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What happened to my beautiful Azalea japonica? I bought it in full bloom about two weeks ago (here in Central Europe), repotted it after a few days (which was perhaps a mistake), initially placed it in a sunny spot (perhaps another mistake) and watered it daily and a quite a lot (with regular water).

Now within the last few days all of its blooms have collapsed, many have fallen off, and there is a a white substance on many leafs. So I guess the azalea has caught some disease (even though its natural blooming season is also coming to an end.)

What is this and how can I treat it? Will this be contagious to my other plants? And what are some general best-practice rules for handling azaleae?

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UPDATE Here is another photo. The terracotta pot is approx. 30 cm in upper diameter. The original one was approx. 26 cm in diameter and made of plastic. I've also run a quite test with a simple (Seramis) moisture indicator and it currently says "dry".

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  • Can you add another photo showing the whole plant and its pot please? Does the pot have drainage holes? What soil did you use when you repotted? – Bamboo May 9 at 10:31
  • @Bamboo Thanks for your response, but I generally do not like to post wider-angle photos of my private environment here out in the open (call me paranoid :). I understand that this hinders help to some degree. Yes, the pot has a draining hole; as usual, I put a little stone there so that (hopefully) only water can pass thru. Does this help towards further diagnosis? – Drux May 9 at 10:59
  • @Bamboo I terms of soil I used the special kind for rhododendrons. FWIK pH is important here. – Drux May 9 at 11:02
  • I wanted to see the size of pot relative to the plant, that's all... can you not do just a shot showing that and very little else? – Bamboo May 9 at 12:10
  • @Bamboo Yes, I'll do that tomorrow. (It's now dark outside here.) – Drux May 9 at 20:18
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Size of pot is fine, and you used the right potting soil, so no problem there. You are right that it wasn't a great idea to repot whilst the plant was in bloom, but I suspect it was probably difficult to keep it sufficiently well watered before you moved it. Equally, standing it in full sun would have meant the blooms didn't last as long - these plants prefer partial shade or dappled shade.

The blooms are fading now, obviously, and the whole plant does look a bit droopy (does it need watering?) but the new leaves showing are healthy.so you're not in danger of the plant dying immediately. Remember, because you recently repotted, there will be a rootball sitting surrounded by the new soil, and that will take some time to put out new roots into what's surrounding it, so it may be that you are not watering sufficiently well. Water until it runs out the bottom of the pot; ongoing, water with a litre or so when the surface of the soil feels just about dry to the touch.

The white fluffy bits on the leaves might be azalea whitefly, although usually, you know if its that because if you gently shake the plant, they fly up into the air. Inspect the deposits closely with a magnifying glass if necessary, including beneath the leaves - if its whitefly, use a suitable insecticide spray available in your area. This link describes azalea whitefly with images - it recommends a particular spray under Diagnostics, but there will be other insecticide sprays available for this problem https://www.treecarescience.com/tree-problems/insects-mites/azalea-whitefly-diagnostic-guide

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  • Excellent! May I also ask whether you think it is important that I use distilled water going forward. What are acceptable parameters for tap water that is healthy for these kinds of plants? – Drux May 10 at 19:10
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    Rainwater is best, if you have a water butt in the garden or a collection system somewhere. Otherwise, when rainwater wasn't available, I have always mostly used tapwater with no ill effect (UK tap water!) other than the build up of lime scale on the rim of the pot over time, or water from my condensing tumble drier (which is distilled of course), or boiled, cooled water (which gets rid of the lime) – Bamboo May 10 at 19:28
  • Thanks again, this time esp. for hint concerning tumble drier. – Drux May 11 at 5:57
  • So now that some time has passed I can say with confidence that your advice was correct: I had underestimated how much water this plant needed in its main blooming season. I am now (still) regularly watering it indeed until water runs out the bottom of the pot. The azalea has recovered and even the pests much much receded.. – Drux May 21 at 7:05
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Azalea blooms do not last long and your leaves look good , so I think the blooms are just finished. When Houston TX plans their "Azalea Gardens Trail" it is always a challenge to pick the best weekend to catch the most blooms.

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The white flecks look like Azalea whitefly. Examine under magnification to verify this. Treatment is possible after blooms are gone, but be careful to follow product instructions. Make sure to use rainwater or distilled for azaleas to try to keep pH on the acid side. Tap water is often hard water containing carbonates which makes it alkaline - check with your local water authority for the pH if you are obliged to use municipal water.

Azaleas are small rhododendrons and are often kept in small shallow pots to keep their growth constrained for use in greenhouses and balconies, so moving to a larger pot might have been unnecessary.

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  • Thanks especially for suggesting Azalea whitefly and distilled water. – Drux May 9 at 20:22

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