Fertilizer On Hydrangeas

Question

Bad advice on putting fertilizer on hydrangeas in Spring. A fertilizer like 10-10-10 encourages leaf and plant growth at the cost of blooms! Use aluminum sulfate of similar low power fertilizer for hydrangeas. I learned this the hard way. You should revise the 5 steps advice for growing hydrangeas. Thanks, we need to know we can depend on your advice.

Answer 1

This is not true for every situation. They are picky bloomers. Aluminum sulfate is usually only used to adjust pH and influencing the bloom color. In most cases, this is not a preferred way to lower the pH since it stays around in soil for a very long time, and becomes toxic. Sometimes this goes to the point of halting all growth, though is takes quite a long time.

I would say that the pH of the soil was not where it should have been, or that there was an excess of unavailable nitrogen and bound up phosphorus. Another thing to consider about phosphorus interaction with aluminum sulfate would be that, eventually, it binds out phosphorus. This makes it unavailable.

Every situation is different, so it is best to always test your soil before doing anything to it. This will tell you exactly what the soil needs or doesn't need.

Your local extension service can help with more accurate results than home tests.

https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm