When to feed plants

Question

Hi! I have a couple of rhododendrons and an apple tree and other plants like roses etc.
I have never fed the Rodadendron, which is nearly 6 years old, but have changed the topsoil and given it sequestered iron. However, last year it was repotted with fresh new compost.
But, I still had to give it at least 2 doses of sequestered iron. The other one is 2 years with me. Again I have given it the iron also. Last year , the older one was atttacked by weevils for which I treated it with weevil killer. Will the weevils recur?
Most importantly , I would like to feed them this year but I am worried I will give too much and burn the roots. I do have the feed specific for rhododendrons. But,I feel I may be safer with blood fish and bone, but I don’t know if I can give this to to the rhododendrons and it will it be ok for all the other plants also or do I need to get some other feed for them. All my plants are in pots as I don’t have any soil in the garden.
Shall I just be brave and give the rhododendrons the feed I have bought for them about 2 years ago and never opened ?
Thank you in advance. I do appreciate your help.

Answer 1

Rhododendrons should be planted in a container mix for azaleas. This will have the correct pH for rhodes, one of the things necessary for healthy growth. container plants must be fertilized as the potting mixes do not nourish the plants the way garden soil does. If you used a potting mix that included fertilizer (I stay away from these because it complicates more than it helps, in my opinion. Fertilizer needs are plant specific and a generic formula makes it hard to meet these needs.) Use a long-acting fertilizer in the spring that is for acid-loving plants. Long-acting fertilizer meant for rhodes will not burn roots. Hollytone by Espoma is one example. When soil pH is too high (alkaline), the plants can’t utilize iron efficiently. Use compost as a top-dressing and mulch the roots to keep them cool. Whether your fertilizer is still good depends on how you stored it. If kept under 80 degrees F, it should be OK. Feel free to contact the companies website.