Hi, I stay in Bangalore, India. Recently I bought a pink hydrangea which just finished blooming. I have cut off the flower now. The leaves are yellow and curling downwards. The pH of the soil is around 6. 5 or slightly more. I read on some internet sites that the plant probably has iron deficiency. I was wondering if I could put an iron nail in the soil? I read somewhere that it might work, but i wnated to know if anyone has actually tried it out. Also, how often do I have to fertilize and what are the types of fertilzers I could use? Can urea be used? Thanks in advance. Vandana
Iron Deficiency in Hydrangea Plant?
Hello Vandana. I have read that about the nails on various internet sites too but it really doesn't work to help the problems you may have. A high acidity soil and too much water can either tie up the iron or make it unavailable to the plant. There are alot of good iron additives on the market, I would stick with those. Keep in mind that aluminum is necessary to produce the blue pigment for which bigleaf hydrangea is noted. Most garden soils have adequate aluminum, but the aluminum will not be available to the plant if the soil pH is high. For most bigleaf hydrangea cultivars, blue flowers will be produced in acidic soil (pH 5.5 and lower), whereas neutral to alkaline soils (pH 6.5 and higher) will usually produce pink flowers. Between pH 5.5 and pH 6.5, the flowers will be purple or a mixture of blue and pink flowers may be found on the same plant.
Be sure the soils contain a good amount of compost/organic matter and I recommend using a slow release fertilizer, as the quicker ones can cause root burn problems along with stopping blooming altogether. Osmocote is a good slow release fertilizer but there are others on the market, not sure what you have available where you are.?? Something that is slow release with a rating of 10-10-10 or 16-16-16 is okay. Even something with a higher middle number is okay. You do not want a high first number as that can stop blooming altogether and generate just a bunch or rich foliage. Remember the first number is for Up (foliage), the second number is for Down (root system) and the third number is for All Around (helps feed both the upper part and lower part of the plant). I usually feed my plants in the early spring and early fall.
Here is a link to an article that might be of help to you as well: