70 Pruning Landscape Plants Objectives 1. Be able to describe, explain, and defend the reasons for pruning plants and the responses of plants to pruning. 2. Be able to describe, explain, and summarize when to prune plants based on the type of pruning needed or the situation at the landscape site. 3. Be able to describe, identify, explain and provide examples of the types of pruning cuts and their effects on plant growth. 4. Be able to describe and explain the reasons for locating pruning cuts and the ways to maintain shrubs and trees by pruning. 5. Be able to describe and distinguish the reasons for pruning different types of coniferous plants. 6. Be able to describe and explain the proper use of pruning tools and sanitation principles when pruning. 7. Be able to analyze landscape situations to determine the best method(s) for pruning plants located at a site. Reasons for Pruning 1. Maintain plant health and appearance: a. Remove dead, diseased, injured, b. Remove limbs growing c. Remove old flowers or 2. Training young plants: a. Branch attachment, arrangement 71 b. One central leader 3. Influence on flowering, fruiting, and vigor: a. Balance is needed between vegetative growth and b. Remove c. Force new growth 4. Control plant size: a. Nuisance growth - b. General rule: if a plant must be pruned heavily c. Select plants for a site Plant Responses to Pruning 1. Young plants a. Dwarfing effect - b. Invigoration - 2. Mature plants a. b. 3. Influence on Flowering and Fruiting 72 a. Flowering on young plants i. delay flowering by ii. induce earlier flowering by b. Prevent seed production by removing 4. Root Pruning a. Overall effect: b. Induce flowering c. Effects on root system: Timing Of Pruning 1. Light pruning: 2. Removing broken, diseased, dead, or shading parts: 3. Slow or maintain growth a. Timing - completed b. Reasons - c. Precaution - 4. Minimize effects to growth - or maintain rapid growth 73 a. Timing – prune just before b. Deciduous plants – prune between c. Evergreens – prune just before d. Exceptions: Pines and 5. Prune to Avoid Flower Reduction a. Determine where flowers form - b. Flowers form on new wood (current season) i. timing - ii. reason - iii. examples of species - c. Flowers form on old wood (spring flowering plants) i. timing - ii. reasons - iii. examples of species - d. General Rule for Flower Formation: i. plants flower before June 1: ii. plants flower after May 31: 74 iii. exceptions may exist 6. Cold injury a. Pruning may reduce tissue b. Timing – prune just before c. Avoid stimulating new growth Types of Pruning Cuts 1. Heading Cuts a. Definition: Cutting plant stems or branches back to a bud, stub, or cutting a larger branch back to a bud or small twig. b. Results of pruning: c. Shearing: definition – 75 d. Stubbing: definition – e. Topping: definition – f. Roundover: definition – g. Potential problems i. stubs can become 76 ii. vigorous new growth iii. new growth may be weakly 2. Thinning Cuts a. Definition: Removal of a branch to its point of origin or shortening a branch by cutting to a lateral branch that is large enough to assume the terminal role. b. Note: i. the lateral branch should ii. a branch stub is c. Advantages: i. plant retains 77 ii. better air and light penetration iii. vigorous shoot growth d. Caution – vigorous shoot growth can be induced with thinning cuts Location of Pruning Cuts 1. Objectives: a. Clean cut without a stub i. location - ii. reason - b. Locate the cut for rapid 2. Cut location for rapid closure: branch removal a. Make the cut outside i. bark ridge appears ii. branch collar appears b. Natural target pruning is the technique used when cutting c. Reasons to keep branch shoulder in place include: i. a physical barrier 78 ii. callus grows iii. wound size 3. Compartmentalization of wounds a. Vascular response: b. Injury walled off c. Branch shoulder becomes plugged, d. Comparison of amount of walled-off or discolored tissue: i. proper pruning cut location - ii. cut too close to trunk - 4. Appearance of pruning wounds after making the cut: a. Stub – cut is made b. Incomplete callus formation i. donut-shaped callus forms ii. horseshoe-shaped callus forms 5. Flush cuts: a. Cut location: the cut is made 79 b. Reasons to avoid include: i. ii. iii. 6. Pruning cuts on: a. Small branches i. cutting back to a bud: cut at an ii. cutting back to small branch: iii. hide pruning cuts b. Large branches i. definition: ii. 3-cut method needed to a. location of first cut - on the underside of the branch about b. location of second cut - on the top of the branch up to 80 c. location of third cut - c. V-shaped (narrow angle) branches i. location of final cut should be