Answer: Asparagus roots are initially planted very deeply (about a foot deep) and covered little by little until the trench is filled in. Over time the roots seem to move to the surface. An old patch may deteriorate if the initial soil preparation was poor, if the plants were crowded, if they have been overharvested, or if ongoing soil replenishment has not occurred. Asparagus is a heavy feeder and does best with an application of well rotted manure and compost in the fall as well as a top dressing in late spring after harvest has finished. Some gardeners will also apply a complete granular fertilizer in early spring. Asparagus should also be mulched to keep out weeds and help maintain a cooler moister root run. These application of organic matter nto only feed the soil, they also keep adding bulk over top of the roots. Although it needs perfect drainage, asparagus also needs adequate water to grow and produce well, so the drought and now the root disturbance plus the competition from the weeds may have combined to weaken the plants. You might try giving them some TLC this year ( put several inches of compost over top as a mulch now and make a heavy application in the fall of both compost and aged manure; water deeply if there is a dry spell) and see if they come back for you next year. The roots are actually very deep and huge systems, so I would hope for the best if they can regain some strength this year.
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