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Western (Northern) Catalpa- Catalpa speciosa
It is surprising that a tree that looks so different from the other Colorado-adapted trees, is so successful. What stands out immediately are the huge leaves which can be 3”x 6” or even 6” x “12” and are heart-shaped. And in June, this large shade tree blooms exquisite, ruffled, bell-like, white, fragrant flowers with yellow and purplish coloration .And in the fall the passerby might be surprised to see the long thin pods 10”- 18” long.[Read More]
Growing trees in Colorado, especially big shade trees, can be very challenging. Few of the specimens in our community “forests” are native to Colorado, and areas where big trees are abundant are often so different from our conditions that those trees do not adapt well here. Some of the difficulties trees face here are: alkaline soils, nutrient-poor and shallow soils, low humidity, hot and drying winter sun, strong winds, untimely wet snows in spring and fall, rapidly changing temperatures, and low rainfall. Add to these the confining root zones in which many trees are growing in urban environments, and it is easy to understand why our trees are often stressed, subject to borer and fungus problems, broken and short-lived.[Read More]
This member of the pea family (Fabaceae) can get 50’-60’ high and 30’-40’ wide, though most that I’ve seen in Colorado are under 45’. Nearly everybody thinks of this tree as interesting or picturesque.The branching is more open than most trees and the bark is gray to dark brown, rough and deeply ridged even on small branches. The leaves are bluish-green and somewhat tropical-looking being double compound, each one 18”-24” long and forked with small leaflets alternating on the stem. Fall color is yellow. As the species name implies, this tree is dioecious, having the male and female flowers on separate trees. The flowers are greenish-white, supposedly fragrant and not conspicuous. On the female trees, tough, leathery seed pods follow that are 4”-6” long and 1 1/4”-2” wide. These hang on after the leaves fall and into the winter.[Read More]
Common Hackberry (Celtis occidentalis)
Why would anybody be interested in a tree that is just the common variety? In this case, we Coloradoans can be very interested because “common” means it will grow just about anywhere. In our harsh country that provides a good living for people planting and replanting and pruning and re-pruning trees, the Common Hackberry is somewhat of a relief. It will grow to 7000’. Our 25 below zero winters do not bother it as it is hardy to zone 2, which helps a lot in adjusting to our sudden warm-to-cold swings. It is also not picky about soils, tolerating both acidic and our usual alkaline conditions; rocky is fine, heavy clay is OK; it really likes rich, moist, but grows right along in poor, dry, windy, polluted cities. [Read More]
Planting a tree puts us in touch with one of the most essential parts of a tree that is often overlooked—the roots. When a seed germinates, the first part to develop is the root. The seed has stored nutrients, but if the plant is to live, it must immediately make a relationship with the nourishment of the earth. Then it can make the sprout that pushes into the sunlight to start photosynthesizing. So the first matter of importance in planting a tree is to honor its roots—their condition, their future environment and their nourishment.[Read More]
Alex Shigo is a world-renowned authority in arboriculture, the science of trees. His delving curiosity and sharp scientific analyses carried him beneath the bark into a realm previously little understood. He worked 26 years for the US Forest Service investigating decay in trees, and through the process of dissecting over 15,000 trees with a chainsaw, he has uncovered much valuable information about tree structures and tree systems that have revolutionized the practice of tree care. As he puts it in the preface to his book Tree Pruning, “A major problem throughout the history of tree pruning has been the scant attention given to pruning as it affects the health of trees, while great attention has been given to pruning as it affects the desires of man.” Even though he is busy writing, giving workshops and talks and doing consulting, he agreed to answer some pressing questions for The Colorado Gardener.[Read More]
European Mt. Ash (Sorbus aucuparia)
