Planting Trees and Shrubs

Planting trees and Shrubs is a challenging task. We found an interesting article about it in the book called “TREE AND SHRUB  GARDENING  FOR NORTHERN CALIFORNIA” by “Bob Tanem” and “Don Williamson”, Here is an excerpt of the article.

Before you pick up a shovel and start digging, step back for a moment and make sure the site you’re considering is appropriate.  The most important thing to check is the location of any underground wires or pipes.  Even if you don’t damage anything by digging, the tree roots may cause trouble in the future, or if there is a problem with the pipes or wires you may have to cut down the tree in order to service them.  Most utility companies will, at no charge, come to your house and locate any underground lines.  Prevent injury and save time and money by locating utilities before you dig.

     Check also the mature plant size.  The plant you have in front of you is probably pretty small.  Once it reaches its mature height and spread, will it still fit in the space you have chosen? Is it far enough away from the house, the driveway and the sidewalk? Will it hit the overhang of the house? Are there any overhead power lines? If you are planting several shrubs, make sure they won’t grow too close together once they are mature.  The rule of thumb for spacing: add the mature spreads together and divide by two.  For example, when planting a shrub with an expected spread of 4’ and another with an expected spread of 6’, you would plant them 5’ apart.  For hedges and windbreaks, the spacing should be one-half to two-thirds the spread of the mature plant to ensure there is no observable space between plants when they are fully grown.

WHEN TO PLANT

     For the most part, trees and shrubs can be planted any time of year, though some seasons are better for the plants and more convenient than others.  Fall is the best time to plant trees and shrubs in Northern California.  The root system continues to grow in through winter and will be more established before the heat of summer.  Bare-root stock must be planted in winter because it is available only at that time, and it must be planted as soon as possible to avoid moisture loss.  B & B is only available in winter, from December to February.  If the plant comes in a heavy soil, we recommend that this soil be washed off before planting, especially for such plants rhododendrons and Japanese maples.  Container stock can be planted at any time of year, with the exception of frost-sensitive plants, such as cape plumbago and princess flower, which are typically planted in the spring after all danger of frost has passed.

    Many gardeners avoid planting during the hottest and driest part of summer, mainly because of the extra work that may be involved with supplemental watering.  Because irrigation is a way of life here, avoiding summer may not be an issue.  Not many gardeners enjoy planting in the winter rains.  In our colder winter regions in the northeast and east, planting in spring is recommended because it gives the plants a chance to become established before the next winter sets in.  

     The time of day to plant is also a consideration.  Avoid planting during the heat of the day.  Planting in the morning, in the evening or on cloudy days will be easier on both you and the plant.  It is a good idea to plant as soon as possible after you bring your specimen home.  If you have to store the tree or shrub for a short time before planting, keep it out of the direct sun and ensure the rootball remains moist.  Keep in mind that most nurseries water their plants every other day, (every day for 4” pots).

PREPARING THE HOLE

     Trees and shrubs should always be planted at the depth at which they were growing- just above the roots if you are unsure what the depth was for bare-root stock.  You should notice a different color at the base of the trunk noting the soil line in the field.  The depth in the center of the hole should be equal to the depth of the rootball or container, whereas the depth around the edges of the hole should be twice the depth of the rootball or container.  Making the center higher will prevent the plant from sinking as the soil settles and will encourage excess water to drain away from the plant.

     Be sure that the plants are not set too deep, particularly in a moist climate, because roots can’t breath properly and the bark and crown are likely to rot if they are even a few inches too deep.  Most potted field-grown trees are planted too deep in the pot to help keep the freshly dug tree from tipping over, and there may be mulch on top of the soil as well.  Planting such a tree to the same depth as the level in the pot is not a good idea.  Scrape off the soil until you find the root mass, and then plant so that the top of the root mass is slightly above soil level.

