Magnolias are tall-growing evergreen trees that produce large, fragrant blossoms that are pure white in colour. The leaves of the magnolia are a dark, glossy green and can reach a length of 25 cm (10 inches). The shedding of some leaves is normal for any magnolia tree, but if it drops large numbers of leaves the tree may have a problem.
Pick up one of the leaves and examine it carefully to see if it has white or black spots on it, which indicates that the magnolia tree is infected with a fungus or mould. If spots are detected on at least 25 per cent of the fallen leaves, treat the tree with a fungicide solution.
Dig up 5 ml (2 tsp) of soil from under the magnolia tree and place it into the nitrogen test tube of a soil test kit. Fill the tube with distilled water and the powder supplied with the kit. Compare the water colour of the tube to the chart on the kit to ensure that there are high levels of nitrogen in the soil. If nitrogen levels are low, add a high-nitrogen fertiliser to the soil under the tree.
Grasp one of the tree limbs and look to see if new buds are forming at the same time that the leaves are falling off. If new buds are visible and it is late winter or early spring, then the magnolia is simply shedding its old leaves in preparation for developing new ones.
Walk on the soil directly under the magnolia tree to see if it feels soggy, or if water squishes up out of the ground. Magnolia trees must have well-drained soil, and if the soil is soggy, the roots of the tree will rot, causing it to lose leaves.