CO-Horts Blog

Monday, July 31, 2017

Tree Trunks Tell A Story

Tree Trunks Tell A Story
By CSU, Golden Plains Horticulture Associate, Linda Langelo

Do you notice the texture on the trunks of your trees?  Most of the time we may not even notice the trunk's texture.  If the texture has changed direction, this might indicate a stress!  There are four basic stresses for a tree:

  1. Compression: is a squeezing action.
  2. Tension: is stretching or pulling action.
  3. Shear: occurs when components slide relative to one another.
  4. Torsion: is a type of shear stress caused by a twisting force. 
It is important to keep in mind that these stresses can occur in combination or alone.   The trunk will tell the story.

According to the International Society of Arborists (ISA) an article titled, "Tree Risk Assessment: Loads and Growth Response," by Smiley, Matheny and Lilly:  "When gravity acting on a branch pulls or bends it downward, the bending moment creates tension in the top of the branch (fibers are stretched), while the bottom of the branch is under compression (fibers are pushed together).  In the middle of the branch, the "neutral plane" experience shear stress, where the fibers in tension and compression meet and try to slide in opposite directions.  Bending, therefore, involves at least three stresses: compression, tension, and shear, and may also have a torsional component."

The picture of a tree trunk below quickly captured my attention:

Catalpa Tree- Photo Credit-L. Langelo

Interesting trunk, right?  As you walk around the tree, the trunk twists in a spiral motion.  This is an example of torsion of a tree's trunk.  At one point in the history of this catalpa tree, a violent storm or high winds had enough force to twist the fibers of the tree.  Therefore, it looks like there are lines that curve up and around the tree.  Wind, particularly high winds are dynamic forces on trees.  Now that this torsion has occurred this tree has become a hazard.  This is a structural defect and it is a matter of time before the next environmental occurrence will take the tree down. 

There is science behind how a tree responds to environmental forces.  For example, think about the individual branches and then factor in the leaves.  In other words, aerodynamic drag -- leaves in the wind.  The ISA has formulas designed to measure these forces accurately.  Data is collected to measure these forces to predict the tree's response.  There is a great deal of math involved with tree sway motion.  Trees can be pushed to lean because of wind speed and aerodynamic drag.

In this example, which shows a leaning tree, we could say that this tree is a hazard.  The structural roots may have a harder time keeping this tree in the ground due to some of the science we know that has created this situation.  

However, there is more science:

  1. Statis load, which is a load that has no movement.  As trees grow larger, they become static.
  2. Dynamic load such as wind.
What happens to a tree in a violent windstorm is based on the mathematical data, which is placed in a model/formula accounting for all possible factors.  The model is dynamic model and it considers all the following factors:

  1. Mass of trunk, branches and leaves.
  2. Spring -- wood Young's Modulus-the measure of stiffness of an elastic material.
  3. Damping has three components:
    • Aerodynamic drag -leaves in the wind
    • Viscoelastic damping -stem/root/earth
    • Mass damping -limb sway interaction
Damping is the measure of vibration or oscillation (movement of a wavelength or back and forth movement of a tree branch).  The greatest amplitude of the vibration or oscillation is oscillation damping.  This is a form of resistance and the tree's ability to withstand a high wind.  Factored in is stem, root and earth damping.  Every aspect of a tree is taken into account.

This is the simplest way of describing how hazardous a tree can be.  There is more to a leaning tree or a simple crack in the trunk.  There is a history behind the crack, it may record the time of a violent storm or tornado or dramatic change in temperatures.  Here is a picture of what is called a shear force when tree fibers are sliding relative/opposite directions to one another:

There are times when Mother Nature is not responsible for tree hazards.  Here is an example below:

This is another type of compression from the staking material used to hold the tree in place against violent winds.  This has constricted the tree's fibers severely.  This threatens the health of the tree and further weakens the strength of the trunk.

