Why prune? Part 2

Remember the connection between pruning and growth. In simple terms, the plant's roots draw up water and nutrients to feed the plant, so the roots grow and expand at a rate of supply to the leafy top growth. If you suddenly remove a lot of branches the roots will continue to supply food, resulting in a crop of interior, weak, spindly shoots usually close to where the branch was cut off.

Pruning less drastically - i.e. removing only a few branches at a time - allows the plant to produce new, sturdy growths that will in time make healthy replacement branches. Together was is frequently referred to as NPK, which is nitrogen, phosphate, and potash can be applied early in the summer. Avoid a late application because it will promote soft growth that is prone to winter frost damage. Nitrogen promotes fast growth which is good in the case of hiding a eyesore from pruning. To much nitrogen will will encourage thin, weak growths toward the top of the plant.

Phosphate helps to establish a good root system that holds the plant firmly in the ground and collects water and food. If roots have been damaged during plants or transplantation a application of phosphate will help the plant to produce replacement fibrous roots.

Potash Aids in the production of flowers and fruit, and when applied in autumn it will firm up growth produced late in the summer to make it more resistant to winter freeze. Smaller trace elements such as magnesium and iron are already in the soil and available to the plant's roots.

An important aspect of a plants growth is the soil. In sandy, free-draining soils, they will quickly leach down out of reach of the roots. Heavy clay retains nutrients better, but tends to become waterlogged in winter.

Pest and Disease Control

Plants are prone to damage from pests and diseases. In some cases an attack may be crippling, resulting in the death of the plant. Other troubles only cause short-term marking of foliage or minor stem damage.

If discovered early, the infected parts may be pruned off to slow down or stop a pest or disease attack and prevent the problem spreading to other plants. Make sure to never compost diseased pruning. Burn the material and use the wood ash as beneficial potash mulch around other plants.

A lot of pests may disfigure a few leaves, but for the majority of them they are not worth losing sleep over. Other pests, such as the cherry black fly, may be eliminated by pruning. The leaves at the tips of branches of fruiting cherries and the ornamental flowing are attacked in the late spring by dense colonies of black aphids. Nipping out and burning the affected tips of large ornamental trees is a simple alternative to applying insecticides.

The caterpillars of some moths, and especially the brown-tip moth, can completely defoliate plants such as hawthorn, apples and roses. Colonies of grey-black, hairy caterpillars hide and feed under a dense silken web. Prune out and burn the silk nests in late autumn after leaf-fall.

Wildlife do enormous damage to plants. Pruning out damaged bark may allow the tree to recover, but the best remedy is fencing off the area or protecting the individual plants with wire mesh.

Birds, especially the finches, love the fat, winter fruit buds of apples and plums. They can significantly reduce crop yield. Where branches are stripped of buds a spring pruning will encourage more shoots that will produce more buds, but unless you protect the tree with a net the birds will return to continue the destruction.

As with many disease, pruning to remove the infected part is part of the only method of saving the plant. There is no control for some diseases, such as Dutch elm disease and honey fungus, and the shrub or tree will quickly die. If you have lost a plant to honey fungus there is no chemical control. It may help to dig a trench 30cm deep around the recently killed plant, throwing the excavated soil to the inside of the trench.

The spread of silver leaf disease which is common in plum or cherry trees can be slowed down by removing diseased branches as show as the disease shows. Cut the infected branch at least 15cm below the point where browning staining of the wound is evident. The spores of silver leaf disease are less active in the summer so pruning them out then is critical.

Cankers attacking the bark of apple, pear, and ash trees appear as sunken areas of bark, usually discolored with bark cracked or flaking. Cankers have the ability to girdle off branches, so it is important to cut off at least 15cm below the diseased area. If only a small wound or bud is infected, the area can be cut out and treated. Badly affected trees should not be saved because of the risk of disease spreading from the roots.

Imaged borrowed from "Garderens' World"

Bacterial canker is another killer of plum, cherry, and peach trees and is often first noticed by sunken areas of bark that are oozing amber-colored, resis like gum. The procedure for this is the same as dealing with other cankers.

Fire-blight is common in Calgary in apple, hawthorn, and pyracantha. The flowers wilt and wither before dying. Pruning may slow down the spread in a mature plant but cutting back the infected parts by at least 60cm below where the damage shows. For more information on this disease refer to a previous blog made by Kephas Landscaping Inc.

Fungi are also the cause of die-back and black spot diseases. Early pruning to remove the infected stems will reduce the risk but is unlikely to be a complete cure.

Coral spot fungal disease is easily recognized. The dead portions of woody stems are covered in small, raised, bright orange or red pustules. The control is to cut out all dead twigs and branches and burn the prunings.

Clematis wilt disease gets a bad press. The issue is from slugs chewing the stem at ground level. Clematis varieties is caused by soil-borne fungus entering through a wound at soil level and preventing the plant from drawing up water. The first indication is the complete collapse of the stem or the whole plant. The recommended procedure is to cut the affected plant back to the healthy stem or below soil level. The plant may then grow back from new shoots and dormant buds.

Another common damage to plants or trees is where branches are broken by storms, or the weight of a crop of fruit, which should be dealt with as soon as possible by removing the branch back to the main limb or the trunk. The pruning cuts should be left smooth to reduce the risk of fungal disease spores landing on the rough surface and infecting the plant. Whenever possible it is ideal to remove heavy falls of snow from plants to prevent similar damage.

Image borrowed from "Tree Unlimited NJ"

Prevention is always better then a cure. So applying potash fertilizer in early autumn to harden up the growth of young soft wood which is routinely damaged by frost or biting cold winds. If the damage is already done, prune in late spring or when risk of frost is part to remove the affected parts.

A good practice when dealing with diseased plants to to dispose of the material properly and disinfect tools to prevent the spread to other trees.

This spring Kephas Landscaping Inc will be taking time to present blogs with information related to arboricultural or landscape care and design. Kephas Landscaping is a landscaping, tree care, and snow removal company located in Calgary, Alberta.

Information gather for this blog was compiled from "How to prune - by John Cushnie"