Cut them at the ground when they are all pretty much dead brown. Even when they are yellow some nutrition is being supplied to the crown. Tom

Asparagus grown in wide open spaces with snow cover would benefit from leaving the foliage. The tops help to catch the snow for a natural mulch. In our area, I leave the tops and mulch with leaves, straw, whatever, as the snow cover may not be dependable. Although, this may be overkill, as once the plants are established, I have never lost any to winter kill.

Hi leinie3113 - yes you will get different opinions on what to do because different things need to be done in different zones. Here in my part of Zone 6 we never get much snow but do get periods of hard freeze in late winter. Since I grow in confined garden beds what works best for me is to mow off the tops once they have turned brown - usually after the first frost - and then mulch the beds well. I use both shredded leaves and some hay for a total of about 4-6 inches of mulch. It insulates, feeds the beds and the soil, and helps control weeds come spring.

Dave

Once they've been in for a good year, they are quite resilient. Mine don't get much care for winter. I let the ferns dry down in the fall, waiting for other things to freeze down good, then give the sheep access to the garden. They will pretty well clean the ferns up, leaving a few stalks on the ground by spring. Then take the lawn mower to them in March or early April to clean the rest of the trash off before the new spears start to grow.

When I planted it, I loaded the trench with phosphate since that doesn't move too well in the soil and asparagus like it. Probably put it down at a rate of 400 lbs/ac of 0-48-0. Every few years I will through some 30-10 on the plants in the summer when side dressing the rest of the garden.

It would probably be better to mulch good each year, but that doesn't happen although occasionally some manure flies onto the asparagus when spreading it on the rest of the garden. Still, it produces quite well. About 30 plants produce enough for lots of meals in the spring and enough to freeze for winter use, plus give a bunch to various neighbors.

Moral here is to let it die down for winter, clean up the ferns when you want, try things but don't worry too much about killing them if you don't do it just right. Find out what works for you in terms of plant vigor and work maintaining them.

One good reason to cut down and remove the tops of the plants is because asparagus beetles can overwinter in the stems. I always cut mine and dispose of before the winter, but ONLY after they have turned quite yellow to brown, and the weather has gotten quite cold -- late October or early November in Michigan.

As far as the benefit of mulching goes, Asparagus is definitely fully hardy in Michigan, and certainly is in Oregon, so it isn't required to protect the plants. But, I always put a thick layer of leaves, a mix of oak and maple, over my asparagus bed in the fall, because it keeps down weeds and rots into beneficial compost.