Why does my lemon tree have yellow leaves?
Citrus Tree Problems.
As you anticipate the joy of plucking that homegrown lemon, it's disappointing to discover your tree has more yellow leaves than yellow lemons. What's going on? Here are the main reasons lemons develop yellow leaves and how to keep them green and lush.
PROBLEMS AND SOLUTIONS
Keep in mind older leaves may not return to green after applying these remedies but new growth should be green and healthy and the yellow leaves will fall.
1. NOT ENOUGH FERTILISER
Much like teenagers, lemons burn through lots of nutrients. When the tree runs out of nutrients its older leaves may become yellow. Apply a complete citrus food twice a year aiming for mid summer and late winter. Water well before and after applying fertiliser. Spread the fertiliser over the soil around the tree. Follow the application rates suggested on the container.
2. NOT ENOUGH IRON
A lack of iron can cause lemon leaves to yellow. As a quick fix water the tree with iron chelates, which is a form of soluble iron available from garden centre or hardware stores.
3. NOT ENOUGH WATER
Lemon trees need regular and deep watering that reaches the root system. When plants dry out they don't get enough nutrients. Lack of water can be a major problem for containerised trees. After watering check that the water has soaked into the soil and not simply drained away leaving the roots dry. If the soil below the surface is still dry, apply a soil wetting agent to encourage the soil or potting mix to better absorb water and water again.
4. PESTS
Citrus bugs, scale and aphids can affect the health of the lemon and its leaves. Seeing ants along the stems is a sign that the tree has pests. Aphids appear on new growth and can be squashed or hosed off. Scale appears on stems or backs of leaves. Apply horticultural spray oil (follow the instructions on the container). Adult citrus bugs are green and with care can be knocked from the tree into a container of soapy water. Wear sunglasses when doing this as these pests squirt a toxic liquid that can burn eyes. Spraying with horticultural oil in winter reduces pest numbers. Without the pests, the ants too should disappear.
5. TOO COLD
Lemon trees prefer a warm subtropical climate, but grow in cooler climates if sheltered from cold winds and cold winter conditions. When the tree is cold its roots are unable to absorb enough nutrients to keep the leaves green so they turn yellow. Shelter lemons from cold winds with plastic, a screen or a hedge. Keep the plant watered through winter but don't apply fertiliser until spring when temperatures warm and the tree shows signs of new growth.
6. ROOT BOUND
Lemons that are grown in containers may outgrow the space in one to two years, leaving the plant unable to take up enough water and nutrients to thrive. To provide more space, repot the lemon into a slightly larger container with fresh potting mix. Select a good quality potting mix and work in about 10 per cent by volume of compost. For long-term success, grow a dwarf lemon in a large container.
7. ENGULFED IN WEEDS
Lemons don't like sharing. To keep trees green, leafy and productive remove all competing weeds and grass from under and around a lemon. Replace the weeds with a 2-5cm layer of coarse organic mulch mixed with aged manure. Keep mulch away from the tree trunk.
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