Giving New Plantings the Best Start
Planting a tree or shrub in your landscape can be very exciting, but it can also be the start of a painful loss of what was once an interesting, possibly expensive, plant. On the surface planting seems to be a simple task – dig a hole to fit and put in the tree green side up. But to ensure success you should strive to recreate the natural habitat of that plant.
The first step is to choose the right plant for the right place, or as many of us do, find the right place to plant that tree you had to have at the nursery! This means considering your hardiness zone, heat zone, soil type and drainage, average moisture, etc. We have had all winter to daydream and plan for planting season, so we’ll assume you have chosen plants that have the genetic ability to thrive in your garden, or at least tolerate the climate and soil.
Possibly the most common planting mistake is planting too deep. There are a number of contributing factors, but first let’s consider a tree growing naturally, that is from a seed. The seed germinates at or within a couple of inches of the soil surface. The radicle (root) grows down and the plumule (shoot) grows up. This means that only the roots are covered by soil. Root tissues are adapted to grow in the moist environment of the soil and resist naturally present decay organisms. The bark of the trunk is different. Undamaged, it provides protection from insects, rodents, and air-borne fungi. If it is covered in soil it succumbs to subterranean fungi.
If you pull up a seedling in the forest you will see a clear difference between the roots and shoot. This is what we should strive for in our planting – only roots in the ground. While you are in the forest, observe the flare of saplings and mature trees. The flare is the area of transition between the trunk and the roots; it is an obvious widening from the trunk to the root plate. In nature it occurs at the soil line.
Old planting advice says to plant the tree at the level it was grown in the nursery. Too often when a plant is brought home from the nursery it is already too deep in the soil. Traditional nursery production methods pile more soil on top of the flare. In container grown plants, the seedling is often placed in the bottom of the pot and soil is added to fill the pot. In field operations cultivation to control weeds pushes soil on top of the root ball. The soil in your landscape is not the same as in a nursery pot or field. Modern advice is to locate the first roots growing directly from the trunk and place those near the surface of the soil. If you cannot see an obvious flare at the surface or there is a gap between the trunk and the soil you must do some searching.
With balled and burlapped trees, you can probe the soil ball with a stiff wire. If you can find 3-4 main roots within 3 inches of the surface you can plant at the same level the tree was growing. Any deeper and you need to carefully remove soil to find the main roots. Sometimes you can find the roots poking through the sides of the root ball. Be sure to remove wire baskets, twine, trunk wrap, and any other packing material. It is just that –packing material -designed to protect the plant during shipping. If it would not decay naturally in less than 6 months, it will impede root growth or cause girdling.
With container grown trees, you often have a mass of roots that you need to untangle. Avoid root bound plants, because you will have a difficult time untangling enough roots to avoid girdling, and they tend to dry out quickly. Bare-rooting container trees is a good practice. Soak the container in water to loosen up the growing medium, and then untangle the roots while keeping them moist. This will allow you to find the flare and eliminate potential girdling roots. Bark or peat based growing medium also creates a soil interface problem that may cause your root ball to dry out too quickly or remain too saturated.
It may be little scary to remove any roots at planting, but it is better to remove circling roots that could girdle the tree a few years down the road just as it is really becoming a nice specimen. I have seen more than a few mature trees that appear healthy only to suddenly decline or topple over in a gust of wind. On closer inspection the trunk looked like a pole going straight into the ground – no flare. This is a sign of potential girdling roots as a result of deep planting. Just do a Google search for ‘girdling roots’ to see the horrors you can avoid!
Mulching is another tree care task that is often done incorrectly. Look again to nature to see how it should be done. Just a couple of inches of organic mulch is best. Never apply more than 3-4 inches total and keep it away from the trunk. While it may not be the most attractive, composted arborist wood chips make some of the best mulch for your soil. It has a good balance of carbon and nitrogen and breaks down to improve the soil. Be careful with some organic mulches such as pine straw and hardwood bark as they can grow fungal mats that actually repel water. You can alleviate this problem with a rake; just stir them up a bit.
Don’t forget to water in your new tree, and leave any pruning for a year or two to allow some recovery time. Hopefully your efforts will pay off with a tree that will out-live us all, just as nature intended!
About the Author: Jared Weaver has served as the City Parks Arborist/Forester in Bowling Green, Kentucky, for the past decade. He is the Southeast Regional Director and represents our region on the ACS Board. He grew up in rural Pennsylvania, which instilled a love of plants, gardening, and the outdoors. He served in the US Army before moving to Bowling Green to attend Western Kentucky University where he majored in Horticulture with a minor in Art.
Excerpt from the March 2017 Southeastern Conifer Quarterly. Gain access to archives of past newsletters and the National Conifer Quarterly by becoming a member of the American Conifer Society.