Brian Minter: It’s never too early to start thinking about pruning

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As we are experiencing one of the most challenging summers so far in our gardens, it’s time to assess many of our plants, particularly when it comes to pruning.

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We tend to think of pruning as a winter activity during the dormant season, but, in fact, summer pruning is often important for keeping our plants in check and for making sure we have both blooms and fruit next year.

First, a warning. Even though their foliage may be burned, and you are tempted to prune, beautiful mophead and lacecap hydrangeas will not bloom next year if they are pruned now. The new growth already contains next year’s blooms, and if pruned back any time over the next 11 months, you will be essentially cutting off next year’s flowers.

The only exceptions are the lower buds near the base of the plant or the many newer varieties that bloom on new growth. This is true for many other flowering shrubs, like forsythias, camellias, azaleas and rhododendrons, and for flowering trees, like ornamental cherries, plums, dogwoods and magnolias, which have already set next year’s blooms.

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This is important to note because many inexperienced home gardeners, and even some maintenance landscapers who do fall and spring tidy-ups, are unaware of which plants should be pruned now and which ones should be left until after they have flowered.

Vining plants, too, like grapes for example, need regular pruning to allow for better air circulation and more exposure to sunlight to help ripen the fruit. However, with more hot weather ahead, enough foliage should be left to prevent sunscald on the fruit. This pruning is critical because, once we reach the humid nights of August, mildew can quickly ruin a grape crop.

Thinning out all our vine crops now is very important to prevent many late summer fungal diseases from spoiling next year’s flowers, fruits and berries. From fruiting kiwis to flowering clematis, honeysuckle and wisteria, an August thinning and pruning is essential. Be careful with clematis varieties, like the montanas and alpinas which flower on older, woody growth. Make sure you leave enough older stems that will flower in late May and June. The same is true for climbing hydrangeas (H. anomala petiolaris) which are now setting next year’s buds.

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Climbing and rambling roses also need some attention at this time of year. Last year’s nice-looking stems, as well as the vigorous new growth of this year, will be the most productive flowering stems next year. Save four or five healthy stems and prune them back to about four to six feet in length. Then remove a lot of the wild, rampant growth.

All our floribunda, hybrid tea, grandiflora and shrub roses should have old, spent flower stems pruned back, leaving two to three leaves or plant nodes to push up new growth and more late summer blooms. A little thinning now will allow more air and sunshine to penetrate and will keep the roses healthier. A good feeding now with a quality rose food will also help reinvigorate your roses for flower production well into fall.

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In order to maintain their ideal size and shape, many varieties of Japanese maples, whether in containers or in garden beds, can also be tidied up now. If they have produced a lot of fast-growing stems, a selective pruning of soft, new growth — not big, thick stems — is in order. You’ll be surprised how this careful grooming improves the look of your plants and opens them up nicely.

Fruit trees may have a great deal of sucker growth that needs cleaning up now. Much of it is wasted growth that clutters the tree. Some smart thinning will keep your trees in shape and help maintain their size. Instead of cutting these stems flush with the major branches, I leave a couple of nodes to see if a fruit-bearing spur develops.

As a rule, upright growth is just upright growth; sideways or horizontal growth will often turn into fruit-bearing branches. On various fruit trees, you can now see the development of buds for next year’s flowers — so, make sure you preserve these stems.

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Small fruits, whether they are cane or vine bearing, could use a little selective thinning at this time of year to keep them shorter and more open for fewer disease issues as we move into humid August weather. Massive wild growth should be herded back to keep it under control.

We still have six weeks of harvest time, but a little selective thinning of vining tomatoes, especially the indeterminate varieties, will help you get more quality fruit while keeping your plants growing. Remember too, late blight will show up in mid-August.

Tired-looking perennials also need a little attention. Lavender is top of mind. As it’s blooms finish, especially on the angustifolia varieties, a hard pruning will result in nicely rounded plants that will send out new growth immediately and will look great well into the fall and winter. Earlier blooming perennials, such as coreopsis, salvias, monardas, astilbes and shasta daisies, can look a little sloppy at this time of year, and a hard pruning will improve their shape, and you’ll get fresh new blooms, especially on the many newer repeat-blooming varieties. You may also want to replace tired-looking, older perennials with heat-loving late summer bloomers to keep your garden looking fresh well into fall.

So, just when you thought garden chores were waning, along I come with more ideas on how to maximize the performance of your plants! But I assure you that a little careful pruning at this critical time will boost your plants for the balance of this season and will prepare them for next year.