Shrub Pruing Basics, Part 1, When to Prune

Landscapes make our houses into homes. Trees and shrubs not only contribute pleasant feelings to our surroundings they add up to 15% to the value of your property.

It often takes several years for newly planted shrubs to establish and then before you know it they are on their way to becoming leggy overgrown monsters.

Most shrubs will appreciate even the smallest amount of pruning and reward you with rejuvenated foliage and more abundant buds.

Time to prune

The first key to correctly pruning your shrub is to know what you are growing. Proper identification is essential to correctly prune your shrub. Many shrubs flower on last year's growth and if you are pruning yearly you may never get flowers. The classic example of this is the lilac. Shrubs like these should only be pruned immediately after they bloom to ensure a good set of flower buds for next year.

In contrast to the old wood flowerers some shrubs only bloom on this years new growth. These shrubs should be pruned before the growing season begins.

As with so much of nature there are shrubs that don't fall into either of these categories and flower from both last years growth and this years growth. These typically flower later in the growing season and can be pruned while dormant or right after blooming.

Pruning Chart

Location of Flowers	Best Time to Prune	Typical Plants
Last Years Growth	Right After Flowering	Lilac Forsythia Saskatoon
New Growth	Before Growing Season	Clematis Spirea Hydrangea
New and Old	Right After Flowering or While Dormant	Potentilla Rose Mock Orange

There are some shrubs that we grow primarily for foliage, like red osier dogwood, elderberry, willows, and barberry. This group should generally be pruned in the winter season before growth begins. Moose prune their dogwoods in the winter and so should you.

Most conifers like spruce, juniper and cedars can be pruned at anytime with the exception of pines. Pines are best pruned in early summer when the new growth is emerging. These long shoots known as candles can be cut or pinched off at the half way point and the shrub will set new buds for future growth. If you prune pines after the shoot has fully elongated and you will be left with a half shoot. Without buds on the end it will loose its needles and leave you with a dead stick.

Contact your certified Arborist for more information on shrub pruning and watch for the second part of this article dealing with tools and techniques.

The Big Freeze

February 18, 2007

As you look out your window longing for spring take comfort in knowing that your trees are not really frozen. “That’s impossible with the temperature so far below freezing!” you may think. If your trees were frozen in the traditional sense, like your garden tomatoes, they would be dead.

Hardy perennials and trees have three strategies to prevent them from joining their green cousins every fall. An understanding of why your tomatoes are dead will help you realize why your trees are simply dormant.

In the fall when temperatures drop to the freezing point, ice crystals begin to form in the plants cells. While they are pretty to look at in a snow flake, forming inside a living plant cell

the results are devastating. The sharp water crystals puncture the plant cell causing its contents to leak out. The cell dies as a result. What you see is a wet limp leaf or stem that usually turns black. Commercial food production uses a fast or flash freezing to prevent ice crystal formation and keep your vegetables from getting mushy. Trees are by in large composed of water so how can they survive freezing weather?

Trees have several strategies to prevent ice crystal damage. Even the smallest amounts of

dissolved solids in the water in a tree will lower the point at which ice crystals form. This increases the plant’s ability to survive temperatures slightly below freezing. This is the same reason that salty ocean water freezes at a lower temperature than fresh water. In the case of plants, it is the dissolved sugar that prevents the plants from freezing at just below the freezing point of water.

As the temperature decreases the tree must be prepared by moving water out of the exposed plant cells and into areas that don’t freeze, like the roots. This causes the drying of the exposed upper stems and branches as well as concentrating the remaining sugars in the cells to prevent freezing. Much of the moisture remaining in the cells can be shifted to locations just outside the living cell in the intercellular spaces. Once outside the cell there is no danger that water crystallization will damage the cell.

The entire process reverses itself as the weather heats up in spring. Many plants are injured by rapid warming and freezing that can occur in areas that experience extreme changes in temperature. The ability to survive longer unusually warm spells, while not breaking dormancy, is an issue that affects winter hardiness. Plants that bloom or leaf out early in the spring, are more likely to be damaged by spells of unusually warm winter weather. For more information on winter hardiness contact an ISA Certified Arborist.

Good Leaf Bad Leaf

Now that the yearly crop of leaves has fallen it may be of interest what to do with them next. In this age of recycling it is all the rage to compost your leaves to recycle the nutrients. Well this is a great idea in principle depending on the trees on your property you may want to reconsider this approach. Back in the good old days people used to burn all there leaves and spread the ashes on there garden. While this practice isn’t the best from an air quality standpoint it does eliminate over wintering disease and insect problems on the leaves that may survive composting or just piling up in the woods. While it’s no longer recommend to burn your leaves, selected recycling and compost may be your best solution.

Trees that have old insect infested fruit, like apples, should have this disposed off site or buried to prevent the insect pests from over wintering in the fallen fruit. Similarly leaves from trees that frequently have outbreaks of fungi like lilacs, dog woods and ash trees should be gathered and thoroughly composted for more than one year away from the affected trees. Many trees have gall or other mites that disfigure the foliage with cocks combs or nipple like lumps. These should be moved off site or disposed of to prevent re-infection. Leaf shredders are an excellent way to speed up the process of composting, mixing leaves with other vegetable waste from the house and turning it frequently will promote proper composting.

Now that leaves have fallen and trees are dormant there are things you can do to help them get through severe winter weather. Even though the tops of your trees look dormant there is plenty of action in the root zone. Ensuring the plants have lots of available water at this time can improve survival when temperatures start to rise in the spring. Fall fertilization and watering your evergreens are two cultural practices that can make a big difference in winter survival and help your trees thrive next spring. Be careful when fall fertilizing follow label directions carefully and use low nitrogen slow released fertilizer. Watering and fertilizing can take place from now until the ground freezes. If you want more information on fall tree care contact an ISA Certified arborist, they are experts on tree care and plant health.