How deep did you plant them and what is the soil like?
My Jersey Giants are about 6 inches deep with the root system spread out not touching the next plant. 30 crowns should give you about 4, eleven foot rows.
The soil should be rather rich with a pH between 6.0 and 7.0 and well drained. When first planted a trench is dug to about 6 inches deep when the soil temp is 50Ã‚Â° or above. Place the crown in the trench with the roots spread out. Barely cover the head of the crown with soil and organic matter. Lightly water and as the plant begins to grow gradually fill in the trench around the plant. I didn't harvest during the first year to let the plants get well established.
Asparagus are very heavy feeders, don't like competing with weeds and do best in well drained soil in a sunny location.