A surprise, mischievous smooch under the mistletoe is a December tradition steeped in folklore. Many historians believe that pre-Christian Europeans believed the plant possessed powers as an aphrodisiac, fertility stimulant, and poison eradicator, to name just a few. Our contemporary adaptation of this yuletide custom is far more innocent but still retains the spirit of romance.
Ironically, while mistletoe is synonymous with affection, it is far less hospitable to many tree species.
Dwarf mistletoe. Colorado State Forest Service
Mistletoe is the common name for several families of parasitic plant species that grow on the branches of trees by root-like structures which bore under the plant’s bark. These “roots” extract nutrients and moisture from the host plant; over time, the host plant will develop deformed or discolored growth, called witches’ brooms.
Infected trees decline from the top down and may die prematurely. Damage can, in some cases, be reversed with proper pruning maintenance. Details can be found in this Colorado State University fact sheet.
In Colorado, five western North American species of dwarf mistletoes (Arceuthobium species) infect conifers. Common host trees include lodgepole, limber, pinyon, and ponderosa pines.
Unlike the decorative European mistletoe (Viscum album), that has woody stems, white berries, and smooth leaves, dwarf mistletoes are small, leafless, yellow-ish plants with inconspicuous berries.
By this time in the year, I’m at the point of good riddance! with the weeds and careful tending (shout out to this cold spell for sealing the deal). Pretty much everything is done and put to bed. I then spend the next two weeks really dialing into my houseplant game before I get bored and start Spring dreaming. My Fall break from the garden is short-lived so I start listening to old episodes of now-defunct podcast series and dream with new ones. Here are a few of my favs:
Gardenerd Tip of The Week
Gardenerd.com is the ultimate resource for garden nerds. We provide organic gardening information whenever you need it, helping you turn land, public space, and containers into a more satisfying and productive garden that is capable of producing better-tasting and healthier food.
My thoughts: The host lives in LA, so this one is great for winter listening as we get chillier, I love hearing about the warmth of Southern California and what’s coming into season. Interviews with other experts and educators in the horticulture field discussing plants, but also cultivating grains, discussing bees, and seeds. Each episode ends with the guest’s own tips, many of which are news to me and have been incorporated into my own practices.
On the Ledge
I’m Jane Perrone, and I’ve been growing houseplants since I was a child, caring for cacti in my bedroom and growing a grapefruit from seed; filling a fishtank full of fittonias and bringing African violets back from the dead.
Houseplants, if new to the podcast start here for an overview, and guidance.
Jane is a freelance journalist and presenter on gardening topics. Her podcast has a ton of tips for beginners, and more advanced info for longtime houseplant lovers, as well as interviews with other plant experts. The website is also useful to explore the content of an episode if you aren’t able to listen. I could spend an entire morning traveling in and out of the archives.
My thoughts: As the growing season comes to a close, my indoors watering schedule starts wobbling between what the plants need and my summer habits of watering too many times per week–welcome back, fungus gnats! Here’s an entire episode on them
Plant Daddy Podcast
We aim to create a listener community around houseplants, to learn things, teach things, share conversations with experts, professionals in the horticulture industry, and amateur hobbyists like ourselves. We also want to bring the conversation beyond plants, since anybody with leaf babies has a multitude of intersectional identities. We, ourselves, are a couple gay guys living in Seattle, Washington, with a passion for gardening and houseplants. A lot of our friends are the same, though each of us has a different connection, interest, and set of skills in this hobby, demonstrating a small amount of the diversity we want to highlight among plant enthusiasts.
My thoughts: Plants are visual, podcasts are auditory- episodic overviews with links to viewable content available on their website. Are you also seeing Staghorn Ferns everywhere? They have an entire episode (photos included!) on the fern and how to properly mount it for that vegan taxiderm look. Matthew and Stephen are self-identified hobbyists with a passion for plants all the way down to the Latin–it’s impressive.
The Epic Gardening podcast…where your gardening questions are answered daily! The goal of this podcast is to give you a little boost of gardening wisdom in under 10 minutes a day. I cover a wide range of topics, from pest prevention, to hydroponics, to plant care guides…as long as it has something to do with gardening, I’ll talk about it on the show!
