Irrigation must adapt to weather. It was unnecessary for exposed vegetation during rainy winter weather. It became necessary through drier spring weather. Now, it must adjust for increasingly warm and dry summer weather. This is not as simple as application of more water more frequently. Excessive irrigation causes soil saturation, which damages roots.

Soil saturation is unfortunately common within landscapes that gardeners maintain. The risk of desiccation is more of a concern to gardeners than wasteful irrigation. Desiccation is certainly more apparent than symptoms of saturation. Besides, gardeners assume the costs of neither water nor damaged vegetation. Chronic damage can become significant.

Soil saturation is less common within gardens that lack gardeners, but is not impossible. Soil within pots can become saturated if vigorous roots clog drainage holes. Water which lingers too long in saucers under pots maintains saturation. Irrigation that is too frequent, too generous or both maintains saturation. Of course, different soil types drain differently.

Soil saturation deprives roots of the aeration that they need to survive. A few species are somewhat tolerant of saturation, but fewer tolerate it for long. With few exceptions, newer roots avoid saturation, so disperse shallowly. For trees, this limits stability and increases their likelihood of displacing pavement. Even shrubbery might develop buttressing roots.

Roots that dispersed prior to saturation are vulnerable to rot as soil saturation increases. This not only destabilizes trees, but also compromises their health. Formerly healthy turf grass and ground cover become chlorotic. Some turf grass becomes infested with fungal pathogens, and perhaps moss. Flowers and fruits might shrivel before they develop fully.

It is impossible to prescribe ideal irrigation schedules and application rates for every site. Climate, soil type, slope, exposure and vegetation types are all considerations. Moisture requirements change seasonally and as vegetation matures. Only direct observation can help determine appropriate irrigation frequencies and rates. It is a very involved process.