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Sometimes people preface a question with:
"Hate to bother you but..." or "What you wrote about pruning, this book says we shouldn't..."
We're so glad you-all "bother" to keep us on our toes about pruning's "Why," "when" and "how." We've been pruning for a long time and have adopted certain schedules and procedures. We're pretty comfortable with them. The plants in our charge respond well, in general. Yet when you ask us to write things down, it does make us revisit our bases.
What we rediscover when we return to "Go" is that we must comb through many directives. Some conflict. Most lack a "why" that allows us to figure, "What if we do X, instead?"
To illustrate, check this collection of advice regarding Magnolia pruning. We pulled it from sources we respect. It's presented to show you how each item affects our pruning decision. Our "take" on the matter is on the right, from the directive on the left.
|The New Royal Horticultural Society Dictionary of Gardening
"(Magnolia) Pruning is... shaping the plant at planting time by removing weak and badly placed growth and tipping back long shoots. Routine pruning is usually restricted to removing deadwood and watershoots, but where a specimen outgrows its allotted space, it can be pruned hard back immediately after flowering."
|A Magnolia can be kept smaller than its potential.|
| Arboriculture: Care of Trees, Shrubs and Vines in the Landscape,
Richard W. Harris, Prentice-Hall, NJ
"Rapid plant development can be best maintained when the required pruning is done before the period of rapid growth that usually occurs in spring. Most deciduous plants can be pruned any time during the dormant period between leaf-fall and spring growth with similar results."
Callusing should be somewhat more rapid if a wound is made a few weeks before or after growth begins, assuming that bleeding is not a problem. ...wounds on ash, honey locust and pin oak callused about equally rapidly in the next growing season whether cuts were made in the spring, summer or winter, but about 20 percent more slowly when they were made in the fall.
|Winter's a good time.|
|From an interview with Dr. Alex Shigo (1930 - 2006), pathologist with the United States Forest Service, and our subsequent correspondence, April, 1994
"If you make your pruning cuts correctly, you can prune at any time of the year."
|Follow plant health guidelines: Clean, sharp tools. Respect the branch bark collar.|
|The American Horticultural Society Pruning & Training, Christopher Brickell, Dorling-Kindersley Ltd., London
"In general, avoid pruning established magnolias unless essential. Many species bleed and should only be pruned from summer to before midwinter."
The Pruning of Trees, Shrubs and Conifers, George E. Brown, Timber Press
"Magnolias usually show great powers of regeneration and may throw strong young growths from really old wood. Advantage can be taken of this by cutting damaged specimens back carefully... This power of regeneration is also a great help in overcoming the effects of bad training in a young specimen, especially with bush types such as M. soulangeana, which branch low. Large scale pruning, if it becomes necessary, should be carried out in late July, thus avoiding the risk of bleeding..."
|Think twice before pruning
a soft-hearted person's magnolia during rapid sap flow in March...
|Arboriculture: Care of Trees, Shrubs and Vines in the Landscape, Richard W. Harris, Prentice-Hall, NJ
"Bleeding can be minimized if predisposed species are pruned in the fall and early winter instead of late winter and early spring... bleeding is usually not harmful to plants, but if it is heavy and persistent it can cause bark injury below the pruning cut and can retard callusing in the lower portion of the wound."
|...even though bleeding doesn't usually hurt the tree...|
|The Standard Cyclopedia of Horticulture, L.H. Bailey, The MacMillan Company, NY As a general rule, however, the best time to prune is in late autumn to early spring, when labor can be had and before the rush of spring work comes on. In practice, it resolves itself largely into a question of the convenience of the operator.||Ah, so!|
We include botany and basic gardening books when we do our pruning research, and also plant encyclopedias by those authors who have impressed us as the most hands-on and first-person in their reporting. We look for between the lines information and anecdotes as well as pruning pronouncements and most of those have no expiration date so a 1940's book or ancient farm diary can count, in many cases!
The human schedule is what matters
"What if we deviate from the rule?" We ask this often because it's rare that we gardeners can be everywhere we need to be, when the time is "right" for a given plant and particular procedure.
We've interviewed a lot of gardeners, including dozens who maintain public gardens and found one thing they all have in common is, "So many demands, never enough time!" For the home gardener, a child's soccer game causes us to put off a garden chore. At a botanical garden, it's the announcement that the Emperor of Japan is coming to visit so everyone must drop what they're doing to help finish the projects in the Japanese garden!
Many rules we learned in school and training haven't held up to what we've seen when we stick our heads inside plants as we travel. We've seen trees a century old and older that have been pruned "Wrong" that whole time. And I wonder if someone informed Mr. Hunnewell, when he decided 150 years ago to populate this spot on the family estate with Italianate topiary trees, that "You can't cut a white pine (trees on the right) or spruce (center) that way?"
What's Up 170: Prune magnolia, books, beech, Rose Bowl