Trees need fertilizer, just like you need food and water.
Fertilization equates to nutrients, and trees are living beings. If the natural soil where your trees or shrubs are planted is lacking these nutrients, your trees may fail to thrive — or even die. Malnutrition in trees prevents them from growing to their full height and makes them more vulnerable to insects and diseases.
Trees need two major types of nutrients: macronutrients and micronutrients.
Macronutrients include nitrogen, potassium, magnesium, sulfur, phosphorous and calcium. Nitrogen is especially important because it’s needed for growth and it is easily depleted from soil. Micronutrients include iron, copper, molybdenum, zinc, manganese, chlorine and boron.
You usually can tell if your trees have iron deficiency (the most common), because their leaves turn yellow. Most micronutrients are needed only in traces for most trees, and in many cases the soil already has enough.
When shopping for fertilizers, you’ll see that all labels are clearly marked, indicating the amount of nutrients provided per 100 pounds. You can choose organic or inorganic fertilizer options. Usually, inorganic options are soluble and get the nutrients to your tree faster; organic options take a while to be released.
Blend organic and inorganic fertilizers to get the best of both worlds. Keep in mind that some inorganic fertilizers have a coating to slow nutrient release, making them act more like organic fertilizers.
If you have trees in an urban/suburban area, they can get stressed just like you, but these environmental stressors can be reduced with fertilizers. If you have a new tree, pull any weeds that grow around it and keep it pruned and watered.
If you really want to know for certain if a fertilizer is necessary, a soil test can tell you. Take a sample if you can before planting, and repeat the test every four years. Or look at shoot growth — if your tree sprouts new shoots of at least 6 inches per year, no fertilization is necessary.
Playing it Safe
You (or a professional) can tell a lot by leaf color, too. Yellow leaves usually are asking for attention, but that can be tough to gauge in the autumn!
Also consider the history of the property. If trees are in a place that has been regularly fertilized, you may not need to continue. Soil can and does change over time, and what was necessary a few years ago might not be required now. However, nothing trumps the expertise that only an arborist can offer.
To find out if your trees need fertilizer, or for a complete inspection of your property’s trees and shrubs, call Reliable Tree Care. We’re available for tree and shrub fertilization, inspections, trimming and pruning year-round, and boast a crew of professionals with years of experience.