Do not replant an old asparagus bed with new asparagus plants. Instead, choose fresh ground to avoid build-up of diseases. Prior to planting in early October, remove any perennial weeds and incorporate at least one bucketful of organic matter, such as garden compost or well-rotted farmyard manure, along the base of the trench.To plant, dig a trench 30cm (12") wide and 20cm (8") deep. Work in well-rotted manure to the bottom of the trench and cover the base with a 5cm (2") layer of the excavated soil. Make a 10cm high (4") ridge of soil down the centre of the trench. Place the plants on top of this ridge, spacing them 30-45cm (12-18") apart within the row. Replace the rest of the soil, leaving the bud tips just visible. Leave 45cm (18") between rows and stagger the plants between adjacent rows. Water in and mulch with 5cm (2") of well-rotted manure or other weed-free organic matter.