After the asparagus harvest ends in late spring what wasn't picked is left to grow on over summer and autumn so that the crowns below the ground can build up again in preparation for the next harvest in the following spring. 
The problem is that the stalks of the mature asparagus fronds are quite brittle at their base and can be easily knocked over, which effects the productivity of the crop and can be a nuisance if the stalks fall over on paths next to the bed.
 
My solution is to fence the asparagus be in.  I do this by driving stakes into the ground at each corner of the bed at at the halfway points along the length of the bed.  I then run two or three strands of twine  between the stakes to create a barrier holding the stalks in the bed in an upright position. 

It is pretty well the same method used to support broad beans.