In regards to staking, when doing so for long periods such as several seasons, this weakens the strength of the trunk.  I had a client who staked Kentucky Coffee Trees with a two inch caliber trunk for over 3 years.  By the time I was called to visit with the client, he became aware of his misunderstanding.  These trees were being grown for sale.  When the stakes were removed, the trees were more weeping than upright.  A few were able to rebound, but most still had some weeping/bending in the trunk.

On a personal note, I do not stake trees.  At the knee of the root ball I place a huge rock(s) around the root ball to allow the tree to sway until the roots are established.  So far I have not had a problem.  But again, that is my personal choice and experience. If you want more information on how to properly plant and stake trees, please click on this link:

But I digress......

Every trunk tells a story.  There is much to the story of each tree.  Every tree has to stand up to a lot in its lifetime.  Let's give them the best chance we can.  

Thursday, July 27, 2017

Herb Gardening 101
By Sherie Caffey, Horticulture Coordinator, CSU Extension-Pueblo County

Herb gardens are great. They are one of the most useful, and versatile types of gardens you can grow. Outdoors, herbs can bring beauty, fragrance, and flavor to your landscape. Indoors, herbs can brighten up your home and give your cooking a fresh kick in the dog days of summer or the dead of winter.

Whether you are growing an herb garden indoors or out, light is a very important factor to consider. Generally, it is ideal to give your herbs a minimum of six hours of direct sunlight per day. Western and southern exposures are ideal. Indoors, if you do not have a west or south facing window to put your herb garden in, you will likely need supplemental lighting. There are many great grow lights that can be purchased, but they can be a little pricey. To keep it cheap, you can use two 40 watt white fluorescent bulbs, and leave them on your plants for about 14 hours per day. Keep the bulbs about six to twelve inches away from the plants.

Soil is another important thing to consider. Here in Colorado, we tend to have alkaline soil that is often low in organic matter. Outdoors, before planting your herb garden, you can mix in plant based compost to a depth of about 24 inches. This will help to build organic matter and give your herbs a light dose of nutrients as well. For herbs in containers, you can use a soilless media, which is readily available at many garden centers. There are also soil mixes, but you should be sure it is free of weed seeds, insects, and diseases.
Water may be the most important consideration to make when growing a great herb garden. You should check the plant tag for the herbs you buy, or do some research, to figure out what their water requirements are. Plant herbs next to each other that have similar water requirements. Drip irrigation is preferable for in ground gardens, because overhead watering tends to promote disease. Containers will usually require more watering than in ground gardens. The amount of water depends on the size and material of the container, the type of plant, and the environment the plant is in. Water containers at the base of the plant, and try to avoid splashing the leaves. Overwatering your herbs makes your chances of attracting pests or getting fungal diseases much greater.

Harvesting your herbs may be the most exciting part of herb gardening. Outdoors, harvest in the morning on a sunny day with no rain, after the dew has dried. Indoors, harvesting can be done whenever the herbs are needed. It is generally best to harvest the outer leaves first. Never take more than one third of a perennial plant at a time, and for annuals, leave at least four inches of plant, along with some greenery and growth nodules so you can have more harvests. If you plan to use the leaves of the plant, you should pinch off any flowers that grow. The plant will put more energy into the flowers once they appear, and the leaves will be less flavorful. If you want to use the flowers, such as lavender or chamomile, or the seeds, like coriander (cilantro plant), then you should leave the flowers there, but harvest any leaves you want to use before bloom.

If you are a great herb gardener, then you probably have more herbs than you know what to do with. I would say that is a great problem to have! There are many options to preserve the herbs you grow, so you can use them throughout the year, or maybe give them away. Drying is a great option. You can either air dry them, or dry them using a dehydrator, or even easier, a microwave. Dried herbs tend to be more potent than fresh. As a rule of thumb, use one teaspoon of dried herbs for every tablespoon of fresh herbs that you would need. You can also freeze your herbs to make them last longer. You can either flash freeze them on a cookie sheet, or you can chop them up, put them in ice cube trays, and fill them with water and freeze them. These herby ice cubes can get popped right into any recipe you are making, or even into your summer time iced tea.

