By Donnie Dabbs, General Mgr.
Fertilizing typical and drought-tolerant trees in the landscape requires a knack for applying in the right season, proper administration and for using the best product for the tree. Fertilizer is often misunderstood and misused. Fertilizer is not really direct food for trees, but instead, a boost to your trees providing the ingredients needed for photosynthesis and growth. Fertilizer should not only be used when minerals are lacking or absent in the soil but also to maintain a good chemical balance within the soil all year long. Your top ten, typical choice of standard trees for most landscapes range from King and Queen palms to Agonis, Magnolia and Lagerstromia varieties. Drought-tolerant trees can be fertilized much in the same way. These trees should be fertilized on a regular schedule, depending on the geography and status of the tree. Trees in areas that receive a lot of rain usually have a lot of natural nutrients in the soil and only require about one to two times a year of fertilizer application. However, in more arid areas, like the Southwest, you should fertilize up to three times a year to produce more nutrients in the soil and to keep the plant healthy in each season. The best times for fertilizing is in early spring, mid-year and in the fall. The early spring is a good time because tree roots are coming out of the dormant period and require a boost to be healthy as they are starting to grow. Mid-year is also important because trees are experiencing more heat, absorbing water faster because of the heat and therefore going through nutrients quicker. To put in fertilizer during this time gives the tree a boost and replenishes those nutrients lost. During the Fall, tree roots have cooled a bit but there isn’t as much rainfall as during winter months. Avoid fertilizing trees and shrubs stressed by drought during the summer months. If water is unavailable, do not fertilize at all because plants will be unable to absorb the nutrients.
“Typical mistakes most commonly made during fertilizing is over fertilizing,” said Don Dabbs of Briggs Tree Company (a wholesale, grower-direct nursery in Southern California), “Using the wrong chemical balance for the tree is also a mistake commonly made.”
Fertilizers are divided between the chemicals nitrogen, potassium and phosphorus. Nitrogen is for greening the tree, adding more foliage and nurturing the leaves. Potassium is applied to prevent diseases and helps with producing more, healthier flowering. Phosphorus boosts the root system and also helps with flowering. A Triple 15 fertilizer has 15 parts nitrogen, 15 parts potassium and 15 parts phosphorus. This combination of chemicals are perfect for trees, as you don’t want to use too much of one of these chemicals. For instance, if you use too much nitrogen, the tree will burn. The other mistake is to over fertilize. Use the amount that is specified on the bag and don’t apply more or less than this specification. Avoid adding too much fertilizer which can harm the tree and the environment. Excessive fertilizer produces rank, weak growth that breaks easily and is susceptible to injury from cold, drought and pests. Also, fertilizer not absorbed by the plant roots may contaminate groundwater and surface water. Again- too much chemical is not good for any one tree. There are different forms of fertilizer that contain a balance of the correct chemicals. One form is fertilizer in granular form. When planting a new tree, put this fertilizer in the ground just under the root ball. For trees already planted or established, spread fertilizer on top of the plant and water generously so the fertilizer seeps into the soil. Since most of a tree’s roots can be found in the top foot of soil, broadcast the fertilizer evenly with a rotary or drop-type spreader over the root zone area to fertilize the tree. For new trees, try using new fertilizer tabs that slowly release fertilizer and penetrate into the tree over a period of time. These tabs should be used in the ground planted near the root ball and never used on top of the soil as this will waste fertilizer. Systemic liquid, spray-on fertilizers seeps into the tree leaves, limbs and bark and is absorbed into the root system. Just remember- the best practice is to use a balanced amount of chemicals.
When fertilizing trees, keep these two points in mind: (1) Fertilizer is beneficial when it is needed; but (2) Use it in the right amount, at the right time and in the right place.
For over thirty five years, Briggs Tree Company has operated as a wholesale nursery, having expanded to over 200 acres in production. Founded by Donald A. Briggs, Jr. in the early 1970’s, Briggs is still family owned and operated supplying:
- 4-inch annual and perennial color
- water-efficient plants
- ..and a premier line of trees in various sizes
Briggs prides themselves in employing knowledgeable and experienced staff who will answer any questions regarding plant material. Briggs Tree Company, Inc. Corporate Headquarters is located at 1111 Poinsettia Avenue, Vista, CA 92081 Please call 760-727-2727, or visit us online at www.briggstree.com for more information.