Pruning Arborvitaes

Leif’s article for this week’s Northfield News discusses what one should be doing for the clean-up of their landscape plants after the stresses of Mother Nature this last year – especially in Northfield. Locally, the plants with the most damage from the severe hail storm are the arborvitae and other evergreens.

“Keeping a landscape in good shape is always a challenge, but in the Northfield area over the last year, gardeners have experienced quite a range of abuse from Mother Nature. Last summer we had drought conditions, the horrific hailstorm, then a long period of winter with very little snow cover, and finally the memorable Easter Week cold snap that followed 80 degree temperatures.

Drought stressed plants were left in tatters by the hail, and plants that woke up early this spring were frozen off by the April deep freeze. All over town the results are visible. Evergreen shrubs and trees have plenty of brown spots showing up that need to be carefully pruned out. Leafy shrubs and trees need to have badly damaged branches pruned out so new growth can fill in gaps without dead branches impeding and misshaping the new growth.

On evergreen shrubs start by carefully clipping out discolored brown and shriveled foliage even if doing so will leave a gap. Once the dead or damaged material is removed, you can see the shape better and trim moderately on the live parts to get a pleasing shape.

Keep in mind that it may take a couple of growing seasons and more pruning to get evergreen shrubs to really shape up. A big help will be monthly applications of soil acidifying fertilizer such as Miracid. Vigorous growth fills in more quickly and color is improved.

You may have noticed the deciduous (leafy) shrubs and trees have a number of areas where bark is damaged by hail and have already begun to grow new bark back over the wound. Remove any loose bark, fertilize lightly the first half of the growing season, and it won’t hurt to spray fungicide on the wounds to prevent infection until the wounds finish closing up.

Even places where one or more branches were completely stripped off the tree trunk, good long term results are possible as long as canker or fire blight or some other infection does not work its way into healthy tissue. To get a balanced looking tree a couple of years down the road, you may find it necessary to cut back the length of some branches so they match better with the broken or missing branches.

Plant Spotlight: Magnolias. There are 6 to 8 varieties of Magnolia that are Zone 4 hardy for Minnesota gardeners. By following a few strategic planting tips, you should be able to enjoy the beauty of the spring flowers for years. Making the proper choice of a planting location is the most important step. Since Magnolias send out their flower buds before leaves in the spring, as soon as the sun starts to warm the ground and the tree, it will start to activate flower buds. By choosing a location where the late winter/early spring sun doesn’t reach early on, you will postpone bud activation until the danger of killing temperatures should be past. Amend the soil with some peat to help acidify it more – plant your tree and enjoy!

Varieties that have proven to be exceptionally hardy for us are the Merrill’s Magnolia with its snow white flowers, the Royal Star with star shaped white flowers and the wonderful pink of the Leonard Messel. The Merrill’s is the one that will grow the tallest – potentially growing close to 30′ or more while the Royal Star is the little one reaching only a maximum of 10-12′. Leonard Messel is the compromise at 15-20′ in mature height.”

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