You can find a lot more information on growing specific herbs, and on using and preserving herbs on the CSU Extension website, 

Monday, July 24, 2017

Beneficial Buddies in the Backyard

Posted by Mary Small, CSU Extension Colorado Master Gardener Coordinator
I regularly scout in my backyard. No, I’m not building a campfire or setting up a tent. Rather, I look around to see what’s going on out there in terms of pests, plants and plant growth.

My most recent “find’ was this beautiful dragonfly – a female Widow Skimmer. She was just hanging out  on a spent daylily stalk. Widow Skimmers are so named because after they mate, the male takes off, leaving her to lay the eggs by herself. Usually dragonfly males stick around and “guard” the eggs for a while.

Widow Skimmer Dragonfly

Like all insects, dragonflies have 6 legs – but they can’t walk! The dark wing mark toward the outer tip of the wings acts like a weight to help stabilize the insect while flying. It dampens the wing vibration. The costa, the outermost “leading edge” of the wing is a vein that helps the insect “slice” through the air while in flight.

The term “eating on the fly” or “eating on the run” may have developed around dragonfly feeding habits. They capture their insect prey while in flight and consume it while in flight. They eat a variety of insects including mosquitos, gnats, flies, bees and even other dragonflies.

Halictid bee
This shiny metallic green insect is a Halictid bee. These insects are not only attractive, but also important pollinators. Just look at the huge pollen basket on her legs! The females typically dig burrows with individual cells in them. The burrows are usually made in bare soil in a sunny location. They lay an egg in each cell of the burrow and provide nourishment in the form of pollen balls and nectar for the larva to eat when it emerges. The adults provide pollination services for a wide variety of flowers. I caught this one on a New Mexico evening primrose (Oenothera neomexicana).

Posing praying mantid
Here’s a recognizable insect – the praying mantid. I love how it looks like it's smiling! Maybe it just ate or is eagerly anticipating it's next meal! I can’t tell you which one this was, since I was more focused on photographing its “face” than identifying it. It was "resting" on a flower stalk and blended in  so well with the surroundings that I almost didn't see it. (That’s to their advantage in their feeding behavior).

Many believe mantids are voracious predators of “bad” insects – but that’s simply not true. While they might eat some “bad guys”, they just as easily might not. They prefer faster moving insects to slower aphids and caterpillars – and those insects that are within their reach. Mantids will ambush or even slowly stalk their prey. They grab the prey with their front, spiny legs so quickly that it’s difficult for humans to observe! I may have caught this one waiting for dinner to come along, but it sure was posing nicely in the meantime.

Tuesday, July 18, 2017

When Beauty IS the Beast

When Beauty IS the Beast
By Irene Shonle, CSU Extension in Gilpin County.

What would you say if your neighbor told you she was growing a plant that was beautiful, long-blooming, drought-tolerant, deer-resistant, and spreads very quickly?  You might say, “Sounds too good to be true.”  In fact, it may be too good to be true.  Here in Colorado, we have a problem with many non-native “invasive ornamental” plants which do too well in our climate, and have escaped from cultivation and are wreaking havoc in our natural areas.  Many of these are on our State Noxious Weed List, making them illegal to sell or plant.   As gardeners, it is our responsibility to know these plants, and avoid planting them.

The Brooklyn Botanical Gardens estimates that there are 300 dangerously invasive weeds present in the continental U.S. and Canada and of these, half were introduced as ornamentals. They were brought to this country intentionally and allowed to gain a foothold before their harmful effects were known.  
When they arrived in this country, none of the mechanisms that keep plants in check, such as insects, disease, and competition came with them.  In natural areas, unmanaged populations can displace native plants, reduce biological diversity and alter ecosystem processes. These impacts affect bird, insect, fish and mammal populations which depend upon native plants for food, shelter, and protection from predators.

