Some questions about fertilising and fertilisers for azalea

[isaaquitas]

Hello everyone I had a few questions about fertiliser. I currently use a organic liquid fertiliser on all my bonsais. I recently bought fish emulsion. For the trees that I want to grow the most can I use it every 2 weeks at the same time as the liquid fertiliser or should I wait? Also, the bottle doesn't say how much liquid fertiliser to use per bonsai. I usually just mix it in with 3 litres of water and evenly apply it on all of my bonsais is that fine? For my azalea's I have them in Kanuma soil. Do I need a specific azalea fertiliser or is the liquid fertiliser good? I also heard that there are fertilisers that help with flowering, are these worth getting? Any advice would be greatly appreciated.

 

[Shibui]

Any general purpose fertiliser will be OK for azalea. I would alternate the 2 - the organic liquid then 2 weeks later the fish emulsion. Some growers use fert weekly and still get good results.
Mix any fertiliser as per directions on the pack. You should be able to apply as much as you like to the pots because excess will just run right through the soil without hurting the trees. Obviously that's a complete waste so just enough to wet the soil properly is a good amount.
Azaleas are just trees so they use the same nutrients as other trees. Any fertiliser will be OK for azalea.
Azaleas prefer acid soil. In some places the water supply is pH adjusted above 7. Continued use of tap water can raise soil pH above comfortable levels for azalea so where that occurs there's special acidifying fertilisers that help balance the water. Whether you need that depends on your water.
There are fertilisers with lower N and higher K ratios that are reputed to help with flower production. It seems to work here. You should be able to get specific azalea and camelia fert at your plant nursery. That may take care of the acid as well as supply extra K for flowering. If that's not available any fert that's aimed at flowers or fruit will have the required levels of N and K. Look for tomato fert, citrus fert or something that's labelled 'flowers and fruit'
You need to understand that flower buds are forming around the end of summer even though they are still too small to see at that stage. I use a growth fert - like both your liquids - through spring and summer then switch to a 'flowers' fert in late summer to help boost spring flowers.

Hope some of that helps.

 

[isaaquitas]

Any general purpose fertiliser will be OK for azalea. I would alternate the 2 - the organic liquid then 2 weeks later the fish emulsion. Some growers use fert weekly and still get good results.
Mix any fertiliser as per directions on the pack. You should be able to apply as much as you like to the pots because excess will just run right through the soil without hurting the trees. Obviously that's a complete waste so just enough to wet the soil properly is a good amount.
Azaleas are just trees so they use the same nutrients as other trees. Any fertiliser will be OK for azalea.
Azaleas prefer acid soil. In some places the water supply is pH adjusted above 7. Continued use of tap water can raise soil pH above comfortable levels for azalea so where that occurs there's special acidifying fertilisers that help balance the water. Whether you need that depends on your water.
There are fertilisers with lower N and higher K ratios that are reputed to help with flower production. It seems to work here. You should be able to get specific azalea and camelia fert at your plant nursery. That may take care of the acid as well as supply extra K for flowering. If that's not available any fert that's aimed at flowers or fruit will have the required levels of N and K. Look for tomato fert, citrus fert or something that's labelled 'flowers and fruit'
You need to understand that flower buds are forming around the end of summer even though they are still too small to see at that stage. I use a growth fert - like both your liquids - through spring and summer then switch to a 'flowers' fert in late summer to help boost spring flowers.

Hope some of that helps.

That help a lot thanks

 

[Paradox]

If you need a fertilizer for acid loving plants, look for miracid. I've used that on my azaleas and they seem to like it a lot.

 

[isaaquitas]

If you need a fertilizer for acid loving plants, look for miracid. I've used that on my azaleas and they seem to like it a lot.

Do you think this would be needed even if my azalea's are in 100% kanuma soil?

 

[Paradox]

Do you think this would be needed even if my azalea's are in 100% kanuma soil?

Really depends on the pH of your water and the fertilizer you are using

 

[isaaquitas]

Really depends on the pH of your water and the fertilizer you are using

My water should be between 6 and 9 pH and I use a balanced organic fertiliser every week and every 2 weeks I use fish emulsion

 

[Paradox]

My water should be between 6 and 9 pH and I use a balanced organic fertiliser every week and every 2 weeks I use fish emulsion

As shuibui stated, tap water with more alkaline pH can change the soil pH over time.
If your water is pH 8-9 a lot, I'd try to reduce that before watering. I have no idea what the pH of that fertilizer might be.

