Prune boxwood in winter

Our boxwoods are quite large – too large for the space they’re in. I meant to cut them back last summer but never got around to it. Is it too late to prune them now?

Most boxwoods don’t require regular pruning unless you’re keeping them sheared in a formal garden space, but if you need to control the size of the shrub, now – or late winter to early spring – is actually the best time to do the job.

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Pruning oakleaf hydrangea

Our oak leaf hydrangea bloomed beautifully this year, and the flowers have turned pink or brown but they’re still on the plant. The shrub is huge and needs to be cut back. Is it too late to prune it now? I want to make sure it blooms again next year.

Landscape designer and plantsman Troy Marden, in his book Southern Gardener’s Handbook, says that pruning oak leaf hydrangea can be “tricky.” It blooms on old wood, and next year’s buds may already have begun to develop. If you prune it now, mid-August, you likely will be cutting off some of next year’s flowers. Best to prune the plant shortly after the flowers have turned from white to beige, he suggests.

There’s no reason you can’t remove any dead branches or stems now, though. Use sharp pruning shears, and cut dead twigs and stems off close to the branches. In fact, hydrangea experts note that dead stems should be removed every year.

Shortly after the shrub blooms next spring, consider removing about a third of the older living stems at ground level, which should revitalize the plant.

Prune to preserve the sweet scent of mock orange

Our two mock orange shrubs are full of blooms right now, but they haven’t been pruned in many years and they are very tall and lanky with a lot of dead wood, and look terrible the rest of the time. When can they be shaped up or pruned?

Mock Orange

The flowers of the mock orange shrub last only a week or two in late spring in USDA Hardiness Zone 7a (where The Garden Bench calls home), but they can provide a stunning show, and the fragrance, which is said to resemble orange blossoms, is delicate and sweet.

Those flowers bloom on the previous year’s growth, so you should prune the shrubs right after they finish blooming this year, which allows time for new growth to mature and bloom next spring.

If the shrub is in really bad shape but still vigorous, you can actually do a rejuvenation pruning, removing the oldest stems at ground level to encourage vigorous new growth. Information from the National Gardening Association suggests cutting out about a third of the stems. Pruning the shrub every year encourages it to grow more densely.

In general, mock orange (Philadelphus is the botanical name) grows best in full sun but can tolerate a little shade. It does well in most types of soil, as long as it has good drainage. Mock orange is good to use as a background shrub or a specimen plant in the landscape. If you’re considering a new shrub, be sure to plant it where you can enjoy that sweet, though fleeting, fragrance.

Book giveaway – winners!

Last week we announced a book giveaway – two copies of Southern Gardener’s Handbook by Middle Tennessee author Troy B. Marden. Commenters Rhonda and Amanda were picked in random drawings, and they’ll receive copies of the book from the publisher, Cool Springs Press. Thanks for your comments!

Prune azaleas soon after they bloom

Our azaleas are too large and need to be trimmed. When is the best time to prune them?

In general, azaleas rarely need pruning, but if you find you need to reduce the size of the shrubs, the best time to prune them is right after they finish blooming. The buds for this year’s azalea blooms began forming last summer, so if you prune now, before they bloom, it means you are cutting off many of the flowers before you have a chance to enjoy them.

Southern Living garden writer Steve Bender, who edited the new edition of the Southern Living Garden Book, suggests this method for pruning azaleas: determine where the height or width needs to be reduced. Then, using hand pruners (or loppers, if the branches are thick), reach in and cut back individual branches to different lengths to create a mounding shape. Do not, he admonishes, use hedge trimmers to shear azaleas. Besides looking boxy and unnatural, this results in flowers and foliage that grow only on the outer portions of the shrubs.

Two other notes from Steve’s advice, which you can read here:

-If you do the job at the proper time, you can cut evergreen azaleas back pretty hard – even back to bare wood — and they should survive and flourish.

-If yours are the ‘Encore’ type of azaleas, which bloom in spring and again in late summer or fall, prune right after the spring bloom.

Prune crape myrtle without committing ‘crape murder’

I have developed my crape myrtles into tree forms. Every year I have to cut back the suckers that grow from the base of the trees at ground level. Is there anything I can do to eliminate the suckers?

The suckers that grow from the ground around crape myrtles can be the result of improper pruning. If you top the plants every year (and garden experts sometimes refer to this as “crape murder”) they respond by sending up shoots from the base.

