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Home | Mikl’s Articles

Mikl’s Articles

Fireblight: How to recognize it and deal with it (1997)

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]

Groundcovers Project in its 18th Year

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]

Serviceberry

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

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 Here

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]

Heat-Tolerant Plants

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]

Small Shrubs that Fit In

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]

Managing Grasshoppers without Poisons

Nolo Bait is not a poison. It is a parasite that only affects grasshoppers and Mormon Crickets. It will not harm people, pets, wildlife or beneficial insects. It is most effective on small grasshoppers. In 3-4 weeks up to 50% of the grasshopper population will die. In addition, their eggs will be infected for the following season, and because grasshoppers are cannibalistic, they spread the disease. Put out shallow trays of the bran bait in small quantities. Wind, rain and contact with soil organisms can reduce bait available to grasshoppers.

Ducks, chickens, turkeys and guinea fowl can significantly reduce grasshopper populations. They must be fenced and put inside a safe structure every night to protect them from predators. They will also eat some plants, like vegetables.[Read More]

Managing Weeds Organically

 

This is the perfect time to apply Corn Gluten to prevent new weeds.

There are simple steps you can take now to keep your garden organically weed-free all season long 

[Read More]

Smoketree

Cotinus, known as Smoketree, is a genus of woody plants appreciated for their “smoky” flower plumes and for their leaf color, especially in autumn. Michael Dirr in his famous Manual of Woody Landscape Plants says “…it may be the best of all American shrub/trees for intensity of color.” Two species and many selections and hybrids offer leaf colors ranging from rich blue-green, maroon red, purple-red and yellow-gold; and the fall colors are even more vibrant. With the current passion for new plants, it is curious that Smoketree is not seen more often in our western landscapes.[Read More]

Lavandula – The Lavenders

Lavenders are great xeriscape perennials for Colorado, which bloom in the heat and dry of July and August. They are native to the rocky hillsides of the Mediterranean region. Here as well, they like good drainage, full sun, our alkaline soil and dry, loamy humus. Lavenders are aromatic herbs with gray foliage, the leaves as well as the flowers being strongly fragrant.[Read More]

Roses that Survive and Thrive in Colorado

After last November’s 77 degree cold plunge to 13 degrees below zero, most roses suffered die-back, some died to the ground and some died completely. But there were roses that had only minimal damage and some that will bounce back with a good show of vigorous growth and generous flowering this year. Here are some observations and conclusions about growing sustainable roses in Colorado.

Roses are cane shrubs, similar to blackberries and raspberries. Their wood has a pithy center and is not as hard or as strong as a lilac. Consequently roses are more vulnerable to insects, diseases, desiccation and cold, but another consequence is that they can grow and regrow much faster than woody shrubs like lilac and viburnum.[Read More]

Lawn Alternatives and Groundcovers

In our American communities, one of the responsibilities of home-ownership is to keep the ground covered. Bare earth, like weeds, indicates lack of care. So then, how do we cover the ground? The cheapest, fastest, and easiest way is to roll out bluegrass sod. “Instant” landscapes can be accomplished with a supervised construction crew that knows little about plants. And as long as water was plentiful, bluegrass was the unquestioned solution.[Read More]

Sungari Redbead Cotoneaster

The 2017 Plant Select shrub introduction is a woody plant with a tongue-twister of a name, a long history of survival at the old Cheyenne Horticultural Station, and has a heart-warming story of two great local plantsmen who brought it out of obscurity into Colorado gardens.

Cotoneaster racemiflora soongorica or Sungari Redbead Cotoneaster is a very tough and beautiful shrub, having survived over 40 years of neglect at the closed and unwatered Cheyenne High Plains Horticultural Research Station. It grows 6′-8′ high and wide with arching branches. The dark green leaves that are gray-white underneath, are attractive in themselves, and the flattened clusters of white, Hawthorn-like flowers are some of the showiest of all cotoneasters. They attract bees and other pollinators. Following the flowers are showy red fruits, a quarter of an inch or more in diameter. These berries are not messy and are popular with garden birds. They cluster along the thin branches, appearing as ropes of beads — hence the common name.[Read More]

Pest Management for Bees

Overview: The Good News: 100,000 insect species; only 200 pests. We do not need neonics or any toxic pesticide to grow plants well. The solution is human attention, biodiversity, nutrient-dense soils, application of nontoxic management, and tolerance.

The Bad News: Most people and most nurseries don’t know the good news. They believe the chemical companies that we need to fear and attack insects and fungi as enemies.

