I have the SAME exact problem. I also have sandy soil. I put my seeds in back around the end of May and they still are stuck @ about 4 feet with some decent size leaves, but nothing huge. I got my seeds from Gurneys and i think the package said they were from Holland or something like that. I'm about ready to demand my money back! I think i might go chop them and try again next year. Thankfully i've got my bananas that have done good and actually grow. Its been very hot and sunny this summer, so there isn't any reason for them not to grow.

I cut mine down today. Figure i'll get a head start for fall. I'm going to try again next year, but i think i'll get different seeds. For some reason my leaves were a dark green and not a purple like my neighbors?

Maybe get some seeds from your neighbor if they grow good and are healthy.

i am still hoping to get some good ones going.

They like rich soil.mine get huge topping the house.I have a pair of green ones growing in old compost pile in dog kennel.They are already 15 feet plus& If I was better about watering them...would be large like some of the other years. My ones from 2 yrs ago...the seeds blew everywhere from hurrican rita...Still come up too.I know that area is sandy to about 3 ft.

poor soil = shorter plants
rich soil= tall huge plants

also mulch them.yes they do branch out.mine seem to branch out around 3-4 feet.I got red& carmencita which is green with pink veins but the younger foiage is bronzeish cast till older then is green,but is neat.The hummers love them.

The year Ivan came to water...sept.It blew my plants down& they had some uprooting.we're 7 ft when that happened.I transplanted them,cut the tip of stalk when it got ratty& they still grew to 15 ft,but we're shaded lower 3 ft

Their is a short version out called impala..suppose to stay under 3 ft.I've never found seed...but know its there.I grew one that was from a large seed(it was size of runner bean)I can't find it either.It use to be the one that would return from root.I lost it when moved pond.

I agree about the rich soil. I dug holes and put in straight kitchen scraps, etc. without even composting first. Then filled in just a little soil and planted the seeds. They grew HUGE. This was many years ago but they were 15 ft tall at least before a hard freeze got 'em. Also, we have heavy clay soil, that may have helped.

Last year I had 3 of the common castor bean that got over 13ft. They had lots of water and I kept the seed heads pruned off. This year I chose a different location, less water and have been letting the plant produce seed. They have only grown 8 or 9 feet this year.

Lot's of sun, rich, loose, soil heavy on the compost, plenty of water and mulch well with organic matter such as leaves, hay, kitchen scraps, etc. Last but not least. Keep the flowers picked off for the tallest plants. Mine regularily get to 25' this way.