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Home | Mikl’s Articles | Articles: Pruning

Articles: Pruning

Prune Now to Keep Woody Plants Smaller

Do you have a tree or shrub that you’d like to restrain from getting much larger? For the next 3-4 weeks, pruning will be the most effect in reducing the size of woody plants. As we near the Summer Solstice, this year on June 21, we are approaching the midpoint in the growth cycle. This is the time when the days are longest and sunlight is strongest in the northern hemisphere. Woody plants start growing rapidly in early spring using energy that was stored in the roots and branches last fall. By mid-summer, the tree’s resources are being stored in the foliage to support photosynthesis.

So, when we prune at this time, we are removing these resources for growth. This is why summer pruning slows growth. By late summer and fall the nutrients are again being stored in the roots and branches, so pruning removes fewer growth-inducing resources. This is also the reason that fertilizing in late summer and fall is the best time to strengthen a tree or shrub, and support development of the buds that will become next year’s flowers and fruits. Note that solstice pruning of trees and shrubs that bloom in mid to late summer will remove the current year’s bloom and fruiting potential (Bluemist Spirea, Russian Sage, Golden Raintree, Rose of Sharon, Seven Son Flower, etc.)

Incidentally, If you would like to keep certain tall fall-blooming perennials more compact and stocky and less floppy or top-heavy, you can shear them back by a third to a half in late June/early July. This works well for tall asters and goldenrods, Blue Sage (Salvia azurea), Agastache.

Summer Solstice!

Welcome to Summer! Experientially, summer began last week with several days of intense heat that were challenging for people, pets, other critters, and plants. But in terms of hours of sunlight, the longest day of the year in the Northern Hemisphere will occur this Thursday, June 20 at 2:50 pm here in Colorado, officially beginning our summer season. Mikl has some thoughts on one of the interesting opportunities the Summer Solstice offers for gardeners with trees and shrubs. [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]

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.