Chlorosis in azalea?

[Klink]

During the summer i have noticed signs of chlorosis (i believe) in my azaleas, both are on a west facing balcony, covered from sun directly above, in Denmark.

The first plant (very yellow) is a garden azalea, which i bought as a test plant one and a half years ago. It did well last year, so i got the 2nd a satsuki (kisshoten) this year, but moved to a different area so obviously the water changed.

During the summer they started yellowing, which i assume is chlorosis due to hard water (24-30dH)/high soil ph (garden test kit reported~7), both but on leaf growth, but hardly any branch length compared to last year.

Both get organic rhododendron fertilizer and are in their nursery/store soil (test tree had an emergency repot so have baked moler clay added) and the satsuki looks to have some kanuma in the mix, it seems dense but water enters readily when watered.

During the winter, they got mostly rain water with tap water supplimented when getting dry. Over the summer it has been a mix between tap and "distilled" water, this is when the first signs started.

After i saw the yellowing of the leaves i did the soil test and switched to carbonated water (lower ph and cheaper than 50-50 tap and distilled) and added some some iron "sticks".

Do you agree with my diagnosis?
Have some other remidies to add help the trees? (I see sulphur mentioned, but cant seem to find pure sulfur here in Denmark in amounts that makes sense to buy for an apartment use and storage)

And how quickly should i be able to notice improvements?

 

[Mellow Mullet]

Looks more like sun scorch or a fungus than chlorisis. You can add a little ironite for chlorisis and they will green up, if that is what it is.

 

[Klink]

Looks more like sun scorch or a fungus than chlorisis. You can add a little ironite for chlorisis and they will green up, if that is what it is.

Hmm that is odd, they are more sun-sheltered than previously, although it has been very windy.

The iron is already added

 

[EHA]

Using carbonated water will not change the pH of the soil much. What nurseries use to lower irrigation water pH is sulphuric acid and nitric acid (very dangerous in concentrated form). Using sulphuric acid for lowering home irrigation water pH is impractical and dangerous and one would need access to a pH meter to mix the pH correctly. A better option for at home is to use citric acid powder bought at a grocery store (baking section). Citric acid has a low residual action and lowers soil bicarbonate content. Again it would be ideal to have access to a pH meter to do it properly but literally a pinch of citric acid (less than a gram) would drop the pH of 5 litres pH 8 tap water (not hard water) to about pH 5.8. Using elemental sulphur powder is well known to drop soil pH in agriculture, but it is a super slow process because elemental sulphur needs to be broken down by soil microbes first before it will lower the pH of the soil. Usually in potted plants that suffer from soil pH nutrient lock out we need fast acting intervention. Even a teaspoon of household vinegar to 2 liters of water once a week will be more effective than the carbonated water. As always when experimenting with lowering water pH it is best to have a pH electrode or pH test kit because it is easy to lower the pH too much and then kill plants. So use with caution and test on material that you do not value to high as a start.

 

[Deep Sea Diver]

Whoa…. Not sure we are headed down the correct path here. Definitely a couple issues here. The problem is the two trees are imho not exhibiting the same issue.

First - would treat the water as suggested earlier. Very hard water should be treated before use on plants. Would need about 23–29 grams of pure citric acid to soften your water.

Second - wondering why media of one pot was bolstered with molar clay, which makes media more alkaline… ? Kanuma is acidic and will help your plants thrive. Was root washing and repotting in Kanuma not feasible?

Third please show the content of the fertilizer and tell how frequently the azalea is being fertilized and what strength.

Cheers
DSD sends

 

[Klink]

First, the moler: according to the manufacturer the clay has a pH of 5.5, but to my knowledge it should be stable enough to be considered inert, so i do not understand the alkaline part, can you elaborate?
When i got the first plant (in moler now) it is ended up staying wet/waterlogged for weeks after a single rain, so i repotted it and found some dead zones in the root, and mixed in the moler for drainage since it was what i had access to. As stated it was more of an emergency thing.

Regarding the water, i am looking into getting a ph-meter so i can ensure the ph after adding acid. RE the citric acid, i think you forgot a Volume of water, 23g to how much water?

For the fertilizer, i do not have the box with me so i cannot look further into the content, what i can find online(if i remember the brand) is that it has a ratio of 10-2-7 and may contain some chicken derived Organics. I have used it according to manufacturers guideline for area, but fed more often (after the prior pellets were completely gone visually from the pot)

So you agree with Mellow that a fungal infection could be the cause as well?

 

[Bonsai Nut]

Azaleas are acid-loving plants. Rainfall is naturally acidic, but any irrigation water you want to be on the acidic side - pH 5.5-6.5. Even with horrible quality mains water, you can usually accomplish this with a reverse osmosis filter or water softener (that uses potassium chloride (not sodium chloride) to recharge the elements).

