Thinning Shrubs vs. Shearing

Many experts advocate removing 1/3 of the stems. I will jump for joy if you remove 1/4.

     Those who have been using hedge clippers for a number of years may have noticed something: no matter what you do, your shrubs keep getting larger. And while the outer shell stays nice and green, there is less and less below and inside. This is a result of unrelieved shearing without thinning.


     When you cut off the end of a branch most plants will grow two or more new tips to replace the old one, and the leaves become more dense. Within limits this is a good thing -- especially in shady areas where plants tend to open up.


     But repeated shearings make the outer shell too dense. The leaves on the top and sides block sun and air from the interior and the branches there die back. The effect is even worse when you have pruned in the notorious "W" shape that I mentioned earlier. Now you have an overhang that cuts even more sun from the plant's lower limbs.


     Even in formal gardens regular shearing needs to supplemented with thinning to allow sun and air to get to the interior of the plant.


     And here we come to my Number One Pruning Rule for multi-stemmed shrubs. It is simple, it is easy, and almost no one does it. Every spring you should cut up to 25% of your stems to the ground. If this sounds too scary, cut down one or two this year. When you notice in July that you can't tell the difference, you will be bolder next spring.


     You should go after the largest, oldest stems first, then stems that are going in a direction you do not like or ones that cross through the plant and rub against other branches. By doing this you accomplish four things:


     1. You open up the plant to more air and sun.


     2. You improve the shape of the plant by getting rid of stray and crossing stems.


     3. You rejuvenate the plant as old weary stems are replaced by new ones.


     4. You help control the plant's size because the oldest stems are the tallest and thickest and the most difficult to trim at the top. 


     I'll talk about pruning the the upper parts of shrubs next time.