Magnesium deficiency

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Time to act
Time to act

Do Time to act in January

Do Time to act in February

Do not Time to act in March

Do not Time to act in April

Do not Time to act in May

Do Time to act in June

Do Time to act in July

Do Time to act in August

Do Time to act in September

Do Time to act in October

Do Time to act in November

Do Time to act in December

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.



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


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.



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.