Even if you are supplementing with iron, as water and soil pH rises, your plant will struggle to take up enough iron and manganese.



Living in southern California, my mains water out of the tap was 8.5 pH and very hard - high in calcium and sodium (due to proximity to the ocean). Delicate plants I would hand water with reverse osmosis water. For larger plants, particularly for citrus trees in landscape, I would use acid fertilizer that was high in iron. I used a product that was recommended to me by a nurseryman who grew citrus commercially.



There are also water soluble acid fertilizers that will lower soil pH without the hassle of treating your water:

 

[Deep Sea Diver]

First, the moler: according to the manufacturer the clay has a pH of 5.5, but to my knowledge it should be stable enough to be considered inert, so i do not understand the alkaline part, can you elaborate?

—-Oops! sorry about that…. didn’t have Danish molar clay data so used general clay characteristics.

When i got the first plant (in moler now) it is ended up staying wet/waterlogged for weeks after a single rain, so i repotted it and found some dead zones in the root, and mixed in the moler for drainage since it was what i had access to. As stated it was more of an emergency thing.

——When you say emergency repot what exactly do you mean? Usually this means an entire, proper repot. In an azaleas case changing the media would require completely root washing the plant before adding new media. Placing a different media in specific area in an azalea rootball is never a great idea. as this causes different areas of wetness and dryness within the rootball. This causes root issues.

Regarding the water, i am looking into getting a ph-meter so i can ensure the ph after adding acid. RE the citric acid, i think you forgot a Volume of water, 23g to how much water?

—- Sorry again 3.78L of water

For the fertilizer, i do not have the box with me so i cannot look further into the content, what i can find online(if i remember the brand) is that it has a ratio of 10-2-7 and may contain some chicken derived Organics. I have used it according to manufacturers guideline for area, but fed more often (after the prior pellets were completely gone visually from the pot)

—- The reason I ask is azaleas are very susceptible to fertilizer root burn. Azaleas in pots with bonsai media use much less fertilizer than azaleas and rhodys in garden beds. That’s the reason you were requested to provide the media composition.

So you agree with Mellow that a fungal infection could be the cause as well?

——- Actually not. Thinking one has a chlorisis issue while the other has both a chlorisis issue coupled with something else, which I suspect is root related. (Hence the ferts and media questions)

—-Here’s the reason we differ. @Mellow Mullet is an outstanding azalea practitioner with many azaleas located in the US Southeast where azalea fungal issues can be pervasive.

—-On the other hand we are located in the US Pacific NW in a similar, but not exactly, climate to you. We many azaleas (over 300) where fungal issues are relatively unknown. Instead most bonsai azalea issues here are from root and sun problems. The major causes are over fertilizing, overwatering, underwatering, planting in two separate medias and in some areas, pH issues.

Cheers
DSD sends

 

[Glaucus]

The symptoms on both azaleas are not the same. Both seem to have immature growth plus a colour. But the colour is not the same on both.
The first does seem classical chlorosis. Darker green veins. So I would say possibly an iron deficiency. I would try chelated iron complex for this. Fe2+-EDDHA. Dilute it until you can barely still see it has colour. Like by putting it in a transparant drinking glass and holding it up. If you can just barely see some pink, that is a good concentration to apply. I forgot what molar concentration this is.
Liquid fertilizers that have chelated iron can also be used.

The second, I agree it does look a bit like too much sunlight. But that's a bit of a strange symptom for a balcony in Denmark. Maybe it gets really hot because of the concrete around it?

Out of my 2000 or so azaleas, none look like your second one. People often talk about fungal issues for azaleas when the leaves are spotted. Not sure if that is a thing here. I don't think I can find a plant right now that would have these 'fungal issues'. But I did see some symptoms like these when I put plants in a polytunnel during winter when there is very little UV light. Then some leaves can drop with black spots on them.

Though I believe I have had plants in my growing field with zero sun look that way as the second azalea. Maybe it is a chronic heat that makes them look like this.
With chronic drought, the azalea loses the green pigment and if the flowers are red, the leaves become red. And if white, they become pale. With acute drought, the leaves wilt and shrivel up.
So chronic drought and acute drought are not the same.

Not sure if carbonated water is a good thing to use. Might be too acidic. Using citric acid to lower the pH of the water is probably a lot better.
If they are in good fresh soil or substrate, I would water more often and add very dilute chemical fertilizer each time, ideally one with chelated iron.
And check the ambient temperature on hot days. Possibly the concrete on a balcony can get to be 50C.

Azaleas actually can grow fine in soil or substate with around 7 pH and tap water with 8 pH and moderately high carbonates.
But it is not ideal and can eventually give these issues.