Thursday, July 28, 2005





A recent economic study by the University of Florida and the University of Tennessse shows that the green industry is one of the fastest-growing segments of U.S. ag., and is among the nation's fastest-growing businesses overall.

The green industry generates $147.8 billion in output or sales, 1.9 million jobs, $64.3 billion in labor income and $6.9 billion in indirect business taxes. Wholesale and retail trade sectors contributed almost a third of the $95.1 billion in value-added impacts cited by the study, which represent the value of output less the value of purchased inputs used in the production of goods and services for final consumption.


St. Louis Tree and Shrub Drought Damage and Care

The St. Louis area has just suffered the third driest spring in recorded history. What effects will occur with additional drought and extremely warm weather? We are already noticing symptoms of drought stress on many woody plants in landscapes, and forests throughout Missouri. These past few days of rain and cooler weather significantly helps, but we still need to be concerned about the after-effects of the record breaking drought.

An often asked question at the garden center is "Should I plant new trees or shrubs? or Should I fertilize my lawn and plants? or What can I do to prevent damage to my plants"?

The answers to these questions are simple. Plant correctly and consciously water your newly planted landscape and you’ll do fine. Refer to the Greenscape Gardens planting guide

Drought is a meteorological and environmental event. The absence of rainfall for a period of time will cause the depletion of soil moisture and damage to plants. Drought is a normal, recurring feature of our climate; it can result in significant problems with plant health.
To understand the impact of drought on woody plants, it is helpful to understand the water needs and relations in the plant. Without water, there is no plant life. Water is necessary for nearly all biological and biochemical processes within plant cells. Water is also necessary for uptake and transport of nutrients. Transpiration is the primary mechanism driving the movement of water from the soil, to the roots, to the xylem, to the leaves, and to the air.

The primary physical effects of drought are damage and death of the roots. The feeder roots and root hairs are the most important part of the root system for uptake of water and nutrients from the soil. Unfortunately, they are also particularly sensitive to drying out and are the first portion of the root system to be affected by drought. It is important to understand that 99% of the root system of a woody plant is located in the top three feet of the soil, and a good portion of functional root system (non-woody feeder roots and root hairs) is in the top 12 inches. When feeder roots and root hairs dry, shrivel, and become non-functional, a water deficit develops in the plant because these roots can no longer provide sufficient water to the top of the plant.

In addition to direct damage to the roots, a significant secondary effect of drought is that it weakens plants and predisposes them to secondary, opportunistic pests. These include diseases such as cankers, vascular wilts, and root rots. Many drought-stressed plants also show increased sensitivity to de-icing salts, air pollutants, and pesticides.

Drought also has important physiological effects on plants. Drought triggers many changes in the metabolism which can substantially alter the physiology of a plant. These changes include levels and types of hormones produced by the plant and alterations of basic processes such as photosynthesis.

Symptoms of drought are quite variable and are manifest in many different ways depending on the plant species and the severity of the water deficit. However, it is generally agreed that the symptoms of drought are often not evident in the tree or shrub until sometime after the event has occurred-- even as much as one or two years later! This can make diagnosis very difficult. As a consequence of this delay in symptom expression, symptoms of drought stress can be seen now, will continue to develop as this season progresses, and will be also be evident next year. Symptoms include loss of vigor in needles and leaves, drooping, wilting, yellowing, premature leaf or needle drop, bark cracks, and twig and branch dieback. Leaves on deciduous trees often develop a marginal scorch, whereas needles on evergreens turn brown at the tips. Trees and shrubs can also exhibit general thinning of the canopy, poor growth, and stunting. In extreme cases, drought can result in plant death.

Since we can’t control the weather and there is no cure for this problem, there are some steps that we can take to cope with drought and minimize its impact on plants.

1. Watering:

At Greenscape Gardens we water daily to maintain the plants vigor. Most plants, including trees and shrubs, require approximately one inch of water per week. For most soil types, water is best applied at one time as a slow, deep soaking of the entire root zone to a depth of approximately 8-10 inches. The length of time required to "deep-water" will vary depending on soil type and water pressure. If possible, it is helpful to use efficient systems for delivering water such as soaker hoses, directed sprays at the roots, and trickle irrigation.

