For most situations, supplemental irrigation will be required at some point during the growing season. The best insurance against excessive moisture is proper bed preparation and sufficient drainage. Keep in mind that the majority of over watering problems, assuming a well-prepared site, occur from too frequent irrigations rather than too much water applied at any one time. If supplemental irrigation is in place, apply enough water at every watering to assure complete bed coverage. Also, an irrigation schedule should take into account rainfall and be adjusted appropriately to be most effective.
Plants depend on the soil for water, anchorage, and nutrients.
Frequent heavy rains in combination with poorly drained beds will reduce plant performance and increase the chances of root rot problems. On the other hand, beds with excellent drainage combined with little water holding capacity could require irrigation as frequently as every other day. Nutrient deficiencies and toxicities are common in the landscape, although they are easily avoided if proper steps are taken. Follow proper bed preparation guidelines given in Horticulture Information Leaflet No. 551 to avoid water, pH, and nutrient stress situations. Again, stress prevention and avoidance is much easier than relying on stress tolerance.