This is surely one of my favorite ornamental trees for the front range which can be used up to 8000’.It is an upright oval tree spreading with age 25’-30’ tall aned 15’-25’ wide. If cared for, it will be attractive throughout the season. The bark is a shiny, orangy-brown. The serrated, compound leaves are dark green and in the fall turn yellow and reddish-gold. The clusters of flowers are white, blooming in spring with a peculiar fragrance that some people appreciate more when they’re gone. Clusters of red-orange berry-like fruit follow which color the tree through the fall, accenting the orangy leaf colors. These fruits are greatly loved by the birds and are in fact edible for people. They are known as Rowan berries and are used in Europe in making a brandy. In ancient times the Rowan tree, also know as the Quickbeam, was greatly revered by the Druids and used against lightning and witches’charms. The berries were considered extremely valuable having the “sustaining value of nine meals”, healing the wounded and giving a man the strength of ten men. I had to try this, of course, and found I couldn’t eat even 10 berries. Later I learned they need to “blet” or shelf-ripened. The birds do spread these around, and Mt. Ash seedlings are not uncommon.[Read More]
The Pinyon Pine has several advantages over other evergreen trees in a Colorado landscape. For one thing, its size doesn’t consume so much horizontal space. Compare the modest mature Pinyon at 10’-15’ in diameter with Austrian or Ponderosa at 25’-35’ diameter or Blue Spruce at 30’-40’ diameter. A few of these “average” sized evergreens look innocent when freshly planted, but who hasn’t seen them blocking sidewalks and doorways, tearing off gutters and shading solar collectors and windows in the winter? The Pinyon with its gently rounded top only gets 12’-20’ high, which suffices for many screening needs and still leaves the view. If it isn’t crowded, it stays branched to the ground with dense foliage of short, medium green to gray-green needles, two to a bundle. The cones are small 1 1/2”-2” long, brown to reddish-brown, which open to a rosette form and in the wild yield Pinyon “nuts”. These seeds are good-tasting and oily, with a piney flavor much appreciated by birds, animals and humans. They are also nutritious, being higher in protein and carbohydrates than pecans, but lower in fat. For some reason , these “nuts” are unlikely to develop in small urban plantings.[Read More]
One of the most beautiful ornamental trees is the Eastern Redbud, Cercis canadensis. It is a native of the eastern and southern U.S. and has “naturalized” in older Boulder neighborhoods. It’s most distinctive feature is its reddish purple buds followed by intense purplish-pink pea-like flowers in late April before the leaves come out. This wondrous and heart-warming display is greatly appreciated so early in spring but cannot be counted on if winters are too harsh.
It is a smaller tree 20’-25’ high and wide with attractive bark and heart-shaped leaves which are shiny and purplish when young. Fall color is yellow. It is said to be hardy to zone 4 and we have many fine specimens in Boulder.[Read More]
Shade trees 40’-60’ high and wide are great on the south and west sides of our houses and offices. They reduce temperatures and reduce cooling costs in the warm months, but they are not always appropriate. We don’t want dense shade where we grow most xeriscapes, rock gardens, herb gardens, most natives and many perennials. In addition, there is no need for big shade trees on the north side, and the morning sun is usually welcome on the east side of our houses and workplaces. And many plants prosper in morning sun and afternoon shade. It is also significant that a 20’ tree costs far less to have pruned than a 40’ tree. So it seems to me we should be growing small trees under 30’ tall on the east and north sides of our buildings.[Read More]
Trees have it hard in Colorado. If it’s not the shallow and lean topsoil, it’s the low rainfall and low humidity, or it’s the heavy wet late spring or early fall snows, or like last November, it’s the dramatic temperature changes. After a warm and beautiful fall without a killing frost until November 11, we experienced a 77 degree drop in temperature between November 10 and November 12. This was one of the three largest temperature drops ever recorded in the Denver area, the other two were in December 2013 and January 2014.[Read More]
Trees do a lot for us humans, so we shouldn’t forget to give them some support. When I look at the treeless ten acre lot next to our nursery, or when I see an old photo of the CU campus with bare land around Old Main, I remember why we can’t take trees for granted in Colorado. Trees really have it hard here, but there are things we can do to help them survive and thrive.[Read More]
The roots are the hidden support system of our giant plants, the trees. They anchor their woody trunks to the ground, store food and bring in water, nutrients and oxygen. In this article I will discuss what is going on down there. In the next issue I will discuss more practical applications of this understanding.
