CO-Horts Blog

Monday, November 29, 2021

Don't Forget About Mulch!

If there is one tip I could give for just about any landscape situation, it would be mulch. Mulching is a great thing to do for your soil and your plants, and a great natural way to keep weeds down. There are many types of mulch and using them correctly can be beneficial for many reasons.
A mulch is a material that is applied to the soil surface. Mulches function to protect and improve soil. Different types of mulch have different advantages for your landscape. Generally speaking, mulches reduce the amount of moisture that evaporates from the soil, which conserves water. Mulching a planting bed can reduce the need to water by 50%. Mulches also stabilize soil temperature. This can be beneficial for shallow rooted plants that are susceptible to freeze damage during the winter. Many mulches will help improve the structure and fertility of the soils they are added to. For some types of mulch this may require mixing them into the soil at some point during the year. One of my biggest gardening battles has been with controlling weeds. Mulch can inhibit the germination of weed seeds, which is a big help! Your trees will also benefit from mulching around the trunk. Trees that have mulch around their trunks grow larger and healthier than trees that have turf growing all the way to their base. The mulch “donut” should be two to three feet wide. Leave two to four inches of bare ground near the base of the trunk, if it is touching the trunk it increases the chance of your tree suffering from girdling roots. There are two categories of mulch, organic and inorganic. The difference between the two is that organic mulches were once alive, and inorganic mulches were not. Grass clippings are an easily obtainable organic mulch. They are perfect to mulch a vegetable bed. Add a 1/4-inch-thick layer and let it dry before adding the next layer. Adding a couple sheets of newspaper (avoid glossy sheets) under the clippings will give extra defense against weed seeds. Make sure you are not using clippings that have been treated with herbicides, which can be harmful to your vegetable plants.
Wood chips are another popular choice of organic mulch. They are good for areas that do not need the soil worked every year, such as between raised beds or in perennial plantings. They are better suited for the soil surface, working them into the soil (without composting them first) can tie up soil nitrogen, leaving an insufficient amount for your plants.
Pea gravel is an example of an inorganic mulch. It is visually appealing in a landscape area where you don’t have plants, or where your plantings are permanent. It can cause heat to build up around plants, however, which may increase water requirements, so it is better suited for water wise, heat tolerant plants.

Friday, November 19, 2021


November in the Garden

By Patti O’Neal

Jefferson County


The year is winding down, and for the most part, so are our gardens.  There are still many tasks that can be accomplished.  Some of us are just done for the year and want everything cleaned up and ready for next year, while others of us continue to push the limits of our gardens to produce yet more.

Either way, there are things that can still be done to care for our gardens, tools and wildlife.     

The weather has been beautiful this fall, so I hope you have been watering your trees and shrubs and any newly planted perennials to get them stored up for winter.  As weather may fluctuate going forward, remember to get the hose out at least once a month and give trees and shrubs a drink on lovely days when the temps are above 50 degrees and the ground is not frozen.  Water at the dripline for the most benefit to the tree. 

Apply tree wrap to young trees that may be positioned in your landscape to be harmed by flash freezes and cold temperatures.  Use appropriate material designed for this purpose.  Wrap well, over-lapping the paper or fabric about two thirds up the trunk.  Remember to remove the wrap mid to late April depending on weather.  Then wrap again next fall if needed. 

If you have not yet cleaned up all your leaves, use a mulching mower and go over them and let the small pieces mulch the lawn. 

If by any chance you still have piles, mow over them and use to mulch your flower beds with them, add to compost, mix into your vegetable garden beds, store a few bags for next summer when carbon material is harder to come by or if you have used all you can, donate them to a local urban farmer who will use them to regenerate their soil for the coming year.  Remember to leave some leaf litter in some strategic out of the way places for the native insects to overwinter safely.  Likewise, don’t clean it up too early, before egg hatch or you will throw the wonderful creatures away before they can hatch and begin to protect your landscape.  

Providing water is the single most important thing you can do for native insects and birds as well.  Place a bird bath where a heater designed for this task can be plugged in to keep the bath from freezing over.  This will give you much pleasure to watch them drinking and bathing during the next months.  In addition, don’t be too quick to cut down perennials that go to seed.  This is a rich food source for native birds as well as shelter for native insects for the winter.  If you enjoy birds, providing a rich source of fat starting as soon as possible (if you have not already) in the form of suet and rich seeds in squirrel proof feeders will encourage birds that do not migrate to enjoy your yard. 

