Understanding Fertilizer Spike Numbers

Did you know that fertilizer spikes for your trees have a generalized rating system that helps you understand how much of certain nutrients are in them?

Tree and plant spikes are rated with three consecutive numbers. The numbers look like X-X-X which translates to N-P-K. What does that technically mean?

Nitrogen (N) – Phosphorus (P) – Potassium (K)

The numbers are in that order and represent percentages. So when we’re looking at a fertilizer that has a labeling of 20-25-10 it would mean 20% nitrogen, 25% phosphorus and 10% potassium. The missing percentages to make 100% are miscellaneous elements that help growth. These include iron, boron and more (source.)

Pretty simple.

For different kinds of plants or trees, you’ll want the formula to have higher or lower numbers on the NPK system. Different numbers encourage different or better growth depending on what you’re trying to grow. From this handy howstuffworks article:


“A fertilizer labeled 30-20-20 would be good for leaf development and would be most recommended for foliage house plants, while flowering house plants would prefer one richer in phosphorus, such as 15-30-15. Most foliage house plants get along fine with an all-purpose or high-nitrogen fertilizer, while one with a high proportion of phosphorus is best for flowering house plants.”

The next time you shop for fertilizer for your trees and plants, you are going to be an informed customer! Think about what you need to fertilize and what type of tree or plant would do best with in regards to NPK.

So why might you go with a professional tree service to come in and inject fertilizer as opposed to using the over-the-counter tree spikes that are available at your local home service store? The answer is pretty simple – any good tree company will have a unique blend of fertilizer that is specialized for your area and your unique needs.

A one-size-fits-all approach isn’t the worst thing in the world when it comes to fertilizer but for those that truly love their trees and want to see some major growth, an Austin tree service company is the way to go.

At Brents Tree Service, our unique fertilizer blend is just right for your Texas tree. We also inject it directly into your tree’s roots so the accuracy is far greater than it is with sinking spikes near your roots.

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