Far less is known about tree roots than about the trunk, branches and leaves. This is understandable since the roots are hidden from our view, and once you dig them up, they are no longer what they were. We are awed by the massive trees swaying over our houses and streets, but usually we give little thought to what is going on under the surface. However, when spring thawing is followed by powerful winds and we see an 80’ spruce toppled over with its roots in the air, which are only 9” deep; that gets us thinking.[Read More]
What would we do without trees? What structures could we invent and construct that would hang over our houses and offices, providing shade and cooler temperatures? Such a structure would have to hold up under 80 mph winds and heavy wet snows, and would have to retract in the winter to let in light. Trees provide these values and much more, giving off oxygen, providing housing for birds, and protection for understory plants. Thus it is very important to take good care of our trees, and the most fundamental level of that care must be directed to the roots.[Read More]
A New Model for the 21st Century
A newer science that is not tied to petroleum profits is emerging to challenge the industrial approach to agriculture and gardening. Of course, the enormously powerful and politically connected corporate giants like Monsanto, Bayer and Dupont will continue to make money, but after 60 years of dominance, the “Better Living Through Chemistry” model can no longer hide its fatal flaws. Mountains of evidence now point to the effects of chemical agriculture: poisoning the earth, driving global climate change, causing major health problems, killing pollinators and destroying the life of the soil. The good news is that a more long-range, wholistic view is starting to take its place. This new approach is being called Biological Agriculture and Gardening.[Read More]
It has been suggested that this period of the 21st Century might well be called The Age of Biology, because the biggest challenges will be biological and the biggest breakthroughs will be in the realm of biology.
In this article, we will continue the discussion from the last issue on Biological Agriculture and Gardening, but this time going into specifics of biological thinking, biological discoveries and applications that improve plant and food success with biological solutions.[Read More]
Food safety is one of the most critical issues of our time. What we eat is directly related to our health, and health care has a direct impact on our personal and national economies. Major chemical companies like Monsanto, Bayer, Dow and Dupont have introduced 86,000 synthetic chemicals into our environment, food, drugs, cosmetics etc and most of them have never been tested for toxic effects on human health and the environment. Since the mid 1990s, some of these same companies have been filling our grocery stores and feed stores with genetically engineered food products which may be causing serious health problems but are being approved by our government without safety testing.[Read More]
Most of us were taught that gardening is about control, about battling unruly, ravenous nature to succeed with our objectives. And a very complex and prosperous industry sprang up in the late 1940s to provide us with the power and weapons to meet those expectations. Petroleum products from World War II chemical weapons, defoliants and bombs were reformulated to solve our plant problems and feed the world. These chemical fertilizers, pesticides and herbicides have now had 50-60 years to show that this aggressive, heartless and poisonous approach has failed. Foods with little nutritional value and a polluted world are inspiring a strong international movement toward sustainability.[Read More]
The key to minimal maintenance and a low input approach is Gardening Without Fear. The solution to gardening without fear is twofold: being empowered to garden successfully and being relaxed and tolerant. If we are fearful, we will react to every little problem, worry and criticize ourselves. Then we might seek an immediate solution like some poison.
We have been guided to believe that we need these petroleum products by companies that sell them. In fact, these products weaken the support systems of plants and make them more vulnerable to diseases, pests and drought. The truth is—we don’t need them.[Read More]
Last month we raised the issue of invasive introduced plants and the idea of being responsible gardeners who respect our native habitat and make an effort to not release invasive plants into the wild. We began with obvious noxious weeds that are having strong negative impacts on our native populations of plants and animals. This month again I am profiling weeds which have been declared as noxious, but this time a question is beginning to arise about under what circumstances are some of the less aggressive weeds invasive? In other words, is it possible that we might find a middle way that guides us strictly with the truly harmful invasives and more leniently with the less aggressive and more useful weedy plants? These are questions I am asking myself and will be asking in future interviews. We also welcome your views on this issue.[Read More]