Don’t put your tools away untended.  Now is the time to give them a good scraping of caked on soil with a wire brush then soap and water on the blades, taking them apart if possible to clean more thoroughly and drying well.   Use 00 fine steel wool to clean any rust from the metal surfaces and linseed oil to rub into the wooden handles.  

Hang long handled tools off the floor if possible to keep humidity from the metal parts and you can store hand tools in a bucket of sand with a small amount of linseed oil to keep them from rusting.  Pruners should be taken apart if possible, cleaned and sharpened and re-assembled and stored in a dry place. 


There is still time to plant bulbs if you have not gotten them in the ground yet.  The actual chill requiredfor bulbs is approximately 16 weeks and we haven’t even had that yet this year, so keep planting flowerbulbs and garlic if you want.  Then mulch them in well so they do not heave when the temperatures finally do drop. 

Make sure you have the proper season extension materials for any vegetable crops or sensitive plants that will need to be covered for frost protection.  Horticulture fabric, often referred to as frost blankets, can be found at nurseries and big box stores.  This fabric is designed to take any moisture and not harm the plants, unlike sheets and other household fabrics that hold water, will lie on the plant material and cause it to freeze rather than protect it.  It is helpful if there is a structure over the plants with which you can support this material to keep it off the plants and hold in any warmth the soil may have acquired during the day when the sun is out. 


If you have potted plants you have not gotten into the ground yet, here is a way to winter them over if you do not have time before the temperatures drop or you haven’t yet decided where you want to put them.  You can dig a hole in the ground and plant the pot and all up to the rim of the pot and winter them over that way.  Water and mulch and they can be planted next spring when you have allotted more time.  I love to use the large pots I plant my lettuce crops in once I have emptied them of my fall lettuces.  If you are a raised bed or in-ground vegetable gardner think of this as well.   The ground is already soft and so much easier to get them in successfully.  That way you do not loose them to procrastination! 

Store your crops appropriately.  If you have grown vegetables to enjoy over the winter months there are some key techniques you should know.  Not all crops require the same humidity or temperatures to hold successfully.  Make sure you have the proper storage areas for the various crops you want to hold over.  Of course, thinking of this earlier in the year, like when you were planting them, would help to inform which of those crops you could hold over most successfully, or give you time to construct  or purchase items to help you store them.  But there are still ways to find the most appropriate place in your home or shed or garage, that can host your crops to make them hold for the longest the most safely.  Consult the fact sheets below for charts and tips to help you get the best storage with the most flavor and nutrients from your crops.  

Work never seems to end in the garden.  But I wouldn’t have it any other way.  Soon the last of my fall crops will be done, except for the spinaches, leeks, carrots and chard that I keep going right up until Christmas.  They only get sweeter with a hit or two of frost, so they are easy to keep.  Then the catalogues start arriving and the dreaming portion of my gardening year begins again.   Happy Gardening!


Further Reading : The following fact sheets will give you additional information on completing the tasks mentioned above with evidenced based research from CSU and other universities.    

“Fall and Winter Watering,”

“It’s Time To Wrap Your Trees,”

“Winter Tool Care,”

“Frost Protection and Extending the Growing Season,”

“Storing Vegetables at Home,”

“Storage of Home Grown Vegetables,”


Monday, November 15, 2021

Healthy Soil- Too much of a good thing?

Recently I attended our annual forum where all the Extension staff across the state come together and we learn and share.  The sharing of programs, county issues and among us plant folk, plant and soil issues are the most telling.  There seems to be a common theme this year, gardens being over amended and a misunderstanding of organics and fertilizer versus compost is evident.  Both compost and fertilizer can be organic, but they are not the same thing. 