My thoughts: The Netflix-episode-when-you-just-don’t-feel-like-a-movie kind of podcast. Addresses the best varietals, composting, soil pH, and troubleshooting some common issues in the garden. With daily episodes archived back to December 2018, there is a quickly digested thought for some of your own curiosities. The website is also a wealth of knowledge.
Eatweeds Podcast: For People Who Love Plants
Eatweeds: An audio journey through the wonderful wild world of plants. Episodes cover modern and ancient ways wild plants have been used in human culture as food, medicine and utilitarian uses.
My thoughts: most recent episode (and appropriately timed!) On edible acorns. My fav topics include foraging and wild yeast fermentation; and when I really start missing the Pacific Northwest, The Wild and Wonderful World of Fungi sends me back to a misty forest wander politely decorated by les champignons. Posting of this pod is sporadic–only 25 episodes since 2014.
You Bet Your Garden
You Bet Your Garden® was a weekly radio show and podcast produced at WHYY through September, 2018. The show’s archive is available online. It was a weekly syndicated radio show, with lots of call-ins. This weekly call-in program offers ‘fiercely organic’ advice to gardeners far and wide.
My thoughts: Host, Mike McGrath, spends much of the show taking calls and troubleshooting, reminiscent of another public radio behemoth with Click and Clack, the Tappet brothers. McGrath incorporates a lifetime of organic gardening tips with humor. McGrath features one tip to find a local “rent a goat place” (no joke) to get goats to eat the most troublesome weeds to a concerned caller considering setting much of her yard on fire.
Cultivating Place: Conversations on Natural History and the Human Impulse to Garden
My thoughts: sort of like On Being, but for gardening.
A fav episode:
If you aren’t so sure about this podcast thing, and just want a place to start, start here.
Do you really need a brain to sense the world around you? To remember? Or even learn? Well, it depends on who you ask. Jad and Robert, they are split on this one. Today, Robert drags Jad along on a parade for the surprising feats of brainless plants. Along with a home-inspection duo, a science writer, and some enterprising scientists at Princeton University, we dig into the work of evolutionary ecologist Monica Gagliano, who turns our brain-centered worldview on its head through a series of clever experiments that show plants doing things we never would’ve imagined. Can Robert get Jad to join the march?
Last Monday, my dear friend and Community Forester, Chuck Sugent, and I took a neighborhood stroll to identify trees because I find myself recommending (or “oh, that’s an oh-no-no’ tree!”) at the farmer’s market; but when it comes down to it, I can hardly identify any trees at all and rely on the Front Range Tree Recommendation List. or the Denver approved tree list. My learning style is not entirely visual but seeing and discussing something certainly increases the likelihood of future accurate recitation. After a minor location miscommunication (“Heading your way!” “Good thing you sent that. I thought I was heading your way. Oy!”), we set off through a tree-lined neighborhood between downtown and City Park.
Chuck is the kinda guy who’s gonna be the good guy: he’s got the information, and he wants to share it (perhaps with an old-timey gangster of New York wiseguy affectation). So he took no pause when I suggested the idea of a tree walk. We’ve talked about the CMG program and community forestry in terms of our own participation for community stewardship, and have oft discussed a crossover—and thus, we went! We set off to name the trees and, in addition, ended up pretend-pruning, dreaming, and trouble-shooting all the ailments. Everything I espouse, I learned from Chuck (it was a very informative afternoon). Here’s an absurdly simplistic overview of the main players:
Gorgeous and quite popular. Responsible for the pinkening of the city each spring. Many varieties of different sizes and fruits. Also, edible. I grew up with a crabapple tree at my grandmother’s house which was the source of many summers dares to the youngest of us to “just try it! You’ll love it!” followed by giggle fits at the sight of desperate acceptance puckering away at the tiny bite. So—raw is a no, but cooked with sugar and acid makes for delicious desserts; or my family fav: Crabapple whiskey. Fill a jar with crabapples, a cinnamon stick, ginger, cloves and top with whiskey. Tuck it away until Christmas, strain and serve.