More Good News: The concern of ordinary citizens who call nurseries and businesses and ask them if they are using systemic neonic poisons in their plants, is having a powerful effect. These companies now know we care and will buy plants that are neonic-free if we can. This could get them to change.[Read More]

Pruning Article for Boulder Home and Garden

For many people, pruning is the maintenance job they most fear and dread. And it is good to be wary, because a tree that is badly pruned can dominate a landscape with its ugliness for years, can be more prone to breakage and disease, and can have a much shorter life.

Tree and shrub pruning have four basic aspects: the practical or aesthetic interests of the owners, the biology of how trees “heal”, the physics of what makes a branch strong or weak, and the art of how to create beautiful forms.[Read More]

Pyrethrum Insecticides: Are they Safe?

Pyrethrum is one of the best known botanical insecticides, effective against a wide variety of insect pests and generally considered safe to use. Is it really safe? To answer any question about pyrethrum it must first be explained that what is referred to as “pyrethrum” can be many different products. There is pyrethrum, the raw flowers; pyrethrins,the extracts from the flowers; and pyrethroids, synthetic pyrethrum. In addition many other insecticides and enhancers are often added to formulations which are called “pyrethrum”.[Read More]

Bees, Neonics and the Organic Way

Pesticides were never a good idea. They were designed to make money from petroleum, not to benefit the public good. Pesticides, fungicides and herbicides are poisons that were developed to kill life. Not only has this approach poisoned our earth and ourselves, it has failed to control Nature. Our soils are less productive, and weeds and pests have adapted by becoming resistant. Stronger poisons are not the answer.

In the last 20 years, the new “nicotine” pesticides (neonicotinoids) have become the industry standards because they are less toxic to people and animals than the old organophophate pesticides, and that is good. But the neonicotinoids (neonics) are even more toxic to insects; they last 3 months to 5 years; all parts of the plants are poison, and the poison goes into our water.[Read More]

Noxious Weed Profiles

Diffuse Knapweed, Centaurea diffusa is a relative of the cottage garden flower, Bachelor’s Button and a native of southern Europe and the Ukraine. I used to think that Bindweed was a bad weed, but that was before Diffuse Knapweed moved into north Boulder and has taken over several acres all around me. It is classified as a biennial that can be a short-lived perennial. I am beginning to think that if it is mowed and flowers little, it is perennial, but if it grows to a mature plant producing thousands of seed, then it is a biennial or annual.[Read More]

Yucca glauca (Soapweed)

This tough native xeriscape shrub is seldom given credit for being a broadleaf evergreen, but in the duldrums of dry summer and in the winter, these plants are very useful. I especially like to see it piercing through the white snow in its green, bold, formal, sharp rosette. The stilleto-like leaves are 1’-2 1/2’ long and rosettes increase from the rhizomatous roots. In the garden these off-sets can be cut off with a spade if the plant needs to be kept from spreading. The very sharp leaves are difficult to weed around so I use a dense groundcover around mine (Sedum spurium ‘Bronze Carpet’ makes a nice contrast). This very sharpness which the plant has developed to keep from being browsed to death, can be employed to protect other more delicate plants, like a clump of species tulips, from the deer and rabbits. These yuccas are also useful for traffic management, so best kept a good distance from walks  and entryways.[Read More]

Noxious Weed Profiles II

We are continuing to profile noxious weeds in order that we all get to know them. Although not the most fun aspect of gardening, it is important that we help to control their spread so as to avoid impacting our native plant and animal populations, and in some cases, helping to reduce the spread of weeds into our own gardens. An added benefit of learning to recognize weeds is that any plant that appears in our garden that we do not recognize to be a weed, may be left to grow. Wonderful wildflowers and other desirables can thus windfall their way into our gardens.[Read More]

When to Prune Trees

I have been an arborist for 35 years and spent a lot of my life studying trees and so I have these comments on When to Prune Trees:

  1. Yes, wounds close more quickly when pruned in spring
  2. Yes, for certain pest problems like Dutch Elm disease, it is important not to prune when the beetles are flying and best not to prune fireblight in the early spring.
  3. And trees without leaves do have a clearer view of the branching, but climbing into the branches gives a far better view and pruning with the leaves on helps determine thinning density as well as judging weight on a branch.
  4. Alex Shigo, often called the Father of Modern Arboriculture, wrote that pruning can be done anytime unless a tree is stressed, in which case it is better not to prune when a tree is putting on leaves or dropping leaves.
  5. Summer is a good time to prune fruit and other trees when you are trying make or keep them smaller.
  6. Fall is the best time to prune for fireblight, after the leaves have started turning color and before the leaves fall off. This is the time when you won’t spread the fireblight on your tools, so you don’t have to disinfect after every cut.
  7. Cytospera canker disease should be pruned out in dry weather, which usually is not spring.
  8. The most important factor is not the timing; it is the accuracy of making a pruning cut that neither cuts off the branch collar, nor leaves a stub. Then wounds will close most quickly.
  9. I asked Dr. Shigo if it is harmful to prune Maple and Birch in early spring when they bleed. He told me it is not harmful. And it seems to me that it doesn’t bleed for more than a few days.

