GUIDE TO DETERMINING GROWTH DIFFICULTIES IN ORNAMENTALS

After the landscape or garden is installed, homeowners may encounter growth problems. Those due to poor drainage or improper planting and pH may not become evident for several years. The following is intended as a reference from which a homeowner may determine the nature of certain growth difficulties of ornamentals. These are the more common problems which should be investigated before assuming insects or diseases are the causes of poor health of ornamental shrubs.

Symptoms: shrubs stunted, weak growth, poor leaf color, limbs gradually dying, sudden death

Possible Problems:

1. Poor Soil Preparation and Nutrition
   Improper preparation of soil before planting is a major reason for unhealthy growth of shrubs planted in clay soil. Also, if basic nutrients are deficient, plants will decline after installation.
   Recommendation: Work some form of organic matter into existing soil before planting shrubs. Composted leaves, livestock manure, or pine bark mulch may be used. Determine the type and amount of fertilizer necessary by having your soil tested, at no cost, by the NC Department of Agriculture. The Cooperative Extension Service Office, (910) 484-7156, has boxes and instructions for soil testing.

2. Drought Damage
   Drought is likely to affect any shrub but the effects are more severe on plants set in poorly prepared soil. If soil is hard and crusted, water will run off and never reach the root zone. Most shrubs will need periodic watering during the first growing season after transplanting. Suspect lack of water if a recently planted shrub dies.
   Recommendation: Mulching with materials such as pine bark or pine straw will conserve moisture, and amending soils will allow water to penetrate to the root zone where it is absorbed by the plant. Water heavily every 7-10 days during dry periods rather than lightly once a day.

3. Poor Soil Drainage
   Clay soils that have not been amended with organic matter will be poorly drained. Also, plant damage will be encouraged if plants are situated near a water drainspout or in a depression. Foliage becomes pale, and leaf drop occurs throughout the year. Poor drainage will eventually lead to root rot problems.
   Recommendation: Divert drainspouts past plants. If plant is in a depressed or other poor drainage area, dig it in winter and raise the planting level by planting "high", using raised beds, or installing drainage pipes to drain the area.

4. Planting Too Deeply
   Shrubs should be planted no deeper than they grew in the nursery. Azaleas, camellias, boxwoods, rhododendrons, and dogwoods are particularly sensitive to deep planting. They should be planted 2" above the previous soil level.
   Recommendation: Check to see if plant is set deeper than it was previously grown. If so, dig plant during winter and replant higher.

5. Improper pH of Soil
   Most shrubs will grow well over a wide range of pH, from 5.5 to 7.0. Some acid-loving plants such as azaleas, camellias, and rhododendrons prefer a slightly more acid range, 5.0 to 5.5. The naturally occurring pH for the Cumberland County area is 4.5 to 5.3. Lawns prefer a pH between 5.5 to to 6.0 and vegetables prefer a pH from 6.5 to 7.5. These differences are not as slight as they may seem. A pH of 5.0 is ten times more acid than a pH of 6.0. A pH of 5 is one hundred times more acid than a pH of 7.0.
   Recommendation: If you have never added lime or had your soil tested, it may be too acidic and will cause poor plant growth. Always determine pH by having the soil tested by the NCDA. Adding acidifying fertilizers for azaleas can be overdone and can stunt growth. If the pH is too low, plants are unable to take up some nutrients that are actually present in the soil. Improper pH often results in yellowing of leaves, especially younger leaves. Be alert for construction mortar around new homes; it can raise the pH.

6. Damage to Stem
   Cold Damage: Cold injury is a common problem, especially on azaleas, but it is not readily recognized because the damage is often not evident until the hot weather of the next summer. The injury is identified by a splitting of bark, often toward the base of the plant or stem.
   Recommendation: Prune out the dead parts, cutting back to healthy wood.

   Lawn Mower or Weed Eater Damage: Suspect lawn mower or weed eater damage whenever injury occurs at the base of a tree or shrub. Injuries from these machines can result in a bruise or cut whose effects may not show up for several years. These wounds are often the entry point for insects and diseases. Be especially careful with dogwoods.
   Recommendation: Prevention is the best policy. Place stakes or some type of barrier to prevent damage. Mulches eliminate the need to mow close to tree trunks.

7. Sudden Death of Shrub
   Over-Fertilization
   Dying of tips or borders of leaves can be a symptom of too much fertilization. Injury can result within one week after a too-heavy application of fertilizer. Symptoms may be leaf drop and dying of shrubs even during the growing season
   Recommendation: Water heavily to leach out the excess fertilizer. Light, frequent watering may be needed after that until new roots form to replace the burned roots.

8. Root Rot Diseases
   There are several root rot diseases which are frequently a problem on shrubs, especially azaleas, rhododendrons, etc., in sites with poor drainage. Death of a succession of individual branches over a period of time, called "flagging", is often indicative of root rot disease.
   Recommendation:
   1. Remove diseased plant, improve drainage, and replace with a resistant species.
   2. For a high value plant or a large area of diseased materials:
      • lift plants in November/ December, remove dead roots and any soil clinging to roots,
      • improve drainage,
      • treat entire area with Subdue* fungicide according to label directions, and
      • replant or use a non-susceptible species.

   If you suspect root rot disease, you may have the plant analyzed by the Plant Disease and Insect Clinic at N.C. State University. Bring the following to the Cooperative Extension Service Office: 1) one quart of soil which includes a handful of fine feeder roots (found at drip line of plant); and 2) a 12"-15" sample of stem and foliage showing the damage to the plant (must be live tissue). Place material in separate plastic bags. Call (910) 484-7156 for additional information.

   * This fungicide is expensive but extremely effective and can be purchased from companies specializing in horticultural chemicals.