Thirsty mother lovers. They grow quickly and provide lots of shade. We have a ton of them in our metro canopy, but they are currently on a moratorium from planting in city right-of-way areas.
Black Locust has a darker trunk than the Honeylocust. Tiny leaves, gorgeous lemon color through the fall. However, tiny leaves make a mega mess–however, however, the leaves decompose quickly and return the nutrients to the soil. Also, a popular choice in this area, and continues to be on recommended tree lists for a new planting (NOTE: many varieties are on the recommended list, but the Sunburst Honeylocust is also on the moratorium list for street planting in Denver)
Classic Canadian flag. Gorgeous flaming fall coloring. The moisture level is moderate for this group, and they do not tolerate salty soil very well but are fairly drought tolerant.
This one makes Chuck’s shortlist of recommended trees for the metro area. The Hackberry has no known local pest, is native to Colorado, and drought tolerant. The Hackberry can get up to 50 feet tall, so consider this one for a street-side as a shade option. Lovely red berries darken to maroon in the Fall and provide home and a food source to the critters. Chuck calls this one a Hammer Tree; an all-around good selection.
When we happened upon our first Linden of the walk, Chuck took a step aside and said, “There are two kinds of Linden trees, and here’s how I remember them: LLL.” At this point, he raises his voice to denote the first type “LARGE LEAF LINDEN” followed by a substantially lower volume for the “littleleaf Linden.” He proceeded to crack himself up, and we carried on. There are many cultivars of Linden recommended in this area. Lindens are an attractive pyramidal shape, sensitive to salty soils, and their flowers attract bees and birds. Beware of the area you are considering, Lindens do not love high heat areas and should be planted away from any hardscaping.
Ever sturdy and reliable. The oak leaves have a bit of a leathery texture to reduce evapotranspiration, making them more drought-tolerant, and an excellent tree choice for this area. Their leaves differ in pattern depending on the cultivar but typically have the characteristic lobes and sinuses. The Bur Oak (recommended for the Metro area), is roughly obovate with many lobes and is pale and fuzzy underneath.
If you’re reading this… need I say more? See Plum for contingency planning. We have a million (estimated 1.45 million in the Denver Metro area) Ash trees. Aside from the EAB creeping into town, the Ash tree has a tendency to appear real leggy under the canopy when not properly pruned. We saw many examples of Ash trees with a lot of deadwood inside the canopy; this can be problematic when the wind picks up. They served a great function for our canopy by growing quickly and providing robust shade; but unfortunately, we’ve got to continue considering the impending Armageddon. What build projects shall we consider for a future influx of Ashwood? Denver also has a moratorium on planting Ash trees in public right-of-ways.
The purple leaf plum is my fan fav, and will likely be planted in my own front yard next Spring since my future self called and said: “This giant elm thing in your front yard was planted improperly, is massive, and when it goes, your front yard is gonna be U.G.L.Y.” Contingency planning in full swing. I encourage y’all to take a walkabout your own homes and chat with future self, especially regarding anything that is shade bearing. Something I picked up from my buddy whilst traipsing on the tree walk: purple leaf plums require regular pruning for flowering (Is anyone else as smitten by the plurality of prunes in this context?) Remove the deadwood and prune 1/3 the length of new growth. We found a perfect example and made pernicious prunes with finger scissors.
Colorado Blue Spruce
Beautiful. Also better at a higher elevation. We did see a few stunners, though, and learned a neat trick for tree ID: the leaf of a fir tree will be flat and flexible. Spruce, on the other hand, will be square and sharp (see what he did there?). Grab a leaf, roll it between your fingers, and name it quickly with this handy guide.
May make it to a mature size but inevitably will crash and burn. I’ve been touting this gospel for a while now, and take every opportunity to point out a struggler to my wife. which has become problematic, because now she counters by showing me all the healthy Aspen in the Metro area. The truth of the matter is an aspen tree (or maybe even a small clump of them) has the ability to thrive with the proper tender loving care… for a while. Above and beyond the statistically insignificant number of Aspen in the front range who appear to be doing well, they aren’t built for this elevation, and forcing them to do so causes undue stress, and makes them more vulnerable, hastening their predisposition to die anyway. Don’t do it. Go to the mountains more often and enjoy them in their own territory.
