A spray hose can help alleviate simple insect infestations.
at this time of year. Spruce and pine trees growing on clay
loam soils, in my experience, are adverse- ly affected by low soil nutrient levels. Pest activity as previously described, is enhanced with insufficient quanti- ties of appropriate nutrient levels in the soil. Needle colour will not be a healthy green except those needles growing near the tops of the tree; and more likely their colour will be a straw yellow or grey yellow. Green needle evergreen conifers need well-drained soils with adequate quantities of nitrate, phosphate, sulfate and iron oxide nutrients. How do you know if the fertilization
levels in your soil are either inadequate or excessive? Unless you get your soil tested by an appropriate lab, you gener- ally do not know. There are soil testing kits available you can use. Coniferous evergreen trees such as spruce, fir and pine require lighter well drained soils consisting of fine sandy loams, or even sands or gravelly soils. Maples tend to be excellent indica-
tors of appropriate soil nutrients in their rooting systems. Inadequate nitrate and iron oxide will prematurely turn the leaves of many maples yellow during the summer months. This can be promi- nently displayed in silver maple
and
Amur maple leaves where low levels of soil iron oxide and nitrates take on a spectacular effect by producing bright yellow leaves. The leaves quickly wither producing leaf browning either as spots or along the edges or both. They usually become diseased and die. Vertical mulching
Vertical mulching is an ideal tech-
nique for rejuvenating older trees. Verti- cal mulching is a method used to allevi- ate, to a certain degree, soil compaction within the critical root zones of trees. Compaction reduces air and microscopic water in the fine tree roots causing a significantly reduced ability of the tree to
localgardener.net
Maintaining healthy soil by adding compost or mulch can help make plants healthier and more resistant to insects.
Fertilizers can be beneficial for plants, but improper application can damage or kill them.
access needed soil, air and water. Under these conditions the tree’s ability to access soil nutrients is also significantly reduced. Vertical mulching will also lessen
damage due to excessive water, preserve necessary aeration during wet periods, allow sub-soil water penetration during dry periods, and promote the formation of fine feeder roots. To vertically mulch your tree, power
auger or drill holes two to three inches wide, and about eight inches deep in clay loam soils. Space the holes 12 to 20 inches apart under the affected trees starting at about eight
feet from the
trunk. Continue the holes out toward the edge or beyond the branches corre- sponding to a total distance of about half the tree height from the trunk. Fill holes with a mixture of pea gravel, or sand, or
a mixture of compost with pea gravel or sand. A layer of three to four inches of good quality organic mulch, such as aged wood chips, composted leaves, or decomposed straw spread evenly over the entire critical root zone will also help trees, especially those in a forest environ- ment. So you see, chemical solutions need
not be the first line of defense. Simpler, organic, more Earth friendly solutions are available, preferable and effective. h Further information can be obtained by
contacting Michael Allen by e-mail: vibur-
numtrees@shaw.ca Michael Allen
M.Sc.F,. RPF (ret.) is a
consulting urban forester, tree diagnosti- cian, certified arborist and owner of Viber- num Tree Experts. He can be contacted at
treeexperts.mb.ca or at viburnumtrees@
shaw.ca
Early Spring 2016 • 25
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