 

[isaaquitas]

As shuibui stated, tap water with more alkaline pH can change the soil pH over time.
If your water is pH 8-9 a lot, I'd try to reduce that before watering. I have no idea what the pH of that fertilizer might be.

Ok thanks I will check the pH of my fertiliser and water

 

[Shibui]

6 is just a little acid. The azaleas would love that but 8 and 9 are alkaline and will gradually change the soil pH even with Kanuma. You can continue with the liquid fertilisers if you like but watch for yellowing leaves.
I can't find what fertilisers are available in Portugal so you will need to do some searching or check at your local plant supply shops for a specific azalea fertiliser which should have the required acid formula. At the first sign of yellowing leaves I'd switch to an azalea specific fertiliser.

'Balanced' simply means the fertiliser has the required ratio of ALL the macro nutrients. It does not infer anything about pH but is likely closer to neutral.

Your water supply company should do regular water testing, including pH, and post the results somewhere on their website. It may yake some trawling but you should be able to locate the results for the last year somewhere.

 

[isaaquitas]

D

6 is just a little acid. The azaleas would love that but 8 and 9 are alkaline and will gradually change the soil pH even with Kanuma. You can continue with the liquid fertilisers if you like but watch for yellowing leaves.
I can't find what fertilisers are available in Portugal so you will need to do some searching or check at your local plant supply shops for a specific azalea fertiliser which should have the required acid formula. At the first sign of yellowing leaves I'd switch to an azalea specific fertiliser.

'Balanced' simply means the fertiliser has the required ratio of ALL the macro nutrients. It does not infer anything about pH but is likely closer to neutral.

Your water supply company should do regular water testing, including pH, and post the results somewhere on their website. It may yake some trawling but you should be able to locate the results for the last year somewhere.

Do you recommend any fertilisers that I could order online?

 

[Shibui]

I tried searching for 'azalea fertiliser' and 'acid fertiliser' but seem to only get results for Australia and USA which is not much use to you.
Do some online searching at your end or visit your local garden centres for more local advice.

 

[Glaucus]

Fertilizer feeds the soil, not the plant. You want to use fertilizer to add back to the soil what is not present. This is also kinda true for bonsai substrate, but also kinda not true.
All plants kinda use NPK in a 3-1-2 ratio. Azaleas are a bit on the lower end for the nitrogen, as they do not grow as fast as say tomato plants. Or pines or maples. Those would actually benefit from a higher nitrogen ratio at times. Note that phosphorus is often the tricky element in fertilizer. This one can most easily be too high. 5 ppm phosphate is enough for azaleas. So I dose fertilizer using that value.
Source:

(as well as some research papers). For other horticultural plants, maybe 10 ppm is better. And for trees, I am not sure.
So I usually dilute my fertilizer/fertigation to 2.5 ppm phosphate.

Fertilizer can have an effect on soil pH. And this has to do with how much of the nitrogen comes from ammonia and how much from nitrate, assuming it is a chemical fertilzer.

Consumer fertilizer labeled for say roses, tomato plants, hortenia&rhododendron, they are basically priced based on how much money people are willing to spend on their roses, or tomato plants, etc.

Any bonsai fertilizer regime depends on the substrate and the watering regime you have in your climate.
Azaleas are very sensitive to fertilizer burn/buildup of fertilizer salts in the soil.
The Japanese make their own fertilizer balls using rape seed and fish meal. Or they use a product like biogold.
These they put on top of the kanuma, often using baskets.

