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Index : Trees
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- 26. Forming Shrubs Into Small Trees - Top
- Some large shrubs lend themselves to growing in what is called a ‘standard' form. This is when a shrub is trained to grow with one central stem or trunk with it's foliage elevated well off the ground in tree-form.
Shrubs having a dominant central stem and strong lateral branches are best for training into standards. These include; Xylosoma, Oleander, Texas Olive, Japanese Privet, Mexican Bird- of-Paradise, Pittosporum (also called mockorange), Photinia., and ‘Majestic Beauty' Indian Hawthorn.
Standards are great for using as patio and entryway trees; any place size is at a premium. Of the recommended varieties, oleander and xylosoma are the largest growing. Both will reach a height of from 15 to 20 feet with equal spread. Mexican Bird-of-Paradise, Japanese Privet and Texas Olive can be trained to grow to a height of 10 to 12 feet. Pittosporum, Photinia, and Indian Hawthorn ‘Majestic Beauty' will top out between 6 and 10 feet tall. All will grow in full sun with the exception of Japanese Privet, Pittosporum, and Indian Hawthorn which need mid-day and afternoon shade.
Young plants can be trained by pruning off all but one of the stems. Choose the stem that is growing up the straightest to train. This stem may have to be staked initially. This is particularly true of plants such as xylosoma and Mexican bird-of-paradise whose stems have a tendency to grow crooked. By staking the stem up vertically, it will grow straighter and at a faster rate. At the same time side shoots which would normally grow out from the main stem will be inhibited from growing. In addition, more of the plants energy will be focused in the main stem.
Stake the stem as you would if applying a splint. Attach the stem tight against the stake by tying with plant tape or plant ties. These ties will have to be checked regularly and loosened as the plant grows to prevent the ties from cutting into the stem. After the first year of training, the stake should be removed so that the stem may flex freely in the wind and develop strength.
As the plant grows, continue to prune off most of the side-shoots that grow out from the main stem. However, allow a side-shoot to grow here and there, but cut them back to keep them very short. Side shoots along the main stem will help encourage development of a strong, thick trunk.
When the plant has reached a height where you want to develop branching, cut the main stem off entirely. Below the cut, several strong side-branches will develop. You can choose one of the upward growing shoots to continue growing up as the main stem. If one of the shoots does not grow in an upward fashion, using a bamboo stake tied along the main trunk and then tie up one of the shoots against the bamboo stake. This shoot will develop into the main vertical stem.
If you don't want to take the time involved in training a young plant into a tree-form, you can purchase one "ready-made" at many local nurseries. Choose a plant that has a strong trunk. If the trunk is tied to a stake, cut the ties and see if the plant can stand up on it's own. If it can't, don't buy it! It's virtually impossible to strengthen a weak trunk.
As your ‘standard-form' shrub continues to grow, be sure to keep new shoots that grow from the trunk pruned off. To create a denser canopy of leaves it may be necessary to cut back the length of the stems from time to time. Don't cut back too far on the stems. Usually removing 4 to 6 inches from the end of the longer stems will be sufficient to encourage the stem to branch and become fuller.
Answers to gardening questions may be obtained by phoning the Extension Center Plant Clinic, weekdays for 8:30 a.m. to 4:30 p.m. at 626-5161. Green Valley residents my phone 648-0808, Mondays, Wednesdays, and Fridays from 9:00 a.m. to 1:00 p.m. for answers to gardening questions.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161. - Updated: August 6, 2001
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