Is it possible to plant invasive ornamentals responsibly?
Not really. As soon as the "responsible" gardener who knows about the plant’s invasive characteristics is out of the picture (moves away, gives away cuttings or transplants, goes on vacation), the plant has the chance of becoming a problem. Also, seeds can be eaten by birds, carried by cars, dogs, or the wind and then may be planted in new locations. Gardeners, no matter how diligent, cannot control for natural processes.

What can I do?
  • Choose native or non-invasive plants for your garden.
  • Do not plant invasive ornamentals. Remove any invasive ornamentals in your garden.
  • Become familiar with invasive species and report their presence on public lands.
  • Ask your greenhouse and/or nursery to stock more natives and no invasive non-natives.

Two resources to learn more about native plants include the CSU Extension Native Plant Master Program ( and the Colorado Native Plant Society (

Our worst ornamental invaders
Our worst ornamental invaders in Colorado include: purple loosestrife, ox-eye daisy, Russian olive, tamarisk, Bouncing Bet, Dame’s/sweet rocket, perennial sweet pea, Dalmatian toadflax, yellow toadflax/butter and eggs, Mediterranean sage, common tansy, scentless chamomile, and myrtle spurge. 

Purple Loosestrife (Image :City of Boulder)
Purple Loosestrife (Lythrum salicaria) is an extremely aggressive weed which is overtaking U.S. wetlands at the alarming rate of 475,000 acres each year. It thrives in moist soil--near rivers, streams, irrigation canals, drainage ditches, lake shores, wet meadows and marshes. It's easiest to identify when the purple-magenta flowers bloom from mid-June through mid-September. The blossoms have five to six petals and grow in clusters at the end of long spikes. Each plant is capable of producing 1-3 million seeds annually. Some cultivars carry the claim of sterility but recent research has shown that these varieties can and do produce viable seeds.
Planting Alternatives: Spotted gayfeather, (Liatris punctata) Russian sage (Perovskia), butterfly bush (Buddleia), Delphinium or larkspur, blue vervain, lavender, wild lupine, violet sage (Salvia x superba), Fireweed (Epilobium spp).

Oxeye daisy
Oxeye daisy (Chrysanthemum leucanthemum or Leucanthemum vulgare) A member of the Sunflower family, is an erect perennial plant with white ray and yellow disk flowers which bloom from June through August. A native of Eurasia, this aggressive plant has escaped cultivation and become a troublesome weed in the mountains. In Crested Butte, the “Wildflower capital,” this plant is crowding out many of the wildflowers they are famous for.
 Planting Alternatives: native daisies (Erigeron spp), Shasta daisy, Black-eyed Susan (Rudbeckia hirta), and Blanket Flower (Gaillardia aristata), and native yarrow (Achillea lanulosa).
Scentless chamomile
Scentless chamomile (Tripleurospermum inodora) is very similar to Oxeye daisy, except it has ferny leaves and is an annual.  It is very aggressive in seeding disturbed areas in the mountains.  
See oxeye daisy for planting alternatives. 

Yellow toadflax
Yellow toadflax (Linaria vulgaris) is so widespread that you can often find it mistakenly listed as a native wildflower in field guides, and not as a noxious weed.  Unfortunately it still is sold by some seed companies as “butter and eggs” or as “wild snapdragons.” Always look on the back of wildflower seed mixes for a listing of what's included in the mix. If toadflaxes are listed, PLEASE DO NOT buy that product.  Yellow toadflax is adapted to a variety of site conditions, from moist to dry and does well in all types of soils. Because of its early vigorous growth, extensive underground root system, and effective seed dispersal methods, yellow toadflax is difficult to control. 
 Planting Alternatives: Annual snapdragons, Coreopsis, yellow columbine (\2001 Plant Select® selection Aquilegia chrysantha ‘Denver Gold’), or the 1999 selection SilverbladeTM Evening Primrose, (Oenothera macrocarpa spp. incana 'Silver Blade'), Golden Banner (Thermopsis spp.), Wallflower (Erysimum asperum, Showy goldeneye (Heliomeris multiflora).

