Plucking, the selected removal of stems from boxwood to facilitate air circulation, light penetration and inner growth of leaves, is an integral part of any preventative maintenance program for boxwood. In addition to fostering the health of the parent plant, plucking provides a source of cuttings for propagation. See “propagation/rooting.” This paper will focus on the process and benefits of plucking.
In a preventative maintenance program for boxwood, the plucking or thinning referred to above is a high priority. When carried out on a regular basis, this process promotes the health of a plant by allowing the sun to penetrate and air to circulate within the body of the plant. Plucking is accomplished by reaching into the plant and breaking out stems from two to eight inches in length over the entire area of the plant. Obviously the size of the stems which are broken depends on the size of the plant. In plucking smaller plants up to fifteen inches, smaller stems two to four inches should be chosen for breaking. When the plants are fifteen to 24″ then larger stems four to six inches can be broken, and with plants above 24″, the stems can be four to eight inches without hurting the appearance of the plants. The process is similar to a barber or stylist thinning hair. The goal is to lighten and thin the plant creating small openings for sun and air to filter in.
Boxwood which are grown in the direct sun have a greater need for thinning than those grown in partial shade. The sun grown plants tend to develop very dense, thick foliage which prevents the light and air from entering the plant. Often when opening and observing these plants, one finds piles of deal leaves caught in the middle of the plant and aerial roots which have developed because of the moisture held by the dead leaves. Circulating air dries out the interior of the plant and eliminates dampness. This dryness prevents the growth of any aerial roots. The interior of plants should be hosed out with a strong stream of water periodically in order to clean out any accumulation of dead leaves and other debris. The cleanliness of the interior of plants is critical in the prevention of diseases which thrives in dampness.
Another characteristic of plants grown in direct sun without any thinning is that the green leaves are only a couple inches deep on the plant. Because light cannot penetrate the plant, the leaves can only grow on the outside. Plucking allows light to penetrate and leaves then develop deeper within the plant. A depth of six to eight inches is not at all uncommon for a healthy plant and may even extend twelve itches deep on boxwood which are 30″ in height and diameter.
Plucking can be done at any time of the year without hurting the plant. However, as noted above, late winter/early spring has some advantages. If plucking is accidentally too heavy in places, the growth of spring will quickly cover up most mistakes. It is very difficult to describe how much to thin a plant. One should thin evenly over the entire surface of the plant and continue to thin until the exterior texture of the plant is very loose. This looseness provides pathways for the light and air.
The shape of a plant can be modified over time through regular plucking. Often boxwood may be growing over a walk or through a railing. In these instances, one can pluck very heavy in the area that needs to be taken back. This does not mean that you take it completely back in one plucking leaving a bare sided plant. One can pluck a plant two or three times a year while still leaving the boxwood looking fairly normal. The principal is the same-as in one’s checking account. If the rate of plucking is heavier than the rate of growth, the plant will diminish in size over time. A large scale massacre of a plant is not necessary and in addition, harmful to the plant. Simply consistent plucking in strategic locations will change a plant to your desired size and shape with time.
Hopefully, by this time it is obvious that one never “shears” boxwood with a hedge trimmer. It is often said that one-should never say “never.” However, I believe that with respect to this topic I can say “never use shears.” Shearing violates all the principles which plucking attempts to accomplish. Only the outer, layer of leaves is removed in shearing. The plant then is just as dense as it was before shearing. In addition, the shearing will contribute to new growth only on the outside of the plant which results in the plant having an even greater outside density than prior to shearing. This greater density obviously inhibits light penetration and air circulation. Also, contrary to plucking which facilitates the inner growth of leaves, shearing only promotes outer growth. Shearing also destroys the natural appearance of boxwood. It creates a very smooth, manicured look which is very different than the traditional cloud-like textured appearance of boxwood.
One last benefit of plucking is that if done at the right time of year you will be able to use your clippings to propagate new plants in the summer. Additionally, plucking at Christmas can provide ample boxwood for decorating in your home.
Stephen D. Southall
English Boxwoods of Virginia