Beyond my self-imposed (and singularly played) trivia that entailed me interrupting, pointing, and shouting guesses; we also discussed the conversational piece of tree maintenance. Chuck indicated he has many chats with his neighbors about their trees and takes these moments to build his community and integrate his passion with friendly educational moments. We discussed the evidentiary tribulations of a tree in demise, that twists it’s trunk and bears the stripes of turmoil. We debated the suckers: their yappy attempts to address internal stress, and what to do with them (should we leave them and let it try to capture the energy it is craving? OR whack them back always? And when?) We talked about injury to a tree, and how the tree may cover and scab the wound, but the wound remains and the tree is still vulnerable. Chuck showed me a hackberry tree covered in galls. We both got lost in our attempts to recall the origins but settled on something about defense mechanisms and how they rarely hurt the tree.
As we were nearing our last corner on the way home, Chuck remembered a tree we hadn’t encountered that he loves. I’ve developed a habit this summer that whenever I see this tree, I shout it’s name, probably because it’s so fun to say, but shouting also seems appropriate just to communicate the whimsy of the CATALPA! Just try and say it without a bit of a shout. The Catalpa is also a recommended and robust tree for our area. It’s got those built-in wands and/or swords for play, and bright green wide leaves provide a huge amount of shade. . They are another tough tree, worthy of your scape.
Other items on Chuck’s “Oh no-no” list? Planting a tree too deep? Oh, no-no. Scoffing at the bare root and opting for a burlapped and caged tree? Oh, no-no. Planting anything from the Birch fam in Denver? Oh no-no. Hiring an arborist annually to tame your trees? Oh, no-no. With a little reading, Youtube-ing, or friendly forester finding, folks can save bunches of bucks by learning how to make the minor pruning adjustments to your tree every year to avoid the future big bills from an arborist. Trees can easily be grown and cared for by their owners working from reliable and factual info. Of course, always consult a pro when your tree questions start toeing the line safe vs. unsafe.
As DMG’s we get loads of questions about trees at the farmer’s markets. We try our best to offer small sagelings of fact-checked info, but what I’ve found to be more helpful is keeping the company of a forester. Trees are just as essential to the garden crew as our lawns, beds, and weeds. I encourage everyone to branch out (a thousand apologies for that one) and get connected–or get involved and become a Community Forester, yourself!
PS. Did you know if you live in Denver you can get nearly *free* trees?
By McKenna Hynes
Apprentice Colorado Master Gardener since January 2019
Here we are in mid-January and most deciduous trees and shrubs (excluding conifers) have shed their leaves. But long after the last frost and through a couple of modest snow storms, there are still trees around the front range with leaves that are stubbornly hanging on, as you can see from the photos I took in my neighborhood last week.
Marcescence is the retention of dried, dead leaves during the winter. Typically, as woody plants prepare to shed their leaves in the fall, cells at the junction of the twig and the leaf petiole (stem) release enzymes and form an abscission layer, which aids in the separation of the leaf. Marcescent leaves do not develop this thin-walled cell layer and therefore, do not drop readily.
Early severe cold weather can cause marcescence as the development of the abscission layer is halted and the leaves do not release. Front range gardeners will recall an extreme case in November 2014 when an exceedingly mild fall was interrupted by a one day temperature plunge from a high of 58 degrees to a low of 16 degrees. The result was subsequent damage and loss of many hardwood plants the following season and beyond.
Some plants are more apt to hold leaves longer, including several oak species, hazelnuts, American lindens and beech trees. According to Jim Finley of Pennsylvania State University, “Marcescent leaves are often more common with smaller trees or more apparent on lower branches of larger trees, which in forest conditions would be growing beneath taller trees where the reduced sunlight might slow the abscission process.” Lower leaves are therefore exposed to cooler temperatures, resulting in leaf retention. It should be noted that upper leaves can also exhibit marcescence.
