March 10, 2013

Maine Gardener: With pruning, it's all about the how

By TOM ATWELL

March is a great time to prune many of your trees and shrubs -- although getting to them through the snow might be tough this year.

With deciduous trees, it is easier to see the branches when there are no leaves. With spring-blooming plants, you can bring some pruned branches into your house and get them to bloom early.

Orchardists especially recommend pruning fruit trees in March, reducing the number of blossoms so you get fewer but larger fruit when it is harvest time.

But that is not why I am writing a pruning column now. Cass Turnbull, founder of Plant Amnesty and a landscaping professional in the Seattle area, spoke last month at New England Grows in Boston and, probably not coincidentally, has just published the third edition of her "Guide to Pruning."

Turnbull does not necessarily believe that the best time to prune is in March, saying that "when you prune isn't nearly as important as you have been led to believe. How you prune is what counts." And, "My favorite maxim is 'Prune when the shears are sharp.' "

Still, she says, spring is the kindest time for pruning because the plants will grow back the fastest. It also is the best time for "radical renovation," which is the term she has for cutting fast-growing shrubs back to the ground and letting them resprout to create a newer shrub.

If your goal is to preserve blooms, she says you should prune right after the plants bloom, adding that if you are selectively pruning and doing a good job -- not just shearing or topping the tree to get it to the size you want -- you are going to get plenty of blossoms anyway.

I first heard Turnbull speak at New England Grows in 2008, and I have followed her pruning principles ever since. I never saw the first two editions of her "Guide to Pruning," but she handed out enough pamphlets that I got the basics.

Her book gives a lot more information, with entire chapters on pruning shrub types: mounding-habit shrubs, cane-growing shrubs, tree-like shrubs, vines, trees and ground covers. She includes specific pruning instructions for dozens of common plants.

The book, published by Sasquatch Press, is a 366-page, large-format paperback with oodles of illustrations, and is listed at $23.95.

But if you don't want to read the book, I'll give you her basic pruning guidelines.

With proper planting, pruning would be unnecessary, Turnbull says. But people generally buy too many plants for their property, and gardens get overcrowded.

"There is a deep need in the spirit of man to control nature," she said, so people go out and try to keep the plants the size they want them to be rather than letting them grow to the size that the plants want to be.

Turnbull founded her group Plant Amnesty (plantamnesty.org) because she wanted to stop tree topping, which is more common in Washington state than in Maine. If a tree is getting too large, people will just cut the trees off at the height they want them to be, thinking that will work. She showed pictures of that kind of work done on huge trees as well as smaller shrubs.

The problem with that kind of unselective pruning is that it causes water spouts -- fast growth of a lot of small branches heading straight up -- is unhealthy for the plant, and makes it look ugly. Basically, you end up with a tree that looks like an upside-down broom.

Instead, you should make selective cuts. The first step is to cut out all of the absolutely dead branches.

Once the deadwood is gone, decide what the plant's pruning budget is: That is, how much can you cut out of the tree or shrub? Cane-growing plants like forsythia and lilacs have a pruning budget of up to 50 percent, meaning you can cut out branches containing half of the plant's foliage without making the plant sick. For trees and tree-like shrubs, the budget is 15 percent.

Start at the bottom of the plant and work up.

"While doing good pruning, you are on your hands and knees with your butt up in the air," Turnbull said. 

Remove branches that are so low they are touching the ground. Remove branches that are hitting the house, blocking paths or covering windows. Remove limbs that are rubbing against each other or crossing. Remove the ones that are going in the wrong direction.

But you are not going to be able to do all of that in the first year, especially with trees and tree-like shrubs.

"If you take out everything that is wrong with a tree, you have over-pruned," she said. To get a tree that has been allowed to get too large back into shape could take five years or more.

With mounding shrubs such as rhododendrons, evergreen euonymus, holly and spirea, the best method is "grab and snip," reaching in toward the center of the plant and cutting large branches at a junction. Surrounding leaves will hide the cut. These plants have a pruning budget of about one-third.

For low-growing evergreens such as juniper, you have to lift the upper branches and cut out the bottom branches. The middle of these shrubs have dead and brown needles, and this is the only way you can cut them without the dead showing.

With cane-growing shrubs, you should cut the oldest and largest limbs right down to the ground, allowing the young suckers to rejuvenate the plant. These have the highest pruning budget, and are the best candidates for radical renovation.

You should step back and look at the shrub after every few cuts, figuring out what is the next-worst branch, and keeping in mind the pruning budget for the plant you are working in.

"And if you are paralyzed with indecision, it is time to move on," she said.

Or you could read her book. I can't think of a pruning question it doesn't answer, and she'll give you a few laughs as well.

Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at:

tomatwell@me.com

 

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