We recently passed Boulder Valley’s “average last frost” date (May 9).With all this rain, it sure feels like Spring! Lots of gardeners are asking if it’s safe to prune now, especially roses and shrubs. The answer is YES! But…..
Pay attention to the characteristics of the particular shrubs and roses you’re thinking of pruning. [Read More]
October 2020 went from record high temperatures in the 80s to record lows, 19 degrees by October 25. May 2021 also made some shocking temperature changes. These rapid and dramatic changes can cause woody plants to die back, lose branches or die completely.
Mikl has been waiting and waiting before pruning this spring, because sometimes our woody plants can leaf out very late. Here is a way to tell when to prune: [Read More]
Despite the access we have right now to our snow-free gardens, in general it’s not time to begin garden clean up. Undoubtedly (hopefully!) we will receive more snowfall in February and March and it is beneficial to keep leaves on the ground and last-year’s stalks on our perennials because this cover provides habitat for overwintering beneficial insects and it helps to keep the plant roots and crowns warmer.
In late February and early March it will be time to cut back certain Clematis vines, depending on their category. Here is an in-depth guide to the three Clematis Pruning Groups. [Read More]
Colorado is said to be the worst state in the US for fireblight, and 2018 was considered by many to be one of the worst years in Colorado. Fireblight is a serious disease affecting apples, crabapples, pears, Mountain Ash and hawthorn, and sometimes quince and pyracantha (supposedly up to 73 species of plants).[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]
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]
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]
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]
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]
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]
