Most plants display a process called apical dominance in which the bud at the top of the stem (apex) sends a hormonal signal down to buds at lower levels. This signal inhibits these buds from breaking and growing. The further away from the top, the lower the intensity of the signal. This results in plants that have short branches near the top and longer branches as you go down the stem.

Annuals and herbaceous perennials that we grow in the landscape tend to flower at the tips of branches. Therefore, the more branches on the plant, the greater the number of desirable flowers for us to see. By pinching off the apical (top) bud on the plant, the side buds begin to grow resulting in a stocky, more branched plant. This results in more places for flowers to form. Generally, pinching is done in the spring to allow time for the plants to develop the branching.

Traditionally, petunias and geraniums (Pelargoniums) were pinched to avoid the long, stringy stems that did not produce a lot of flowers. The newer "wave" petunias have a very weak apical dominance and tend to branch freely without being pinched.

In shrubs, Rhododendrons and azaleas are sometimes pinched to form a bushier plant. Pine trees in Christmas tree plantations are pinched in the early summer to produce thick, lush foliage. This is great for Christmas trees but is not so great for landscape plants. The process encourage such thick foliage that it holds more moisture and makes the plants more susceptible to fungal needlecast diseases.

Pinching is not the same as deadheading.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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