You can use whatever consumer fertilizer product you'd like.
If you want a chemical liquid fertilizer, I am now using Yara Tera Azur, which is marketed at acid loving plants. You can buy this as a consumer, but only in 25kg bags.
You can order it online here: https://www.duengerexperte.de/de/YaraTera-KRISTALON-AZUR.html no business register number of professional license required.
This is a fertilizer higher in ammonia. Most chemical fertilizers are very heavy on nitrate, as nitrate is the easiest for the plant to take up. And nitrate doesn't usually cause any toxicity. Ammonia can.
This type of fertilizer is used for high quality ornamental plants in hydroponics/greenhouses/fertigation. It is the highest quality in water solubility and purity (meaning low NaCl) for fertilizers offered by Yara, the main fertilizer producer in Europe.
If you want a kg of that stuff, maybe I should sell it to you. Because I have a 25kg bag and even for me that will probably last me maybe 500 years.
But you don't even need anything special. Any fertilizer will do. As long as it does not clog up your kanuma/substrate. Or burn your plant. Or cause toxicity because of a ratio imbalance.
In the wild azaleas grow on eroded rocks with very little soil in very rainy areas. And they do not need fertilizer there. Of course, if you want maximum growth because you are in development, you want more. But for an azalea, minerals that are in the tap water, drop out of the sky (nitrogen deposition/sahara sand) and release from the rock/soil, go a long way to providing their fertilizer. The main issue is chlorosis when the pH becomes too high and iron uptake becomes an issue.
Though I have also had azaleas in kanuma that showed signs of possible nitrogen deffciency (chorosis without veins).

Note, I do not grow any bonsai in kanuma currently.
For my garden&field azaleas, I use a very low NPK ratio organic fertilizer. I have like a 3-0.5-1 NPK clover pellets fertilizer. Which is very low, almost at a mulch level NPK. And a fertilizer advertised to lower soil pH. Not sure why they claim it will lower pH, though.
For potted azaleas, I use osmocote.
DCM also has specific rhododendron fertilizer, but that's just partly organic

 

[isaaquitas]

Fertilizer feeds the soil, not the plant. You want to use fertilizer to add back to the soil what is not present. This is also kinda true for bonsai substrate, but also kinda not true.
All plants kinda use NPK in a 3-1-2 ratio. Azaleas are a bit on the lower end for the nitrogen, as they do not grow as fast as say tomato plants. Or pines or maples. Those would actually benefit from a higher nitrogen ratio at times. Note that phosphorus is often the tricky element in fertilizer. This one can most easily be too high. 5 ppm phosphate is enough for azaleas. So I dose fertilizer using that value.
Source:

(as well as some research papers). For other horticultural plants, maybe 10 ppm is better. And for trees, I am not sure.
So I usually dilute my fertilizer/fertigation to 2.5 ppm phosphate.

Fertilizer can have an effect on soil pH. And this has to do with how much of the nitrogen comes from ammonia and how much from nitrate, assuming it is a chemical fertilzer.

Consumer fertilizer labeled for say roses, tomato plants, hortenia&rhododendron, they are basically priced based on how much money people are willing to spend on their roses, or tomato plants, etc.

Any bonsai fertilizer regime depends on the substrate and the watering regime you have in your climate.
Azaleas are very sensitive to fertilizer burn/buildup of fertilizer salts in the soil.
The Japanese make their own fertilizer balls using rape seed and fish meal. Or they use a product like biogold.
These they put on top of the kanuma, often using baskets.

You can use whatever consumer fertilizer product you'd like.
If you want a chemical liquid fertilizer, I am now using Yara Tera Azur, which is marketed at acid loving plants. You can buy this as a consumer, but only in 25kg bags.
You can order it online here: https://www.duengerexperte.de/de/YaraTera-KRISTALON-AZUR.html no business register number of professional license required.
This is a fertilizer higher in ammonia. Most chemical fertilizers are very heavy on nitrate, as nitrate is the easiest for the plant to take up. And nitrate doesn't usually cause any toxicity. Ammonia can.
This type of fertilizer is used for high quality ornamental plants in hydroponics/greenhouses/fertigation. It is the highest quality in water solubility and purity (meaning low NaCl) for fertilizers offered by Yara, the main fertilizer producer in Europe.
If you want a kg of that stuff, maybe I should sell it to you. Because I have a 25kg bag and even for me that will probably last me maybe 500 years.
But you don't even need anything special. Any fertilizer will do. As long as it does not clog up your kanuma/substrate. Or burn your plant. Or cause toxicity because of a ratio imbalance.
In the wild azaleas grow on eroded rocks with very little soil in very rainy areas. And they do not need fertilizer there. Of course, if you want maximum growth because you are in development, you want more. But for an azalea, minerals that are in the tap water, drop out of the sky (nitrogen deposition/sahara sand) and release from the rock/soil, go a long way to providing their fertilizer. The main issue is chlorosis when the pH becomes too high and iron uptake becomes an issue.
Though I have also had azaleas in kanuma that showed signs of possible nitrogen deffciency (chorosis without veins).

