Nothing...its a Sabal

Sabals are definitely slow growers. They need really warm weather to start growing so they probably won't grow noticeably until temperatures start hitting the 80s with some frequency. My sabal minor is starting to grow, but it has always been a really fast grower for a Sabal (Usually puts out 4 fronds a year). I don't do anything special, it's just that every palm is different and even in the same species some are faster growing than others! Mine was pretty cold tender it's first few years which was probably a drawback to it's fast growth.
-Alex

As Jim said..."it's a sabal.". On top of that, they're not particularly good potted palms at any age.

Sabals are 'different' palms. I finally came to the conclusion that they are not that deep rooting. Try a wider container. I know, most of our palm pots are DEEP and relatively narrow. Most Sabals though are notoriously slow--even in tropical climates. I do find faster growth with some species--Mauritiiformis, bermudana not bad, so too with Louisiana and Mexicana.

It appears that my potted sabal palmetto is a "spurter".