Q. You have always have stated to prune shrubs and trees when they are dormant, but it seems mine do not go dormant in the winter. They continue to grow even though they get water only once a week. I halved their fertilizer application but they continue to grow larger than I want them to. Why do they grow when they should be dormant and when should I prune them to slow their growth and spread?
A. Shrubs desire to reach their mature size. Keeping them smaller than this will require more maintenance than selecting one that is the size you need. Select shrubs by determining the size you need and finding one that fits that size at maturity.
Dormancy here is not the same as dormancy in Minnesota. Dormancy here, in some cases for some plants, means that they may stop growing as much, not that they stop growing at all. Just depends on the plant and its location.
Where the plant is located in the landscape also dictates its level of dormancy. Very warm microclimates in the yard may mean that some plants never totally shut down during the winter while in colder spots they do. Hot south and west facing walls with little winter wind are the warmest locations.
Cutting back on water and fertilizer will help but they do not act like an “on and off switch” for plants. Think of fertilizer and water more like a “rheostat” where it can increase and decrease growth but not totally shut it down. At some point though, turning down the water and fertilizer will damage the plant. The real solution is to match plant mature size to the site.
Focus your pruning on older growth and remove it from deep inside the canopy leaving the younger growth still flourishing. Prune in the winter months. Avoid trimming on the edge of the canopy whenever you can. Hide your cuts if at all possible. They should not be obvious. This will help keep them smaller.