Magnesium deficiency

Symptoms

The absence of magnesium is detected by yellowing between the leaf veins and around the leaf margins. Other colours might break through as the green fades.

Find it on: potatoes, apples, cherries, grape vines, tomatoes, camellias, rhododendrons

Time to act: summer, autumn, winter

Problem categories

Overview

Magnesium is needed to give leaves their green colour, so when there's a deficiency, yellow breaks through between the veins and around the leaf edges instead. Other colours, such as purple, brown or red, might also appear. Older leaves suffer first, and will die if they're not given any treatment. The nutrient can be leached out of light, sandy, acidic soil by high rainfall. Or if there is too much potassium in the soil, the plants absorb that instead of the magnesium.

Solution

The absence of magnesium is detected by yellowing between the leaf veins and around the leaf margins. Other colours might break through as the green fades.

Organic

For a long-term solution, apply a yearly mulch of home-made compost. This will conserve moisture, prevent the leaching of nutrients during heavy rainfall, and provide the soil with sufficient quantities of magnesium to keep your plants healthy.

Chemical

Use a magnesium leaf spray, such as Epsom salts, on potatoes for a quick, temporary solution in summer. Apply Epsom salts or calcium-magnesium carbonate to the soil in autumn or winter to remedy the deficiency for next year.

Discuss this problem

Talkback: Magnesium deficiency

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puttycat 24/11/2011 at 15:28

How much Epsom Salt to how many liters of solution?

Chrissieinyeo 24/11/2011 at 15:29

I have a plum tree which is 4 years old and I have just harvested 14lb of delicious plums, however, whilst I have been living abroad and my home has been rented out he tree hasn't been pruned and is now a very peculiar shape. All the life is on one side. How much can I cut off to make it more equal, one side is very dead and other is Ok but I need to shorten some of the branches, can I do this without killing the tree and should I leave the dead side long?

anniegirl 24/11/2011 at 15:29

I find this page very helpful, knowing little of the nutrients I need for each plant. I'm learning but it's a slow slog. Thank you.

Bexta 06/07/2012 at 22:09

Why do you spray leaves with Epsom salts when they're not eaten? Why not treat the soil? Confused!

sotongeoff 07/07/2012 at 07:40

You are feeding the plant throught the leaves-it is called foliar feeding and the plant can take food through the leaves as well as via roots-clever isn't it?

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