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I noticed my freshly rooted 10 months old hortensias yellowish leaves. Knowing green color comes from chlorophyll I searched on Internet [lack chlorophyll] and got familiar with chlorosis.

Based on the first two photos, is it chlorosis? or missed I something? (The 3rd photo is my 5 years old plant, that seems clearly as a chlorosis) but what about the young ones?

The soil is appropriate Ph hydrangea soil which I always use, but who knows how the Ph changed over the time...

What can an amateur European gardener do, who does not easy access "usual" amazon.com products? I've read about watering with citric acid or ascorbic acid, but not even clear it is a one time watering treatment, or regular every day repeated...

First two photos are the 10 month old plants, the third is the 5 years old plant, not necessary the same case.

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Edit: Added 4th picture:

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  • Can you add another photo of the 5 year old plant showing the whole plant and its pot please? I just want to see what size it is... When you say you used 'appropriate ph soil' for hydrangeas, what does that mean exactly - was it ericaceous or ordinary potting soil or some other soil? And lastly, when you potted up the cuttings, what soil did you use - was it new potting soil or older soil from a bag you've had a long time? Or some other soil? Sorry for all the questions, but it makes a better answer possible.... – Bamboo Jul 22 at 10:09
  • I forgot to ask - have you fertilised the 5 year old plant and if so, what with? – Bamboo Jul 22 at 10:16
  • Many thanks for asking: I've added a 4th pic with an apple to see the sizes. The soil is was a low pH pack, label said it for hydrangeas. The potted ones are in the very same soil, from and old bag. I still have 2 old bags, are they useless? Btw I am mainly interested the problem with 10 month old rooted ones, to make them healthy and grow strong, those are from an other old and pure white plant which are completely healthy – g.pickardou Jul 22 at 12:16
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It sounds like a nutrient shortage in the potting soil you used might be likely - most potting soils are made up with a slow release fertiliser which lasts about 6 weeks to 3 months (depending on the manufacturer and whether the product is kept indoors or outside), so it's likely your old potting soil no longer has any useful nutrient levels. That doesn't mean it's utterly useless, you just need to add a general fertilizer when you use it to pot up plants - in the UK, I would use Growmore for this.

Were it not halfway through July, I would suggest giving some granular general fertiliser now, but depending where you are in Europe, now is not the time to encourage lots of growth which may not have a chance to harden off before cool temperatures arrive. You could, though, use Phostrogen or Miracle Gro general purpose, which is mixed in water, and will provide nutrients rapidly but not last long, or any other make of liquid fertiliser that is general purpose. Use it once or twice for a week and then see if things improve. Otherwise, they're not in dire straits and about to expire from nutrient shortage, they will make it to next spring and you can fertilise then instead.

The other possibility is too much sun exposure on some of the leaves - that can cause yellowing and eventual death of the leaf - I note the yellowing leaves on the bigger plant are facing forwards where there's more light, so perhaps that's a possibility

In regard to the 5 year old plant, it's a bit on the small side for its age, but not too bad a size, though it may well need a larger pot next year. The fact the flowers are pink means the soil it's growing in is alkaline. Hydrangea macrophylla flowers turn blue in acid soil - this plant is kind of the litmus paper of the plant world, and if you add iron to it, it is likely to turn blue or a kind of mix of blue and pink/wishy washy mauve.

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