Note, I do not grow any bonsai in kanuma currently.
For my garden&field azaleas, I use a very low NPK ratio organic fertilizer. I have like a 3-0.5-1 NPK clover pellets fertilizer. Which is very low, almost at a mulch level NPK. And a fertilizer advertised to lower soil pH. Not sure why they claim it will lower pH, though.
For potted azaleas, I use osmocote.
DCM also has specific rhododendron fertilizer, but that's just partly organic

Thanks for this amazing and detailed response. Do you think that if I want to feed my azalea's specific fertiliser it will have to be chemical? I currently feed all my bonsais organic fertilisers only every week. Also, have your plants liked the 25kg bag of fertiliser? I am just amazed by the quantity of flowers that the azaleas and bonsai nurseries produced and I was wondering how to get the same results with mine. Is it true that phosphorus can promote flowering also I am slightly confused by what ammonia does to the soil. Any advice would be greatly appreciated.

 

[isaaquitas]

I tried searching for 'azalea fertiliser' and 'acid fertiliser' but seem to only get results for Australia and USA which is not much use to you.
Do some online searching at your end or visit your local garden centres for more local advice.

Thanks, I will look around locally to see if I can find anything

 

[Glaucus]

Thanks for this amazing and detailed response. Do you think that if I want to feed my azalea's specific fertiliser it will have to be chemical? I currently feed all my bonsais organic fertilisers only every week. Also, have your plants liked the 25kg bag of fertiliser? I am just amazed by the quantity of flowers that the azaleas and bonsai nurseries produced and I was wondering how to get the same results with mine. Is it true that phosphorus can promote flowering also I am slightly confused by what ammonia does to the soil. Any advice would be greatly appreciated.

I have only used a tiny amount of Yara Tera Azur. So I cannot really say how well that worked for me. But that kinda is beyond the point. The chemistry of the fertilizer is clear. It is complete fertilizer. All the elements are listed plus their amounts.
The open question is how much you need to add to your soil/substrate/plant.

No, your fertilizer doesn't have to be chemical. But I would say that chemical fertlizer works very well with potted plants in substrate. Because you have to water a lot, you wash or let the rain wash out a lot of the minerals. Then you add a lot back. But most wash out again. So you fertilize often, at lower dosages, with a lower concentration of chemical fertilzer. With organic fertilizer, you just put a bunch on your soil 3 or 4 times a year. It is also more about feeding the microbiology of your soil, since it has to be broken down. Note that a lot of consumer fertilizer products actually are a mix of chemical and organic. Unless you buy pure blood meal, pure fish meal, etc, the product likely has chemicals added. Often the phosphate is chemical. And about half of the nitrogen is. And most of the potassium is also chemical.

I don't believe phosphate or potassium increase the number of flower buds. This is probably a common myth. Low N fertilizers are used to harden/finish off plants before sale. Or to fertilize in late autumn to make the plants slow down growth in preperation for winter. Often professional growers often want compact plants. Not elongated ones. Nitrogen is associated with elongated growth. The amount of flower buds probably has to do with the cultivar and the pruning done, to get a lot of terminal buds. Long shoots mean less flowers on azaleas.
I believe most commercial azalea and rhododendron growers use osmocote from ICL/Everris. Maybe with added fertigation, though. Not sure. But probably the osmocote is their main fertilizer.

As for the pH effect, NH4+ is a positive ion. NO3- is a negative one. So when the plant takes up an ion, they take up a charge, and they need to also transport out a charge. Or else there will be an electric potential across the cell membrane. Now all living organisms have these, but they keep it at a certain value. So that means that for taking up NH4+, the plant has to give back to the soil another positively charged ion. This can be a H30+, which increases the pH of the soil.
In contrast, the plant may expell a OH- or HCO3- when it takes up a NO3-, which increases soil pH. This is why acid lovind plants usually have more ammonium. For example, ammonium nitrate rather than potassium nitrate. The Yara Azur product has much more ammonium than the other colours/flavours of that product.

