Pruning and Training Average Life Expectancy of Small Trees and Shrubs Street Trees

Downtown: 7 years City Average: 32 years Best City Site: 60 years Rural Site: 150 years

Dr. Laura G. Jull Dept. of Horticulture University of Wisconsin-Madison

Plant Selection Prune based on client’s  One of the most important decisions needs but keep in mind  Poor plant choices become plant health and natural maintenance problems form of plant  Plant the right plant in the right place  Use adaptable plants specific to site, whether native or not  See UW-Extension Publication A- 3864: Choosing the Right Landscape Plants: Factors to Consider at http://learningstore.uwex.edu

Objectives of Pruning Principles of Good Pruning

 Control size  Always assess entire plant before making any cuts  Direct and train growth  Never prune without a good  Influence flowering and fruiting reason  Corrective pruning  Keep in mind growth rate of  Maintain health and appearance plant, form, mature height and . Remove dead, diseased, or damaged tissue width  Safety: hazard trees  Don’t forget flower and fruit  Rejuvenate old, overgrown plants display  Specialty pruning: topiary, espalier,  All plants have a finite life, pleaching, pollarding, bonsai may not be worth rejuvenating half dead shrub

1 General Responses to Pruning General Responses to Pruning

Responds by making new Breaks apical dominance growth elsewhere Removal of terminal shoot/bud Stimulates budbreak at cut . Sap flow stops to terminal Response varies based on: . Shoots just below wound sprout . . Growth habit Related to reduced flow of auxin . . Plant age Common example: pinching of tips of annuals causes bushiness . Size Removal of lateral shoot . Timing . More terminal growth . Severity of pruning

General Responses to Pruning General Rules of Pruning Shrubs generally look their best with Cutting back hard into older natural habit and size wood Well positioned pruning cuts . Only on suitable plants . Key to restoring balanced outline . Some plants may respond poorly . Maximizes flower and fruit display with poor growth, no flowers, or die of shock . Maintain plant health and vigor Dormant buds at base of plant Remove unwanted growth when stimulated on some plants only young! Clean pruning cuts . Close faster than if torn or bruised . Small as possible, prune regularly

Types of Pruning Tools Types of Pruning Tools

Pruners: by-pass blade . Stems up to 1/2” in diameter Loppers Pruning saw Pole pruners: tall shrubs Hand shearing clippers: hedges, topiary Electric hedge trimmers . Safety glasses Anvil type of pruners: . Ear plugs By-pass type not recommended Chainsaw: leave it to an expert! of pruners are best

2 Types of Pruning Tools Tools Maintenance

Clean and dry daily By-pass type Final wipe with oily rag loppers Sharpen often with file Disinfectant if pruning diseased plants .10% bleach solution, rusts .Alcohol Pruning saw .Lysol: easy to use, no rust

Heading Back: Removal of the terminal Types of Shrub Pruning Cuts portion of a shoot back to a larger lateral branch or bud, reduces height, hides cut Heading back Renewal (selective thinning cuts) Rejuvenation: cut all the way back to within 4”-2’ Pinching Deadheading: spent flowers Shearing: formal hedges

Heading Back Proper Pruning Cuts for Smaller Limbs

3 Heading Back Pruning Cuts Heading back cuts  Envision the direction of shoot  Most species tolerant to this type of growth that will result from pruning pruning besides most trees: cut . Chaenomeles spp.: flowering quince  Avoid poorly shaped plants with . Chionanthus virginicus: fringetree crossing branches or crowded . Clethra alnifolia: summersweet clethra center . Cotoneaster apiculatus, C. horizontalis: cranberry and rockspray cotoneasters  Prune back to an outward facing bud . Daphne x burkwoodii: daphne  If opposite, can prune back to buds . Diervilla lonicera: dwarf bush or remove one of them, leaving honeysuckle outward facing bud . Deutzia spp.: deutzia  Do not leave a stub . Euonymus alatus: burning bush

