Outdoor Spike Palm Is Yellowing

Spike Palms with Drought Stress

• Spike palms grow long tap roots and are drought tolerant; however, their leaves will yellow and may appear burnt around the edges when they do not get supplemental water. Mature, well-established trees should be given 10 to 20 gallons of water every 10 days during dry periods. Newly planted spike palms should be given 1 to 2 gallons of water every day or two for the first month. For the remainder of the first year or two, give them 2 to 3 gallons of water twice each week.

Spike Palms and Fluoride Toxicity

• Spike palms are highly sensitive to fluoride, and tap water usually has fluoride in it. When spike palms are exposed to excessive amounts of it, the leaf tips and edges turn yellow or brown. Spike palms can tolerate fluoride levels as high as 1 part per million. If the tap water has high levels of fluoride, catch rain in a rain barrel and use it to water spike palms. Superphosphate fertilizer also contains fluoride. Do not use it to fertilize spike palms.

Spike Palms with Nutrient Deficiencies

• When grown in nutrient-poor soil, spike palms can develop nitrogen and iron deficiencies, which will cause the foliage to yellow. They grow best in fertile soil that has a high level of organic matter. The trees may also produce fewer and smaller leaves, and can appear stunted. Sprinkle 1/2 cup of a balanced 10-10-10 or 12-4-8 fertilizer around the tree and water it into the soil. Do not use slow-release fertilizer. Regular fertilizer will reach the roots quickly to give the tree a boost of nutrients. Spread it evenly over the soil beneath and a few feet beyond the tree canopy. Switch to slow-release fertilizer in the following late fall or early spring.

Spike Palms with Fungal Disease

• The foliage on an outdoor spike palm will turn yellow when it is infected by a fungus that causes verticillium wilt. The branches will also wilt and eventually die, usually on one side first. No cure exists and the tree can be killed within a week, although it may hang on for years after becoming infected. Prune off the branches that are showing symptoms. Disinfect the pruning tools with household disinfectant between each cut to prevent the spread of the disease. Give the tree 10 to 20 gallons of water every 10 days, depending on the size of the tree. Spread 1/2 cup of 10-10-10 or 12-4-8 slow-release fertilizer on the soil around the spike palm, and replenish it as needed, depending on the formula. Slow-release fertilizers may last anywhere from three months to one year. Do not apply fertilizer in late summer or early fall as it may cause the growth of new leaves that may not mature before winter.