Fine-pruning the Landscape

Transcription

1 Fine-pruning the Landscape I. Pruning A. Much conflicting information, but there's no one right way. Why? Because: 1. Techniques vary based on the desired result and available resources 2. In different locations plant may grow/respond to pruning differently 3. Mistakenly ask how and when before realizing the importance of why B. Why is key to sort out contradicting or vague how's and when's. 4 Why's: (Focus on end-winter/earliest-spring pruning objectives): 1. To restrict size 2. To improve shape 3. To promote vigorous growth 4. To remove dead, diseased or dangerous wood C. Don't mistake the relationship between flowering and pruning 1. Flowering is not initiated by pruning, but might make flowers show more. 2.We prune for one or more of the "big four" reasons, not flower 3. IF flowering is important in our plans: We attempt to prune in a way and a time that doesn't prohibit bloom III. Pruning to restrict size A. The most common objective, for many reasons. Books vague/misleading, we misunderstand or can't visualize plant's potential. B. Fortunately, almost any plant can be kept small. 1. Growth rate determines difficulty/amount of work to keep it small. 2. Some plants look better under heavy pruning than others. C. Pruning to restrict size rates the simplest directions. 1. Let the plant grow to the desired height and width. 2. Prune annually to remove all growth beyond those limits. A tip: learn to distinguish current wood from old wood. 3. Then cut 15 to 20% of branches (1 of every 5 or 6), shortening each by half again as much as first cut Keeps new growth coming from the plant's interior, and avoids hollow ball look. Fine Pruning the Landscape- Page 1

2 4. Prune to restrict size at any time of the year. Best done when season's growth is all set: from August,until spring budbreak Best to avoid periods of most active growth: Spring as leaves expand; autumn as leaves drop. Always avoid wet weather, since diseases spread then to keep a tree small 1) Select main "keeper" limbs (1-5, right) Keepers' branches each cover distinct portion of crown (1-5, below) 2) Remove other limbs (ex: A,B,C, right) 3) Prune annually or every two years One main limb at a time Shorten main limb by 1-2 years' growth Cut to side branch of 1/3 diameter positioned to become graceful new tip Work back along limb, shorten side branches D. Overgrown shrubs? When the plant is already too big 1. Cut it back hard: Smaller than needed, by one year's growth (prevent hollow-ball look) May be easiest on the plant to do this in very early spring You will lose flower, but only for one or two seasons Retain any grafts Pine family: juniper/arb/pine/spruce/cypress/fir Won't sprout from bare stubs. Cut to a leafy side branch. 2. Wait for new growth, then begin normal restriction pruning as above Prevent undue stress while it re-grows 3. What if it dies? That might happen: Poor health or can't-grow-from-bare-wood species (japsc) You lost only the "wait for new growth" time toward replacing the plant Fine Pruning the Landscape- Page 2

3 E. If flowers are important, modify the pruning schedule 1. Plants that flower before June 15, prune hardest right after flowering finishes 2. Plants that flower after June 15, prune hardest in fall or early spring. IV. Pruning to improve shape A. Improve is such a subjective term - good thing plants are so agreeable. B. Timing is important: Done after the season's growth has finished, requires less touch-up trimming during the growing season. August. Winter thaws. Many old and tightly clipped shrubs in Europe pruned just once per year after the year's growth is set, even once every two years C. Easiest to enhance the natural shape, rather than impose unnatural form D. Can be overwhelming, especially on long-unpruned plants. Use four step method: 1. Remove dead, diseased and dangerous wood. Narrow crotches can be dangerous in terms of potential breaks On some species, narrow crotches are norm In many cases, a narrow crotch can be spread if young wood Undercut large branches and saw off weight-y end 2. Remove suckers and water sprouts Suckers sprout from roots or trunk below graft Water sprouts: gangly straight-up wood growing from more horizontal branches - Common on fruit trees - Look for new/2 year old wood with few/no leaves except at tip 3. Remove crossing wood (rubbing, cluttering) Easy to see on deciduous shrubs in winter 4. Prune for aesthetics After steps 1,2,3, it's easy to see what you're doing Aim for clean lines Be aware of apical dominance (illus., right) - Top bud - apex - grows most - Trim to above bud facing the right direction - Will produce branches to fill where you want V. Pruning to stimulate vigorous new growth A. Why renewal? For younger wood with cleaner lines, better bark color, larger leaves 2-7 years old may bloom better than older wood Fine Pruning the Landscape- Page 3

