes are just not big enough to accommodate a grove of aspen trees. If you plant an aspen in a small yard, you've probably just planted an aspen for all of your neighbors, too!

Photo: Amy Lentz - Aspen trees in Rocky Mountain National Park. 

So, instead of choosing an aspen tree for your Front Range yard, here are a few interesting alternatives. They won't be exactly the same, but they have similar qualities with much less caution required. 

1. Serviceberry

Serviceberry trees are great for smaller landscapes. They can be purchased in multi-stem form, giving them that 'grove' look without the suckering. They also offer a few things that aspens don't - spring flowers, summer edible fruits and nice fall color. The 'Standing Ovation' cultivar is a taller form, giving it more of that aspen look, whereas the 'Autumn Brilliance' has an intense orange-red fall color.

Photo: PlantTalk Colorado 1213 - Serviceberry

2. Tatarian Maple

Tatarian maple is another tree that can be bought as single or multi-stemmed. The 'Hot Wings' type has guaranteed bright-red summer seed pods creating the appearance of flowering. This tree is better suited to the harsher conditions and low-water or xeric settings once established.

Photo: Adams County Extension Tour the Xeric Garden @ Riverdale Regional Park

3. Redbud

If you like the smooth bark of the aspen, the redbud has a similar appearance in its younger bark but with a more grayish tone. The leaves are larger, but also have that similar heart shape. The redbud also offers a nice display of early spring lavender blooms in most years. Plant this tree in a more protected location from wind and intense sunlight.

Photo: Amy Lentz, taken outside the Boulder County Clerk & Recorder Offices in a very protected northeast facing corner

4. Oakleaf Mountain Ash

If you want something 'mountainy', the oakleaf mountain ash has 'mountain' in it's name! It has low to moderate water needs and has a uniquely shaped leaf, pretty flowers, red berries and nice orange-red fall color. It's not a true ash, so it is not under threat by the Emerald Ash Borer. In fact, it is not known to have any serious insect or disease issues. 

Photo: City of Sheridan, WY - Arboretum

5. Columnar and Fastigiate Trees

So many to choose from! These types of trees are more narrow than wide, making them good for tighter spaces where you might commonly want to plant aspen trees. There are a lot of deciduous trees listed on our CSU Fact Sheet. A couple to consider might be the 'Princeton Sentry' ginkgo or the 'Prairie Sentinel' hackberry. 

Photo: Wikimedia Commons - 'Princeton Sentry' ginkgo