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Before pruning your plants, it is always a good idea to consider what time of year is best for pruning them. Trimming your plants back too early or too late could affect your tree's health or how many flowers it can produce. Want to know which ones you should never chop in the fall? Grumpy's got all the answers.

Bloom Time Is the Key

Many of the commonly butchered shrubs and trees bloom in spring. This means that they've already formed their flower buds. So if you go crazy with the loppers and wail away on a spring-bloomer during the fall, you just might cut off the flower buds and you won't get any spring blooms. To help you avoid this blunder, I have put together a list of plants you should never prune in the fall.

Plants You Shouldn't Prune In the Fall

Rhododendron and Azaleas

Azaleas
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Azaleas are a part of the genus of Rhododendron, making their pruning times the same. These flowers grow on old wood or last season's growth, so it is important to trim these blossoms back in the right season to ensure new blooms every year. We recommend cutting them back within a three-week period after they stop blooming in the spring. This will ensure they have plenty of time to make new growth for next year.

Flowering Cherry, Peach, and Plum Trees

Cherry Blossom
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All members of the Prunus genus, including Cherry, Peach, and Plum trees, are healthiest when they are pruned in the spring and summer. This is due to the fact that the plants in this genus are particularly susceptible to a fungal disease called Silverleaf, which can cause lost branches. This fungus is carried by the wind and infects trees and shrubs through their wounds. Since this fungus creates most of its spores in late autumn and winter, cutting back your prunus trees during this time could cause your tree to be infected by Silverleaf.

Callery Pear Tree

Bradford Pear Tree
(Pyrus calleryana 'Bradford')The Grumpy Gardener feels quite passionately about Bradford pear trees. To be specific, he passionately despises them."Its flowers smell like tuna, it explodes in the wind, and its thorny seedlings come up just about everywhere," Grumpy says. Instead, choose well-behaved trees such as crabapple, Chinese fringe, or flowering cherry.
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Callery Pear trees should be pruned in late winter, after the worst of the cold has passed and before their buds begin to get bigger. Pruning earlier in the fall or winter months could cause excess growth and extra suckering. This tree in particular is more susceptible to limb loss, which can cause your tree to become unbalanced or asymmetrical. For this reason, pruning is very important to control the shape of your tree, especially in its first few years.

Crabapple Trees

Crabapple
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Prune your crabapple trees in late winter or early spring after the worst of the winter cold has passed for the best results. Suckers, or the little shoots that grow out of the base of the plant, can be pruned at any time. Crabapple trees don't need extensive pruning, but some pruning can help control shape, rid of dead branches, promote growth, and even help prevent or treat disease in the tree.

Forsythia

Forsythia
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The bright yellow forsythia shrub should be trimmed back in the spring after the blooms fade. Since their blooms grow on old wood, waiting until later could cause there to be not as many blooms in the spring. Pruning is necessary to controlling your fast-growing forsythia. Forsythia, if unkept, can grow up to 10 feet tall and wide. Trimming back your forsythia yearly can help prevent its unruly spread.

Lilac

Lilac
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It is important to prune your beautiful lilacs after blooms have faded in early summer for the best growth every year. Cutting back your lilacs is critical to managing them and keeping them from growing too high. In fact, your lilac bush can grow up to 30 feet on its own. Trim about a third of the plant back, and cut the shoots that spring up from the base of the plant.

Loropetalum

Loropetalum
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Loropetalum should be trimmed back in the spring after they finish blooming. Pruning loropetalum later can cause a risk of cutting off flower buds which can result in having fewer flowers next season. Remove dead branches, cut back damaged limbs, and remove any shoots or unruly stems that take away or distract from the overall shape of the plant.

Oakleaf Hydrangea

Oakleaf Hydrangea
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Begin pruning your Oakleaf hydrangea in spring soon after it stops flowering. These hydrangea plants don't need hefty pruning, but cutting them back no more than one-third yearly can help promote growth and maintain shape.

Saucer or Star Magnolia

Star Magnolia
Magnolia stellata This magnolia species produces distinctive blooms with clusters of long petals. 'Centennial' has white blossoms, 'Jane Platt' blooms rosy pink, and 'Water Lily' produces pink buds and fragrant white flowers.
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Magnolia trees in general don't heal as well as some other trees from pruning, so make sure not to get too carried away. Trim them back after they finish flowering so you don't risk losing flower buds for next year's growth. Cut the lower branches off the trunk to form your star or saucer magnolia into a tree shape. Trimming back your tree can also help prevent the spread of disease—cut back branches with canker sores on them about five inches below the sore. Use gardening shears for clean cuts.

Spirea

Spiraea
Beginning in spring, this shrub bursts into blossom, filling up its branches with blooms of many hues. (They also attract butterflies.) Gardeners in the Deep South should try Little Bonnie Dwarf Spiraea from the Southern Living Plant Collection—it will add just enough color and lush, blue-green foliage that lasts. Plus, it can tolerate our Southern summer swelter.
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Plan to cut back your Spirea bush after it finishes blooming in the spring for the best growth in the next year. Cut off shoots that spring up, and remove any diseased or dead branches. Trimming back your spirea will help it keep its shape and promote blooms each year.

Viburnum

Viburnum
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Viburnum should be pruned in late winter or early spring to promote growth. While it doesn't need much pruning, it is good to cut the plant back occasionally to control its shape and help rejuvenate it. Cut back about one-third of the plant annually for best results.