4 B. Standard to remove 1/3 of a shrub's trunks each year or reduce tree's main branches by 1/3, annually 1. Renewal best done in early spring but can be done any time 2. If winter stem color important, trim only in early spring 3. Cut more? Sure. Cut to base! Often grows back at tremendous rate. C. Prune the remainder of the shrub to restrict size or enhance shape Note: Blue/pink hydrangea branches will not bloom if the terminal bud is removed VI. Pruning to remove dead, diseased or dangerous wood A. Whenever necessary B. Keep plant health in mind 1. Use clean, sharp tools. (Every timeyou prune.) 2. Suspect disease? Sterilize tools between cuts/plants use rubbing alcohol, bleach or hydrogen peroxide 3. Avoid wet weather when fungi and bacteria spread most readily 4. Cut to remove ALL diseased wood -- look at color of interior wood 5. Make clean cuts to branch base, leaving the bark collar (illus. below, right) Thickened, turtle-neck type ridge where branch meets branch Fastest growing part of the bark, seals over wounds most quickly Natural barrier to any infection entering remaining branch/trunk Branch stubs create later trouble, weakness in points above 6. Or cut to just above a desirable bud that points where a new branch is needed. If a vertical branch, make a slanting cut above the bud 7. Avoid tears into bark collar: Remove weight by undercutting then cutting down from above (below, left) Finish with a cut to just outside the collar (below, right) C. About sealing pruning cuts: pruning paint, tar, wound dressings: 1. Research shows it ineffective to detrimental. Plant can seal itself, better. D. About branch strength branches (right angle to trunk) are strongest 2. Some species and varieties have only narrow crotches Fine Pruning the Landscape- Page 4

5 Pruning Notes: Disease Issues Some disease, pest and troubling situations to be aware of birch - bronze birch borer. Insect. Attracted to stressed trees. Do not prune hard. burning bush - die back. Unknown cause, thought to be environmental. No prevention or cure. Remove dead wood. cherry - black knot. Fungus. Avoid pruning in wet weather. Prune off damage. Sterilize cutters. dogwood - anthracnose/flower & leaf blight. Fungus. Prune during dormant season or at least avoid wet weather. Prune off damage. Sterilize cutters. evergreen euonymus and many others including roses, forsythia) - crown gall. Bacterial. Prune off damage. Sterilize cutters. Consider removing plant if damage cannot be pruned off and kept off. juniper - phomopsis tip blight. Fungus. Avoid pruning in wet weather. Prune off damage. Sterilize cutters. juniper, esp. Virginia juniper - cedar-apple rust. Orange gelatinous masses on branch tips in spring. Fungus, spreads in wet cool weather from junipers to apples/crabapples/hawthorns. Prune off masses in dry weather. maple, birch, beech - "bleeding" (heavy sap flow). Cosmetic problem only. Prune during February thaw or after leaves fully formed in summer. oak - oak wilt. Fungus, insect-borne. Prune only during plant's dormancy. If must prune while leaves are green, seal all cuts to reduce scent (latex paint OK; wood glue OK) pear, apple, crabapple, firethorn - fireblight. Bacterial. Avoid wet weather. Prune off damage cutting 6" below symptomatic wood. Sterilize cutters. pine - tip borer. Insect. Not encouraged by pruning but often creates need for pruning roses - rose rosette disease. Virus, vectored by eriophyid mite. No remedy once symptoms seen but pruning may spread the virus to still-healthy plants. Sterilize pruners, remove symptomatic plants. Fine Pruning the Landscape- Page 5