Heading back cuts Thinning or Renewal: Completely remove 1/3 of largest diameter branches back  Most species tolerant to this type of pruning to the base of the plant on a yearly basis, . Fothergilla spp.: fothergillas opens it up, allows for new sucker growth . Hamamelis spp.: witchhazels . Hibiscus syriacus: rose-of-Sharon . Hydrangea paniculata: panicle hydrangea . Hypericum kalmianum: Kalm St. Johnswort . Prunus tomentosa: Manchu cherry . Prunus triloba: double flowering plum . Syringa meyeri ‘Palibin’: dwarf Korean lilac . Syringa patula ‘Miss Kim’: Miss Kim lilac . Viburnum carlesii, V. x juddii: Koreanspice and Judd viburnums . Weigela spp.: weigela

Species Tolerant to Renewal Species Tolerant to Renewal Pruning Pruning: Suckering Shrubs  Potentilla fruticosa: potentilla  Aesculus parviflora: bottlebrush buckeye  Prunus x cistena: purpleleaf sandcherry  Aronia spp.: chokeberries  Rhus spp.: sumacs  Berberis thunbergii: Japanese barberry  Rosa rugosa: rugosa rose (suckering types)  Cornus spp.: shrub dogwoods, except for  Salix spp.: shrub willows Cornus mas  Sorbaria sorbifolia: Ural falsespirea  Corylus americana: American hazelnut  Spiraea spp.: spireas  Forsythia spp.: forsythias  Symphoricarpos spp.: snowberry, coralberry  Kerria japonica: Japanese kerria  Syringa vulgaris, S. x hyacinthiflora, S. x  Ilex verticillata: winterberry chinensis: common, early, and Chinese lilac  Morella pennsylvanica: northern bayberry  Viburnum dentatum, V. trilobum, V. opulus, V.  Philadelphus spp.: mockorange lentago, V. lantana: arrowwood, American and  Physocarpus opulifolius: eastern ninebark European cranberrybush viburnums, nannyberry, wayfaringtree viburnum

4 Rejuvenation: Severely cutting back stems Rejuvenation of shrubs, used on suckering, fast growing overgrown, leggy shrubs only Cut back to strong, large stems to redevelop main framework of branches, remove side branches first Cut back entire plant to 3-12” from ground (depends on species) Do not prune below graft union Do in dormant season ONLY Can do gradually over several years Will produce numerous shoots from pruned stumps, thin to 2-3 per stump Species to rejuvenate heavily: shrub willows, elderberry

Rejuvenation Other species tolerant to rejuvenation: redtwig dogwood, potentilla, Japanese Pinching: Removal of tips spirea, Annabelle hydrangea, Genista, of shoots to allow for lateral smokebush, shrub roses (if some branches to break, increases winter kill) bushiness of shrub Combine with thinning of older branches: potentilla and spirea Dieback shrubs: butterfly bush, Russian-sage, purple beautyberry, bluebeard, vitex

Deadheading: Removal of faded flowers, Shearing: For formal hedges only, new avoids fruit and seed formation, can encourage growth is sheared off to maintain tight, second flush of flowers geometric form, higher maintenance

Cut back to an outward facing bud

5 Shearing Rules: Do not continue to cut top Shearing Rules: Bottom of hedge should of sheared hedge back to the original point of be wider than the top of hedge last year’s cut, get witches brooming, leave 1/2- 1” of previous season’s growth

Do not shear plants that can produce showy Species Tolerant to Shearing flowers or fruit or lack latent buds (junipers)  Produce latent buds farther down stem, tolerant of close clipping, dense habit, non-showy flowers or fruit  Plant often grown for foliage only or as a screen . Berberis thunbergii: Japanese barberry . Buxus spp.: boxwoods . Cotoneaster lucidus: hedge cotoneaster . Euonymus alatus: burning bush . Ligustrum spp.: privets . Lonicera x xylosteoides ‘Clavey’s Dwarf’: Clavey’s Dwarf honeysuckle . Ribes alpinum: alpine currant . Taxus x media, T. cuspidata: yews . Thuja occidentalis: arborvitae . Tsuga canadensis: Canadian hemlock (young) . NEVER shear Cornus stolonifera, C. alba, C. sanguinea, very prone to stem canker

