June 24, 2017

1 - Annual rejuvenation pruning may be used to reduce and maintain the size of Spanish broom shrubs.

Yard and Garden June 24, 2017


I have two huge (8x8) Spanish Broom plants that have finished blooming and I need to trim as much as possible without damaging them. I know they are difficult to cut. How and when is best? Any help would be appreciated. I live in Las Cruces and these plants were planted about 8 years ago.

- Mary B.
Las Cruces


You can prune your Spanish broom shrubs now, or you can wait for the dormant season. You are correct that they may be difficult to prune because of their “broom” habit and because they grow densely and you should cut the oldest, largest, least floriferous stems which are at the center of the plant and hard to reach.

The “broom” nature of Spanish broom and other related plants causes a problem if you cut branches back partially. Some gardeners recommend this kind of pruning, but the result is a cluster (broom) of branches that forms at the top of the branch that was cut back. There are often few side branches below the broom growth. You may consider this unattractive and it can result in branch breakage in some situations.

The best way to prune Spanish broom is to remove up to one-third of the largest, oldest branches, cutting them as near to the ground as possible. These branches to be removed are usually in the center of the shrub and difficult to reach. Cutting them near the ground usually results in development of new shoots from the base of the cut branches. If you cut some of the largest branches each year, you can maintain the shrub at a smaller size. It may take three or four years to cut enough large branches to significantly reduce the size of the shrub, but there should be improvement in size after even the first year. As new growth replaces what you cut and grows in size, they will need to be removed also. A pruning cycle one-third of the branches each year for three years (one-third of the oldest branches) will result in a smaller shrub. You may find that you do not need to prune so much each year as you get the plant to the size you prefer.

Some gardeners will cut all the branches of Spanish broom to the ground in one pruning activity. In most cases the plant will rapidly regrow and after a few years may need cutting again. While a healthy plant will tolerate extreme pruning, an unhealthy or plant stressed by a hot, dry summer may die. The one-third annual stem removal reduces (does not eliminate) the possibility of plant death.

If the pruning chore becomes unmanageable, there are cultivars of broom plants, some with different flower colors that may be used to replace the larger growing forms.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


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