A rule of thumb is to harvest for
two weeks in the third year, four weeks in the fourth year, and
eight to ten weeks in following years.
Preparing Asparagus Plants for Winter
As for preparing asparagus for winter, it is important to allow the
tall ferny foliage to die down on its own, just as you would with
spring flowering bulbs such as daffodils. Once it is completely
yellow and dead, cut it back to two-inch stubs. If the patch has
not been troubled with insect or disease problems, the foliage can
be composted. Rake off and compost the summer mulch. Replace it with
a four to six inch layer of shredded leaves, clean oat straw or
composted grass clippings AFTER the ground has frozen.