Dame's Rocket
Dame’s Rocket (Hesperis matronalis) is also known a Dame’s Violet or sweet rocket..  It tends to invade riparian and wetland habitat, but can also “naturalize” in other habitats.  It can still be found in “wildflower” seed mixes. If Dame’s Rocket is listed, PLEASE DO NOT buy that product.  This native of Europe may be either a biennial or perennial, and may be from 1-1/2 to 4 feet tall, while flowers range in color from white to pink to purple. There are four petals, which help to distinguish it from phlox. Dame’s Rocket flowers from April through July.

Planting Alternatives: Blue Columbine (Aquilegia caerulea) Native Bee Balm (Monarda fistulosa menthaefolia), woodland phlox (Phlox divaricata 'Chattahoochee). Native harebells, (Campanula rotundifolia), Showy locoweed (Oxytropis lambertii)

Bouncing Bet. Photo credite: John M. Randall/The Nature Conservancy
Bouncing Bet (Saponaria officinalis) can form dense stands of plants, especially in disturbed areas as along roadsides.  It grows up to three feet tall, with clusters of pink to white flowers on the tops of the plants.  Each flower has five petals, all with a distinctive notch at the end.  The plant has a strong creeping rootstock and opposite, strap-like leaves.  It flowers from July to September.
  Planting alternative: Garden phlox, (Phlox paniculata), the 2000 Plant Select®  selection Prairie Jewel Penstemon, Rocky Mtn beeplant (Cleome serrulata),

Monday, July 17, 2017

Be Local, Go Native and Be Diverse

It’s funny how your experiences can come together.  I’m sure many of you take part in buying local food, but what about your information and the plants in your landscape? 

Starting with local information, here is a bit of history.  Thanks to President Lincoln, the land grant college system was created.  To make a long story short, each state has a college within in this Land Grant system.  Most have the word State in their title like Colorado State University, Iowa State etc…  These colleges were started to bring college to the people and not just the rich.  Out of that grew Research Stations to help the local Agriculture industry and then Extension to help spread that information to the community.
Colorado State University, Old Main
So that leads to me and the wonderful coworkers in this Extension system.  Many counties or areas in all states have an Extension office with experts that can provide you with local great information in Agriculture, Landscaping, and Family Consumer Science and many more topics.  Some of our programs you may have heard of include 4H, Master Gardener, Native Plant Master and Food Safety Master.  Volunteers in these Master Programs go through garden training, many specific to their climate and soils, so they can help spread fact based information to their local community.  Many offices like ours in Mesa County run a Master Gardener Desk where these wonderful trained Volunteers can help answer your home landscape questions giving the Agents more time to help Green Industry professionals and growers.  Can’t get much more local than that.
So, what about the plants in your landscape?
Colorado State County Map

This winter I attended a talk by Entomologist (an insect guy) and Environmental Science Professor Doug Tallamy from the University of Delaware.  I knew native plants were important but he finally connected the dots for me.  In short, native plants are the key to supporting our natural food web.  Prof. Tallamy talked about how he followed a sparrow family.  Most of us think of birds eating seeds.  But seeds are only available at the end of the season.  Mom and dad sparrow made multiple trips to a local tree, I believe an oak, and brought their babies several hundred caterpillars.  I no longer worry about a few insects on a tree.  In fact, I just had a landscaper come in.  He had gone through our Master Gardener program and had learned about IPM, Integrated Pest Management, which is where you observe and only treat when the levels of insects reaches a certain threshold and the system.  He had a client with woolly aphids on a cottonwood tree.  But he also observed many, many lady bugs.  He brought in a sample for us to look at and all we could find was the fluff left from the woolly aphids, but no more aphids.  They were all eaten.  So that is an example of the food web taking care of the issue.  No conventional or organic sprays needed.  In summary, by planting natives, you provide food for the native insects, which in turn feed the birds, lizards, and other small critters which are in turn eaten by bigger animals and insects and animals creating balance to the whole system.   I also attended a talk by David Salmon of High Country Gardens, and he too was following the recommendations of Prof. Tallamy.

