Paintedlady, I've rescued asparagus out of weeds. If you can isolate one plant, dig a large enough soil ball for it so you get as much root as possible. You can then either put the soil ball in a bucket of water or simply water it well. Once the soil is soft on the latter, you can carefully pull out all the weed roots (usually couch I find), which causes almost no disturbance then plant. If soaking in water, most of the soil and weeds will fall off and you can plant what's left as if a new crown. The roots will have soaked up enough water to handle the 'pruning' and keep growing.
Provided enough roots are left, asparagus are pretty tough.