My MIL had a bed that had been growing for 25+ years. According to DH, you have to thin the bed out once in a while or the roots get too crowded to make big fat shoots. I haven't had mine long enough for that to be a problem, lol- we had our first asparagus feed this past spring and it was.... WONDERFUL. I do know you can't let stuff like blankety-blank quack grass get in there or it will choke out the asparagus. The most important thing though, is to prepare the soil very very well. After all, those roots are going to be in there for years. You can top dress with fertilizer of your choice every year, but that doesn't replace having a rich humusy soil to start with. Oh, also-- do not overwater or the roots will rot. (don't you love when they say something like that and you're asking - How much is Too Much???)