Posted: 13/06/2013 at 13:40
Hi there - not sure that I can say what's going on or why but wonder if for some reason there's a naturally high nitrogen level in the soil and/or it's a type of soil which again, naturally suits these plants !!!
I'm sure others may have alternative similar comments !!
I do know that in our own garden the same plants grow differently depending on the particular soil and location in which they are situated - clay, sand, mixture of both, full sun, shade etc etc.
I must say I have never come across such tall alstromerias. I imagine you need a lot of staking material !!