Monday, December 7, 2015

Properly Planting a Canadian Hemlock

The Scenario:

In October our arborist were hired to plant several Eastern Hemlock (Tsuga Canadensis) trees in Alpharetta Georgia. This particular evergreen was chosen because of its natural feel and ability to grow well in the shade. The ’14 tall Eastern Hemlocks were ordered and shipped from a long-standing nursery located in the Northern US.

Preparation & Planting Conditions:

After many weeks of perfect planting weather, the trees arrived from the North during a major rainstorm that affected the burlap of these 1,800 lb. trees. The ground in the metro Atlanta area was 100% saturated approximately 3 feet down to the clay ‘hardpan’. Usually after extensive rainfall, the rain runs off the Georgia clay pretty rapidly. The entry to the clients’ property was extremely soggy so we constructed a temporary road with over 100 sheets of plywood. To protect existing trees in the transport path, we tied back some ornamental Japanese maples and lifted lower oak branches. In the final stage of preparation, we designed a 4-point strapping system to lift the trees and dug each planting hole by hand. 

Planting the Hemlock – Phase 1: Placing the Tree

The rootballs of the hemlocks were covered in natural burlap, but due to the nonstop rainfall the balls became very unstable. One of the most important phases of successful planting is the rootballs and all roots need to remain fully covered with the original planting soil from the grower. This is the environment where they grew from a sapling, and why it’s a critical step in successful planting.

Remember trees are never supposed to be lifted and/or moved by their trunks. The lifting apparatus and machine need to be applied and used correctly so as not to disturb any of the original soil. In consideration of the compromised burlap, we had the rootballs shrink-wrapped to assist in supporting the roots and original soil.

The area of planting had zero access for a tree spade or a crane to set these trees in place. Eleven tree holes, approximately 7 to 8 ft. wide and 34 inches in depth [approximately 2 to 2 ½ times the diameter of the rootball] were hand-dug. The depth of the hole was calibrated to leave the rootball 2 to 3 inches above grade. Hemlocks do not like ‘wet feet’ but they love moist soil with the proper run-off. After considering the slope of the terrain, the sides of the planting holes were sloped to an angle to properly direct and handle the runoff.

Phase 2: Preparing the Soil & Rootball

The second most important phase of planting Eastern Hemlock trees is soil preparation. Hemlocks need a great deal of space in the planting hole with a large amount of soil amendments. Worm castings work well and have been used for over 100 yrs by experienced gardeners. This pre-mixed organic planting soil was integrated next to the rootball.

Next is a step that most contractors and builders skip – they do not remove the burlap and wire mesh from the rootball. Why? This process is time consuming, methodical, and most do not know how to remove the burlap and wire without disturbing the rootball soil. To accomplish this without damage, carefully set the tree into the planting hole, cut and remove the wire mesh as low as possible (but not directly underneath the ball), remove the burlap tacks and cut the burlap along the base with a sharp razor cutter. Then we carefully root-pruned every exposed root for optimal growth.

To complete the planting process, we added approximately 12 cubic feet of the specialized soil amendment next to the soil that remained on the ball. You will then backfill the hole and compact lightly to prevent any air pockets. We top-dressed with a layer of the organic matter then mini-pine bark nuggets of about 2 inches or less.

Phase 3: Watering & Pest Prevention

Eastern Hemlock trees are very peculiar and need to be monitored on a weekly basis. The third most important consideration is to properly water your Eastern Hemlock (but do not overwater these trees). Hemlocks need to be watered in a pencil like stream for approximately 20 minutes every week to ensure the rootball is saturated. As far as pests, the woolly adelgid is an aphid-like insect that has devastated Hemlocks in the Northern portion of the U.S. As a defense, saturating these trees with insecticidal soaps and horticultural oils can assist with the tree care and protection.

Usually when a tree arrives from a nursery you’ll notice how dense the rootball is. Comparatively it can feel like concrete or similar to the substrate of the Georgia clay planting holes. Fortunately, the unprecedented rain penetrated roughly 36 inches of soil as well as kept the rootball soil moist. What Mother Nature achieved naturally would have required 1000’s of gallons of water. In addition, the rain was a great benefit as the hemlocks were able to acclimate to the cooler weather.

Recap of Optimal Planning and Preparation:

Remember that proper planning and soil preparation are time consuming but critical to successful tree planting. Take the time to plant correctly or hire a veteran ISA tree arborist that is experienced in planting. Planting a tree in a confined space may appear nice for a season but may die within 2 years if done incorrectly. Drought, construction, and the equipment used in the planting process all play a major role in the success or dieback of a newly planted but otherwise healthy tree. After planting a tree successfully you can appreciate and observe its beauty for a lifetime.

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