The Thuja Green Giant Arborvitae are touted as one of the fastest growing evergreen trees on the commercial market. Will they really live up to this adoration?
Here at the nursery, we have grown and sold the Thuja Cedar Green Giant Trees for over 15 years. The plants are hybrids so they are propagated by cuttings as they will not come back true from seed. Some years we field transplanted some of the cuttings to grow on for larger projects. When field transplanting, we typically used Thuja Green Giant liners that were 6 to 8 inches tall. At the end of the first growing season, the field plants varied from 10 inches to 30 inches tall. By the end of the second summer, their heights often reached 22 to 40 inches.
Arborvitaes are a slow growing plant variety (generally less than 12 inches per year of new growth), which is why I believe when this crossed hybrid was found to be a more rapid grower, it become the "spokestree" for the variety. I do not know from where the studies about the extreme growth rate came, but in my own experience, I haven't seen the extreme of 5 feet of new growth per year on this plant.
A few years ago, I lined the entrance of my drive with over 100 green giants (18 inches tall). Being far away from the house, I was not able to regularly water them as they needed and, to make the situation worse, the soil was extremely compacted. After the stress of their first year planted having to survive through drought, they pulled through amazingly and I only lost 2, which is pretty impressive. Today the green giants that line my drive are now mostly over 8 feet tall and beautiful.
Green Giants, as my drive way example describes, will grow in the poorest of soil. However, compacted soil seems to stunt their growth considerably. If you have compacted soil, till the area mixing in bags of aged compost or aged manure mix and coarse sand. Till the area going down as deep as possible (at least 12 inches deep). This will work to help with drainage and instantly put nutrients back into the soil. Then, plant the green giants. Giving them the best possible start for growing is always the best encouragement.
For the first year, apply supplemental water as necessary to keep the soil cool and moist. Apply shredded bark mulch around each plant going out at least 20 inches from the base of the plant leaving a welled area of about 3 to 4 inches at the base of the plant so that the bark does not touch the trunk of the plant. This welled area is for watering and air circulation.
Their first year in the ground the plants will work to develop a stronger and deeper root system. Fertilizing is not recommended during this time as it encourages more top growth rather than root expansion. Any top growth during this time is a plus, but don't expect it as this will not happen to any extent until the following year.
The green giant grows a little differently. Where most arborvitae grow as a whole, this one sends up a vine looking leader from the top. This leader hardens off and over the next few years it begins to build the tree around itself sending up the leader again each year. A little odd, but you will see what I mean.
While I am not a fan of seeing the Thuja Green Giants. advertised as one that puts on amazing growth each year, these are plants that be used for hedges, privacy screens and even as specimen trees. Having real expectations that it will not grow as quickly as some of the faster growing deciduous trees do, but appreciate its uniqueness and you will not be disappointed.