Compost image, Colorado State

I want to point out before I go further, that Extension and Extension staff have conventional and organic options on all our factsheets and that we all care about our environment, it’s why we have the jobs we do because we are passionate about our world.  I think it is very important understand and get the facts about your soil prior to adding amendment or fertilizer.  This is very similar to practicing IPM- Integrated pest management where you observe / monitor, proper id, learn more about the issue (or system), determine action, choose tactic(s), evaluate.  IPM is monitoring the situation, gathering the facts and doing something when needed.  So think of these similar steps in your landscape and how to improve your soil.  Get the facts before applying anything and to improve when you need to improve, plant the right plant in the right place and you will be successful.  If you have never done a soil test, this is the foundation of the garden and a good place to start.  The CSU lab is currently moving so not testing currently, other great laboratories that understand our Western soils are Ward Laboratories, Servitech and American Agricultural Laboratory Inc.

Once you pick a lab, stick with them as their procedures might be slightly different.  You want to be able to compare apples to apples down the road.  Please read how to take an appropriate sample and tell them exactly what you are planting (your crop): buffalo grass, tomatoes, plum tree- the more specific you are, the better the recommendation they can give you.

University of Hawaii Soil Management

Let’s go back to the word organic.  It was first used to describe the organic matter (basically plant material: leaves, roots, stems, & microorganisms) that is in the soil.  We still use it this way, but it has also morphed into products that are naturally based.  Here I am sticking to the original definition.  Our native soils in Western Colorado are naturally 1-2% organic matter.  This is why our native plants do not prefer high amounts of compost being added to our soil, it’s not what they are acclimated to.  Then somewhere along the way organic morphed into meaning using naturally sourced fertilizers and pesticides.  We know from experience and as shown in the soil pie chart that we want up to 5% organic matter in the soil for the general typical landscape plants and vegetable and flower gardens.  When soil test results get closer to this 5% organic matter, the need for nutrients like nitrogen will drop because it is being released of some nutrients from the organic matter (plant based and microorganisms).  This article from Minnesota gives a good explanation of other reasons too much organic matter is not good. Of course our soil is going to be different, but the having too much organic matter is the same.  We general have good minerals (phosphorus, potassium, sulfur) in our soils.  Occasionally we will see a micronutrient low due to the pH of the soil, high pH affects the accessibility of certain nutrients to specific plants.  Example: Silver maples have trouble accessing iron in high pH soils resulting in chlorosis.  Adding more iron to the soil doesn’t work unless it is chelated. 

Microbes in the soil, invisible to the naked eye-
                                                                    Colorado State
Example 2: Someone was having trouble growing vegetables, since the pH was high they continued to add sulfur, which was already at a good level.  This caused a toxicity of sulfur in the soil which causes a reduced rate of growth and necrosis.  Since we have high amounts of calcium carbonate in our soils and there already is enough sulfur, our soils are buffered which means it is very hard to change the pH so we focus on what we can change and improve.  So please do a soil sample, talk to Extension if you need more explanation, pick the right plants for your soil and you will be successful. 

Lastly, pick the right soil amendment if your organic matter is below 5%.  This includes using compost and it is ok to ask for a sample of compost and have it tested before you buy or use it.  Compost is a soil amendment, though it may help with nutrients down the road, it is not considered fertilizer or a major source of nutrients.

If your plants are needing fertilizer, than use the appropriate fertilizer. Here is understanding fertilizer.

Hopefully that helps in understanding that you can have TOO MUCH of a good thing.  It is like finding out that watermelon is good for you and you eat the whole watermelon, you might not feel so good afterwards.  It is important to keep things in balance.  By adding too much of one thing, other things have to become out of balance.  Look back at the soil pie chart, if there is too much water, there would be less air.  If too much organic matter, there would be less mineral particles, water or oxygen.  ALL are important. 

So hopefully if nothing else, you will do a soil sample and think about what your soil needs before you add something.

Susan Carter, Tri River Area Horticulture and Natural Resource Agent



Thursday, November 4, 2021

Nothing to Sneeze at: Tree Pollination and How it Impacts You

Posted by: Lisa Mason, Arapahoe County Extension

“Is it true that cities and towns plant only male trees, and male trees tend to cause more allergies for people?”

The answer to this question is far more complex than just choosing to plant male or female trees, so let’s explore tree pollination and diversity in the landscape! 

This question stems from a theory that female trees produce seeds and thus require more cleanup and maintenance, while male trees require less maintenance because they only produce pollen. However, that pollen can trigger allergies!

