This well fed, healthy Lace leaf Japanese maple (Acer palmatum dissectum) is from our Pocket Bonsai Gallery. It originally appeared on the cover of Bonsai Today# 84.
N-P-K (Macro nutrients)
You will see three numbers on all fertilizer packages—for example 7-9-5 or 15-30-15. These numbers represent the strength and ratios of the three major nutrients (also called macro nutrients) in fertilizers. The three nutrients are nitrogen (N), phosphorus (P), and potassium or potash (K). They are critical to any plant’s health. Here’s a more complete explanation.
The NPK on this Dyna-Gro liquid is 7-9-5. The ratio is: 7 parts nitrogen, 9 parts phosphorous, and 5 parts potassium.
Strength and Ratio
Strength is an element’s percentage of the total weight of the fertilizer. Ratio is the relative amounts of each element. A fertilizer with an NPK of 10-10-10 is twice as strong as one with an NPK of 5-5-5, but the ratios of both are the same. You can reduce the strength of a liquid fertilizer by increasing the amount of water in the solution. However, the ratio will remain the same.
Balanced N-P-K for bonsai
There is no perfect N-P-K for all bonsai varieties in all situations. However, if you want to be safe, use a fertilizer with a fairly balanced N-P-K. One that we like is Green Dream organic pellets, which has an N-P-K of 6-6-6. When it comes to liquids, we use Dyna-gro 7-9-5. These are only examples; ones that we use and sell. There are numerous other fertilizers that work quite well.
The label on this Dyna-Gro Bloom fertilizer shows an NPK of 3-12-6. Low nitrogen (3), high phosphorous (12), with an in between amount of potassium (6). This type of ratio is used to encourage flowering and fruiting. It is also sometimes used as a late summer fertilizer for non-flowering plants, as you want to promote root, trunk and branch development (phosphorous and potassium), and you don’t want to promote leafy growth (nitrogen) late in the season.
Unbalanced fertilizers
You will sometimes see fertilizers with unbalanced—and often high—N-P-Ks like 0-10-10, or 30-10-10. Some people use these for specific purposes, but plenty of successful bonsai growers never use unbalanced or high N-P-K fertilizers. If you do want to give them a try, you need to know what you’re doing. Stay posted.
There’s much more to say about NPK and fertilizing in general, so stay posted.