There are a variety of tree fertilizers out there. Knowing which ones to use can be very confusing. And, to make matters worse, many quality tree friendly products are really “fertilizers” at all. Most of the products in the line I use for my companies treatment programs are alternative products (I don’t like the word “organic,” it is confusing to many and misleading). Here is a list of the products I think are the best:
- Fertilizers – Urea has been regarded as the best nitrogen source for trees lately. It comes in many forms, but I believe that urea-formaldehyde and methyl-based urea are the best choices. I use a product called Coron that is a methyl-based urea.
- Mycorrhizae (my-core-rize-uh) – These are fungi that grow on the existing root system of trees and then make their own root like system. The fungi then share the water and nutrients they absorb with the tree in exchange for sugars. These fungal spores are readily available to be applied to the soil. This is a great way to improve the water absorbing ability of a tree, and can be very beneficial during our hot, dry summers.
- Humates – I use a raw form of humic acid derived from leonardite. Humic acid is by-product of composting organic matter and is know to provide many, many benefits. The two most important benefits (in my opinion) are soil structure improvements and hormone balancing. We know that humic acids help break up tightly compacted soils which improves water and air penetration into the soil. Much of the hormone balancing effects are not fully understood, but I can confirm that regular use of humic acid applied both to the soil and sprayed into the canopy result in noticeably healthier trees. We use humic acid with every treatment we apply.
- Growth hormones – I’m going to keep this simple to avoid a science class article. Application of a balanced mix of growth hormones has a fantastic effect on helping foliage develop to its maximum potential and stimulating root growth. If you can find a product that has a balanced mix then go for it. But, if you don’t know what you are doing, then skip this one.
- Micro-nutrient, vitamis and enzymes – All the good stuff we need just a little of. This is like taking your vitamins. Use of these products helps both tree growth and development and improves soil health, in turn, helping the tree. A tree fertilizer / treatment program without these products is surely incomplete.
- Soil restructuring – This is a process, not a product. But, soil restructuring is one of the most powerful tools we have to help trees in extreme urban environments. The idea is to take sterile, urbanized soils and reincorporate rich organic matter back into the soil. Fundamental in garden theory, but very difficult to accomplish on the scale of a large tree.
You should have noticed in my fertilizer discussion that only nitrogen was included. There was no mention of phosphorus or potassium. It has been my experience that application of these two fertilizers don’t generally provide noticeable improvements in tree health. Due to this fact and that high phosphates cause problems with the local streams in central Texas I don’t see the point in applying these other fertilizers.