Similarily, organic fertilizers are broken down into ammonia as well. When biomass is broken down, the N is inside the amino acids, mostly. And those are broken down to ammonia. The plants then could take that up. Or bacteria could further oxidate it to nitrate, through the nitrification process. Plants can then also take up the nitrate/NO3-. Nitrification also lowers soil pH. Eventually, nitrate can be converted back to nitrogen gas, which escapes back into the atmosphere, which is about 70% nitrogen gas. Then, bacteria have to do nitrogen fixation once more for biology to use nitrogen as a chemical building block, to make amino acids and nucleic acids, etc.

You are asking questions, so I give detailed answers. But you don't need to overthink this. Just throw some fertilizer at them. Just not too much. And observe the results. If those are not good, you adjust.


Oh, for tap water, it is not so much the pH that matters. It is the bicarbonate (HCO3-) content/hardiness that matters most. That determines how much the tap water affects soil/substrate/root enviroment pH.

 

[isaaquitas]

I have only used a tiny amount of Yara Tera Azur. So I cannot really say how well that worked for me. But that kinda is beyond the point. The chemistry of the fertilizer is clear. It is complete fertilizer. All the elements are listed plus their amounts.
The open question is how much you need to add to your soil/substrate/plant.

No, your fertilizer doesn't have to be chemical. But I would say that chemical fertlizer works very well with potted plants in substrate. Because you have to water a lot, you wash or let the rain wash out a lot of the minerals. Then you add a lot back. But most wash out again. So you fertilize often, at lower dosages, with a lower concentration of chemical fertilzer. With organic fertilizer, you just put a bunch on your soil 3 or 4 times a year. It is also more about feeding the microbiology of your soil, since it has to be broken down. Note that a lot of consumer fertilizer products actually are a mix of chemical and organic. Unless you buy pure blood meal, pure fish meal, etc, the product likely has chemicals added. Often the phosphate is chemical. And about half of the nitrogen is. And most of the potassium is also chemical.

I don't believe phosphate or potassium increase the number of flower buds. This is probably a common myth. Low N fertilizers are used to harden/finish off plants before sale. Or to fertilize in late autumn to make the plants slow down growth in preperation for winter. Often professional growers often want compact plants. Not elongated ones. Nitrogen is associated with elongated growth. The amount of flower buds probably has to do with the cultivar and the pruning done, to get a lot of terminal buds. Long shoots mean less flowers on azaleas.
I believe most commercial azalea and rhododendron growers use osmocote from ICL/Everris. Maybe with added fertigation, though. Not sure. But probably the osmocote is their main fertilizer.

As for the pH effect, NH4+ is a positive ion. NO3- is a negative one. So when the plant takes up an ion, they take up a charge, and they need to also transport out a charge. Or else there will be an electric potential across the cell membrane. Now all living organisms have these, but they keep it at a certain value. So that means that for taking up NH4+, the plant has to give back to the soil another positively charged ion. This can be a H30+, which increases the pH of the soil.
In contrast, the plant may expell a OH- or HCO3- when it takes up a NO3-, which increases soil pH. This is why acid lovind plants usually have more ammonium. For example, ammonium nitrate rather than potassium nitrate. The Yara Azur product has much more ammonium than the other colours/flavours of that product.

Similarily, organic fertilizers are broken down into ammonia as well. When biomass is broken down, the N is inside the amino acids, mostly. And those are broken down to ammonia. The plants then could take that up. Or bacteria could further oxidate it to nitrate, through the nitrification process. Plants can then also take up the nitrate/NO3-. Nitrification also lowers soil pH. Eventually, nitrate can be converted back to nitrogen gas, which escapes back into the atmosphere, which is about 70% nitrogen gas. Then, bacteria have to do nitrogen fixation once more for biology to use nitrogen as a chemical building block, to make amino acids and nucleic acids, etc.

You are asking questions, so I give detailed answers. But you don't need to overthink this. Just throw some fertilizer at them. Just not too much. And observe the results. If those are not good, you adjust.


Oh, for tap water, it is not so much the pH that matters. It is the bicarbonate (HCO3-) content/hardiness that matters most. That determines how much the tap water affects soil/substrate/root enviroment pH.