Note that tree pollen is only one of the sources of allergens in the air. According to the Asthma and Allergy Foundation of America, grasses are the most common cause of allergies, and ragweed is the top contributor to weed allergies.  Other allergy triggers include other weeds, pet dander, dust, and mold. Wildfire smoke has also contributed to poor air quality across the west aggravating allergy symptoms and other health conditions.

Understanding Pollination and Tree Reproduction

Trees produce pollen as part of their reproductive process. To understand tree reproduction, look inside a flower such as a tulip or lily. You can easily see the male and female reproductive organs in the flower.

Pollen is produced by a male reproductive organ called the stamen. The stamen includes the anthers and filaments (see photo below). The female reproductive organ on a flower is called the pistil, which comprises of the ovary, style, and stigma. For trees to reproduce, pollen is transferred from the stamen (male organ) to the pistil (female) organ. These pollination biology concepts apply to other plants, but this article will focus on trees.

Anatomy of a “perfect flower.” Credit: University of Missouri Extension

Wind-Pollinated or Insect-Pollinated?

Pollen is transferred between trees in a variety of ways to facilitate tree reproduction including wind-pollination or insect-pollination.

Wind-pollinated trees produce mass amounts of pollen to increase their chances of the wind carrying the pollen to the appropriate tree to reproduce. Examples of wind-pollinated plants include conifer trees (pines, spruces, firs, etc.), aspens, cottonwoods, ash trees, elms, all grasses, etc. Wind-pollinated plants tend to cause more allergies due to the amount of pollen in the air.

Insect-pollinated plants have a more efficient process of pollination because they rely on insects to transfer the pollen from plant to plant. Pollen grains are generally larger and often are sticky allowing the insects to intentionally and unintentionally carry pollen on their bodies. Bees are among the most efficient pollinators because they have hairs all over their body that easily carry pollen. Other pollinating insects include flies, beetles, butterflies, and some wasp species. Hummingbirds are also pollinators in Colorado, and around the world other animals such as birds, reptiles, and bats and other mammals pollinate plants. Examples of insect-pollinated trees include lindens, apples, crabapples, cherries, northern catalpas, Ohio buckeyes, Kentucky coffee tree, eastern redbud, etc. Insect-pollinated trees generally do not cause allergies. The flowers on these plants are big, showy, fragrant, contain pollen and nectar, and are visually attractive.

A bumble bee visiting a linden tree. Photo: Lisa Mason

How do Male and Female Trees Play a Role?

To add more complexity, the biological processes vary among trees. Trees are either: 1) monecious, or 2) dioecious. 

  • Monecious – trees have male and female parts on the SAME TREE.
    • Perfect/complete flowers – trees have BOTH male and female parts on the SAME FLOWER.
      • Since both male and female parts are on the same flower, the pollen stays near the flowers, and these trees are unlikely to cause allergies. Apple trees have “perfect flowers.” Many of these trees are insect-pollinated or they will self-pollinate. Some “perfect flowers” may also be “incomplete flowers” if they have both reproductive parts, but they lack petals or other flower parts. Elm trees have “perfect flowers”, but lack petals.
    • Incomplete flowers – trees have male flowers AND female flowers on the SAME TREE.
      • Oak trees and black walnut trees have male and female flowers on the same tree. Plants can be wind- or insect-pollinated.
    • Polygamous – trees that have a combination of “perfect flowers” and male and/or female flowers on the plant. Ohio buckeye are polygamous because they have “perfect flowers” and they have male flowers.
  • Dioecious – trees have either male OR female flowers, but NOT BOTH.
    • The male plants produce pollen, and seeds are produced on the female plants after they are pollinated. Dioecious trees are typically wind-pollinated. Male trees tend to cause allergies. Female plants do NOT have pollen. Ash, willows, aspen, and some maples are examples of dioecious trees. 

A complete flower cluster known as an inflorescence on an Ohio buckeye tree. Photo: Lisa Mason

Let’s Talk Cottonwoods!

Cottonwood trees receive a lot of attention in the spring and summer when cotton is flying in the air! They are an example of a dioecious, wind-pollinated tree. Cottonwoods have male and female trees. The male trees produce pollen around April but not cotton. After pollination, female trees produce capsules full of cotton seeds. The capsules open around June, and the wind will carry the cotton to spread the seeds. A common misconception is that cotton causes allergies; the pollen that is released much earlier in the season is what can cause allergies. When the cotton is flying, the cause of allergies is typically grasses, weeds, and other trees.

