Pests in Gardens and Landscapes: Quick Tips

Landscape Plants: Fertilizing & Watering

Published   10/17

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Prevent runoff of water, pesticides, and fertilizer from your landscape. Trees and shrubs require less fertilizer and less frequent irrigation than lawns. Too much water is the most common cause of decline in landscape trees and shrubs, either through directly killing plants or making them more prone to disease. Fertilizer runoff into storm drains pollutes waterways. Maintain plant health and protect water quality by fertilizing and watering correctly.

Fertilize appropriately.

  • Many woody ornamentals such as nonflowering trees and shrubs don’t require fertilizer, even at planting.
  • Determine the actual cause of unhealthy-looking plants before fertilizing. Nutrient deficiency symptoms are often due to unhealthy roots, poor soil conditions, or improper care.
  • Fruit trees, vegetables, and flowering annual plants have variable fertilizer requirements. Follow plant care guidelines carefully.
  • If fertilizer is required, choose a slow-release type, such as organic fertilizers, that will feed the plant throughout the season.
  • Fertilizer should be applied at the drip line of trees and shrubs and not directly on the trunk or crowns. See the illustration on the back of this card.
  • Avoid overfertilizing. Too much fertilizer can result in plant damage, excessive plant growth, and additional water needs by the plant.

Water properly to promote plant health and avoid runoff.

  • Water plants during the early morning rather than during the heat of the day or in windy weather.
  • Use drip irrigation and soaker hoses to deliver water only where needed.
  • Check soil moisture before watering.
  • Use mulches on the soil surface to conserve moisture, control weeds, and maintain a uniform soil temperature.
  • Discourage root and crown diseases by watering established trees and shrubs at their drip line.

Irrigation scheduling.

  • The amount and frequency of water needed vary greatly, depending on plant species, soil conditions, and the local environment.
  • Newly planted trees and shrubs need more frequent watering for up to two growing seasons until they become well rooted. Once established, plants can be weaned to tolerate less frequent watering. Proper weaning develops deep roots and helps plants better tolerate drought.
  • Water established trees, shrubs, and ground covers deeply but infrequently. In the absence of rain, most trees and shrubs benefit from a once-a-month thorough watering.
  • Normal lawn watering isn’t a substitute for the thorough watering required by the deeper roots of trees and shrubs.

Water trees at their drip line. The drip line is the area directly below the outermost reaches of the branches.

For more information about fertilizing, watering, and other lawn care practices, refer to The UC Guide to Healthy Lawns.

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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