I have found that manganese and iron added to the soil seems to prevent this. Some old timers would swear by epsom salts for palms but I know of no study as to their effectiveness. The taller they get it seems the weaker they get in Florida's humid climate.
It's too bad Washingtonia palms always look anemic in the American Southeast compared to how towering and impressively tall they get in the American Southwest. The healthiest and best robusta specimen I've ever seen in Florida is still barely a third the total mature height they get in California, for instance. Fun fact: El Paso, Texas is the most Eastern portion of the USA where the Washingtonia filifera will grow naturally without any maintenance or protection and still look fantastic. While the Washingtonia robusta is less cold hardy than the filifera, the robusta can handle high moisture and humidity better than the filifera can. This is why we see the robusta in the American Southeast, but not the filifera. The filifera can't handle high precipitation rates and high humidity. It just doesn't do well in humid areas of the USA.
@@daleandrews3552 You even have filiferas? Lake Charles, eh.. some of my mom's family lives there. Just a pointless side note. I remember as a kid visiting LC and it seemed like the Congo or Amazon to me, being from NYC. Ha! Anyway... I'm surprised you have any filiferas. I passed thru Northern Fl, Georgia and S. Carolina recently and the weather there is just like Lake Charles... and I didn't encounter a single filifera. And I'm a palm freak. So I was looking. I saw many unhealthy and sad-looking robustas.. but... not one filifera. Also, what's interesting... you'll never see an American Southeast staple, the Sabal, in California. I've never seen a single Sabal palmetto or any of the million Sabal sub species in the American Southwest. The Sabals seem to abruptly stop around San Antonio.
