Apical Dominance in Hedges describes how the central stem of most plants grows more strongly than the side stems….
Apical Dominance in Hedges means that, if left untrimmed, they will initially grow into a leggy shrub. Obviously, this is undesirable as strong lateral growth is essential to create a hedge. However, it is both natural and, from the plant’s perspective, desirable. Hedging plants, like all shrubs and trees, divert considerable energy to growing the central stem and its foliage. Plants must reach the light needed for photosynthesis.
How Apical Dominance in Hedges Works
How Hedging Plants (and most other plants) maximise their vertical growth is a fascinating example of adaptive evolution. The apical bud growing at the top of the central stem produces a hormone called Indole Acetic Acid or Auxin. The hormone is then carried down the stem, reaching the lateral buds further down. These lateral buds produce side shoots but auxin keeps them dormant. The plant can therefore concentrate its energy on producing a tall, strong central stem with good foliage. Once this stem has grown to its full potential, the apical bud finally opens and the production of auxin stops. The lateral buds can now open and side branches start to grow. Each of these branches will also produce an apical bud and the process continues…
Importance of Apical Dominance in Hedges
Growers of Hedging Plants want height and width; a vigorous central stem for height and thick side branches to fill in the gap between plants. Therefore, apical buds should be removed when the hedge is forming. Of course, apical heading, as this technique is known, does not stop the central stem from growing. It does, however, allow the gardener to balance vertical and horizontal growth and so create what we all recognise as a hedge.