Marcescent leaves eventually drop, either due to wind, snow load or the push of new spring growth. Under normal circumstances, marscence does not damage trees.
Ailanthus altissima or Tree of Heaven, is a notorious, fast growing, invasive plant which left unchecked can quickly become a large shrub or substantial tree. An urban nuisance, you’ve likely seen it jumping out of cracks in sidewalks, pushing through established shrubs and lining alleys where little else will flourish. I recently found a seedling growing in the corner of my pebble-lined basement window well, a testament to its ability to survive in poor soil with little moisture. It will grow most anywhere except very dense shade and swamps and is capable of choking out desirable plants, forming thickets and damaging sewer lines or building foundations. The vigorous lateral root system sends up numerous suckers and the plant will also easily establish by seed. Remember the novel A Tree Grows in Brooklyn? The title’s tree is Tree of Heaven – aptly used as a metaphor for determination and survival.
In the late 1700’s the tree was brought to this country from China and was heralded for its rapid growth. According to the U.S. Forestry Service, a young specimen can grow 24′ in the first four years and a mature tree can easily reach 50’ or more and produce over 300,000 seeds annually.
Ailanthus altissima has several distinguishing characteristics detailed in this Colorado State University publication. Sometimes mistaken for Sumac, Tree of Heaven leaves are pinnately compound (made up of several elongated leaflets) with a glandular notched base and smooth edge. The smooth leaflet margins differentiate the plant from Sumac, which has a jagged leaf margin. When Tree of Heaven foliage is crushed it has a foul odor resembling rancid peanut butter, hence another common name, Stink Tree. Clusters of yellow-green flowers emerge in spring; later in the season, female plants produce tan to reddish, single-winged samaras or seed pods. Large triangular leaf scars are visible on the twigs and are another defining characteristic of this notorious plant.
To eliminate Tree of Heaven, vigilantly pull small seedlings by hand. If the plant is well established, cutting it down will trigger the root system to produce an army of suckers, which in short order can result in a small colony. An effective treatment is to make numerous slashes on the trunk or drill holes into the bark and immediately apply a full strength herbicide containing Triclopyr on the openings. Waiting even longer than 30 seconds to apply the chemical renders the treatment ineffective, as the plant quickly seals the wound in the cambium layer and prevents the herbicide from reaching the root system. It can take multiple applications to kill a well established plant. As always, follow all instructions for the safe use of chemicals. Simply digging mature suckers up without the use of herbicide may be effective over time, but the bossy root system is likely to make this a frustrating and counterproductive exercise.
Espaliers are a beautiful addition for: a kitchen garden wall, the side of a house, plopping under window, a privacy screen or employed as yard zone divider. Espaliers take up very little space and are easily accessible for people with limited mobility, and also a fun height for children to harvest. Moreover, espalier fruit trees have surprisingly bountiful fruit production. And interestingly espaliers often live longer than more naturally grown trees/vines, including some very old specimens. These plants have the advantages of sunlight that reaches all the branches, less breakage, and importantly if planted against a wall they have the added protection against a late frost, and so potentially retain more blossoms.
Photo Credit: Le Potager Garden DBG
When we first moved into our house there was a wall in a small garden that I felt needed a pear espalier. I didn’t feel brave enough (or patient probably) to start a bare-root dwarf fruit tree and establish the training from scratch. So a couple of years ticked by as I waited to win the lottery for a nursery grown one (a four tier espalier can cost over a thousand dollars). The more affordable two tier plants, that are more commonly sold, are perfect for planting under a window, but not for a taller height. To add to this, most of the nursery grafted espaliers have a different variety of fruit on each branch, which although theoretically sounds exciting can actually present aesthetic and practical issues, and not surprisingly the rootstock can dominate in time too.
My experiment was – could I take a mature sapling and train it into an espalier. I am writing this blog as I did not find the information I needed on the internet, and so I plunged ahead into the unknown and broke pretty much every gardening rule. This is an experiment that may or may not succeed. Any input will be gratefully received! The ideas below are not endorsed by any educated gardener.