Overhead watering isn’t very efficient since substantial amounts of water are lost by evaporation and it can promote disease problems. However, if it is necessary to use overhead irrigation, watering early in the day (early morning) helps to limit some unnecessary losses and minimize the risk of disease. New transplants will need special attention, especially during the first 2 years after planting.

2. Selecting the Plant and the Site:

It is important to match the needs of the plant with what the site has to offer as closely as possible since this helps to maximize the vigor of the plant from the time of planting. The old axiom "the right plant for the right site" is especially pertinent in periods of drought. Factors for consideration include the amount space for root development, amount of light, hardiness zone, drainage, exposure, and soil texture and pH. Select drought-tolerant plants, if possible. Correct choices at the time of planting can greatly reduce the need for supplementary water during the life of the plant. For example, if you know you have a very dry, sandy soil, avoid planting drought-sensitive species such as dogwood, hemlock, some oaks, ash, or birch and select more drought-tolerant species such as most pines, many Prunus or junipers. Avoid very dry sites with thin soil profiles or highly exposed sites where water loss from wind and sun can exacerbate a drought situation.

3. Planting Methods:

Use the correct spacing for each type of plant. Avoid crowding since crowded plants just don’t grow well and crowding also increases competition for available water.

Digging and preparing the planting hole:
The old saying "dig the $10 hole for the 50 cent plant" certainly rings true, especially during drought. The "old method" for planting called for digging the hole substantially deeper but no wider than the rootball. It also called for the addition of many amendments to the soil. This method has been replaced by a "new method" based on what we now know about the way roots grow. This new method is applicable for both woody and herbaceous plants. With this method, the planting hole is dug 2 times wider but no deeper than the the rootball to be planted. In most cases, the soil dug from the planting hole is used to backfill the hole. Additional organic matter can be added/blended to help with soil moisture retention. Refer to improving the soil.

This method eliminates settling over time (especially for large trees and shrubs), promotes faster root growth into the planting site since the soil is receptive to lateral root growth, and it minimizes the transitions between soil types as the roots grow from the rootball, into the planting hole, and into the planting site.

Whether you’re planting woody or herbaceous material, proper preparation of the rootball is critical to plant growth. Preparing the rootball is unfortunately often overlooked but it is particularly important during periods of drought. The rootball must be wet but not overly saturated. With container-grown woody and herbaceous plants, the rootball should be moist but not wet at the time of planting. It should also be scored, cut, and teased apart before planting. This is especially important if the root mass is very tight and dense. Refer to Greenscape Gardens planting guide.

4. Mulching:

Properly applied mulches help with soil moisture retention and have the added advantages of weed control and soil temperature moderation. Organic mulches include materials such as shredded bark, and wood chips. The soil should be moist when you apply the mulch—if it is dry, you should water before putting down the mulch. In order to be effective, mulches need to be applied correctly. Mulches that are applied too thick or too close to the base of the plant ("Perryville pyramids") can be harmful. Improperly applied mulches cause many problems: when applied too thickly, the mulch impedes water penetration and smothers the roots. When applied too close to the stem, the mulch creates conditions favorable for the development of stem and crown rots. The rule of thumb for mulching: mulches should be applied approximately 1 inch from the base of herbaceous plants and 6-12 inches from the base of woody plants.

5. Maintaining plant vigor by using sound cultural practices:

It is generally accepted that woody plants under stress should not be fertilized. However, applications of biostimulants, mycorrhizae, or similar compounds (Superthrive) can be beneficial and can help to stimulate root growth and regeneration. Maintain the health of the plants by removing any dead, damaged, or dying branches—this will help minimize problems with secondary invaders and opportunistic pests.


Although the drought has certainly affected many woody plants throughout St. Louis, it is important to realize that there are steps we can take to minimize its long-term impact on plant health.

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