NDSU Extension - Griggs County


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March 23

The Extension Connection
By Megan Vig
Spring has arrived based upon the calendar but it does not quite feel like it yet. In North Dakota, March is generally the best time to undertake pruning work to minimize excessive sap flow. Exceptions to this would be trees noted for heavy sap flow such as maples and birches, you can meet their pruning needs after full leafing out is complete. Some shrubs bloom only on the previous season’s growth: for example Forsythia spp, Syringa spp. – lilac, Viburnum spp. – viburnum and Spiraea spp. – spirea. If you want them to rebloom the following season, you should complete the pruning immediately after the blooming period is over. Pruning these shrubs while still dormant in the early spring removes potential flowering branches for that growing season.
Evergreens generally have a longer pruning season than deciduous plants. In addition to early spring and midsummer, pruning after new growth has hardened is acceptable for pines and spruce trees. Juniperus spp. – junipers and Thuja spp. – arborvitae can be pruned up to mid-August. When a branch is causing safety concerns, you can override the seasonal recommendations for pruning. Go ahead and prune or have the branch pruned by a professional arborist. Safety may be an issue when branches are threatening to fall and cause serious damage to structures or harm to individuals, or they are blocking a view of an intersection or moving traffic.
Pruning is beneficial. It can promote a fuller look in certain species. Disease and insect control is another reason for pruning. Pruning for disease such as black knot of Prunus spp. (chokecherry especially) and fireblight on species of the rose family (Malus spp. – apple, Amelanchier spp. – Juneberry, Cotoneaster spp. – cotoneaster, Pyrus spp. – pear, Sorbus spp. – mountain-ash, etc.) will need to be carried out carefully to avoid spreading the disease to healthy parts of the tree or healthy trees. Right now would be an appropriate time to prune these species. Pruning during the growing season on these species will spread disease.
Always cut 10 to 12 inches below the visible symptoms of these pathogens, preferably during dormancy, and wipe the pruning shears with an alcohol-soaked, hand-sanitizing cloth or a 10 to 20 percent bleach solution to help prevent the spread of these fungal and bacterial pathogens.
Contact the NDSU Extension office (797-3312) for more information on pruning and to pick up the Basic Guidelines for Pruning Trees and Shrubs.

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