The 1/3rd Rule of Pruning Clipped Shrubs

We all have the annoying yew or boxwood which over the years has grown way to large for the space it occupies or has become misshaped with age as the result of pruning exclusively with hedge shears. These plants always end up with a leafless center and all of the growth on the exterior surface of the plant. Inevitably the only option ends up being removing the shrub and replacing it with a new smaller one or hacking it back to bare sticks and living with it for several seasons. The 1/3 Rule of Pruning is a technique professionals and nurserymen use to maintain the shape - and more importantly - the health of the plant. By using this technique you can extend the life of your clipped shrubs and end up with a plant which is gorgeous to look at all times of the year. 

An example of a dead leafless center
An example of a dead leafless center 

Over time clipped shrubs can easily develop dead zones in the center of the plants from constant clipping with hedge shears. It also results in plant growth thickest on the outside of the plant, closest to the sun and air, where they develop "Witches Broom".

The 1/3rd technique stops this from happening. The idea is to remove roughly one third of the interior branching every year to increase light and air to the interior of the plant which will increase new fuller growth from the inside of the plant. Over the course of several years, it results in a plant which is fully formed and flushed with foliage throughout its shape. It can then be shaped and maintained to the desired form easily. 

Witches Broom Example

Step 1

Explore and identify 1/3 of the larger witches broom from within the plant. Make sure to look on all sides as well as the tops. 

Locate the most congested and densest clusters. Notice how full the plant is on the interior of after many seasons of keeping it pruned in this manner.

Step 2

Clip the branch out of the shrub. Don't necessarily take just the ends off, but go deeper into the plant and remove as much of the woody stem as possible and still keep the rough shape of the plant. This may create a bit of an open pocket initially within the plant, but don't worry, this will fill in over time and help create a full shrub throughout.

Example of the Witches Broom removed.

Step 3

Once you've gone through and removed roughly a third of the congested branching equally around the plant, you can then take clippers and shape the shrub as you normally would with garden clippers. Make sure to remove any clippings to prevent disease from spreading.

Step 4

Repeat this process every season for 3 years to get the shrub to a full and rejuvenated position. It can then continue to be pruned as needed to keep the shape of the plant.
An example of a 15 year old hedge, still small, tight, and fully flushed throughout at only 2.5   feet tall.

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  • Ulysses Hedrick