Treating Yellowing Leaves on a Newly Planted Magnolia Grandiflora

A 13-foot magnolia grandiflora, planted three weeks ago in Victorville, CA (USDA zone 9/10), is turning yellow and dropping leaves. The owner waters weekly, uses vitamin B-1 and fertilizer, and amended the planting hole with organic soil builder.

Diagnosis: Over-Care

The tree is likely suffering from transplant shock compounded by over-fertilization and possible over-watering. Newly planted trees should not be fertilized for the first year; excess nutrients burn tender roots. Watering once a week with 1 inch of water (measured with a pan under the sprinkler) is sufficient. Too much water is as harmful as too little.

Recommended Actions

• Stop fertilizing for at least one year.
• Water correctly: Apply 1 inch of water per week; use a pan to measure.
• Mulch properly: Spread 2–3 inches of organic mulch around the base, keeping it away from the trunk.
• Monitor: The tree should recover as roots establish.