There are many sources for information on pruning crape myrtles, but one good one comes from the Virginia Cooperative Extension of Virginia Tech and Virginia State University. Their suggestion:

Prune crape myrtles as you would any other tree or shrub – by cutting back to a bud, a side branch or a main stem, giving consideration to the ultimate shape of the plant. If you need to cut off only part of a branch, cut above an outward facing bud or side branch. If you need to remove an entire branch, cut just outside the branch collar on the stem, where the branch is attached.

Don’t make random cuts in the middle of a branch or stem. Topping a crape myrtle – or any tree, for that matter – can lead to stem decay and more dead branches. It also encourages the growth of weak shoots at the top of cut stems, which can become top-heavy with flowers and break in a strong wind.

The Virginia Cooperative Extension notes that re-suckering can sometimes by suppressed by applying naphthalene acetic acid after the suckers are pruned. Crape myrtles that are given too much fertilizer may also produce suckers, and have fewer flowers. They advise not to fertilize unless a soil test indicates the need to do so.

The best time to prune crape myrtles has passed for this year. Do the job in late winter or early spring, before new growth begins.

 

This weekend: Beautiful bonsai

Bonsai expert Owen Reich invites garden enthusiasts to the Nashville Bonsai Society’s Regional Bonsai Expo July 11 – 13 at Cheekwood Botanical Garden. Reich, Jim Doyle and Young Choe are guest artists, and there will be more than 50 bonsai displays, along with workshops, exhibits and vendors.

The photo above is of a Swamp Rose (Rosa palustris) that Reich collected in Tennessee and trained as a bonsai. “There will be a number of bonsai on display this year created from trees and shrubs native to the United States, as well as high-end bonsai imported from Japan,” he says. The stand in the display was made in Chattanooga by Tom Scott, and the container is a 250 – 300 year-old Chinese container called a Kowatari Shirogochi Pot.

The picture is just a sample of the unique and unusual bonsai on display this weekend. Complete details here.

Prune clematis for a better show of blooms

Question: Our spring-blooming clematis vine has grown tall and seems very healthy, but it blooms mainly at the top. The bottom six feet has very few blooms and not much foliage this spring. Can you tell me why?

Clematis flowers clambering over a sturdy trellis or other support are a lovely sight each spring. When this woody flowering vine gets too top-heavy, with all the flowers at the top and bare stems at the bottom, the problem has to do with pruning – or lack of it. Early-flowering clematis blooms in spring from buds formed last season. Plant experts recommend pruning it each year to help the plant produce the maximum number of flowers. The time to do that is as soon as you can after it finishes blooming to allow time for new growth to produce flower buds for next year.

Horticulturists writing for a fact sheet from Ohio StateUniversity say that sometimes you can cut back into older wood of old, neglected plants to encourage new buds to break. The vines are most likely tangled, so when you prune, make cuts carefully, and train the stems to cover the maximum are on their support.

Note also that there are other varieties of clematis that bloom a bit later, on new growth, and those varieties should be pruned in the winter.

In general, here is what clematis needs to thrive: Loose, fast-draining soil that is high in organic matter, and regular water. Gardeners like to say that clematis prefers to have its head in the sun and its feet in the shade, so provide a thick layer of mulch to keep the roots cool. You can also plant a ground cover such as mondo grass around the base of the clematis vine.

Winter shrub damage: They may be down, but not out

Question: Some of my shrubs look like they’ve been damaged by the extremely cold weather. Should I cut them back or cut off the dead parts?

It’s true, the landscape may be looking a little ragged right now. In Middle Tennessee (where The Garden Bench calls home) long days and nights of cold and wind seem to have smacked down a lot of shrubs that usually breeze through mild winters. It looks like this winter has been particulary cruel to marginally hardy and semi-evergreen plants.

You may be tempted to get out the loppers and pruners, ready to cut off the winter-burned branches and limbs, but don’t be in such a hurry. “Wait until the flush of growth in spring, so you can know where to cut back to, to know what’s really dead,” says Nashville horticulturist Carl Pitchford.

Leafy semi-evergreens, such as nandina, and some of the more finicky tender perennial herbs, such as rosemary, seem to have been especially hard hit. “A lot of those will show winter burn after those cold temperatures,” Carl says. “You just have to wait and see.” With nandinas, for example, you may have just lost the foliage. The cold would not have damaged the root systems, and new leaves should sprout in the spring.

Book giveway: Here’s our winner!

Last week I interviewed Judy Lowe, the author of Month-By-Month Gardening in Middle Tennessee & Kentucky, about gardening in winter. Then I asked readers to leave a comment about their must-do winter garden tasks for the chance to enter a drawing to win a copy of the book (determined by a number generated at random by Random.org)

And the winner is… Judy Lee: “I am ready for spring when winter loses its grip. Let’s go! Let’s garden!