Topping: Removal of all the larger branches back to a certain height on trees or large Timing of Pruning shrubs, not recommended, very prone to decay, internodal cuts To stimulate shoot growth: prune prior to budbreak To retard shoot growth: prune just after leaf expansion Never prune trees or shrubs during leaf expansion Don’t prune at time of planting except for damaged, diseased, or dead wood Prune during dry weather, if possible

6 Prune in Dormant Season: Summer or Fall Flowering Timing of Pruning: Dormant Season Shrubs Best time to prune, can see form . Aesculus parviflora: bottlebrush buckeye . Buddleja davidii: butterfly bush No diseases or insects active . Caryopteris x clandonensis: bluebeard Required for oaks and elms . Cephalanthus occidentalis: buttonbush Good for summer flowering . Clethra alnifolia: summersweet clethra plants . Cornus alba, C. stolonifera, C. sanguinea, C. racemosa, C. amomum: Tatarian, redosier, bloodtwig, gray, and . Produce flowers on current silky dogwoods season’s new growth . Corylus americana: American hazelnut (no flowers) . Prune before flower buds develop . Cotinus coggygria: smokebush . Late winter to early spring . Diervilla lonicera: bush honeysuckle Season for rejuvenation pruning . Genista tinctoria: common woodwaxen Cuts off flower buds on spring . Hamamelis virginiana: common witchhazel flowering plants, but can prune . Hibiscus syriacus: rose-of-Sharon . Hydrangea macrophylla, H. arborescens, H. paniculata: bigleaf, smooth, and panicle hydrangeas

Prune in Dormant Season: Summer or Fall Flowering Shrubs Timing of Pruning: Spring . Hypericum kalmianum: Kalm St. Johnswort . Myrica pennsylvanica: northern bayberry (foliage)  Quicker wound closure as bark is . Lespedeza bicolor: shrub bushclover slipping . Perovskia atriplicifolia: Russian-sage  Can do on summer flowering plants if . Potentilla fruticosa: potentilla . Pyracantha coccinea: scarlet firethorn done in early spring (mid-late April) . Rhus spp.: sumacs  Don’t prune until new, expanding . Rosa spp.: shrub roses growth has hardened off (June) . Sambucus canadensis: American elderberry  Worst time to prune oaks and elms . Sambucus nigra: European elderberry . Sorbaria sorbifolia: Ural falsespirea due to vascular wilts . Spiraea japonica: Japanese spirea  Many insects and diseases active . Stephanandra incisa ‘Crispa’: cutleaf stephanandra  Worst time of year to prune! . Tamarix chinensis: tamarisk . Vitex agnus-castus: chastetree, vitex . Yucca filamentosa: Adam’s needle yucca

Prune in Early to Mid Summer: Spring Timing of Pruning: Early to Mid Summer Flowering Plants Not a good time to prune either Shrubs . Aronia spp.: chokeberries Many diseases and insects active . Caragana arborescens: Siberian peashrub Retards further shoot growth . Chaenomeles spp.: flowering quinces But o.k. time for spring flowering plants . Chionanthus virginicus: fringetree . Produce flowers on previous season’s, . Cornus mas: Corneliancherry dogwood older growth . Cotoneaster spp.: cotoneaster . Prune right after flowering . Daphne x burkwoodii: daphne . Early summer as if wait too long, next . Deutzia spp.: deutzia year’s flower buds are being produced . Forsythia spp.: forsythia Cuts off flower buds on summer . Fothergilla spp.: fothergillas flowering plants . Hamamelis vernalis: vernal witchhazel . Ilex verticillata: winterberry . Kerria japonica: Japanese kerria