     The diameter of the hole for balled-and-burlapped and container stock should be two to three times the width of the rootball or container.  It is also a good idea to loosen the top layer of soil around the edges of the hole with a garden fork or similar tool.  In heavy clay soils or serpentine, you may have to enlarge the initial excavation.

     The soil in the rootball or container is not likely to be the same as the soil you just removed from the hole.  In such cases, you will have to create a transition zone from the rootball soil to the undisturbed soil by adding compost and/or planting mix to the backfill soil.  Heavy clay soils can be mixed half-and half with compost and/or planting mix.  Light sandy soils can have up to one-third compost and/or planting mix added.  If the soil of the rootball is the same as the soil you just dug up, then no soil amendment is necessary.

     When the plant roots grow into the amended backfill soil, they are generally introduced to and can acclimatize to the existing, on-site soil.  The roots then have no problem growing into the undisturbed soil.  What you don’t want is to have two different soil types in direct contact with each other, which creates an interface that water and roots have difficulty penetrating.  It is also good practice to roughen up the sides and bottom of the hole to aid in root transition.  The organic matter in the amended backfill soil that is adjacent to the existing soil will leach into the existing soil, which allows for further root development beyond the hole.  Earthworms will also transport organic matter into the existing soil.

      If the roots do not venture beyond the immediate area of the hole, the tree or shrub will be weaker and more susceptible to problems, and the encircling roots could eventually choke the plant.  A tree will also be more vulnerable to blow-down in a strong wind.  Do not back-fill with straight planting mix either, which also creates a soil interface.

PLANTING BALLED- AND-BURLAPPED STOCK

     Burlap was originally made of natural fibres.  It could be left wrapped around the rootball and would eventually decompose.  Modern burlap may or may not be made of natural fibers, and it can be very difficult to tell the difference.  Synthetic fibers will not decompose and will eventually choke the roots.  To be sure your new plant has a healthy future, it is always best to remove the burlap from around the rootball.  If there is a wire basket holding the burlap in place, it should be removed as well.  Strong wire cutters may be needed to get the basket off.

     With the basket removed, sit the still-burlapped plant on the center mound in the hole.  Lean the plant to one side and roll the burlap down to the ground.  When you lean the plant in the opposite direction, you should be able to pull the burlap out from under the roots.  If you know the burlap is natural and decide to leave it in place, be sure to cut back the top so none of it shows above ground level.  Exposed burlap can wick moisture out of the soil and prevent your new plant from getting enough water.

     If possible, plants should be oriented so that they face the same direction that they have always grown in.  Don’t worry if you aren’t sure-the plant will just take a little longer to get established.  As a general rule, the leafiest side was probably facing south.

     Past horticultural wisdom suggested removing some of top branches when planting to make up for the roots lost when the plant was dug out of the field.  The theory was that the roots could not provide enough water to the leaves, so top growth should be removed to achieve ‘balance.’  We now know that top growth- where photosynthesis occurs and thus where energy is produced-is necessary for root development.  The new tree or shrub might drop some leaves, but don’t be alarmed; the plant is doing its own balancing.  A very light pruning will not adversely affect the plant, but remove only those branches that have been damaged during transportation and planting.  Leave the new plant to settle in for a year or two before you start any formative pruning.

PLANTING CONTAINER STOCK

     Containers are usually made of plastic or pressed fiber.  All types of containers appear to be made of peat moss, they do not decompose well.  The roots will be unable to penetrate the pot sides, and the fiber will wick moisture away from the roots.

     Container stock is very easy to plant.  Gently remove or cut off the container and observe the root mass to see if the plant is root bound.  If roots are circling around the inside of the container, they should be loosened or sliced.  Any large roots encircling the soil or growing into the center of the root mass instead of outward should be removed before planting.  A sharp pair of hand pruners or a pocketknife will work well for this task.

 Place the plant on the central mound.  Orientation is less important with container-grown stock than with balled-and –burlapped stock because container plants have been moved around during their development.

Read more about Tree Transplanting here.