WORTH REPEATING 



PRUNE THAT SHRUB CORRECTLY 



Without Knowing What It Is... 



Chuck Buffett 



r\n easy to use system of simple ob- 

 servations for deciduous and ever- 

 green shrubs exists that help deter- 

 mine how to prune the shrub without 

 identifying the plant. With so many 

 species and varieties of shrubs that 

 are possible to grow, the subject of 

 prunmg them correctly is a mystery 

 to most, says Ray Maleike, extension 

 horticul-turist with Washington 

 State Uni- versity, Puyallup, 

 Washington. Shrubs can be placed in 

 just three simple categories, he adds. 



Horticultural Principles 



Maleike began by briefly explaining 

 several important horticultural prin- 

 ciples related to this pruning system. 



'Simply, a plant goes through alter- 

 nate seasons of growth and dorman- 

 cy," he explains. In spring, when 

 conditions are right, the plant begins 

 growing until something shuts it off, 

 lack of water, for example, or short 

 day length. 



Once the plant starts slowing down 

 and sets its terminal buds, this 

 generally means the plant will not 

 grow any more that season and will 

 enter physiological dormancy. The 

 plant IS released from this dormant 

 state when a certain number of chill- 

 ing hours have been met during the 

 winter. Once the chilling require- 

 ment IS met, this signals the plant 

 that growth can take place again 

 once the right growing conditions 

 occur. 



When pruning a plant, understand- 

 ing the principle ot apical dominance 

 is most important, Maleike says. As 

 plant stems grow, the growing tips 

 synthesize hormones, which inhibit 

 lateral (side) buds from growing. 

 These inhibited buds are called 

 latent buds and will begin to grow if 

 the terminal growing tip is removed. 



The actively growing buds arc usually 

 large enough to be visible and almost 

 always found in leaf axils (the area 

 where the leaf meets the stem), 

 Maleike says. 



Buds can be either simple, flower or 

 vegetative; or mixed buds can con- 

 28 THE Plantsman 



tain both flower and vegetative parts. 

 For example, Ccrrybpsis spicata 

 (Spiked Winterhazel) blooms very 

 early on simple flower buds. Leaves 

 emerge later from simple vegetative 

 buds. On Philadelphus species (Mock 

 Orange) the leaves and the flowers 

 emerge from a mixed bud. 



Maleike observes that most decid- 

 uous shrubs fall into two categories. 

 Shrubs that bloom on the lateral 

 portions of the branches and those 

 that bloom at the terminal ends of 

 branches. 



Spiraea thunber^i and Forsythia spe- 

 cies bloom on the lateral portions of 

 the stem from simple buds, and Ribes 

 sanguineum (Red Flowering Current) 

 and Mock Orange also bloom all 

 along the branch from a mixed bud. 



Syringa species (Lilac) and deciduous 

 magnolias bloom on terminal ends of 

 branches from simple buds. Clethra 

 alnifolia (Sweet Pepperbrush) also 

 blooms on the terminal ends of stems 

 but from a mLxed bud. 



Pruning Lateral Branches 



One reason for planting deciduous 

 shrubs, Maleike says, is for their 

 flowers or ornamental fruit. .Prune for 

 maximum flowering. The rest of the 

 year the shrub doesn't look very 

 attractive. 



For lateral blooming shrubs such as 

 Forsythia, encourage as much new 

 stem growth from the base ot the 

 plant as possible. The first year for 

 stems for lateral blooming shrubs is 

 vegetative with flower buds setting 

 up late in the growing season for next 

 year's floral display. The flower buds 

 in the middle region of the stem will 

 usually be the largest. This middle 

 region of the year old stem will 

 produce the flowers in spring. 



It is important to note that after this 

 stem's flowering no more flower buds 

 will be produced on that stem. After 

 flowermg in spring the stem grows by 

 producing new but shorter stems 

 from lateral vegetative buds. These 

 lateral stems will have flowers on 

 them next year. As the original stem 



gets older, shorter flowermg stems are 

 produced each year, reducing the 

 overall flowering performance ot the 

 shrub. 



Each year, Maleike suggests, prune 

 out one or more of the older branch- 

 es at the base of the shrub just after it 

 blooms to encourage maximum long 

 lateral stems. This will increase the 

 flowering potential ot the shrub. 



A big mistake often made with 

 lateral blooming shrubs that are too 

 tall is to shear off the top branches. 

 This will cause latent buds to break 

 creating greater twigginess and less 

 flowering. If the shrub is sheared late 

 in the growing season, the new 

 growth may not produce many flower 

 buds. Additionally, there will be less 

 light penetration and probably more 

 disease, insect and other pathological 

 problems, .Maleike says. 



Pruning Terminal Branches 



For shrubs that bloom on the termi- 

 nal ends of branches, such as Mag- 

 nolias, the biggest buds will be on the 

 terminal tips. Pruning is done to 

 maximize these terminal tips ot the 

 shrub 



For some plants shearing will be the 

 quickest way to encourage branching 

 and more terminal buds for flowers 

 next year. For single unbranched new 

 stems on shrubs, cut back to desired 

 height to force latent buds to grow 

 creating more stems and terminal 

 flower buds. 



The approach to pruning broadleaf 

 evergreen shrubs is exactly the same 

 for deciduous shrubs, Maleike 

 explains. 



Leucothoe is an evergreen shrub that 

 blooms on the lateral portions of the 

 branch. Prune out the older branches 

 to encourage newer growth for better 

 flowering. 



Rhododendrons and azaleas are 

 examples of evergreen shrubs that 

 bloom on terminal tips. Evergreen 

 shrubs with leaves two to three inches 

 or less in size can be sheared 



continued on back cover 



