Pruning Plant Tops - Plant Hormones and Plant Growth Patterns.

If you read my post on how plants grow, you know that most plants (other than grasses) grow from the top, (specifically in an area called the apical meristem) and I mentioned in this post  some ways this knowledge can help you be a good grower.  There are other ways this knowledge can help with plant growth.  The apical meristem (link to plant growth article) is also where many hormones are created/secreted.  If you cut  off the top of a plant, most of you know the plant will get bushier.  I often do not recommend doing this*, as it stresses the plant to have its apical meristem removed.  Cutting plant tops can be necessary with some growth methods (read my post on the sea of green technique). 
The physiological reason why plants get bushier when the top is cut off or bent is that one of the hormones that will be no longer made by cutting the top of the plant used to prevent the branches from growing, this is termed apical dominance.  Without the plant top, the branches will be grow at an increased rate from their meristem tissue, termed secondary meristems.  This means each branch will elongate, and each branch will secrete more hormones.  In some plants, one of the branches will become ‘dominant’ and suppress growth of the rest of the plants, making the plant start to grow tall again.  Other plants will just become bushy and will have lessgrowth in height.
Good growing,
Dr. E.R. Myers

* I more often recommend bending the top of the plant, this will slow the hormones, and make the plant more bushy (less tall) without the stress of recovering from cutting off the top.  The benefit is that bending  does not result in several days where the plants do not grow because the apical meristem was lost and the growth hormones, are gone.


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