Problem
"My old navel orange tree hasn't fruited much this year and all of the fruits it has are very small. Also, lots of its leaves are yellow and it has strange growths on the trunk and branches. What can be done to help this tree?"

Solution
Citrus, whether they be
oranges, lemons, grapefruit or mandarins, can be a wonderful and rewarding addition to a garden. They do look after themselves quite well however to keep them performing at their peak they need some regular care.

Straggly trees with yellowing leaves and a reduced crop of small fruit indicates that the tree is stressed. Lichens and moss on the main branches show evidence of rot - all up a tree that has been neglected for some time and is in need of a major renovation!

To get this tree back to a healthy state drastic action is required.

Step 1 Collect the fruit the tree has produced.

Step 2 Prepare for some heavy pruning, you'll need good quality secateurs, long handled loppers and a pruning saw. Start at the outer edges of the canopy and prune in, evenly reducing the canopy. As the branches become thicker switch to the loppers.

Branches damaged by rot or borer will need to cut back to healthy wood using the pruning saw. The aim is to take the tree back to a 'skeletonised' state. It may look harsh but this sets the tree up to produce vigorous new growth.

Step 3 Once the pruning is completed fertilise the tree with a complete citrus food, this will provide all of the essential elements for quality leaf growth and fruit production. Water in well with a solution of a seaweed based product such as Seasol. Mulch the area around the tree well.

Maintenance
Reapply fertiliser every season and water with Seasol at least monthly.

Moss and lichen occur naturally on many older trees.

Lichen is generally a grey-green colour and flat. In most situations it doesn't cause any problems for the tree it grows on, it's simply an indicator of the tree being quite old.

Moss, which is normally bright green and fluffy, on the other hand can cause problems. It normally grows in shady damp spots and traps organic matter and moisture. When growing on the bark of a tree this can lead to decay or rot in the branch or trunk. Moss should be removed and the area carefully checked for damage.

Source:Better Homes and Gardens September 2005