Plants in the Home Greenhouse

The opportunity of winter sun in Colorado for heat and light to grow plants in a greenhouse

  1. cold and sunny 
  2. short season
  3. energy from coal and petroleum are expensive and atmosphere-polluting
  4. greenhouse captures free energy
  5. greenhouse is a tool to produce food and
  6. is a cheerful winter room
  7. protects plants from deer, raccoons, hail and grasshoppers.8) efficient use of water

[Read More]

Grow Delicious Grapes!

Got a fence or a pergola waiting for a fast-growing vine? Grow your own table grapes or wine grapes! The grape vines we sell, both table and wine varieties, are the most cold-hardy you will find anywhere. Most of them come from the northern Wisconsin breeding program of the late Elmer Swenson. Remarkably, three of his selections are seedless! All of them have good flavor, all are proven successful in Colorado in Zone 4 and above, and also succeed in high summer heat.

Swenson Red Grape– Very hardy dessert grape with large red to blue fruit with a high sugar content; non slip-skin. Slow growing when young; vigor, crop, and size of fruit improves once established. Bears fruit 2-3 years after planting. Unique flavor with hints of strawberry. Ripens in August, 3-4 week earlier than Concord. Also makes an acceptable white wine. Self-fertile.

Concord Grape– Most common grape in Colorado, very vigorous, hardy and productive. Medium sized, slipskin, blue-black fruit with sweet flesh and tart skin with “Welch’s Grape Juice” flavor for table, pie, juice, jelly, and wine. Ripens late September.

Concord Seedless Grape- Concord Seedless shares the distinctive sweet to sweet-tart flavor of Concords, but ripens earlier and features smaller grape clusters with smaller grapes. This is a woody, deciduous, tendril-climbing vine with clusters of seedless grapes that ripen in September. Excellent grape for juice, jam, jelly, pie, and wine.

Flambeau Seedless Grape– This seedless pink grape has clusters of small to medium-sized berries with a very sweet, low-acid flavor. A great table grape for cold climates as they ripen in early September. It is best grown on a trellis instead of an arbor as the vine has low to medium vigor. Tolerant of alkaline soils.

Saint Theresa Seedless- A superb new table grape for the Rocky Mountain region. This very hardy and mostly seedless purple grape offers abundant large clusters of sweet fruit in early September. These grapes can be eaten out of hand but are best used in jam, jelly, pie, or wine.

The Other Three Vines at the Teahouse

In the last issue I discussed three vines recommended by Jim Knopf for serving the special needs of the Boulder-Dushanbe Teahouse arbors. These vines were Clematis tangutica, Bokaravine Fleeceflower, and Riverbank Grape. Because the legs supporting the arbors are 12’-15’ tall, only the most cold-hardy and vigorous vines could be used.[Read More]

The Native Artemisias

There are several native artemisias that are naturally well-adapted to our soils and climate, drought-tolerant, and useful in our landscapes. These silver-leafed shrubs make great contrasts with green foliage and great foils for flowers of any color. They are now classified under three genuses: Seriphidium, Oligosporas and Artemisia.[Read More]

Xeriscaping with Natives

What group of plants has the longest proven record of success in Colorado for enduring the radical ups and downs of our weather, including droughts? Our native plants, of course. And if we give them similar conditions to what they have in nature, they will succeed with little care. Here are a few of my favorite native plants that have thrived in my xeriscape garden for the past 10-15 years.

Liatris punctata, the Dotted Gayfeather stores its energy in a thick taproot that helps it produce flowers even after a dry summer. The tufts of rough, narrow leaves are little-noticed until they shoot up their thin flower spikes to 10”-16”, and burst into bloom with lavender-violet “feathers” in August or September. They are especially dramatic in groups of four to ten plants, and they can continue to bloom for a month or more. Liatris punctata is native to the foothills and plains of Boulder County, and unlike cultivated varieties, needs no supplemental water once established.[Read More]