@akamainegrower Thanks for the response, why should I definitely avoid the MirAcid? Is it because of risk from urea burn? I looked at the analysis label and near as I can tell, there is nothing special in the MirAcid formula, at all. It's almost identical to the MG All-purpose water soluble fert but with a different NPK ratio (MirAcid is 3-1-1, MG all purpose is a more favorable 3-1-2). There isn't even any sulphur in it for pH reduction like there are in other acid loving/acid adapted ferts.

May I give it a weak application of DynaGro Foilage Pro liquid fertilizer weekly?

MirAcid and liquid fertilizers in general provide a quick shot of nutrients. This is pretty much the opposite of what azaleas and other ericaceous plants want: a slow, steady release of nutrients in small quantities. I have never used the DynaGro product, but it would seem to be unnecessary if you're using a complete controlled release fertilizer or something like Holly Tone (in very small quantities).

Thanks @akamainegrower. I used 1/6 the recommended dose of MirAcid (I imagine only a fraction of that got to the plant because 5-1-1 is such a fast draining mix). Have you had good results with Holly Tone with your potted azaleas? The only CRF I have right now is Vigoro Rose slow-release with micronutrients (12-6-10), would that be OK? How often would you guess I'd have to apply the CRF in a high porosity mix? For my in ground roses in clay soil, a little bit every 4 months seems to be enough, but wouldn't the CRF get flushed out much quicker in my mix? Once a month, maybe? Since I didn't prepare the 5-1-1 with CRF, would I just top dress it?

As someone who grows almost exclusively in containers, let me offer this advice. Rhodies and azaleas do not require a lot of fertilizer. I fertilize mine only once a season with a light dosing of a CRF (osmocote) like I do all my long term woody container plantings. CRF's don't "flush out" - they disperse necessary nutrients over an extended period as the coatings breakdown with heat and moisture :-)) And I supplement that with a dilute application of Miracle Gro for acid lovers periodically during the growing season, primarily to maintain proper container acidity but there are other products (like Green Light's Soil Acidifier) you could use.

Holly Tone or other granular or dry forms of organics are not going to be nearly as effective or efficient at delivering nutrients in a container situation as a non-organic (or water soluble) fertilizer would be simply because the microbial mechanism to convert these organics into a usable form is not present.

btw, I use a potting medium that is more closely aligned with the gritty mix rather than the 5-1-1 and this method has worked beautifully for me for years.

I just potted two azaleas saplings in 511 mix! With Dolomitic lime added!! And then read the label saying "Lime free soil" !!!!!

@gardengal: 'btw, I use a potting medium that is more closely aligned with the gritty mix rather than the 5-1-1 and this method has worked beautifully for me for years.'

I would dearly love to know your recipe. I'm using standard 5:1:1 and gritty mix for everything except my Ericaceous plants.

I know you wrote this over a year ago. Are you still here? Thanks.

I use a packaged acid planting mix amended with more bark and perlite. I use this on virtually all my potted woodies - rhodies, other broadleaved evergreen shrubs, conifers and Japanese maples.

Thanks. I use a local mix used by nurseries here in my area in TN. It's excellent, but wondered if I could make my own.

It sounded from your tweet like maybe you used a variation of the gritty mix.

How often do you usually need to repot? What is the longest you've ever kept a rhodie or azalea in a pot before planting out?