Gardeners are noticing that some leaves on vegetables are turning yellow.

There are several reasons for the yellowing of leaves:

• senescence - the natural process of deterioration which follows the period of development of a plant.
• shading - as the plant grows, the leaf canopy expands, thus reducing the light available to the lower leaves, which then turn yellow.
• water logging - causes yellowing and wilting - the plant will not be happy.
• nutritional problems - usually a deficiency.� The essential element for green leaf production is nitrogen.� Lack of nitrogen is the most common cause of yellowing.� This is easily rectified by an application of a nitrogenous plant food or fertiliser.� Deficiency of certain trace elements also causes yellowing of leaves, for example manganese.