Kurt M. Jones
Chaffee County Extension Director
Chaffee County Extension Director
Sitting here on my back porch, looking past the potted rosemary and basil, I can see my son’s birthday tree in the back corner. Grandpa and Grandma bought us a birthday tree in celebration of our son’s first birthday. With an extension agent son-in-law, I’d better have planted it correctly!
Planting a tree correctly actually starts with tree selection. We purchased a Colorado Blue Spruce for a couple of reasons. First was because of our son’s being enamored with our tree during the holidays last December. Second, this tree fit into our landscape plans well. Finally, it is one of Dad’s favorites.
After looking at the available trees in the nursery, I chose one that had a couple of features that I was interested in. First, I was looking for a tree that had good shape, and more importantly, one “leader” branch that was vertical. I was also looking at the root ball for two items: ease of handling without a tractor, and the presence of stabilizing roots in the top 2 inches of the rooting soil. Roots that are deeper in the ball or potted tree have the danger of being planted too deeply, lessening the chances of establishment or long-term survivability. The tree that I chose was one that was potted (rather than ball-and-burlap) so that I could move it through our fence with a furniture moving hand cart. Larger B&B tree stock often requires specialized equipment to move due to the weight and rounded shape. One drawback of potted trees can be the lack of root ball as compared with the size of the tree, so extra care may be needed to establish a potted tree as compared with B&B trees of similar height.
After getting the tree home, it is time to locate it and dig the hole. We chose a location that will allow for mature size of the tree. It is also relatively level, and it is in a location that we can regularly irrigate year-round. Many of the tree problems that I have seen this year can be attributed to our dry fall and early winter, necessitating year-round irrigation once the tree is established and during tree establishment.
The hole that I dug was saucer-shaped. I dug it 2 inches shallower than the height of the tree ball, and the edges were 3 times the diameter of the root ball. Yes, a big hole. Tree roots will grow primarily in the top 12 inches of soil (rather than developing “tap roots”) and spread laterally from the base of the tree. The depth is dependent upon the available moisture and oxygen levels in the soil; too shallow and there is inadequate moisture, too deep and oxygen levels diminish.
Why the saucer shape? Researchers have found that in some cases, tree roots can turn upon themselves when faced with a vertical soil texture change (like those faced with the conventional tree holes with vertical sides taught years ago). Saucer-shaped holes lessen the likelihood of tree roots turning on themselves, eventually girdling the tree as they mature. Digging the hole larger has been shown to increase root biomass eight times over similar trees with holes dug to fit the root ball.
After digging the hole, I removed the plastic container and the burlap that was also present. Though burlap will eventually degrade, I did not want it wicking moisture away from the tree roots or interfering with root establishment until it degraded. My preference is to remove as much foreign material (wire cages, burlap, strings, pots) as possible when planting trees.
When I got the tree upright in the hole, I began backfilling. I did not use any amended soil in my backfill, instead I planted the tree in an amended location. Tree roots spread laterally from the base, so amendment is best accomplished throughout the rooting zone, not just in the backfilled hole. I also water-packed the backfilled hole, rather than tamping or stomping in the soil around the tree roots. My purpose in digging a large hole was to avoid soil compaction, so I will avoid activities that contribute to soil compaction around the tree.
Finally, I drove some wooden stakes through the root ball into the undisturbed soil underneath to help stabilize the tree during periods of higher winds. Because this is a special tree to our family, I wanted to use underground stabilization rather than straps, wire and T-posts to hold it in place. If you choose to do wrapping around the tree to stabilize it, make sure you use straps designed for that purpose, and remove the stabilization materials after the tree is established (approximately 1 year later). I had the unfortunate opportunity to see some established trees planted about 8 years ago that succumbed to the girdling effects of tree wraps (lengths of garden hose with wire inside). I also mulched the entire area of disturbed soil to help hold moisture and reduce weed establishment.
Though I did not use any, many people believe that root stimulation hormones should be used. Though research is conflicted about using root stimulator, it does not harm the tree and may help with speeding up root establishment. One practice that should not be used is nitrogen-based fertilization. The goal after transplanting trees is to establish tree roots rather than producing tree branch growth. Nitrogen fertilization during the first growing season has been shown to reduce root growth. Finally, I watered the tree ball and surrounding soil.
The simple act of planting a tree. It is a practice that has many opinions, but for our family, planting a “First Birthday Tree” is a neat tradition that I was proud to be a part of.