I've been wanting to get some Azaleas going on the roster. Picked up these 2 from Lowes today and stumbled onto this thread.
Should I repot right away? I dont have any kanuma which I read is a bonus, also my communities water is really hard.
You stated you have hard water, this makes growing azalea tricky. All azalea are calcifuges. They dislike excess calcium in their soils and their water. There are a couple approaches. One is to collect rain water, and only water your tree with rain water. Rain collection can be as simple as what I do. I set out 5 pails, 3 gallon size each, scattered around the yard. After it rains, I dump them all into a covered 55 gallon plastic barrel. The cover prevents the water from evaporating during the late summer dry spells. I leave the lid off the barrel too, during rain storms, if I think of it. If I start collecting rain in April, by the end of June normally I have a full 55 gallon barrel of water to use for my azalea and blueberries during the dry spells we get in July and August. I'm usually able to water my azaleas with rain water 4 out of 5 times all summer long. The occasional watering with your municipal water will not be fatal, just collect enough rain water that most of the time you can use rain water.
If your irrigation water, or municipal water is low in dissolved solids, you can grow your azalea in anything, from Turface, through Akadama and Kanuma. But if you have hard water, you need to design your potting media to compensate. You can design your potting medium to help compensate for the high calcium in your municipal water. Kanuma goes a long way toward compensating for medium hardness, medium calcium content of irrigation water. But if you water is more than 300 ppm total dissolved solids or 250 mg/liter as calcium carbonate total alkalinity, the water will "overpower" the cation exchange capacity of Kanuma. I recommend you use a trick from the landscape nurseries & blueberry growers. Kanuma is not acidic enough for raising high bush blueberries but the composted douglas fir bark, or composted bark in general (not necessary to be douglas fir bark) will release enough organic acids and have a high enough EC to compensate for excess calcium. The standard blueberry mix is equal parts composted bark and Canadian peat moss with about 5% by volume hardwood sawdust added to feed the mycorrhiza species unique to ericaceous plants. To this mix add 1 to 2 tablespoons per gallon of elemental sulfur. Elemental sulfur can be found with a visit to an old fashioned Farm Feed & Seed Store. Or any full line nursery that caters to organic vegetable growers. The elemental sulfur comes in 2 grades, that differ only in particle size. The Sulfur for soil amendment is a slightly coarse grind, the elemental Sulfur for use as a fungicide spray is a much finer grind, smaller particle. Both work identically, in that they dissolve slowly, and provide a slow steady amount of sulfurous and sulfonic acids. Note, rain water won't naturally form Sulfuric acid,, the natural dissolution product is at a lower oxidation state, sulfurous acid, which is weaker, less aggressive, and safe for plant life. Mycorrhiza and soil bacteria play a role in the dissolution of sulfur, all in all it is a natural process. The sulfur freed up reacts with Calcium to make Calcium sulfate, which is mostly insoluble, which locks it up as unavailable to bother the azalea. Apply the sulfur once a year for the soil amendment form. The fungicide form is a finer particle, it dissolves more quickly because of the fine particle. Apply half as much every 6 months.
For grow out containers, nursery pots, and other large and deeper than 2 inch deep containers this mix is excellent. It will compensate for your hard water. One key problem. If you let this mix get "bone dry", the peat moss will contract. When you re-wet the mix, the peat moss will not expand. Repeat the dry out process a few times and you will have a compact brick of bark & peat that will have very little air penetration . This is the chronic problem with using peat moss in any potting mix. The trick is to never let the mix get dry past the lightly moist phase. If you can do that, no problems. For use in bonsai pots, to this mix I add pumice or perlite, about 50:50. Seems to work. Once addition, see the threads by
@cmeg1 and humic and fulvic acid supplements. I found that if I supplement with a solution of seaweed, fulvic acids & humic acids in my water, the peat moss seems to aggregate, and become clumpy, rather than stay a fine powder. When repotting blueberries that got this treatment, the peat-bark mix had better air penetration after 1 year than it did when first made up. This is probably due to the beneficial microbes and mycorrhiza causing the peat to clump up. Just a trick I learned.
FOr what it is worth. If you do mail order in Kanuma, or make the drive to DanSu Bonsai, or Hidden Gardens and pick up Kanuma, adding a top dressing of elemental sulfur will help keep the Kanuma acidic enough even with water over 300 ppm total dissolved solids. It may not be a perfect system, but it avoids having to deal with a peat moss based mix.
Summary, if you can collect enough rain water to mostly irrigate with rain all year, you can grow your azalea in any conventional bonsai potting mix for deciduous trees. If you have to use municipal water for part or most of the year, a designed mix, either Kanuma & sulfur supplement, or Bark-Peat mix with sulfur supplement, will work.
Hope this helps.