ii. use 3-cut method if needed Treatment of Pruning Wounds 1. Chiseling or Paring Wounds a. Recommendations: avoid b. Reasons to avoid include: i. wound size increases ii. callus growth to cover the wound 2. Use of Pruning Paints a. Pruning paint keeps the area b. Expense versus benefits: the price of the product and c. Use only for Pruning at Plant Time 1. Limit pruning at planting time to damaged limbs, crossing 81 2. Reasons to limit pruning include Pruning Specifics for Shrubs 1. Control Size a. Pruning should be part of regular maintenance b. Pinch tips of vigorous shoots c. If lower branches weaken and lose foliage, d. If heavy pruning is needed each year, replace the plant 2. Slow-growing shrubs a. Only light pruning b. Allowing air and light penetration c. Remove vigorous branches d. May need to avoid shearing 3. Fast-growing shrubs - often sprout vigorously a. Contain growth by severe pruning b. Remove 25 to 33% of the oldest i. visualize the plant first 82 ii. prune to maintain flowering wood iii. prune to control plant size 4. Rejuvenation pruning a. Reasons to use this technique b. Procedures include: i. prune during ii. cut branch length back to iii. thin the new growth iv. rejuvenate only once c. Tolerant species include d. Intolerant species include 5. Pruning hedges - formal or a. Shape - should be b. Purpose - to allow Pruning Vines 1. Vigorous vines need regular 83 2. Severe pruning may be needed 3. Prune vines flowering on current year’s wood Pruning Deciduous Trees 1. Goals: 2. Young trees - prune to correct a. Scaffold branches - definition: b. Branch attachment - want strong attachment i. lateral branch size should be ii. angle of branch attachment - ideally between c. Branch spacing i. vertical spacing - ii. radial spacing - five to 3. Mature Trees a. Inspect trees annually as part 84 b. Four types of pruning for mature trees: i. cleaning out - remove ii. raising the crown - removal of iii. crown thinning - remove selected branches a. allows air and light b. avoid lion’s tail process iv. crown reduction - decrease tree height by a. timing - after tree reaches b. drop crotch pruning is used thinning cut – cutting the main trunk bisect the angle made by a line perpendicular to the main trunk and 4. Upright versus Horizontal branches: a. Upright branches - grow vigorously, b. Horizontal branches - usually have i. good for scaffold branches, but their diameter should be 85 ii. apical dominance is weakened, often resulting in 5. Avoid Lion’s Tails: a. Definition: most of the foliage is at b. Potential problems include more stress c. General rule for branch and foliage distribution: half of the foliage should be located i. this distribution helps increase ii. limb weight and wind stress are more uniformly 6. Pruning Messy Headed Trees: a. Definition: trees with b. Problem: many latent buds are present and c. Species: many d. Two ways to handle these plants: i. leave the plant alone ii. control bud sprouting with a sprout inhibitor: a. sprout inhibitors contain naphthaleneacetic acid (NAA) 86 b. one commercial sprout inhibitor is called Pruning Coniferous Trees 1. General Concepts a. Most conifer trees (species) must be pruned differently than deciduous species! b. Conifer growth habit is i. pruned mainly to control plant density, ii. main leader is rarely iii. lateral branches attached next to each other c. BUD DISTRIBUTION (latent buds) - dictate i. bud location : quiescent buds are only ii. pruning old wood, which lacks latent buds, 2. Pines - have a whorled growth habit a. Pines lack buds (quiescent or latent) down the stem, b. Permanent stubs result from pruning c. Two ways to prune a pine i. use thinning cuts by cutting back to 87 ii. prune or pinch a candle to force aa. time to prune candles is when new needles bb. pruning candles results in dense, 3. Spruce, Fir, and Douglas-fir a. Bud location - usually on b. Time to prune current season's growth 4. Hemlock (Tsuga) and Yew (Taxus) a. Buds (quiescent and latent buds) are b. Plants tolerate severe pruning c. Time to prune is just before active growth, but 5. Double-leader Conifers: Co-dominance a. Excurrent conifers may have b. Remove weaker trunk(s) as soon c. Potential results from leaving two or more leaders 88 6. Topped Conifers or Broken out leaders on Conifers a. What should be done? i. where is the barrier to decay? ii. where should a clean cut be made? b. Factors to consider for removal: i. susceptibility to ii. tree species c. REMOVE trees that pose a risk Pruning Coniferous Shrubs 1. Species included are arborvitae, falsecypress, and juniper 2. Latent bud distribution – 3. Growing points are in 4. Pruning back to bare branches 5.