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Wednesday, August 14, 2013

African Sumac Selection Present Problems to Homeowners

Q. I have read over and over that African Sumacs are fast growers. The African Sumacs here seem to be at a stand still! I have two in my backyard since April. They are alive but the canopy and trunk just seem the same, perhaps 10% growth. The trees are sold with tall, thin trunks - like 1/2 to 3/4 " diameter, with a canopy that branches out at 8 feet. There are no branches or leaves below that. The trees are staked high and the stems are all finger diameter. Will they take off eventually?

A. Trees with a long, skinny trunks with no side branches until 8 feet are a problem. This is done at the wholesale nursery to increase their height and make it easier to ship. It is to their advantage, not to yours.

            To have strong trunks, tree trunks to be tapered from top to bottom. In other words, to have good trunk strength the trunk needs to be bigger in diameter at the bottom and get narrower up the trunk. This helps to support the canopy. If they don’t, a good wind will come along and snap the trunks.  

Trees with no taper cannot support their own canopy. Leave any growth on the trunk that develops and stake as low on the trunk as you can to allow the trunk to move. Both of these things will help develop a tapered trunk.
            Trees develop tapered trunks from two major events in their lives; trunks swaying back and forth in the wind and the presence of branches with leaves all along the trunk. Both have a great deal to do with trunk taper and consequently its strength.

            When trees are staked, trunks should be immobilized no lower than it takes to hold the tree upright and still allow some trunk movement. The stakes should be removed as soon as possible after planting; usually no longer than one full season of growth.

            Next, never, never remove branches growing along the trunk if they are smaller than pencil diameter. Once these stems reach pencil diameter or thereabouts, cut them off flush with the trunk with a clean, sanitized bypass-type pruning shears.

            Never plant in a DRY hole. Make sure the soil in the hole is wet when tree roots come in contact with it. Planting in a dry hole can set a tree back, or any plant for that matter, due to root damage.

            Sometimes people say this is “transplant shock”. Well, yes, plants do have a setback, or shock, when removed from a container and placed in the ground. This can happen for many reasons but the DEGREE of setback can be under your control.  

            Why are they growing so slow? The amount of total growth on a plant (add up all new growth above and below ground) is divided by the number of places where growth can occur. Stems in full sunlight or without competition from other branches will usually be the strongest in growth but the total growth must be divided among every place that is growing. This includes the roots and any increase in the diameter of stems and trunks.

            If you want a plant to grow faster, reduce the number of places where growth occurs. Prune out unnecessary stems so that the growth is focused on those stems where you want growth to occur.

            You may see sprouts coming out of the trunk. Leave them. Do not prune them out until they are pencil-sized or larger but leave the small ones to help build caliper or taper.

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