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Winter Tree and Plant Health

As we end a year and look forward to the next, a good thought might be “How can I support my plants this winter season and for next year’s health?” Properly applied organic mulch of the correct type is the best course of action for heavy feeding plants; rock mulch is fine but additional fertilization may be needed. Importantly, it has been discovered through recent research at WSU that fabric, newspaper, cardboard, and plastic mulches should NOT be used around plants due to greatly decreased gas exchange between the soil and atmosphere. Thankfully, additional watering for evergreen plants is not needed so far this winter. Do not let the mild winter we have experienced lull you to complacency. Relatively warm temperatures and continuing precipitation events are not making a strong dormant season; some plant buds are even beginning to swell already. If we once again have a failure of the polar vortex to keep cold air in the Arctic North where it belongs, lobes of bitterly cold air may strike through Puget Sound infrequently in January andFebruary. If such is forecast, having some weed-free hay straw at hand to cover around hydrangea, palm tree bases/stems, rosemary, and over the root crown/plate of other desired plant species unused to such temperatures is prudent. Any left-over straw can be used for organic mulch. Tender, aerial plant parts may not survive one of these cold events- this has included early plum blossoms at least once in the last couple of years.

If the stem of your fruit or ornamental tree has good exposure to southern light, it may be worthwhile looking into painting the lower portion white with latex paint (NOT acrylic or oil-based paint!). This reflects the warming potential of the winter sun, which may cause vertical cracks in the cambium due to the differential between cold and warming parts of the stem. These cracks are harder for the tree to heal and are a good avenue for pathogens to get into the tree. The paint may also act as a protective layer against boring insects.

Step back from all the vegetative growth and look up. Are there recently broken branches hanging at weird angles? Tree stems that seem to be growing together somehow? Any portion(s) of the tree recently deceased? It is good to perform this action a couple of times a year when living around trees (I offer my help if you need it). Sometimes these items can creep up on you unawares between storm events and create an unwelcome surprise.

Ornamental maples very much enjoy a light (1” thick) topdressing of aged (seed-free) manure/soil mixture to help feed next year’s growth. This should be raked to carefully control depth and distribution.

Anything you can do to slow down grass growth near a fruit tree is good- mowing consistently or annually applying a 3-4” measured layer of organic mulch are two ways.

Dormant season pruning is about to commence. Larger cuts on many desired trees and shrubs can be made at this time. Make sure the person doing this is using 91% alcohol or similar to sterilize hand tools.



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