March has arrived and we are kicking off our Plant Health Care season with spring fertilization. In this blog, we will be discussing the importance of fertilizer, which trees should be fertilized, which trees don’t need fertilization, and when to fertilize.
The Difference Between Landscape and Natural Forest Trees
If you compare our landscape trees with natural forest trees, you will notice a few differences that will cause the need for fertilization. Trees in a natural forest setting have leaf litter on the forest floor that decomposes over time and adds nutrients to the soil. Our landscape trees compete with turf grass for water and nutrients and also face other environmental stressors such as compaction, pollution, and lack of protection from neighboring trees.
Which Trees Need Fertilization?
1. Newly planted trees will benefit from fertilization for a few different reasons. The added nutrients will help overcome tree planting stress, become established, and increase root growth.
2. Some stressed trees that have insect or disease problems could benefit from fertilization. Examples of good candidates are evergreens with bagworm damage or Blue Spruces with Needlecast disease, as long as damage is not too severe.
It’s good to remember that trees allocate their resources to four different areas; reproduction, growth, storage, and defense. If a tree is having to allocate more of its resources into defense due to an insect or disease attack, the tree can become stressed. Fertilization can help replenish some of the depleted nutrients.
Which Trees Should NOT Be Fertilized?
1. Most healthy, mature trees don’t need fertilization.
2. Some diseases, such as fireblight, attack new growth. Fertilization would only make the disease spread further, as it pushes out new growth.
When Do We Fertilize?
Spring fertilization begins in early March and continues to Mid-May. We don’t want to push out any new growth in the warmer months for a couple reasons: the new growth is tender and could scorch in the heat. Also, bugs are more prevalent in the warmer months and prefer to feed on new growth.
As you have read, landscape trees have to survive unfavorable conditions of competition with turf, nutrient-depleted soils, and more. If you have a tree that you believe could benefit from fertilization, give your arborist a call discuss a plan of action.