Can anyone recommend a good general purpose plant fertilizer to feed perennials like azaleas, day lilys, rose bushes, gardenias, etc.?

Osmocote

southernboy1: You sir are CORRECT! Osmocote Indoor/Outdoor is the BEST! For outdoor in our Texas heat, I reapply every 3 months for my potted plants. You can test your pot temp and they have a site that correlates pot temp with fertilizer performance. Also, try some mycroznzial additions,

Osmocote ok for vegetable gardens?

Osmocote is fine for any growing thing, it is just fertilizer, does not contain any harmful components

Y'all might also want to consider additions of mycorrhizal fungi, with products like Espoma Bio Tone Starter Plus or Myco Bliss - Mycorrhizal Inoculant for Plants. These will enhance the growth of any plant and the soil. Just a thought. Over the last two years, I have found that these products are almost like magic and they do what they say they will do!

southernboy1 said:

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Osmocote

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This.

We use osmocote at the nursery where I work.
23-4-8 for Spring/Summer.
18-5-12 for Fall/Winter.
13-13-13 for Spring color annuals & perennials.

Nelson's Color Star is all you need. You will thank me later.

https://nelsonplantfood.com/products/colorstar-outdoor-indoor-plant-fertilizer?variant=40886804381740

I have also had good results with Medina products depending on what you are needing.
https://medinaag.com/

Soil test. Determine your most deficient macro & micro nutrients, if a deficiency exists, and target those first. Then go with a good recommendation on an ammendment or fert. You usually don't add oil to your vehicle without checking the dipstick. The soil test is the dipstick.

I get most of my advice from TAMU Agronomy, and Neil Sperry's published tips, and they've never pointed me in the wrong direction.

ETA: soil tests are cheap, and can really help solve some of the more tricky "plant problems." Many people don't even know what Molybdenum is, but plants require very small amounts of it, which naturally occur in the soil. If for example you had absolutely no molybdenum in your soil (unlikely), your plants/crops WILL NOT be able to use nitrogen to form proteins - completely negating your N ammendment(s).

aggieband 83: Would love to have those, but they only come in 50 lbs bags, I will be WAY gone before I could ever use that much, have to stick with the 5 pounders.

southernboy1: Man, you and I are on the same page, use the Hasta Gro for early spring fertilization, Feb to April and EVERY transplant, no shock with this product!!!

Ask the Agronomist (TM) will weigh in on this……. While I'm a big proponent of soil testing (I can't imagine why -), this is a situation where simple may be better. Osmocote is a great slow release fertilizer, but to be at its best likes incorporation. Your perennials are shallow rooted, so some minor shallow disturbance won't hurt them if you go the osmocote route. My suggestion for such shrubs would be to get the Jobe fertilizer spikes. Shooting from the hip, it seems like 3 or so spaced around a shrub lasts about 6 months, and they also have micros. I'd also get some good compost and put a few inches around each plant a couple of feet out from the base.