In February 2000 President Clinton established the National Invasive Species Council. Agriculture secretary Dan Glickman, Commerce Secretary William Daley and Interior Secretary Bruce Babbitt were asked to work together on a plan to minimize the economic, ecological and human health impact of invasive plants and animals not native to the US. The executive order on Invasive Species directs federal agencies to prevent the introduction of invasive species, to control populations of such species in a cost-effective and environmentally sound manner, to monitor populations, restore native species, conduct research and promote public education on invasive species.[Read More]
One of the hot subjects in horticulture these days is the issue of the invasiveness of introduced plants. Since they did not evolve here, they lack natural enemies, and whereas most are harmless, some have engulfed vast areas of wilderness, national forests, range and farm lands. This has led some people to campaign for “natives only” and others to attack the introduction of new plants as an ecological nightmare. In response to these attacks some in the plant industry have dismissed these fears as invalid over-reactions. As Colorado gardeners, most of us can be both excited by new plant introductions that are well-adapted to Colorado conditions, and feel very protective of our natural ecosystem and our native plants. In a series of articles, we hope to uncover some truths regarding these issues and to educate ourselves about how to work with this situation in a constructive manner.[Read More]
The forgotton greenhouse gas and how it relates to growing plants
Nitrogen is one of the most essential nutrients for plants. Nitrogen is required for building amino acids, DNA and RNA, in stimulating growth, supporting health and is a critical ingredient in chlorophyll, the chemical needed for photosynthesis. In our gardens, when nitrogen is lacking, plants are small and yellow, and roots do not perform well. In Colorado, almost all our soils are deficient in nitrogen and organic matter. So we gardeners often add fertilizers and composts to our soils.[Read More]
Local advice from our friend Elizabeth:
Hi All, I have been trying a new technique (at least for me) of starting peas in sections of guttering (which I got at Resource) in the greenhouse, growing them on until they are about 4 inches tall, and then transferring them to a trench in the garden. So far it seems to be working fairly well. The peas germinate really fast and grow quickly in the greenhouse. You could probably do it in a house too. I plug up the ends of the guttering with a piece of foam and duct tape. When I am ready to transfer them, I dig a trench, remove the foam and duct tape, spread the sides of the guttering away from the soil, and slide them out of the guttering into the trench. The sliding is the tricky part. I have found it takes two people to go well: one to guide and encourage the peas along, and one to lift and shake the guttering, as you have to get it to a fairly steep angle for the peas to slide. I’m using galvanized guttering, but plastic might work better as it would be smoother. There’s lots of videos of this on the web. Thought this might be a good solution to slow germination in our really unpredictable springs.
The Canadians, like their English and French ancestors, have a great love of roses. However much of Canada is in zones 4, 3 and even zone 2. Therefore many of the hybrid tea and floribunda roses bred in modern times have not been tough enough for Canadian gardeners. So the Canadians set their own federal agriculture department to work on breeding roses that succeed in Canada. Not only do these roses do well north of our border, they are very successful in Colorado, even in our higher elevation environments. Our 10-20 below zero winters and dramatic temperature changes can kill or significantly injure more tender roses like the hybrid teas and floribundas. So gardeners in Colorado who don’t have time to remove large masses of dead canes, hill soil around the canes to protect them for winter, and who have less inclination to spray and fertilize frequently, find the Canadian-bred roses provide a rewarding and easy-care alternative.[Read More]
In the last issue I discussed the easy broadleaf evergreens for Colorado and this time we will go into the difficult ones. Many people have killed or had poor success with rhododendrons, hollies, azaleas and daphnes etc. so it is good to understand these plants further. Unfortunately in my sunny, low-water gardens, I have had little experience with them so I went to two people who have plenty of experience, Don Zaun and Allan Taylor.[Read More]
It is widely known that nitrogen is essential for plants. It is a major component of amino acids, DNA and chlorophyll. It is necessary for photosynthesis, the alchemical process of turning sunlight, carbon dioxide, minerals and water into oxygen and sugars that is the food that feeds life on earth. In Colorado, most of our soils are deficient in nitrogen.
But too much nitrogen can be a problem, especially high nitrogen chemical fertilizers. Bill McKibben, author of The Art of Balancing Soil Nutrients states, “Although all plant nutrients are critical, none seem to produce such quick and dramatic effect on plant growth as nitrogen does. It is because of this reason that nitrogen has been over-used and abused.” A 20%-30% nitrogen fertilizer can make a spring lawn turn bright green practically overnight, and can make plants in a greenhouse or garden grow and look mature really fast. So what’s the problem?[Read More]
Flood recovery is not a problem most of us have had to deal with before so we can only try to solve the problems individually and make adjustments in the future.
