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Mikl's Articles

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]

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]