Asparagus is a long term crop. Expect 15 year + harvests from a well prepared asparagus bed. Nothing tastes like home grown asparagus and a productive bed is a real investment. Work on 10 plants per asparagus eater in your home.
Start by planting your seed in seedling trays in spring / summer. Transplant into nursery beds for the first winter or two. They can be grown in-situ for the first 2-3 years, but must be transplanted before the start of year 4. Once your plants are ready for transplant, dig a trench to at least spade depth, and fill with well matured compost. Spread a spade-full of calcitic lime per running meter and fill to ground level.
Lift the asparagus crowns in June / July and separate them into individual plants. Using a spade, wedge open the bed and insert the crown with the roots in a fan shape. Space plants 30 cm apart in full sun. Water well and fertilise with an organic fertiliser every Aug / Sept.
In the first year of transplant do not harvest any spears, in the second year after transplanting, harvest for 2 weeks. In year four after transplanting, harvest for 4 weeks and from then on you can harvest for 6 weeks maximum. Well-fed plants will product the best, use a top dressing of compost every autumn and only cut top growth once the winter frosts have killed them off.