Magnesium Deficiency in Orchids

As the winter draws on, we are all wrapping up warm and looking after ourselves to prevent coughs and colds getting the better of us. I’ve been looking at my orchids lately, two in particular, and thinking “why don’t you look 100%?”

Google is quickly becoming my best friend.

Two of my orchids (my oldest Phal and my little Cattleya orchid) appear to be demonstrating a nutrient deficiency. Some of the older leaves look yellow in comparison to the new ones. This fits with a magnesium deficiency. Magnesium is a nutrient that your orchid is able to relocate around itself to help with various functions, mainly photosynthesis. The newest leaves always look much greener than the older leaves because the magnesium has been drawn from them into the new ones. It certainly accounts for why the oldest leaves on my oldest orchid look the way they do – I did originally think they were dying off, but after a year like this, I don’t think so any more.


So, what is a solution to this? There are a few fertiliser products on the market that do have magnesium as a main ‘ingredient’ – referred to as a macronutrient. The best way I can explain a macronutrient in the simplest terms is to relate it to human nutrition. Magnesium is very important to humans as well as plants as it is responsible for so many different things within our bodies – it is the same with orchids.

Unfortunately, the fertiliser I have recently purchased does not appear to have this nutrient as a key ingredient but there is a way around it. After a bit of research online, I found two solutions. The first is to find a source of magnesium that I can add to my watering regime – namely Epsom Salts. My plan is to add Epsom Salts to water every other week, to see if this makes a difference. The concentration I plan to use is a little lower than suggested by some sources, but I’d rather provide less than more of this solution at this stage. If in a few weeks, it does not appear to be having an adverse affect, then I will consider increasing the dosage slightly.

My second plan will be to purchase a fertiliser that contains Magnesium as a macronutrient. I have found a product on the market that I am considering but I would like to see how my orchids do with the Epsom Salts for the time being. When the fertiliser runs out, then I will consider purchasing a new type.

Another experiment now begins – the results will be posted in a few weeks.



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