There are many reasons why plant leaves turn yellow ..Here are some of the common reasons and ways that you can help.
PEST PROBLEM . THE SIGNS ...
Insects living on and eating leaves
How to fix ....Spray plant with neem oil or an insect repellant soap.
OVERWATERING ....Leaves look yellow and wilted .
Poor soil drainage could result in plant roots drowning .
Add sand to soil or replant in a raised bed.
LACK OF SUNLIGHT ....Leaves look jaded and droopy .
The leaves are not getting enough sunlight .Reposition plant location .
DEHYDRATION ...Leaves look dry and feel crunchy to touch.
Plants should get at least 1inch of water each week. Water regularly .
NUTRIENT DEFICIENCIES .
Plants require 13 essential vitamins that they absorb from the soil.
There are 6 nutrient deficiencies that cause yellowing of leaves .
POTASSIUM deficiency ...Edges and tips of leaves are yellow .
Bury citrus rind in soil at base of plant . Add compost rich in fruit and
NITROGEN deficiency .
Tips and central vein in leaves become yellow .
Add organic compost like manure or coffee grounds to soil .
CALCIUM deficiency .
Leaves become misshapen
Check PH of soil ...if acidic add lime ...if alkaline add peat
ZINC deficiency .
Leaves show signs of light discolouration between large veins .
Spray with kelp ..seaweed solution.
MAGNESIUM deficiency .....leaves show signs of white stripe along vein.
Add magnesium compound , Epsom salts or lime .
IRON deficIency ...leaves become yellow with small veins.
Test the ph ...lower to under 7. Reduce the amount of Phosphorus in soil .
Have fun being your plant doctor .