Magnesium Deficiency in Plants

Written by alan edwards
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Magnesium Deficiency in Plants
Yellow leaves can be a sign of magnesium deficiency in plants. (Mel Curtis/Photodisc/Getty Images)

Magnesium is an essential nutrient for the proper functioning of many plant activities. One of these activities is photosynthesis, as magnesium is the central element of the chlorophyll molecule. Magnesium also transports phosphorus throughout the plant, is an enzyme activator and a component of many enzymes, and aids in nutrient uptake control. Having so many important functions, magnesium deficiency in plants can be deadly.


The first warning of magnesium deficiency in plants is that the leaves are pale and not rich green. The primary way to detect magnesium deficiency in plants is to decide if the plant is suffering from chlorosis of the lower, older leaves. Chlorosis is a condition that occurs when a plant does not produce enough chlorophyll. Because chlorophyll controls the greenness of a plant's leaves, chlorotic leaves are pale yellow or yellow-white. In some plants the leaves will curl upwards and may also turn red-brown to purple in colour. Full growing season symptoms include premature leaf drop, weak stalks and long branched roots. Conifers will display yellowing of mature needles, while with new needle growth the bottom needles will turn yellow before the tip needles.

Organic Solution

Gardeners who prefer organic growing do have a solution for plant magnesium deficiency. On an annual basis, apply a yearly mulch of homemade compost. The compost will keep the plant moist and prevent the leaching of nutrients when there is significant rain. And, the mulch will provide the earth with magnesium, which will help prevent plants from becoming deficient in magnesium.

Chemical Solution

For a quick but temporary solution to magnesium deficiency, use a magnesium leaf spray during the summer to return the proper amount of magnesium to the plant. For a long-term solution, wait until fall or even winter and add Epsom salt or calcium-magnesium carbonate to the soil. The needed ratio of calcium to magnesium is 5 to 1. Some experts recommend using dolomite lime, as it has the correct ratio of calcium to magnesium. However, you must be careful not to get lime close to the roots of acid-loving plants (e.g., azaleas) because the roots can be badly damaged by lime.

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