The main problems seem to be:
1) Soil washed away-erosion
2) Soil dumped on top of plants, trees and existing soil
3) Plants washed away
4) Weed seeds deposited on the soil 5) manure and sewage and unknown contaminants deposited on the land[Read More]
In the winter when the deciduous plants have dropped their leaves, the evergreens really stand out. If we go for a walk, especially in the older neighborhoods, what evergreens do we see? The greatest numbers are spruces, firs, pines and junipers. In general these conifers with their narrow needles or scales are adapted to our cold temperatures, strong winds and sunny winter days. But there are other woody evergreens to be seen in Colorado neighborhoods: the broad-leaf evergreens. In general their wide leaves transpire more and are more prone to desiccation in our drying conditions; however by choosing the right plants and siting them in their right places, we can enjoy these less popular but deeply satisfying winter-green shrubs and vines. In this article I will discuss the easy broad-leaf evergreens for Colorado and in the April issue we will talk about the difficult ones.[Read More]
Many Colorado gardeners have been frustrated in their attempts to grow climbing roses. The main problem seems to be that the tall canes die back and though they may bloom, they look like shrubs, not climbers. We are green with envy of the European and Californian gardens with roses cascading over and festooning pillars, walls and bowers. Why can’t we achieve this? I think we can, but not without a very discriminating approach. First of all we must realize that our cold temperatures and especially the rapid cold-hot-cold changes, and our drying winter winds are death to all but the hardiest rose canes.
Henry Kelsey (1984 Kordesii cross) is an Explorer Series rose from Ag. Canada that is hardy to Zone 3 and is considered by many to be the best red-flowered climber for cold climates. It is very vigorous and grows strongly even in lean soils. Whereas it can be grown as a low arching shrub to 4’, it excels as a short climber to 8’-10’ and looks especially good trained down a split-rail fence. The flowers are semi-double with prominent golden stamens, opening a luscious deep red and fading to a pinker medium red. The fragrance is light but pleasant and the clusters of flowers repeat from June until frost. Where I have grown it in a very low water area over the last five years it has performed well and has not died back on the trellis, but repeat flowering is intermittent rather than continuous. One of the truths of xeriscape is that not all plants that grow well on low water, flower as well. Sometimes just one or two deep waterings during bloom time will make a big difference in flower production.[Read More]
Fortunately, there are many choices of drought-tolerant shrubs. And not only can they tolerate drier conditions, the fact that they are taller than most perennials and groundcovers helps them to compete better with weeds, giving them a greater survival potential in untamed, harsh or more industrial locations. In native ecosystems, it is often the shrubs that begin to pioneer a barren ground, and the shade and wind-protection they create, gives more favorable microclimates for other plants to germinate and find a home. There are many fine non-native shrubs for xeriscapes, but in this article, I am mostly going to describe some of my favorite native shrubs for drier conditions.[Read More]
I used to be prejudiced against grasses because I associated grasses with the American monoculture of Kentucky Bluegrass that we all know as “the lawn”. But after testing many kinds of xeriscape plants for over 20 years I finally realized that most sustainable ecosystems have grasses mixed with the other plants. And I also came to appreciate that grasses are strongly self-replicating and that they can be more easily grown from seed than most perennials, so that installation and maintenance costs could be much less. I still think low-water shrubs and Colorado-adapted perennials have an essential place in a sustainable landscape, but I have been wondering how grasses could fit in. Of course Piet Oudolf and Kurt Bluemel have shown the potential for using grasses in a garden, but their examples look well watered and seem like they would be high maintenance. The prairie model so successful in Wisconsin and the Midwest focuses on tall-grass prairie that is out of place here, and so I have been wondering how grasses could be used in a Colorado-sustainable landscape.[Read More]
MULCHING THE GARDEN
Benefits of Mulching:
1) prevents evaporation; holds moisture
2) reduces weeding; makes weeding easier
3) reduces fungal diseases; prevents splashing of spores onto bottom leaves
4) feeds the soil; as mulch decomposes, worms take nutrients into the soil[Read More]
Applying a mulch around our plants can be one of the most effective ways to improve their health and success, especially during hot and dry conditions like we had in 2012. Mulches have many benefits, but it is important to know how to use them to avoid problems.