7 Prune in Early to Mid Summer: Spring Timing of Pruning: Late Summer to Flowering Plants Early Fall Shrubs . Kolkwitzia amabilis: beautyberry Second worst time to prune . Lonicera spp.: honeysuckles (non-invasive ones) May stimulate late season shoot growth, . Philadelphus spp.: mockorange won’t harden off (on species that flush . Physocarpus opulifolius: eastern ninebark growth several times normally in season) . Prunus spp.: cherry, plum, almond . Rhodotypos scandens: black jetbead Slow to poor wound closure . Salix spp.: shrub willows (can prune in late Many diseases and insects active winter) Cuts off flower buds on spring flowering . Syringa spp.: lilacs plants . Spiraea spp.: spring flowering spireas, not S. japonica Best reserved for storm damaged plants . Symphoricarpos spp.: snowberry, coralberry only . Viburnum spp.: viburnums . Weigela spp.: weigela

Invasive Species Pruning Proper Pruning Cuts

 Branch collar: trunk tissue that forms around the base of a branch

 Branch bark ridge: ridge of bark in a branch Best time to prune: late fall and crotch that marks where branch and trunk immediately treat stumps with tissues meet and can extend down tree trunk systemic herbicide

Pruning Spring Flowering 3-Point Method of Shrubs Larger Branch Removal: Leave branch collar and branch bark ridge alone  Heading back or thinning cuts (if suckering), do not shear

 Prune after flowering or when dormant

8 Pruning Summer or Fall Pruning Shrubs Produced on a Flowering Shrubs Standard

 Heading back or thinning cuts (if suckering), rejuvenation, do not shear

 Prune in early spring or when dormant

Pruning Shrubs Produced on a Pruning Shrubs Produced on a Standard Standard

Training shrubs as standards Non-grafted standards: train leading . Clear, tall stem with shrub on top shoot from early age on clear stem, . Formal appearance, suitable for containers needs staking, due in stages . Only certain plants suitable . Shorten laterals . Often topgrafted onto seedling rootstock . Remove laterals later . After first season, shorten laterals by half, . Once at desired height (3-5 1/2’), allow 3 encourage bushiness more sets of buds to develop above 3-5 1/2’ . Remove sprouts on main trunk and suckers . Pinch out terminal bud . Prune to maintain neat, balanced head of foliage . Encourages laterals to break . After first season, shorten laterals by half, encourage bushiness

Pruning Broad-leaved Evergreens Pruning Needle-leaved Evergreens: Pines  Little pruning is needed, few heading back cuts  Little pruning is needed  Do not thin, often lacks  Growth from terminals latent buds on stem  Prune to maintain  Growth from terminals compact habit  Can shear boxwood only

 Remove 1/2-2/3 of elongated candles before needle expansion in spring

 Do not thin or shear, often lacks latent buds on stem

9 Pruning Needle-leaved Evergreens: Pruning Needle-leaved Evergreens: Yews, Spruce, Fir, Douglas-fir hemlocks, arborvitae

Little pruning is  Shrubs with latent buds needed  Heading back in spring to side branch or bud Growth from terminal and lateral buds  Head back or shear in late spring to mid summer after Prune tip of branch flush of growth (yews) back to a lateral bud,  Prune after new growth is can do when dormant hardened (lignified) In early summer, remove 2/3 of an unbranched tip to keep Yew before and after full heading back, mask cuts Keep natural form, do with remaining foliage not prune back into older wood

Pruning Needle-leaved Evergreens: Junipers and falsecypress Pruning Needle-

 Shrubs without latent leaved Evergreens: buds Dwarf Conifers  Heading back cuts to lateral branch, hide cuts Little pruning is  Never rejuvenate or shear needed, shaping into older wood, stay out Remove of dead zone, no shoots reversion shoots will develop or else will  Prune in late spring to early summer dominate  Plant in appropriate place Color reversions away from sidewalks normal on some

Unfortunate Pollarding Pruning: deer Pollarding is not topping! browsing on arborvitae Slow to fill back in Does not regenerate quickly from old, inner wood, but will over a long time Wound wood forms a knob from which epicormic branches develop Wounds are highly compartmentalized

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