I did follow one cardinal rule: “Right Plant- Right Place”. I had my heart set on a pear tree. But at the nursery I chose the European Stanley Plum as the “right plant”. It is a hardy choice for Denver, and a larger tree (not a dwarf fruit- the regular espalier choice) should be alright for my wall? Moreover, this sapling had the right growth pattern, as it was fairly two dimensional and symmetrical. This young tree also sported the required flexible branches for training. Then for the location: the eastern wall, which is bathed in sunlight but not unrelating heat was I felt this “right place”. I followed correct planting rules! CMG How to Plant a TreeContinue reading →
When I moved to Colorado three decades ago I expected to be knee-deep in snow and cold to the bone for months on end. Little did I know, Denver winters have long dry stretches, moderate daytime temperatures and bright sunshine that melts snow before it needs to be shoveled. So much easier than the New Jersey winters of my youth. The downside is that plants often suffer from lack of moisture. This year I’m being especially diligent about winter watering to help newly planted trees, shrubs and perennials make it through their first winter and thrive in the future. Whether nurturing young plants or insuring the longevity of established ones, here are Colorado State University’s recommendations for cold season landscape care.
From November to March, give plants a good drink when four weeks elapse without snow cover or adequate moisture. March is the metro area’s snowiest month (11″); January (7″) and February (6″) average the least.
Water when temperatures are above 40° and early enough in the day for the moisture to soak into the ground before temperatures dip below freezing.
Reflective heat from buildings, the lower angle of the sun and areas prone to intense wind cause root systems to dry out more quickly, watch plants in these areas closely and water accordingly.
Newly planted trees establish slowly – one year for every inch of trunk diameter, (measure 6″ above the soil ). A good rule of thumb is to apply 10 gallons of water per inch of trunk diameter each time you water. Water around the tree, out to the drip line and beyond. The goal is to send moisture to the tree’s entire root system at a depth of 12″. I’ve found running a sprinkler for 30 minutes does the job nicely.
Newly planted shrubs require more moisture than established ones (over one year old). A first year, 3′ tall shrub requires 5 gallons per watering.
Mulch is a plant’s friend – it helps maintain moisture and mitigate the damaging thaw/frost cycle.
Newly seeded lawns and perennials (especially fall planted ones) will benefit from supplemental watering if precipitation is low, too.
When considering the price of trees these days, it makes sense to buy one that offers the biggest return on investment. That’s why I’m a big fan of living Christmas trees.
A living tree is one that makes the season bright, but also adds beauty to the landscape long after the holiday is over.
Before investing in a living Christmas tree, there are a few things to keep in mind about its care:
1. Buy a tree that fits both inside and outside the house. A smaller tree will be more manageable for moving into the house for the celebration and then outside for planting. In addition, smaller sized trees will take less time to get established in the yard after planting.
2. Select the planting site and prepare a planting hole for the tree before the ground freezes. Dig a saucer-shaped hole that’s at least three times the size of the root ball. The hole should be shallow (no deeper than the root ball) and wide. Planting too deep slows root growth and can harm the tree. Be sure to reserve the soil to fill in the hole at planting time.
3. Locate a cool spot to store the tree after getting it home. Keep it in its original container in the garage or on a sheltered porch or patio until it’s time to move it indoors.
4. Unlike a cut tree, a living Christmas tree can be indoors for just a short amount of time. Plan ahead to move the tree indoors for 5-7 days around the holiday. Then move it back to the garage.
5. Place the tree in the coolest room in the house. Avoid placing it close to the fireplace and keep it away from furnace vents that cause hot-cold temperature swings.
6. Water wisely to keep the soil moist. One easy method for watering is to put the tree’s container in a larger container, like a metal tub. Elevate the tree off the bottom of the container with a layer of gravel to keep roots away from sitting water.
7. After the holiday is over, allow time for the tree to get re-acclimated to the outdoors before planting. Place it back in the garage or cool, sheltered spot for a few days. Then take it outside and plant.