Mulch conserves water by reducing evaporation 10%-50%. Usually a 2”-4” deep layer is best, and the material needs to be open enough to admit rain and irrigation and dense enough to resist evaporation. It is a good idea to apply mulch after the soil has been deeply watered or soaked with a good rain. Then the mulch will hold the moisture. Beware of materials like unshredded leaves which can act like shingles, and dry compost or sawdust which are hydrophobic, meaning they are difficult to wet. These problems are worse on a slope where water can run off instead of penetrating.[Read More]
Nitrogen is an essential nutrient for all living things. Where does that nitrogen come from? It comes from the atmosphere, which is composed of 78% nitrogen; but that gas is quite inert, meaning it can’t combine with other elements until it is broken into a simpler form. This process takes a lot of energy to “fix” the nitrogen. There are three processes that can fix nitrogen: atmospheric, Haber Process and biological.
Atmospheric fixation occurs when the high temperature of lightning splits the nitrogen gas so it bonds with oxygen and moisture in the air to form nitrates that fall to the earth with rain. This natural fertilization benefits plants. Some people have asked, Is it my imagination that my grass looks greener after a thunderstorm? Maybe not; it could be due to the nitrogen as much as to the water.[Read More]
GMO has become a dirty word and a symbol for Monsanto’s corporate control over our health. Genetically modified organisms (GMOs) are the result of slamming DNA (genetic material) from one organism with the DNA of another, yielding altered characteristics. The bizarre results are discarded and the profitable ones, like being unaffected by the herbicide Roundup, are reproduced. Current approved GMO crops include Roundup Ready corn, soybeans, canola and this year, sweet corn. The advantage with these crops is that a farmer can have easy perfect weed control, by spraying the whole field with the herbicide Roundup, killing the weeds but not the crop.[Read More]
Here’s a shrub that won’t grow over the living room windows, spread half-way across the driveway or send suckers up in the perennial border. It stays a compact 2’-3’ high and a little wider. It’s name comes from its spring leaf coloration which begins a russet or bronze-red mixed with yellow, changing to yellow-green and then green. The flowers are pinkish and bloom for a long time. Then again in the fall the spring leaf colors return to a golden copper-orange. This variety is very heat tolerant and has been successful in my xeriscape garden for 7-8 years. Occasional winter dieback has been slight and easily sheared off with hedge clippers. I also use the hedge clippers to remove the spent flowers after blooming.[Read More]
Do any of you have dirt under your fingernails? Good. You and all gardeners have direct experience with soil. Those of you who don’t get your hands in the dirt probably will, because soil and soil building is the next frontier. Why do I say that?
Because until recently our understanding of soil and our approach to soil fertility was steeped in ignorance and misunderstanding. We’ve been in the Dark Ages.
Does anybody know the meaning of a new paradigm? It does not mean coming up with a new idea; it means coming up with a new perspective, a new ground from which to begin our thinking. We are entering a new paradigm in relation to the earth.[Read More]
This is a bad year for fireblight which is a bacterial disease which affects mostly apple, pear, crabapple, hawthorn and Mt. Ash. It is spread in the presence of moisture and enters the trees through wounds and open blossoms. Colorado is the worst state in the US for fireblight.
Because of our moist spring and extra wounding caused by hail, there is a lot of infection. Symptoms include black, hooked twig ends, brown or blackened leaves, dried up fruits and sunken cankers that can be a dull orange or black. Fireblight is a difficult disease to manage because there is no cure. Spraying chemicals is not recommended by CSU because they are not very effective, timing is critical and spraying must be repeated.[Read More]
At the end of last season I wrote about how to succeed with climbing roses in Colorado. Besides winter watering and careful siting out of the worst wind, the most important factor is the choice of very cold hardy roses that are grown on their own roots. The books may say we are zone 5 but when the temperature drops from 50 at noon to 5 at two a.m., we better hope our rose is zone 4 or even zone 3 hardy. With climbers this is even more true because if the canes die back to two feet the rose may still bloom but it won’t function as a climber that year. Here are a few of the toughest and most cold-hardy climbing roses for Colorado. [Read More]
Nearly everybody has met the memorable fragrance of mockorange, said to imitate the smell of orange blossoms. There are over a hundred species of Philadelphus, and of these, about 40 are native to North America. Many of the yards of Boulder County and Denver have at least one specimen. What is so good about this shrub? Dirr says, “In flower they are attractive to some, but the rest of the year are real eyesores.” Wyman said their fall color is not vivid, their fruits are not ornamental, no winter interest, but they are “cultivated 50 weeks of the year in order that their flowers may be appreciated for two weeks.” However I happen to love mockorange, and one of the 2001 Plant Select shrubs is ‘Cheyene’ Mockorange. So let’s look into the good qualities.[Read More]
Hardy Geraniums are in general very serviceable and these four have been very useful and successful for me. They are tolerant of diverse and adverse conditions and are especially useful in dreaded dry shade.[Read More]
One of the most damaging and most perplexing diseases of the Front Range is fireblight. It is a bacterial disease affecting apples, crabapples, pears, Mt. Ashes, pyracanthas, quinces, hawthorns and occasionally cotoneasters. Fireblight does not affect cherries, plums, peaches or shade trees.
