I think it's because Florida gives the palm more humidity than it wants and maybe they are less resistant to hurricanes.

They achieve the same amazing height in Rome, which I think has the same latitude as washington DC.

From everything I have read about washys they require dry(heat) conditions to reach max size. It has allways amazed me how well these do in the baking dry heat of Mex ,Cali and Az

Now on the other hand, how are the southern cal coconuts doing?LOL

Also, palms that tall are lightning rods. California thunderstorms are extremely rare. It just doesn't rain there in the summer.

I think this thread indicates why Washingtonis do so well potted in places like the midwest in the summer. Until they get rootbound or get too cold in the fall. Check out LA's temps some time 83-66, 79-62, 82-64. Sound familiar. It's just like a lot of Michigan days or other places in the midwest. They obviously thrive in that weather. I have one that is in a pot I'm guessing at least 100 gallons. About 30 inces high 24 inches wide at the bottom, and 30 inches wide at the top. It has pushed up about 5 fronds since late April (once it went outside). it has really shot uo in June.

Andy,,Just read your post. Wanted to let you know thr size of your pot would make it around 35,- 40 gal. 100 gal pot would take a machine to lift.,,hope im right,,,Bill

Lightning is one answer. Also, Washingtonia (both types) are desert riparian species. The humidity of the SE while tolerated is not what nature intended for these palms.

Washingtonia grow wild as far north as Seattle Washington rain forest. That is how they got their name. They are also native of the springs in my area, Palm Springs area. Don't know why they don't grow as tall in FL. Could it be something as simple as they have not been there as long and so have not grown as long and so have not grown as tall? Some of those old tall ones in CA are 90 and 100 years old. The ones on my street growing up were as tall as the light post in 1963 when we moved there and are maybe 60 feet now.

Some palms may actually find S. Florida way to humid and this may lead to a variety of diseases that curtail their lives. I would imagine that Washingtonias (named after the president, the state and palm genus came after), and most Phoenix, for example, are happier in a much drier climate. Differing soil conditions may also come into play here. Whatever the reason, they are one of my favorites and don't receive the respect they deserve in areas where they grow like weeds.

sad to say, there are no native palms in washington state (and unfortunately havent been since before the last ice age or so). washingtonia (as mentioned named after the president not the state) is native to parts of southern california, nevada, arizona, and northern mexico (w. filifera) and baja california (w. robusta). both have naturalized (and hybridized with each other)beyond their natural range but not in the pacific northwest---winters still too cool and moist for them except in the "banana belt" areas of extreme southern oregon coast---gold beach to brookings.