Everyone loves asparagus. About 30 years ago all male hybrids were developed out of Rutgers University. In fact we had a two acre u-pick field of all male hybrids at that time, probably the first in Wisconsin. Two of the main varieties are Jersey Giant and Jersey Knight. Since they do not set seed like the female asparagus plants, they produce about 50% more spears, and a planting will produce for many years. In the past there were many volunteer asparagus plants that came up from the seed and it was hard to keep the asparagus in rows.
I do not recommend planting the old time variety of Martha Washington. It is too susceptible to disease and the yields are too low.
The ground should be weed free for at least a year before you plant. During this time, increase the organic content of the soil and add any fertilizer that is needed. Asparagus is going to be there a long time.
Plant the roots or plants in the spring as soon as you can work up the soil, usually around May 1 here in southern Wisconsin. Make a furrow in the ground about 5 inches or so deep. Spread the roots out. Place the plants/roots a minimum of two feet apart but usually about three feet in the row. The crown (growing point) of the plant should be about 5 inches deep. As the plant sends up new shoots, gradually fill in the furrow so that by July the ground is level. Planting them deep slows their emergence in the spring. Asparagus spears cannot freeze.
Weed control is very important the first year. Pull and hoe weeds about every week. If you are into chemical control, Preen and corn gluten work as they help stop germination of seeds. Every spring put about 1-2 inches of compost over each plant before it grows. This will provide nutrients and help control the weeds.
Here is the Wisconsin Extension commercial website address. This is a 4 MB file.