Queen Palm Problems
Several bits of information may have a bearing on the premature yellowing of the fronds. One, Queen Palms are native to Brazil (tropics). Thus, they are not well adapted to the Central Coast. However, they will grow here. Two, they require well drained soil. A major problem with palms, in general, is that most people overwater them. Many times palms are planted in a lawn. The amount of water required to maintain the lawn is often too much water for the palm trees. Three, palms, in general, require more potassium than “other plants.” Your use of fertilizer, especially formulated for palms, is appropriate. However, placing the spikes at the “drip line” is too far away from the trunk.
Make and maintain a grass-free ring extending at the least one foot from the trunk. Then apply your fertilizer within this ring. Apply the fertilizer spikes so that the top of the spike is only two to four inches below the soil surface. Fertilizer moves down naturally under normal conditions. The application of fertilizer at three feet under the center of the tree (as your expert said) is a waste of time, money and fertilizer. My guess would be that the trees never saw any of the fertilizer placed at three feet under the tree. That fertilizer is on its way to the water table. There are few, if any, palms roots at three feet in Santa Maria old sand dune soils.
In summary: (1) Make a grass-free ring around each tree. (2) Check your watering regime to make sure trees are not overwatered. Flooding exacerbates the nutrient problem as the palms become inefficient at extracting nutrients from excessively wet soil. (3) Apply granular or spike palm nutrients (should have high potassium percentage as compared to “garden fertilizers”) inside the one foot, grass-free ring around the trees.