Landscape Plants: Fertilizing & Watering

Prevent runoff of water, pesticides, and fertilizer from your landscape. Trees and shrubs don’t need as much fertilizer or water as lawns. Overwatering is the most common cause of decline in landscape trees and shrubs, either through directly killing plants or making them more likely to be diseased. Fertilizer runoff into storm drains pollutes waterways. Keep plants healthy and protect water quality by fertilizing and watering correctly.

How do you fertilize correctly?

• Many woody ornamentals such as nonflowering trees and shrubs don’t need fertilizer, even at planting.
• Figure out why plants look unhealthy 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 different 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.
• Don’t overfertilize. Too much fertilizer can damage plants.

How do you water correctly?

• 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 where it’s needed.
• Check soil moisture before watering.
• Use mulches on the soil surface to conserve moisture, control weeds, and keep 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 to be watered more often 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 and wind.
• Water established trees, shrubs, and ground covers deeply but infrequently. Most trees and shrubs can use a once-a-month thorough watering. when it’s not raining.
• Adjust irrigation schedules during rainy periods to conserve water and prevent diseases.
• Normal lawn watering isn’t a substitute for the thorough watering required by the deeper roots of trees and shrubs.

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