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Drought stress on magnolia (Magnolia) |
The water needs of different plants vary greatly. Some factors to consider include the species and age of the plant, the type of soil in which it is planted, and its exposure. The symptoms of drought stress may be similar to the symptoms of over watering or even to some pest and disease problems. It is important to identify the causes of the problem in order to take corrective steps.
Symptoms and Diagnosis
With mild water deficiency, plants are usually slow growing and stunted. Some plant leaves turn from shiny to dull at first signs of stress. Grasses, which are the first to show the loss of water in the landscape, will show signs of wilt. Footprints in wilted grass persist instead of disappearing as grass blades spring upright.
Under long term water stress, plants might permanently wilt or stop growing; they may have diminished crops and discolored leaves, flower buds and flowers. Plants may eventually die. Bare spots will appear in ground covers. Water-stressed plantings may show the effects of weeds, insect pests, and diseases.
Drought symptoms can be very confusing, and can vary with different types of plants. Woody plants under drought stress can have many symptoms including yellowing, wilting leaves that develop early fall color and burning or scorching on edges of leaves. Plants may drop some or all of their leaves and appear dead.
Most established woody plants recover when watered. Plants that appear to be dead, having dropped all or most of their leaves, might recover when watered. Scrape the outer layer of a twig or the bark to see if a green layer exists indicating it is still alive. Do not remove this plant the first season. Wait until the following year to see if it recovers.
Integrated Pest Management Strategies
1. Water well. Deep watering encourages roots to go deep down in the soil to where it is moist and a lot cooler. Water less frequently but for longer periods, so water reaches deep into soil. Good thorough watering promotes healthier plants.
2. Investigate using water conserving drip emitters or soaker hoses on a timer. Adjust watering frequency and amounts based on season, temperature and amount of rainfall. Overhead watering uses more water and can promote fungal disease.
3. Add mulch to individual plants or beds. Add organic matter such as compost or rotted manure to plantings ---drought becomes less of a problem as soils with high humus levels hold more moisture. Take care to keep mulch away from stems.
4. Plant selection. Use appropriate plants, which catalogs and plant tags often marked as drought tolerant or resistant. Also consider native plants, which generally adapt better, have lower water demands and fewer pest problems.
5. Water only when necessary, based on condition of the plant. Most plants will normally wilt in hot sun, and then recover when watered. Also, a dry surface is not always a sign of water need. The surface generally dries out first and is not a true indicator of what is going on down deep near the plant root. Make use of a hand trowel or soil probe to check for moisture.
6. Give priority to watering newly planted trees and shrubs during periods of drought. Young plants have not had sufficient time to establish deep root systems, and depend on surface water for survival. Do not let the root balls of newly planted trees and shrubs dry out completely or become too saturated. Before watering use a soil probe or a hand trowel. Inspect plants several times a week during drought conditions.
Organic Strategies
All of the recommended IPM strategies are strictly organic approaches.
More images:
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| Dogwood (Cornus) wilting, probably from water stress combine with a full sun location; dogwoods are understory trees |
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| Dogwood (Cornus) wilting, probably from water stress combine with a full sun location; dogwoods are understory trees |
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| Dogwood (Cornus) wilting, probably from water stress combine with a full sun location; dogwoods are understory trees |
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| Scorched leaves on dogwood (Cornus) caused by drought stress |
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| Curled leaves on redbud (Cercis) caused by drought stress |
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| Stressed and dead lawn grass from excessive heat and drought |
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Is it dead or just dormant? Cool-season grasses, such as, fescue, often go dormant under the stress of summer heat and drought.
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Is it dead or just dormant? Cool-season grasses, such as, fescue, often go dormant under the stress of summer heat and drought, but will resprout when conditions change.
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In a lawn of mixed grasses some are less heat tolerant resulting in patches of dead or thinning grass
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Fescue (Festuca) lawn grass growing on a dry slope
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Even heat and drought tolerant plants, such as, zoysia grass, were vulnerable to the extreme heat and drought of the summer of 2012
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Dead areas in a zoysia grass lawn probably due to a combination of the extreme heat and drought in the summer of 2012
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Dead areas in a zoysia grass lawn probably due to a combination of the extreme heat and drought in the summer of 2012; areas next to hard-scaping were particularly vulnerable.
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Evergreens damaged by a combination of the extreme heat and drought in the summer of 2012
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| Even drought tolerant plants, such as, yews (Taxus) & barberries (Berberis), required extra water during the extreme heat & drought of the summer of 2012. |
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Squash plants wilting from drought. G. Holmes, Cal Poly, Bugwood.org
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Severe drought on Norway spruce (Picea)
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Severe drought on yew (Taxus)
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