Just as a warning for those new to asparagus growing...I found a dozen asparagus beetles on my plants today, I've been checking regularly so I think these may be the first, so look out for them. They can make your young spears inedible, and can defoliate any you leave to grow on. Horrible things!
My asparagus is in it's second year - last year there were loads of beetles - very hard to keep on top of! This year I've got some ferns already and no beetles so far ... however there's going to be a hell of a lot more foliage to check this time :BangHead:
They really can strip a plant - I'm pretty sure they killed one of the weaker crowns last year.