Landscape at Copper Creek Mall in Salt Lake City

This week walked through a Mall, yes you heard me right, a mall in Salt Lake City where they had directed a creek and was planted by mostly plants native to the area.  I thought it was beautiful.  It provided an experience and there were many people there enjoying the space.  So you can add a few non-natives, but try plant a high per cent of natives and enjoy.  This creates and keeps a sense of place alive.  If every town and city has the same plants in their landscapes, then they all start looking the same.  I find that boring.  And non-natives can become invasive which is a whole other conversation.  Embrace the natives and plant diversity so if there are issues, it’s not a big loss.  Plus a diversity of plants provides different sources of food for the food web.  Visit your local nursery that carries native plants to buy local.  Big box stores rarely carry natives that grow in your community.
So create a diverse landscape with local native plants and enjoy the wildlife around you.  And don’t forget to visit your local Extension office to get local, revel ant information because we know you can’t believe everything on the internet.  Get your research based information here.

Susan L Carter
Horticulture Agent, Arborist and Native Plant Master
CSU Extension, Tri River Area

Friday, July 14, 2017

Stem Girdling Roots

There have been a couple previous blog posts on dysfunctional tree root systems but we have had a number of really good examples of trees with stem girdling roots come through our office this spring so I thought I would share some pictures of the issue.

A normal root system will grow outward from the trunk of a tree in a radial pattern that resembles the spokes of a wheel (though it will not be as uniform).  There is also normally a pronounced outward flaring of a tree’s trunk where it meets its root system. 

 Due to some nursery stock production techniques and planting practices some landscape trees develop roots which do not grow radially out from their trunks but instead grow across or around them.  

A root of this container grown oak deflected upward when it contacted the container, grew to the surface and then across the surface of the container .  When it reached the other side of the container it then began to circle. If left uncorrected such roots can become girdling roots.

The same tree also was planted deep in the container, ~4 inches of soil was removed from the top of its root ball before I found its first structural root.  

Such roots have the potential to become ingrown into the trunk as they both grow.  This interferes with the tree's vascular system which becomes compressed where it presses up against the offending root.  In cases where the root is circling and wrapped around the trunk the tree may be girdled.

Major stem girdling root on a littleleaf linden
Stem girdling root on the same linden  cut in preparation for removal. 

The root has been removed, note the compressed tissues of the trunk.

Deeply ingrown stem girdling root on a horsechestnut.  We were unable to remove this root but be were able to cut it at either end to stop it from growing further.

Exposed stem girdling root on an autumn blaze maple
Trees which develop stem girdling roots may have reduced vigor, slower growth, be more prone to lean and fail and are more susceptible to a variety of stresses.   Severe cases can lead to decline and death.
Swamp white oak with dieback, little growth and chlorosis 
A root collar excavation revealed the tree was planted deeply and had several stem girdling roots.
The root flare should be mostly above grade and visible.

Close up of  partially ingrown stem girdling root on the above swamp white oak

Austrian pine with leaf scorch and very slow growth. We found several major girdling roots. 

Stem girdling roots on the above pine

Ingrown stem girdling root on the other side of the trunk of the  above pine

Cottonwood which failed above a stem girdling root.
Close up of Cottonwood which failed above a girdling root.

So what can you do to prevent these issues and encourage a normal root system? 

1)When planting a tree, make sure the root flare is exposed by removing any soil or potting media covering it.
2)Plant the tree with its root flare slightly above grade.  The first structural root should be in the top couple inches of the tree’s root ball or at its surface.
3)If the tree has circling roots remove them at planting.  Shaving or boxing the root ball is a good way to do this.

"Boxing" a trees rot ball at planting to remove circling roots.

4)Dig a large planting hole which has a saucer shape.
5)Inspect the tree’s root flare regularly and remove any potential girdling roots before they become ingrown.