TO PRUNE OR NOT TO PRUNE, WE AN­SWER THE QUES­TION

Vancouver Sun - - GARDENING - BRIAN MIN­TER

As the last of our fall colour dis­ap­pears, the or­ches­tra­tion of next spring ’s gar­den can now be­gin.

Tim­ing is ev­ery­thing when it comes to re­siz­ing our plants. Once the fo­liage comes off our de­cid­u­ous trees and shrubs, the op­por­tu­nity to prune has ar­rived. The win­dow for prun­ing de­cid­u­ous trees and shrubs is roughly from mid-No­vem­ber un­til the end of Fe­bru­ary, and in colder re­gions well into March and April.

With our busy sched­ules and of­ten in­clement late fall and win­ter weather, we can’t al­ways choose the ideal time to prune. In our own gar­dens, when sud­denly ev­ery tree and shrub de­cided to spurt lots of new growth, I phoned the late Ger­ald Stra­ley for some ad­vice. At the time he was the plant guru at UBC Botan­i­cal Gar­dens, and he ex­plained that, in re­al­ity and in many sit­u­a­tions, you have to prune when you have to prune, even though the tim­ing may be wrong. He as­sured me that plants will gen­er­ally re­cover nicely.

With that in mind, the main rules I try to fol­low are those of Mother Na­ture. By ob­serv­ing the habits of plants and un­der­stand­ing how and when they grow, flower and pro­duce fruit and berries, you be­gin to learn the best ways to grow and con­tain them.

Flow­er­ing shrubs are, per­haps, the most con­fus­ing when it comes to prun­ing. It’s all about when they form their flower buds for next year’s blooms. That’s the key.

Take, for ex­am­ple, the macro­phylla hy­drangeas: the ones that have big mop heads or lace­cap blooms and cre­ate stun­ning dis­plays in mid­sum­mer. They form next year’s buds from late July through Septem­ber. Many folks wait un­til the leaves fall off th­ese large-grow­ing va­ri­eties be­fore giv­ing them a hard prun­ing to keep them more com­pact. By do­ing so, they elim­i­nate most of next year’s blos­soms. The best time to prune, while still en­sur­ing the devel­op­ment of new buds for next year, is the end of July, even though they may still be flow­er­ing. The newer va­ri­eties, like the “Ev­er­last­ing Se­ries” I wrote about in July, also pro­duce on new growth, so they can be pruned later and still have blooms next sum­mer.

All the ar­borescens types of hy­drangeas, like the old “Annabelle” and the newer “In­vin­ci­ble Se­ries,” set buds on next year’s growth, so no prob­lem prun­ing in late fall and win­ter. The same is true of all PeeGee hy­drangeas (H. pan­ic­u­lata ‘Gran­di­flora’) that have those big, beau­ti­ful, cone-shaped flow­ers; so again, no con­cerns if you prune in fall and even in early spring.

At this time of year, the flower buds are al­ready formed on win­ter-flow­er­ing shrubs such as vibur­num ‘Pink Dawn,’ ev­er­green and de­cid­u­ous aza­leas, cory­lop­sis, witch hazels, rhodo­den­drons, camel­lias, forsythias, flow­er­ing quinces, daphnes, ker­rias, flow­er­ing cur­rants and lilacs, to name just a few. So, don’t prune them now! Typ­i­cally, you prune them just af­ter the blooms are fin­ished for the sea­son and when the new growth be­gins.

Late-flow­er­ing shrubs like bud­dleias, deutzias, hibis­cus, beauty bushes, kolk­witzias, flow­er­ing el­der­ber­ries and spireas all set bud and bloom on new growth and can be pruned even when the new growth be­gins in early spring. Rose prun­ing is a lit­tle dif­fer­ent.

For the more ten­der hy­brid teas, flori­bun­das and gran­di­flo­ras, all you do is tidy them up for win­ter by cut­ting them back about one-third their size, re­mov­ing old, dead and dis­eased wood and ap­ply­ing mulch at least 30 cen­time­tres over the bud unions to pro­tect the growth just above the graft. This pre­vents win­ter winds from dam­ag­ing them and keeps heavy frosts from freez­ing them down to the graft.

Tree roses need to have their stems pro­tected up to and around the grafts with a pro­tec­tive wrap with in­su­la­tion in­side. Hardy roses, like ru­gosas, can be pruned now, but I al­ways wait un­til the close of win­ter as a pre­cau­tion.

Climb­ing roses will look far bet­ter and bloom more pro­fusely next spring if you choose four to five of the best canes that grew this year, at­tach them to an ar­bour or fence at two-me­tre lengths, and then cut back ev­ery­thing else.

On all flow­er­ing trees, the flower buds are al­ready set. I know that some­times the only win­dow you have for prun­ing is in win­ter when th­ese trees are dor­mant, and you can do so, but you would lose many of the beau­ti­ful blos­soms. The tree, how­ever, would still be fine.

West Coast dog­woods don’t take kindly to prun­ing, but if you must, I would prune just af­ter they bloom when they seem to re­spond with less dieback and risk of dis­ease. Lilac trees, too, are some­times re­luc­tant to pro­duce buds af­ter prun­ing. If they need to be trimmed, next spring, af­ter the lilac fin­ishes flow­er­ing, se­lec­tively prune half the plant. Then the fol­low­ing year, prune the re­main­der of the lilac.

Medium-sized and larger de­cid­u­ous trees, al­though they pro­vide pri­vacy and shade, also need to be pruned, both for strength in wind and ice storms and to con­trol dis­eases. It’s im­por­tant to main­tain the nat­u­ral shape of the tree while keep­ing it at a man­age­able size.

Our beau­ti­ful Ja­panese maples strug­gle with long, wet win­ters and are es­pe­cially un­happy with wet feet. I have found it best to prune them in spring when the growth be­comes quite ac­tive. They seem to re­cover more quickly and with min­i­mal dieback.

The other anom­alies are birch and wal­nut trees. Just by their na­ture, the very best time to prune them is in mid-July.

Most ev­er­greens can be pruned any­time of the year ex­cept dur­ing ex­treme heat or cold. Pine and spruce trees, how­ever, are usu­ally pruned af­ter the buds and can­dles pop in late May and June. When prun­ing cedars, try to keep them slen­der to min­i­mize snow dam­age, but at the same time stay within the ‘green’ wood be­cause they don’t send new growth out of older, hard wood.

Fast-grow­ing broad-leafed ev­er­greens, like lau­rels and pho­tinias, can be pruned now or left un­til spring. Aza­leas, rhodo­den­drons and camel­lias are all bud­ded now and are gen­er­ally pruned af­ter they flower in spring when the new fo­liage growth be­gins.

As our herba­ceous peren­ni­als be­gin to look tired and their green fo­liage has turned brown, it’s time to clean them up by sim­ply cut­ting them off at ground level.

Vines, too, should be ti­died at this time of year, es­pe­cially any wild late sum­mer growth. The woody stems of wis­te­rias, climb­ing hy­drangeas and early-blooming clema­tis like the mon­tanas, now have their buds set, so just a tidy up is re­quired.

Prune mugo pine can­dles in half in late May to mid-June to main­tain a com­pact and dense shrub, but most ev­er­greens can be pruned any time of year, ex­cept in ex­treme heat or cold.

The woody stems of wis­te­rias now have their buds set, so just a tidy up is re­quired at this time of year along with climb­ing hy­drangeas, early blooming clema­tis and vines, es­pe­cially any wild late-sum­mer growth.

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