CSU Extension gives all the best practices for tree planting in the Garden Notes called The Science of Planting Trees. Be sure to remove any burlap or wire baskets before backfilling the hole and watering in the tree.
Keep your new tree watered through the winter, at least once a month or more frequently if the weather is dry and warm with a lack of snow cover.
A living Christmas tree may need a little extra TLC, but it’s one of the best ways to keep the holiday spirit alive throughout the year.
By Jodi Torpey Denver Master Gardener since 2005
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Posted onJune 19, 2017|Comments Off on New CSU Resource Targets Emerald Ash Borer
Colorado is preparing to battle a tiny insect that’s destined to change the way our urban forest looks. The Emerald Ash Borer (EAB) is already in Boulder County, and it’s only a matter of time before this destructive pest is found in nearby counties.
Every single ash tree that lines the streets of our neighborhoods is at risk. The EAB loves these trees that make up about 15 percent or more of all city trees.
The newest weapon in the fight is a mobile app. Colorado State University Extension and the Colorado Forest Service joined together to create a free app to help with early detection of the EAB menace.
The app is easy to download to Apple and Android-based mobile devices. Just search for “EAB/Ash Tree ID.”
The app walks users step-by-step through tree identification to determine if the tree is an ash and susceptible to the EAB. If it’s an ash, there are more resources for EAB symptoms, management and links to much more information.
It’s important for tree owners to be aware that ash trees are already at risk so they can be prepared. It’s better to consider management and treatment options sooner rather than later.
The EAB/Ash Tree ID app is the latest tool in the Colorado campaign to raise awareness about the insect pest that has already killed tens of millions of ash trees across the states.
The Be a Smart Ash program, sponsored by the City of Denver, started its communications campaign last year. The Colorado Department of Agriculture is also actively involved in fighting the EAB.
Laura Pottorff with the Colorado Department of Agriculture, leads an excellent one-hour webinar called “EAB: Myth or Monster” for Colorado Master Gardeners. The webinar (taped in May) is available through the CMG online continuing education program and will give master gardeners the information they need to provide research-based information to their communities.
All these resources will help tree lovers start thinking about their options for managing the ash trees in their landscapes. Approaches include replacing ash trees now, planting new trees to take the place of an ash tree in the future, and researching the insecticides to treat trees when the time comes.
By Jodi Torpey
A Colorado Master Gardener
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Posted onNovember 14, 2016|Comments Off on Fall: The Science of Color and Options for Clean-up
In Colorado and many other states in the US, we enjoy fabulous fall color in our gardens, parks and wilder landscapes. We notice it most on trees, but many shrubs and other plants change color in the fall too. Have you ever wondered where all that color comes from? Why do the leaves drop off the trees? And what use are all those huge drifts of dead leaves to us?
Most plants have green leaves. This is because chlorophyll in the leaves absorbs the red and blue parts of the light spectrum but reflects green light-waves so we see “green”. Chlorophyll is used in photosynthesis. This is the chemical process by which plants convert light, carbon dioxide and water into oxygen and carbohydrates – i.e. food for the plant. Chlorophyll is an unstable compound and the plant continuously replenishes it throughout summer when good sunlight and high temperatures prevail.
When temperatures cool and nights lengthen, chlorophyll production stops and so does photosynthesis (the plant’s food production system). As the green-reflecting chlorophyll disappears, other colors “appear.” In fact, these colors were always present in the leaves but now they are no longer masked by the green light-waves reflecting from the chlorophyll.
Carotenoids absorb blue-green and blue light and reflect yellow light waves. This is perceived by the human eye as yellow or greenish-yellow. This is why the fall color of birches and aspens is yellow.
Anthocyanins absorb blue-green, blue and green light and reflect red light-waves. This is perceived by the human eye as red through to purple. This is why the fall color of red oaks, sumacs and some maples is red.
Acer tartaricum ‘Hot Wings’ still green
Acer tartaricum ‘Hot Wings’ turning red
The depth and shades of fall color depend not only on the presence (or absence) of these pigments, but also the temperature and sunlight available. Low temperatures and bright sunlight destroy chlorophyll. So, falls with dry, sunny days and dry, cool nights tend to produce the best fall color.