Thanks, I don't mind the detailed responses they are quite interesting. I think I will try using miracid as I have seen a lot of people use them.

 

[Glaucus]

Thanks, I don't mind the detailed responses they are quite interesting. I think I will try using miracid as I have seen a lot of people use them.

If you can't find any local products and you want to use a liquid fertilizer, maybe try this one that does come at 1kg, though shipping is probably more than the cost of the fertilizer:

Hakaphos Azerka 20-7-10(+3)

Hakaphos Azerka jetzt bequem bei Duengerexperte.de bestellen ✔️ Günstiger Preis & schnell geliefert ✔️ jetzt sparen!

www.duengerexperte.de

Or the Grun one, very similar. They also recommend them for 'Moorbeetpflanzen' aka rhododendron.
20-7-10 with a bit more nitrogen from ammonia than from nitrate, should be good. Very similar to the product I listed. Just comes in 1 kg bags (or probably containers) for a few euro.
Seems this seller split up the 25kg bags from this brand into 1kg amounts.
But in the end, it is all just the same chemicals. And if you grow in substrate, you wash out what the plant doesn't use anyway.
Just be sure to stay below 1.2 mS/cm in terms of electric conductivity (EC), for azaleas. Check what your local tapwater is at using the municipality water data, then make a linear guess on what to dose your bonsai with.
Usually, 1 gram per liter will give 1.2 to 1.5 EC, assuming distilled/RO water. So the linear approx (concenration and EC relation is not entirely linear, though) would be that 0.05 g adds 0.1 point of EC to your tap water. But if you also put a small amount of safe organic fertilizer on the soil, you can also add 0.1 to 0.3 g/l of this fertilizer to your watering can, like weekly or biweekly. Be one the low side to be sure.
For other bonsai like pines and acer probably give them more.

You can probably take the same approach with Miracid. But not sure if you can get an EC table for that fertilizer. There should be a dosage instruction on the package anyway. Use half that for azaleas.

Note, professional grade watersoluble complete fertilizers often lack calcium, because calcium ions form insoluble salts with the other nutrients. So if your tap water is really low in calcium, just be aware of that. You'd need another fertilizer that's calcium nitrate.

 

[isaaquitas]

If you can't find any local products and you want to use a liquid fertilizer, maybe try this one that does come at 1kg, though shipping is probably more than the cost of the fertilizer:

Hakaphos Azerka 20-7-10(+3)

Hakaphos Azerka jetzt bequem bei Duengerexperte.de bestellen ✔️ Günstiger Preis & schnell geliefert ✔️ jetzt sparen!

www.duengerexperte.de

Or the Grun one, very similar. They also recommend them for 'Moorbeetpflanzen' aka rhododendron.
20-7-10 with a bit more nitrogen from ammonia than from nitrate, should be good. Very similar to the product I listed. Just comes in 1 kg bags (or probably containers) for a few euro.
Seems this seller split up the 25kg bags from this brand into 1kg amounts.
But in the end, it is all just the same chemicals. And if you grow in substrate, you wash out what the plant doesn't use anyway.
Just be sure to stay below 1.2 mS/cm in terms of electric conductivity (EC), for azaleas. Check what your local tapwater is at using the municipality water data, then make a linear guess on what to dose your bonsai with.
Usually, 1 gram per liter will give 1.2 to 1.5 EC, assuming distilled/RO water. So the linear approx (concenration and EC relation is not entirely linear, though) would be that 0.05 g adds 0.1 point of EC to your tap water. But if you also put a small amount of safe organic fertilizer on the soil, you can also add 0.1 to 0.3 g/l of this fertilizer to your watering can, like weekly or biweekly. Be one the low side to be sure.
For other bonsai like pines and acer probably give them more.

You can probably take the same approach with Miracid. But not sure if you can get an EC table for that fertilizer. There should be a dosage instruction on the package anyway. Use half that for azaleas.

Note, professional grade watersoluble complete fertilizers often lack calcium, because calcium ions form insoluble salts with the other nutrients. So if your tap water is really low in calcium, just be aware of that. You'd need another fertilizer that's calcium nitrate.

Thanks I will check it out