Here's my dead sourwood as it was pulled out of the ground. |
Sourwood trees usually produce deep lateral roots. Here the larger roots have circled back. Also, there was little real soil within the root mass. |
When planting a container grown plant you need to tease out
some of the roots from the original container shape. This is particularly important when dealing
with a pot-bound plant. In severe cases
it may be necessary to cut the roots to encourage them to expand outward. This was a case where it looked OK for a while. Planting dos: the hole should be no deeper
than needed so that its crown is just above the soil level. The hole should be about twice as wide as
original ball/container; and, back fill the hole with native soil, not more
than half amendments, if any at all. For
compacted soils a wider hole is needed.
It also helps to make some jagged cuts to the sides of the hole rather than making it
a smooth circle. In this way when a
growing root encounters the compacted soil interface it may be forced to
penetrate it rather than just veering off to the side. The goal is to get the roots growing outward and
downward into the native soil-not to create a mirco-environment that the roots will never
leave. Check out this link for more information on proper planting techniques.
Another thing to watch out for, especially in container grown plants, is circling roots. These are thicker roots that reached the edge of the pot and curving around the edge of the pot. Left uncorrected these roots will form a barrier to expansion of the trunk as the tree matures, eventually choking off the flow of sap up and sown the tree. The best option is just not to buy a tree or shrub with circling roots. If you already have one you can try to untangle the circling root, or it may be better just to cut it off for the long term health of the plant.
Sometimes the effect of poor soil contact is seen faster. Because moisture moves from coarser to finer soils by capillary action, a container grown tree or shrub inserted into finer textured soils may dry out unless there is intimate contact between its roots and its new soil home. This is because there is little tendency for soil moisture to migrate from the fine textured native soil to the coarser bark/peat moss/compost mix that the containerized plant comes in. When planting container-grown plants I usually knock away a good portion of the planting mix to expose as many roots as possible and then put these roots in direct contact with the native soil. I use the freed up planting mix as the ‘soil amendment’ to blend with the back fill.
The rounded crown of this once beautiful specimen has been decimated to reduce problems with the power lines. It's interesting that the more upright trees (oaks, I think) located just a few feet back are not interfering with the wires to the same degree. |
Another factor that affects long-term plant survival is siting. By this I don’t mean proper soil and light conditions, I am referring to location with respect to buildings and utilities, both above and below ground. Planting big tree too close to a house can cause a multitude of problems ranging from root damage to the foundation and falling limbs to aesthetic problems like being out of scale with the house or blocking views. Cultivars come in handy when working in a defined space. These plants have predictable sizes and shapes thus reducing the effort to keep them the right size. Utilities are another consideration. You may get away with planting too close to them for a number of years, but when utility work needs to be done, your prized plants will be sacrificed for the sake of keeping the lights on or the water flowing. Probably the most commonly encountered problem is planting large plants too close to overhead wires. This conflict is often exasperated by the desire to have street trees and the first place we look to is the often too small strip between the sidewalk and street. Utility companies publish guides and many communities have regulations about planting under utility wires [for example see this link from Baltimore Gas and Electric]. The general guidelines are to limit the mature size of trees and shrubs under wires to 25’ and not to plant larger materials within 25’ of the wires. Larger plants should be located such that, when mature, their branches will not interfere with the overhead utilities. Recommended plants will vary by region, but here in the Mid-Atlantic, good native candidates include Dogwoods, Redbuds and Hawthorns.
This Bradford pear is starting to interfere with the power lines and the lower branches on the street side have been damaged by passing trucks. This is just not a good location for a tree. |
Passing traffic is another factor to consider with street trees. I had a Bradford pear planted too close to the road (planted by the city) that was repeatedly clipped by passing trucks and delivery vans. It was also growing up into the power lines. Perhaps the plan was that the Bradford would die or otherwise fall apart before it got to be much of a problem. (Note that Bradford pears are proving to be invasive species as well as structurally unsound, and in my opinion are a very poor choice in any North American landscape)
The root flare is probably about 6" below the top of this volcano. An ideally planted tree would have no mulch within 3" of the root flare and the flare would be only an inch or two above the native soil level. |
By putting a little extra thought into site planning and in
helping plants get better rooted you can avoid a lot of disappointments in your long-term landscape investment.