· John Heider's Answer
· Hi Sue-This is a great question and one that many people ask regarding the growth rate of trees and shrubs. Unfortunately the growth rate of a particular plant is hard to know exactly as this would be determined by several factors such as type of soil, adequate moisture, available nutrients, climate, and correct planting measures. This is why growth rates are normally categorized as slow, medium, or fast. According to the Arbor Day Foundation and many Cooperative Extension Services a slow growth rate means the plant will grow 12" or less in one year. A medium growth rate is 13" to 24" a year and a fast growth rate would be 25" or more in one year. I have not grown this holly cultivar myself but did some research that hopefully will help you. I found a few growers that stated their plants have grown approximately 9 to 10 feet in fifteen years. The fastest growth rate I could find for this holly was approximately 14" in one growing season which would give it a medium growth rate. I looked up this plants patent and found the developer of this cultivar stated the plants height after 10 years was about 2 meters (6 foot) with a plant diameter of 1.25 meters (4 feet). This makes me think the 5 to 6 foot plants you had found are most likely close to 10 years old now. Trees and shrubs will normally grow healthier and faster once they are planted in the ground. Once their roots can spread not being restricted the plants will normally put on new growth much more quickly. Purchasing the larger plants I'm thinking will grow to mature height in 4 years or so. If you were to purchase a smaller size I would think you would possibly see 15 inches or so of growth each year. I wish I could give you an exact answer to the plants expected growth but hopefully this will help. With the holly it is important you plant it correctly. Two main things to keep in mind is not to plant it too deeply and keep the new plant moist but never to wet or dry. I noted a link below on how to plant a shrub that may help. Just click on the link to go directly to the article.http://www.gardenality.com/Articles/279/How-To-Info/Planting/How-To-Plant-A-Shrub/default.html
Please let me know if you have any other questions.