Certified GKH Gardening Expert
One thing you can do is remove the grass under the tree 3 feet (0.9 meters) out and fill it with mulch. The grass is competing with the tree for nutrients, plus if you add nitrogen fertilizer to the grass, some may be getting to your tree. Mandarin trees can be fertilized with a citrus fertilizer according to the package directions.
If frost threatens, cover the tree with a blanket. Also be sure it is getting regular watering. Mandarin trees need well drained soil in full sun, so if the soil is not well draining, work in some compost around the tree.
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