|Recently, my palm tree's fan-like leaves quickly turned yellow, starting from lower position of the tree. The whole fan-like leave finally turn into brown color and I have to cut it for aesthetic reason. June is very hot here in Northern California this year. I water the tree with hoses once a week, as I don't have drip system.
Would you tell me if the yellowing is due to water insufficiency or disease or lack of fertilizer (I never apply fertilizer to the palm tree since last March when I bought the house)?
If fertilizer is needed, what type and how often I should apply to my fan palm tree? Is current hot season an appropriate time to fertilize?
Palms may or may not retain their old leaves, so what you've observed may be normal for the plant. The fans can be cut off if they're unattractive to you. It's not unusual for palms to have just one row of leaves at the top of the trunk.
If your palms are acting differently than they have in the past, they may need to be fed, or they may need a deeper soaking than the sprinklers are giving them. Periodic deep soakings will also leach salts away from the roots. If you can get up to the top of the palm to inspect the leaves, you may find spider mites (look for webbing between the leaf fans and the stem). An infestation of spider mites can turn leaves brown prematurely. To avoid the problem, hose the foliage down every few weeks to remove the dust and any spider mites that might have taken up residence. If you want to feed your palm, you can spread several inches of organic matter over the roots so the nutrients released as the organic matter decomposes will trickle down into the soil, or you can broadcast an 8-8-8 complete fertilizer over the root zone. Palms are sensitive to salts, so don't apply any more fertilizer than the label recommends or you'll burn the roots. Your palm may not start growing again until next spring, but if you feed it, and water it regularly, it should perform well.