Feeding Flowering Shrubs

I have a couple emails here. Dottie in North Canton, wants to know, “how often should I fertilize my flowering shrubs, Rose of Sharon, Hydrangeas, Azaleas, with triple superphosphate? I did them once about three weeks ago.”

With triple superphosphate, phosphorus breaks down slowly in the soil, not like nitrogen. Nitrogen goes away very quickly most of the time, depending on whether it is a coated nitrogen or not. But triple superphosphate, generally, you can do it as often as every 30 days on your really big blooming plants like Hydrangeas.

But Azaleas that only bloom once a year, you should be good just doing it once in the spring. If it is a big, big blooming Hydrangea that continues to re-bloom, you are going to use more phosphorus than a plant like an Azalea that only flowers once.

We have Debbie in Perry Township that says “I have a Rhododendron that is old, older than the hills. It is taller than me. I am six foot. It is bigger than my wingspan. Can I take the Miracle-Gro for Rhododendrons and put it on the ground underneath it and wait for the rain to wash it in or do I have to put it in a bucket and water it down?”

Ideally, you want to pre-dilute that. You want to mix it in a bucket and water it down and then put it onto the root system of the plant. It is going to be more evenly distributed that way and there is less chance that you could potentially burn something. I will say this, because you have to use water to use that, it is a really good fat-packing product, but sometimes with a Rhododendron or an Azalea, the all-season granular is a better choice.

You can still use the liquid with it, but if we get a bunch of rain, the last thing you want to do is go put more moisture on that plant. Those plants do not like to be too wet. If we get a bunch of rain and you have the granular all season down, it will naturally release and give the plant some food. Then when we dry out, you can use the liquid as well. The best way is to double feed.

If you have any questions you’d like us to answer, email us at [email protected] or call one of our two locations: Portage (330-499-0101) or Everhard (330-492-1243).