Garden Irrigation – How Often Do You Need To Water?
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By Jonathan Yaakobi
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Regular watering is an integral part of successful gardening in any region that has long, hot dry summers, such as in Southern California, the Middle East, or South West Australia. Regular watering should not entail opening the taps every day or so, or whenever the plants look tired and dry. There is neither the water available for that, nor is it usually best for the garden plants. An appropriate irrigation regime involves understanding the importance of maintaining a proper balance in the soil between air on the one hand, and moisture on the other. With insufficient water, the plant withers and dies, while with insufficient air available in the soil, the roots cannot breathe. In principle, “how often should I water?” is a question of correctly applying that understanding.
Assuming that the soil has adequate drainage, the next most significant factor is the frequency by which water is applied. Light, sandy soils drain excellently, but retain water poorly. It follows that the intervals between each watering have to be relatively short. Conversely, heavy, clay soils possess good water retention properties but drain slowly. As the greater the length of time that the soil is saturated with water, the less air is available to the plants’ roots, watering intervals should be relatively wide. As we shall see with some of the following examples, it is often best to make those intervals as long as possible.
Plants that grow naturally in arid regions are often or not particularly sensitive to low oxygen percentages in the soil. Situations where the top soil layers are permanently moist are liable to cause roots to rot, or at the least, not to develop properly. Many fine ornamental trees and shrubs, such as Melaleuca, Eucalyptus, Callistemon, Leucophyllum , Olive and Cypress, belong to this category. In clay soils, watering once a month (sometimes less frequently) through the summer, is often sufficient for established plants, providing that enough water is applied so that it reaches down to at least 50 cm, (1.5 feet) preferably I meter. Frequent but deep soakings also play the crucial role of leaching excessive salts from the soil.
Most lawn varieties grown in hot, dry, summer climates are heat resistant species. They are not drought resistant however, and of course require regular irrigation. In heavy soils, the interval for established lawns can be over 2 weeks, although 1 week to 10 ten days is preferable for private gardens. The interval for sandy soils can be between 3-5 days. Delaying the watering involves virtually no risk to the mature, healthy lawn. On the contrary, not only does the gap allow air to be present in the soil, but it encourages the deep-rooting species like Bermuda grass, to grow into the sub soil. Such lawn types recover quickly from small doses of drought stress.
Herbal plants are with some exceptions largely of Mediterranean origin or grow naturally in similar habitats. Oregano, Sage, Artemisia, Rosemary and Lavender, to name but a few, all respond well to properly – drained soil, and suffer from boggy, anaerobic conditions. As they do not need be watered as deeply as trees and shrubs, the intervals should be correspondingly shortened.
Herbaceous flowers, whether annual or perennial, have to be watered very frequently on the other hand. In very light soils, those with very small percentages of clay, watering might have to be as often as once a day, whereas in very heavy soils, it may be possible to stretch it out to 3-5 days between each watering.
You may well ask - “What should I do if my flowers are mixed up with the trees and shrubs?” The short answer is that you have to water according to the needs of that plant group that require water most urgently. The more involved answer though is that it is impossible to irrigate intelligently, if different plant groups with entirely different watering needs, are planted together and watered from the same irrigation line.
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Author Bio Box: Jonathan Yaakobi
 My name is Jonathan Ya'akobi.
I've been gardening in a professional capacity since 1984.
I am the former head gardener of the Jerusalem Botanical Garden, but now concentrate on building gardens for private home owners.
I also teach horticulture to students on training courses.
I'd love to help you get the very best from your garden,
so you're welcome to visit me on http://www.dryclimategardening.com or contact me
jonathan@dryclimategardening.com
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