A perennial crop, established asparagus plants will provide an annual crop of tasty spears for up to 20 years. Ensure you choose the spot you will grow your asparagus carefully. Asparagus needs lots of space to grow and requires a sheltered, sunny site with well-drained soil to thrive. Avoid growing asparagus in shady spots, heavy clay soil or containers.
As the plants will be in this site for up to twenty years, itâ€™s vital that the soilÂ is very well prepared by digging it over thoroughly, removingÂ weedsÂ and mixing in organic matter such as well-rotted manure. If your soil is clay also mix in sand. A week before planting, scatter general fertiliser granules over the area and fork in, then rake the ground level.
Dig a trench, 30cm wide by 20cm deep, down the middle of the trench part fill with soil to make a mound 10cm high. Taking the asparagus crowns, sit them 30cm apart on top of the mound, spreading the roots on either side. Take care with the roots as they are very fragile. Cover the crowns with 5cm of soil. As the plants grow, cover them with more soil, aiming to eventually fill the trench.
Keep the newly planted crowns well watered until established and ensure the area is kept weed free to prevent competition for light and nutrients. It is best to hand weed the area as the roots are shallow and this will avoid any damage.Â You should also avoid harvesting asparagus spears for two years after planting, as this weakens the plants and will lead to smaller harvests in the long term. Instead, let the crowns develop ferny foliage, this enables them photosynthesise and grow into healthy, strong plants.
Asparagus is ready to harvest two years after planting one-year-old crowns. Harvest spears when they reach 12cm in length, cutting them off just beneath the soil with a serrated knife. Stop harvesting in mid-June to allow the plant to build up energy for the following year.