(If you are the kind of reader that prefers brief articles, there are summaries of each of the 10 steps in italics and bold below.)
If you’ve never planted a tree or shrub, the task can be daunting. Even experienced gardeners frequently argue about the best planting techniques or operate on outdated information. This guide will give you a simple road map for installing a container grown tree or shrub. We will address the planting of trees and shrubs that are “ball and burlap,” where the plants are cut out of a field and the root ball is wrapped in burlap, in another article.
In general, container grown plants are easier and more forgiving to plant. A plant cut out of a field and wrapped in burlap can lose up to 90% of its root system in the process. In contrast, a container grown plant has 100% of its original root system fully intact. Therefore, it does not need the year or two that it normally takes a ball and burlap plant to recover from the trauma of being transplanted.
Of course, it is more expensive to grow trees and shrubs in containers than in fields. Therefore, container grown plants are usually more expensive. But they are often worth the extra money.
You can install most container grown trees and shrubs any time of the year in Memphis, provided that your planting technique is good and you are very conscientious about watering. But, the time of year that is most forgiving for planting is the spring and fall. The fall is a particularly good time for planting deciduous trees. This is when they are beginning to go dormant and rainfall increases in Memphis. Cool season dormancy occurs at leaf drop, termed “abscission.” Dormancy is a time when many plants go into a self-protective mode. The plants also shif their focus from canopy development to root development, during dormancy. Transpiration slows and nutrient needs drop.
In contrast, the least forgiving time of the year is July and August. This is the time of the year when soil is driest in Memphis. It is when the most supplemental watering is required. Newly installed plants don’t have deep root systems. Accordingly, they can’t access moisture reserves deeper in the ground that more established plants can tap into. However, you can even plant many things in Memphis in this challenging time of the year, late summer, if you carefully follow these planting instructions. But, you must monitor their moisture level every day through the end of September.
So, to install a container-grown woody plant, follow these 10 steps:
1. Make sure the soil is friable.
Make sure the soil is friable, not too wet and not too dry. You can test for friability by picking up a clump of the soil and throwing it against a hard surface. If it is friable, ideal for planting, it will crumble. If it is too wet, it will splat, like a pancake. And, if it is too dry, it is more likely to just be dust.
If the soil is too wet, when you slide the shovel in, particularly if the soil has lots of clay content, it will seal the sides of the hole. The hole will become like an impermeable clay pot from which water cannot drain. If the soil is too dry, it will be difficult to hydrate properly before it dries out the roots along the edge of the root ball. So, if it is too dry, drench it in water and then wait a day or two to test it again.
2. Dig a hole only deep enough for the root crown to be slightly above the existing grade when the plant is placed in the hole.
Identify the root crown and then dig a hole only deep enough for the root crown to be slightly above the existing grade when the plant is placed in the hole. Do not dig deeper than necessary. The plant needs a firm base to keep the root crown from sinking below-grade over time.
The traditional shape of a plant hole is round. Although most people still dig round holes, the Royal Horticultural Society now suggests that the hole be square. This is to discourage roots from wrapping around the root ball in a circle. Their reasoning is that there are studies showing that roots are more likely to break or push through soil when they reach the corners of square holes. They say that, in round holes, the roots are more likely to circle and girdle the plant. This girdling will limit the plant’s potential, particularly in soils with a high clay content. I have yet to try digging a square hole in which to plant a tree. But, regardless of whether your hole is round or square, the sides of the hole should be sloped. The hole should be more like a shallow bowl than a bucket.
3. Loosen tight root balls before placing the plant in the hole.
Loosen tight root balls a bit with your fingers before placing the plant in the hole. Generally, do not chop, slice, or damage the root ball. A severely pot-bound root ball may benefit from a little bit of cutting to loosen it. However, it is better to avoid using such specimen entirely.
Do pull out girdling roots. Girdling roots are those that seem to wrap around the root ball in a circle. Girdling roots will inhibit the long term development of the root ball. The symptoms of a root ball whose development has been limited by girdling roots may not be evident for 2-3 years, or more even, after planting. The plant may initially grow well, but eventually, it will fall into decline. This is because a girdled root ball may be unable to support a mature canopy.
4. Mix the original soil that came out of the hole with an equal amount Dr. Earth Motherland All Purpose Planting Mix, ¼ cup soil sulfur, ¼ cup 12-6-6 fertilizer, and the appropriate amount of Soil Moist to use to back-fill around the root ball after placing it in the hole.
Mix your back fill (the soil that should go back into the hole around the plant) in a wheel-barrow or on a tarp. 50% of the back fill should be the soil that was taken out of the hole. The other 50% should be organic matter, like finely ground pine bark, compost, and peat moss, along with some sand, depending upon sand content of original soil.
We recommend using our Dr. Earth Motherland All Purpose Planting Mix, ¼ cup soil sulfur, ¼ cup 12-6-6 time release fertilizer, and the appropriate amount of “Soil Moist,” for most shrubs and trees. Dr. Earth has a number of different types of planting mix. But, in most cases, its “Motherland All Purpose Planting Mix” is ideal. It contains just the right amount of the various ingredients described above.
The purpose of adding the soil sulfur is primarily to lower the pH. But, sulfur is also an essential nutrient for all plants. The overwhelming majority of woody plants prefer an acidic soil, though the degree of acidity they prefer varies. Sulfur accomplishes this indirectly. Certain bacteria in the soil consume the sulfur. The bacteria then convert it to sulfuric acid and excrete it. Soil sulfur is a generally milder approach than other materials used for acidifying soil, like aluminum sulfate. Therefore, it is less likely to harm plants by making the soil too acidic.
