Back to Irrigation
Benefits of Irrigation
Irrigated plants remain alive, green and healthy through the summer. There are certainly some species that respond poorly to irrigation and may even die from it, but the general rule is that irrigation is beneficial to growth and appearance.
California has an extended drought period, lasting five months or more, during the hottest part of the year. This is a time of acute water stress, where many plants cease growth and even go into dormancy. Although some seedlings will survive this, the vast majority will die. Until the plants can establish a healthy root system that adequately supplies the plant’s needs, they are at risk of death from drought.
This is more than just a horticultural issue. If you are making a major investment in a landscape or restoration project, you will be understandably upset if most or all of your new plants die of drought. A restoration or landscape contractor must guarantee the initial survival of the plants, so cannot tolerate this level of mortality. Irrigation is cheap insurance.
Extended Growing Period
Unirrigated native plants produce little growth after May or June. Some, like live oak (Quercus agrifolia) or madrone (Arbutus menziesii), will retain healthy green foliage, but cease adding new growth by late spring. Others, like monkeyflower (Mimulus aurantiacus) or coastal sagebrush (Artemisia californica) gradually go into senescence over the late summer and fall. They retain their foliage, but by fall it looks wilted and weather worn. Still other species, including many of the perennial grasses, will die back and go into dormancy. Irrigation keeps foliage healthy and hydrated. It can increase the amount of plant growth and/or increase the duration of the growing period.
Many drought tolerant plants respond to the summer dry season by letting their leaves dry up or by dying back althogether. This is particularly true for herbaceous perennials and grasses. Although many people want drought tolerant landscapes, most of them would be dissatisfied by the appearance. In order for a landscape to have aesthetic appeal (at least according to the present standard), we must maintain some level of hydration and vigor. Any landscape contractor knows this. People like green and lush. They become upset with a dried out appearance.
A dried out landscape can be a significant fire hazard. One way to mitigate the problem is to carefully control the amount of dead material by pruning and mowing. The more common way is to keep the landscape green and irrigated. Control of dead organic matter is absolutely necessary, but it can be labor instensive. Irrigating is a great help, and is cheap to do, once the system is installed.