Opening a discussion for recommendations for fertilizing peonies. Usually, the same procedures and products will work just fine with many other perennials.

My first choice is Miracle-Gro bloom booster. 15-30-15 with many micro-nutrients. I like to add a tablespoon of magnesium to about 3 tablespoons of the MG and mix in roughly 5 gallons of water for use during the hot summer. Otherwise in the Spring, just mix it to the same ratio and sprinkle it on the ground, making certain to keep it at least a foot from the crown or at the foliage drip line. I buy the medical magnesium, Epsom salts, at Walmart rather than the gardening bags at Lowes. The medical type is 100% where the garden type is diluted. It is always better to fertilize lightly several times rather than one heavy application.

THanks for starting this thread, Jerry! I have always been confused about how much fertilizer to give to my established peonies.

Jerry, just wanted to say this formula has worked great for me this year!

A sprinkle of standard agri fertilizer (12-12-17 or 15-10-15, whatever I have available) in the early Spring is all my peonies see. They don't seem to be fussy about what they get.
However one year I've tried using homemade compost instead of fertilizer and got smaller flowers out of the Japanese tree peonies, so synthetic definetely helps.

The regular peonies, like many other plants, do not need much NPK. I use MG for the micronutrients which make a huge difference in plant health The extra magnesium is supposed to help the plant process the nutrients. The normal use of the MG, spraying on the foliage, has been disastrous for my peonies. They develop major black spotting just the same as plain water. That is why I use the leaky bucket technique to water the roots but not the foliage.

I have mentioned a leaky bucket to water peonies or other plants. I use a 35 pound cat litter bucket which should be 5 gallons or so since my wife has cats and I always have a supply of buckets available. I drill 1/8 inch holes at the bottom of the bucket in order to have a slow but spread streams of water. Put the water soluble ingredients in first then fill the bucket from a hose and the material is generally well dissolved. For extra dry plants, just refill the bucket with water without adding fertilizer.

I keep meaning to get some buckets and try this. So much to do - so little time. We are having a fairly dry spell and the entire garden could do with a drenching. Will probably water tomorrow with my turtle, goes slow and gives a deep watering. Unless the forecast is accurate and we get rain for the next few days.

Green Lotus is trying to open for the first time. Along with Coral Charm, Joker, and La Perle.

I am with Mary! At this time of year, there is so much to do and catch up. Wish I have a handy helper to prepare these buckets for me.