Fall is approaching, and it is an ideal time to plant woody ornamentals once the summer heat has subsided. Some emphasis on proper planting procedure seems appropriate. Often, when I go out to help a homeowner diagnose a shrub problem, it turns out to be the result of poor planting procedures. The most common plants with this problem are popular plants such as azaleas and junipers.
The planting hole should be dug twice as wide as the root ball and one-and-a-half times as deep. Although the hole is dug deeper than the root ball the plant should not be set too deeply in the soil. Be sure to backfill soil under the root ball so that the top of the root ball is slightly above or level with the soil. Some references recommend setting the bottom of the root ball on a slight pedestal of soil so the soil beneath the plant will not settle over time and leave the top of the root ball below ground level.
Organic soil amendments such as peat moss, top soil, and pine bark mulch may be useful to improve excessively sandy or clayey soils. However they should be evenly incorporated into the planting area and NOT added directly to the planting hole. Poor root growth and/or root rots can often result from this condition as water is held against the roots by uneven or irregular layers of soil texture.
Often when planting azaleas and other woody ornamentals (particularly in sites where there have been failures in the past) it is helpful to rinse the potting medium from the roots before planting.
Many soils in Georgia with high clay content will wick moisture away from pine bark based growing mixes where the majority of the roots are and make it difficult for the plant to obtain the water it needs.
Another common mistake is failing to break up the root ball prior to setting the plant into the hole. This practice helps the root ball to expand into the surrounding soil. Failure to break up the root ball usually causes the plant to continue to be root bound (most plants are to some degree when they are purchased in containers). The roots grow inward, upward or around the root ball without penetrating the surrounding soil.
Digging a hole just big enough for the root ball has a similar effect. Both mistakes result in a stressed plant which is more susceptible to disease and that may inexplicably die during harsh environmental conditions. Often we receive whole plants from the landscape in the clinic with the root system still in the original shape of the pot.
Creating a slightly elevated ring of soil around the plant will help water penetrate to the roots and discourage runoff. Finally a good mulch layer of bark, straw or other material around the base of the plant will keep the roots moist and prevent weeds.
Plants, of course, should be watered immediately after planting to settle soil around the roots and receive regular irrigation in the absence of rain for the next six to eight weeks so that they may become established. The best disease control is a healthy plant and getting plants off to a good start is one of the best ways to prevent disease.