In severely dry falls, the lack of moisture available to the plant may mean that leaves simply die without producing their usual fall colors of yellow, red or purple. The leaves lose so much moisture that the normal chemical processes cannot continue and the leaves dry, turn brown and drop early.
Once the spectacular show of fall color is over, deciduous (i.e. leaf-losing) trees and shrubs drop their leaves. Cooling temperatures and lengthening nights trigger plants into sealing off the point on their stems where leaves are attached so that no more exchanges of moisture and nutrients between the leaves and the rest of the plants are possible. This is called the “abscission layer”. When this layer is complete, the leaves drop (or “fall”).
What use are those dead leaves?
Think about how nature deals with this “problem”. Leaves fall from trees to the ground of the woodland, forest, mountainside, meadow – wherever they are situated. Rain, frost, snow, the trampling of animal feet all help to break the leaves down into smaller and smaller pieces. A huge drift of fallen leaves decreases significantly in size as air spaces between the leaves diminish. An army of creatures from the soil surface, and from beneath it, break down the leaves further through eating and excreting them (think: earthworms, beetles) or chemically decomposing them (think: fungi, bacteria). In this way, the dead leaves are decomposed into the tiny elements that create soil. It’s a mixture of humus and minerals. The humus is the last vestiges of the leaves that are hard to break down like cellulose and the minerals are the chemical components of the leaf tissue, e.g. nitrogen and carbon.
The humus and minerals help to form new soil structure in which new plants can seed, germinate, develop and continue the cycle. The new fertile or replenished soil provides the moisture and nutrients that the now-leafless trees will need to survive winter and re-start photosynthesis and growth in spring.
How to deal with those huge piles of leaves
We’ve seen above that the dead leaves have an important part to play in the garden’s eco-system. So, what can you do?
Just let the leaves remain where they drop on garden beds. They provide great mulch to maintain soil temperatures and protect plant roots and will rot down over winter, improving your soil as they go.
Leave a thin layer of leaves on lawns. Rake or blow them off (if you must) but a thin layer of leaves (especially if you run over them once or twice with the lawnmower) will break down quickly and help re-vitalize your lawn.
Rake or blow leaves off walkways, drives and sidewalks on to adjacent garden beds, so that these hard landscape areas are visible and don’t become slippery. Do not sweep or blow leaves into the street, as they can cause serious blockages in street drainage systems.
For a neater look, you can blow the front edge of borders clear, letting the leaves accumulate at the backs of borders and behind and below larger plants.
Put layers of leaves in your compost bin (even better if you can run the lawnmower over them first) between your layers of green garden/kitchen waste.
Save the leaves in plastic trash sacks (stored in an unobtrusive part of the yard) and let them rot down over winter, to be returned to the garden when they have decomposed. This leaf mold (the lovely dark brown material you get from decomposed leaves) is like “gold-dust” to the soil.
Save the leaves in an open cage made of upright posts and chicken wire to decompose – more “gold-dust”. If you have room, let your neighbors drop their leaves in the cage too.
BUT if leaves come from a diseased plant e.g. one with powdery mildew, black spot (roses), apple scab, anthracnose, they should be collected up and disposed of as garbage to help prevent re-infection in the next year.
Leaf cage made from old timber and chicken wire
Fallen leaves make great mulch (and are warm and cosy for the dog!)
If none of these options work for you, you can dispose of the leaves in degradable paper sacks which are usually available from your local hardware store at this time of year. The sacks can be collected with your normal weekly trash service. Some towns and cities will have leaf drop-off points where you can take the bags for the city to collect. The city will then use the leaves to make leaf mold for local parks or otherwise dispose of them. If you can’t do these things yourself, look for a local lawn service company that can, or hire a local teenager to help.
But, whatever you do, remember that the leaves really belong on the ground. That’s nature’s way, after all.
Acer saccharinum (silver maple) turned yellow
Quercus rubra (young red oak) turned red
Anne Hughes/Denver County Master Gardener
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