Arguably, before planting, you should always get your soil tested. You can do this through the University of Tennessee extension office, through a private lab, or using a high quality home testing kit. But, all organic matter tends to revert to neutral over time, as it decays. Thus, in most cases, repeated applications of acidifying agents are necessary to keep the pH in an ideal range. To date, in many years of installing plants, I have never seen a quarter cup of soil sulfur lower the pH to such a degree that it harmed the plant. But I have seen much better results in every case when I have used it.
“Soil Moist” is a water absorbing polymer that helps keep moisture around the root ball, where it’s needed more, in the first 18 months. This is the critical establishment period for a new tree or shrub.
12-6-6 fertilizer is a time release formulation made by a number of different companies. You could arguably use more on big specimen and less on smaller specimen, but I have never gone wrong with just an average of a quarter cup. After the first year, you will likely want to increase your fertilizer, especially for trees. Ideal fertilization for the spring feeding of trees may require up to 1.5 pounds of nitrogen per thousand square feet under their canopies. But, for initial planting, just use a ¼ cup.
If, for some reason, you are absolutely against using any synthetic products, just leave the soil moist out and use a good organic fertilizer in lieu of the 12-6-6. My favorite organic fertilizer for planting is the Dr. Earth Life All Purpose Formula. It is an organic pelletized 5-5-5 formulation that produces good results. Of course, good organic fertilizers will always be more expensive sources of nutrients than a synthetic. A four pound bag of the Life All Purpose Formula will cost you more than a four pound bag of 12-6-6. Also, you’ll have to use more of the Life All Purpose Formula. You will typically apply 1/2 to 1.5 cups, depending upon the size of the plant being installed. Of course, the Life All Purpose Formula provides beneficial bacterial and mycorrhizae fungal strains not present in the synthetic 12-6-6. So, even if you are not committed to only using organics, if you can afford it, the extra cost of the Life All Purpose Formula may be worth it!
5. Firmly press the back-fill mix in around the root ball so that it slopes away from the root crown, without covering the root crown.
Firmly press the back fill mix in around the root ball. The soil should slope away from the root crown but not cover the root crown. This is to promote good drainage so that the trunk of the plant never finds itself sitting in water. Remember, though the roots of the plant need access to moisture, the trunk of the plant will not tolerate it well.
If the plant is installed too low in the ground or if it later sinks below the existing grade, then the base of the trunk may end up sitting in water a lot of the time. This may lead to rotting of the outer cambium layer of the trunk. The outer cambium layer is the location of the plant’s vascular tissue. If the vascular tissue it lost it will be impossible for moisture and nutrients to move from the roots up into the canopy of the plant. Even a slight impairment of the outer cambium tissue on one side of the plant can cause it to go into decline.
6. Water the plant in to settle the soil.
Heavily water the plant to settle the soil. Add more soil if necessary after. Though plant roots need access to oxygen in soil pores, big pockets of air can lead to exposed roots after a heavy rain. Exposed roots will quickly wither and die, leaving the plant impaired.
7. Place a 2 inch layer of mulch around the plant from the root crown to just outside the canopy of the plant.
Place a 2 inch layer of mulch around the plant from the root crown to just outside the canopy of the plant. The mulch should not be touching the root crown. We recommend pine needles.
In general, no wood ever makes it into a mulch pile because things were going well for it. So, when you use wood mulch, you bring in all the disease and pathogens that caused that plant to end up in the mulch yard. Some people claim that any pathogens cook out in the mulch pile. Yet, I have seen significant evidence that this is not true, regardless of how careful the mulch yard operator is. In contrast, pine trees naturally shed their needles regularly. Moreover, wood mulch is more likely to overwinter the spores of harmful fungi.
8. Lightly spray the mulch with water so that it will matt/knit together as it dries.
Lightly spray the mulch with water so that it will matt/knit together as it dries again. The purpose of mulch is to reduce weeds and slow the evaporation of moisture from the soil. Getting it to knit together helps achieve these goals.
9. Allow the top 1.5-2 inches of soil to dry out before watering again.
Allow the top 1.5-2 inches of soil to dry out before watering again. Alternately wetting and drying the soil keeps it aerated. Aerated soil promotes a healthy rhizosphere, inhabited by beneficial aerobic organisms. If soil remains constantly wet or constantly dry, it may become compacted. Compacted soil reduces the oxygen content, and kills off organisms that aid the plant. Compacted soil promotes anaerobic organisms that will harm the plant.
10. Keep the new plant healthy by establishing an annual fertilization regimen for meeting its nutritional needs.
Each year, most woody plants will benefit from at least a quarter cup of soil sulfur sprinkled under the canopy in late winter or early spring. Additionally, apply at least a quarter cup of 12-6-6 (or the appropriate amount of the Dr. Earth Life All Purpose Fertilizer). You should sprinkle the fertilizer under the canopy in both spring and fall. But, the spring fertilization is more important than the fall fertilization. In addition to lowering the pH, the soil sulfur will also act as a sporicide. This means that it will help to prevent the germination of the spores of harmful fungi that may have over-wintered in the soil. For the same reason, it’s a good idea to add a fresh layer of pine needles each year. This addition of pine needles should be done right after putting down soil sulfur and fertilizer.
The author, John Jennings, is Palladio’s Manager of Horticulture. John is an ISA Certified Arborist and is licensed to apply chemicals for horticultural purposes in Tennessee. John also writes the Garden Variety Column for Memphis Magazine. If you have questions or comments about this article, or any other horticulture related topic, please reach out to him by email at firstname.lastname@example.org. Most days, he can be found in or near Palladio’s horticulture building at 2231 Central Avenue, Memphis, Tennessee 38104.