When the bacterium with the lovely name Erwinia amylovora enters the trees through an opening such as a wound, a pruning cut, the open blossom or leaf pores, the tissues quickly die causing blossoms and leaves and young twigs to suddenly wilt and turn black as if scorched by fire (hence the name “fireblight”). As the bacteria spread through the tissues, secondary infection continues through the season and bark areas die, become sunken and turn black or reddish-orange. These areas are called “cankers”. Sometimes large numbers of leaves turn black but the infection stays confined to small twigs; sometimes entire large branches die; occasionally the entire tree will die.[Read More]
In 1993 I sent a survey to 29 local horticulturists to get their suggestions on the best groundcovers for a demonstration project we were planning at Harlequin’s Gardens. I asked them to list 5-10 groundcovers that could be used to replace bluegrass in low traffic areas, that would need a quarter to a half the water of bluegrass, have few pests and diseases, would grow densely to limit weeds, would look good in most seasons and would not be invasive in gardens. The survey was typed on a typewriter and most of the replies were hand-written. People did drive cars back then. But that was a long time ago and I had a lot to learn.[Read More]
Saskatoon Serviceberry (Amelanchier alnifolia)
A winter-hardy (zone 4) native shrub of the Great Plains and Rocky Mountains. It has beautiful coarsely toothed leaves that are attractive even in the dry summer. The flowers are white and apple-like, fragrant and appear very early in the spring. Delicious blueberry-like fruit follow in midsummer. Birds are very fond of them and the American Indians used to mix these serviceberries with fat and buffalo meat to make their winter staple, pemmican. The Canadians have been working to develop this plant for fruit production.[Read More]
Hardy Geraniums are one of most versatile an adaptable perennials for our area. Available in many colors and habits, they can be useful in sun and shade, moist and dry, as a single specimen, as companion plants and as ground covers. These are not to be confused with the Pelargoniums which are the house plant, container and bedding plant “geraniums” which are not hardy outdoor plants in Colorado. The name “geranium” is derived from a Greek word meaning little crane, hens the common name “cranesbill” which refers to the appearance of the seed heads. The majority of the species of geraniums are native to the northern and mountain regions of Eurasia and North and South America although some are found in South Africa, India, Indonesia etc. Most grow in grasslands, meadows, roadsides and open woodlands. Therefore the natural habitat for most hardy geraniums seems to be sunny and moist or part-shade and moist or dry.[Read More]
Japanese Beetle is one of the most damaging insect pests in the Eastern and Midwestern US, but until recently, Coloradans were spared that challenge. It entered the US in 1916, but took until 2003 before a population was established in Colorado. This first infestation was in the Palisade area on the Western Slope. Even though eradication efforts were mostly successful there, established populations have been found since 2005 in Pueblo, southern Denver, Englewood, at DU and at Denver Botanic Gardens. Populations are being seen now in Boulder and Jefferson County.[Read More]
Most of our native plains plants and shrubs including:
Sumacs
Penstemons
Rabbitbrushes
Desert Four O’Clock
Saltbrush
Heterotheca
Artemisias (Sages)
Thelesperma
Gambel Oak
Sulfur Flower (Eriogonums)[Read More]
There has been a lot of interest at our nursery, and in current plant-breeding programs for smaller shrubs. Most of the old-time favorite shrubs are very large. Most lilacs, viburnums, honeysuckles, forsythias, privets, elderberries, serviceberries, butterfly bushes and hibiscus are 6’-12’ high and often as wide. These are great to provide screening and big masses of color along fences or the back of the border.[Read More]
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