Introduction
Asparagus is a delightful and nutritious vegetable that’s easy to cultivate, offering fresh shoots from mid-spring to early summer. These large, perennial plants thrive in the ground and can produce crops for many years. However, they take a couple of years to establish before you can begin harvesting, requiring a bit of patience.
Why grow asparagus?
Asparagus is rich in vitamins A, C, and K, as well as folate and fiber. Growing your own ensures a fresh, pesticide-free crop. Once established, an asparagus bed can yield harvests for up to 20 years!
Suitability for different growing environments
Asparagus prefers slightly alkaline, well-drained soil, and needs to be grown directly in the ground. It benefits from a thick layer of organic mulch and minimal weed competition. Due to its deep root system, it’s an ideal crop for areas where water conservation is important.
Lifecycle
Asparagus is typically planted from crowns that are one or two years old. These crowns need two years to establish without harvesting. In the third year, you can harvest lightly for about six weeks, from mid-April to early June.
Asparagus plants can grow quite tall, reaching heights of 6-8 feet (1.8-2.4 meters), and they cast significant shade. By October, they start dying back, and are usually cut to the ground in November. During the growing season, they store energy in their roots, allowing for rapid growth the next spring.
Opt for all-male cultivars, which generally produce more robust spears. Non-hybrid seeds yield both male and female plants, and the female plants will produce seedlings that compete with established plants.
Sowing and harvesting periods
- Sowing: Late winter to early spring (February to April)
- Harvesting: Mid-spring to early summer (April to June)
Recommended varieties
Some popular varieties in the UK include:
- ‘Gijnlim’
- ‘Pacific Purple’
- ‘Millennium’
How to sow
Although asparagus is often grown from crowns, it can also be grown from seed, though this adds an extra year to the process. Seeds should be sown indoors in February at 55-61°F (13-16°C). Plant them singly in modules to give them space to grow, as they won’t be transplanted outdoors until June.
How to prick out/pot on
There’s no need to prick out seedlings; simply plant the modules in June. They don’t need to be in their final positions yet, as they can be transplanted in March of the following year.
Where to plant
Choose a site that can accommodate the considerable shade mature asparagus plants cast from July to October. For instance, plant on the south side of a bed intended for lettuce or spinach in August/September.
The soil should be well-drained with plenty of organic material added as mulch or dug in before planting. Asparagus prefers full sun but can tolerate light shade and various soil types. Ensure the location hasn’t previously grown asparagus.
Spacing
For easy harvesting, plant asparagus in double rows, spaced 18-24 inches (45-60 cm) apart, with individual plants 12-18 inches (30-45 cm) apart within the row. Over time, the plants will expand to fill the space.
How to plant
Plant asparagus crowns in March. Dig a trench 1 foot (30 cm) wide and 8 inches (20 cm) deep. Mix compost or well-rotted manure into the trench base and cover with a 2-inch (5 cm) soil layer. Form a 4-inch (10 cm) high ridge of soil along the trench center.
Place the crowns on this ridge, with growing points up, spaced 12-18 inches (30-45 cm) apart. Spread the roots out gently. Fill the trench with enriched soil, leaving bud tips visible. Mulch with a 2-inch (5 cm) layer of weed-free compost or manure.
Protecting your plants
Asparagus shoots can be damaged by frost. Keep fleece on hand to protect them during cold spells.
How to feed and water
Apply a 1-2 inch (2.5-5 cm) layer of weed-free compost or manure annually. Before planting salad onions in March, add a handful of blood, fish, and bone fertilizer. Asparagus needs minimal additional watering except during droughts, but it benefits from the water given to nearby salad onions.
How to propagate, prune/manage While Growing
Keep asparagus beds weeded to maximize growth. Occasionally, remove self-seeded asparagus seedlings from the previous year.
For propagation, divide well-established crowns in late winter or early spring every three years. Dig up the crown carefully, separate it into smaller sections with multiple growing points, and replant immediately with buds at soil surface level.
How and when to harvest
For seed-started plants, wait three years before harvesting. For crown-started plants, begin after two years. Harvest from April to early June in the first year, giving plants time to mature. In subsequent years, harvest for eight weeks, ending in mid-June.
Cut stems 6-8 inches (15-20 cm) long, about 1 inch (2.5 cm) below soil level. Harvest twice a week to prevent stems from growing too long and tough.
How to store
Use harvested asparagus the same day, or store in a sealed container in the fridge for a few days.
How to eat/cook
Asparagus can be steamed, boiled, grilled, or roasted. It’s great in salads, stir-fries, or as a side dish with butter or hollandaise sauce.
How to deal with pests and disease
Watch for asparagus beetles and slugs. Handpick beetles and use slug traps. Ensure good air circulation to prevent fungal diseases.
When and how to remove the plants
Remove plants only when the bed is unproductive, usually after 10+ years. Before that, cut back ferns in late autumn when they turn brown. Cut plants to ground level and compost the ferns.
What to plant before and after
Asparagus is dormant from October to April, allowing time to plant field beans, lamb’s lettuce, or salad onions.
What to interplant with
Although traditionally not interplanted, asparagus pairs well with shallow-rooted salad onions. Plant onions in March, harvest in spring alongside asparagus, and ensure good spacing between plants. The deep roots of asparagus and shallow roots of onions do not compete, and both benefit from shared care.