A male catkin on a cottonwood tree. A catkin is the flowering spike or flower cluster without petals. Photo: Lisa Mason

How are Tree Species Chosen for the Landscape?

Deciding what trees to plant in a landscape depends on many factors including the purpose and goals of the landscape. In terms of the choosing trees species in a home landscape or municipal landscape, all of the following should be considered:

  • Mature size of the tree,
  • Soil, water, and other growing requirements,
  • Management considerations like pruning and susceptibility to insects or diseases, and
  • Weather and climate adaptations (e.g., exposure to cold, heat).

Choosing where to plant the tree is just as important as choosing the species of tree. Nearby infrastructure like power lines and buildings, space for the tree to grow to its mature size, competition from turf or other plants, potential for exposure to de-icing salts in the winter, and potential damage to the trees from human activity, lawn mowers, etc. are all additional considerations.

Different species of trees can achieve different goals. Some trees are more suitable for wildlife habitat or forage for pollinators. Other trees might provide shade or privacy around a home or building. If allergies are a concern, you might select trees that are insect-pollinated versus wind-pollinated. Seedpods on trees can also provide winter interest. If you prefer less maintenance in your landscape, a pollen-producing tree might more suitable.

Another critical consideration for tree selection is DIVERSITY in the landscape! We’ve learned from Dutch elm disease, chestnut blight, and emerald ash borer that when we plant many trees of one species, we risk losing all those trees to insects or diseases. By planting a diversity of species in the landscape—no more than 10% of all trees should be of one species—we create a more resilient landscape.

Even though Colorado can be a tough place for trees to grow, we have a variety of species that do very well. Consult the Front Range Tree Recommendation List to learn more. If you are considering adding a tree to your landscape, do your research to make sure the tree meets your goals. In addition to finding the right place for the tree, make sure the tree is planted and cared for correctly to give the tree the best chance to survive and thrive.

If you need some ideas or inspiration:  The next time you are at your local park or public area, take a close look at the trees. What species do you see? Are they wind- or insect-pollinated? Monecious or dioecious? Do you notice a diversity of trees in the landscape?


Monday, November 1, 2021

Leaning into the Fall Trends

 Posted by: Kara Harders, CSU and NRCS Regional Small Acreage Management Specialist

Crisp air, falling leaves, cooling temperatures, jackets, scarves, and boots. It must be fall in Colorado. 

The people who really lean into this season tend to get made fun of, pumpkin spice latte anyone? Or as the kids say, “PSL”. But there maybe a little to this fall craze in Colorado and it might just be a good thing to get more on board with the season. 

I’m not talking about purchasing the latest fashion or increasing your Starbucks budget, I’m talking about utilizing local produce. According to the Colorado Produce Calendar (see at end of article, or check out here) in November you can find Colorado apples, carrots, cucumbers, onions, potatoes, spinach, tomatoes, and winter squashes. These are the main produce ingredients in many of the things we associate with fall and winter foods such as soups, stews, apple pie, roasts, mashed potatoes, and most Thanksgiving side dishes. While you’re at the store, don’t forget to load up on Colorado beef if you are a meat-eater!

While buying local is always a good idea it counts a bit extra this year. COVID-19 has presented challenges for producers at many levels, ranging from labor shortages, to delivery conflicts, and equipment shortages. Additionally, with I70 being closed this year deliveries between the west and east slopes of the state were made much more difficult. Trying to purchase products from producers in your own state helps the Colorado economy, and even if each person only adds a couple dollars back, that adds up when you consider there are over five and a half million people living here now!

Altruism is great, and buying local is certainly good for neighbors around the state but buying whole, local produce can also benefit you. Consuming more whole foods is always a good idea and when you cook your own food you know exactly what is in it. So, bust out your Grandmother’s cookbook, or better yet, call a family member to chat and see if you can get an old family recipe from them. Pick something that includes some in-season produce that brings back good memories, it’s good for your mental health too. And when all else fails, Alton Brown and Martha Stewart have never let me down.