Fertilizing

When should woody plants be fertilized?

Generally we recommend fertilizing trees and shrubs in the early part of the growing season. This allows the plant to use the fertilizer when it is vigorously growing.

What type of fertilizer is best?

Usually we recommend a fertilizer such as 20-15-15 or one in which the analysis numbers are fairly similar.

How often should trees & shrubs be fertilized?

I fertilize my mature trees every other year. Young trees and shrubs should be fertilized each spring. Mature shrubs which have reached their desired size are seldomly fertilized.

What method of application is best?

Using a root feeder get the fertilizer down to the tree roots the quickest but is also the most expensive. Water flowing through the root feeder dissolves the fertilizer tables and carries them down to the roots quickly. Tree spikes can also be effective but it takes much longer for them to dissolve and work down to the plant roots. Fertilizer should be applied at the drip line of the plants being fertilized.

Should we fertilize trees and shrubs in the early fall?

Fertilizing at this time of year is not recommended. Fertilizing now would tend to stimulate new growth at a time when we want the trees to loose their leaves and go dormant. If you want to fertilize in the fall wait until just before the ground freezes up.

Pruning

Pruning Non Evergreens

What is the best time of the year to prune?

As a general rule, pruning should be done after the danger of severe cold has passed and before plants have leafed out, but there are several exceptions to that rule: Trees such as elms, birch, maples and boxelder should not be pruned until completely leafed out. If pruned sooner they may bleed sap excessively. Shrubs such as lilacs, spireas, honeysuckles and mockoranges should not be pruned until after they flower, unless you aren't concerned about flowers.  If  pruning just after flowering, they will flower again next spring.

Should pruning paint be used on pruning wounds?

Research has shown that pruning points or wound dressing can cause as much harm as good. For that reason we don't recommend using it, except for pruning wounds on trees which are susceptible to bacterial diseases such as fireblight or canker. Can also be used on trees which have had the bark eaten by rabbits or are damaged in other ways. 

Which plants would these diseases affect?

Any of the plants related to the apples such as flowering crabs, mountain ash and cotoneaster can be infected with fireblight. Russian olives are also susceptible to a bacterial disease and can benefit from the use of pruning paint on open wounds.

Pruning Evergreens

What is the best time for pruning ?

There are several answers depending on the species of evergreens you have planted. The best time to prune the spruce is just before or after the new growth appears. The pine should be pruned when the new growth or candles have elongated but before needles have formed on the new growth. Junipers, Arborvitae and Yews can be pruned any time up to August 1.

Is there anything special to consider when pruning evergreens?

Yes, always prune to try and keep the natural shape. Don't use a hedge shears and don't leave stubs. Always cut back to the next bud or side branch. The evergreen sap is so sticky that pruning paint or wound dressings aren't needed.

Can evergreen shrubs be cut back like non-evergreen shrubs?

No, if an evergreen is cut back to the point where there is no green on a branch generally that branch will die. They can not be cut down to ground level and expected to grow back from the roots.

Should the brown needles from last winter be removed?

I would first wait and see how much new growth emerges from the browned areas. It may do a good job of hiding the damaged needles.

Is June too late to prune evergreens?

Definitely not! Spruce trees can be pruned after the new growth has developed. The Junipers, Arborvitae and Yews can be pruned any time up to August 1.

Should the lower branches on large evergreens be removed?

No, not unless the needles have all fallen off or are brown. Before removing lower branches from evergreens consider what it will look like under the tree without the branches. It is very difficult to get anything to grow under large evergreens.

This page was last updated August 2002

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