Arborvitae are sometimes trimmed to a spiral form and sold as spirals. They generally are trained to grow in the spiral form and are more expensive for that reason. Thus, proper maintenance of spiral arborvitae is key to preserving your investment, lest it grow wild and regress into a normal arborvitae. This article will focus on preserving spiral arborvitae.
Spiral arborvitae are most commonly made from emerald green arborvitae. This is because Emerald Green has a much more compact form and grows slower than other arborvitae. At maturity, Emerald Green gets to about three feet wide and fifteen feet tall. The trimming for the spiral will keep it about one to two feet wide and as tall as desired, generally around ten feet.
After buying the spiral arborvitae, plant and maintain it as any normal tree. Observe the arborvitae for signs of pruning. Has it recently been pruned, or is it bushy and vigorously growing close or into the other branches? If the arborvitae has grown, it will need to be trimmed. Trim back, erring on the side of caution. There must always be some green left; if there is more brown than green, the tree is pruned too hard and will be set back. Remove or cut back any branches that are trying to grow too vigorously or be leaders. Remove all branches trying to grow out of the trunk to fill in areas that have been cut for the spiral.
Spiral arborvitae will need to be pruned at least twice during the year. Prune whenever the tree has grown recently, to keep it in the desired shape. Always prune hard, as long as there is good green foliage remaining. Failing to prune for an extended period can lead to loss of the shape from losing the green centers of the spiral from shade caused by overgrowth. Arborvitae sheds needles that are shaded by its foliage, and once they are lost, the tree is only good as a normal tree. In some cases, the whole spiral shape is not lost and can be salvaged, although it will be over-filled and give little margin for future error.
Through timely maintenance and by knowing how far to trim back the spiral, you can successfully protect your investment for many years.