Growing asparagus: when, where & how to plant asparagus
Known for its delicious shoots, which are known as spears, asparagus is a perennial vegetable that can be grown at home. Asparagus needs a permanent place to grow and is a long-term investment but come harvest time, it is well worth it.
Asparagus (Asparagus officinalis) must be one of the most sought-after spring vegetables and quite rightly, as its flavoursome spears are much prized by growers and gourmets. What is more, you can even grow asparagus at home. Read on to learn more about how, when and where to plant asparagus.
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Planting asparagus: crowns vs. seeds
Asparagus can be grown either from seed or from 1-year-old plants called crowns. Planting asparagus crowns tends to be the preferred method, as the first spears can be harvested in as little as 2 years after planting rather than 3 years when grown from seed. Growing asparagus from seed is a more cost-effective method but waiting an extra year before harvesting can be off-putting.
When to plant asparagus?
As a long-lived perennial vegetable, asparagus, if grown in the right conditions, can crop for more than 20 years. However, this is only possible if it is planted and cared for correctly, including allowing it to establish before harvesting.
If growing asparagus from seed, it can either be sown undercover in late winter at a temperature of 14 to 16 °C; here in the UK, February is usually considered the optimum time, or directly outside from March to April. If you are wondering when to plant asparagus crowns, they are usually sold in late winter or early spring and need to be planted on arrival in March.
Where to plant asparagus: pots, containers, or raised beds?
Asparagus is a long-term investment, and fresh soil is recommended to avoid any previous pests or diseases being present. Preferring a free-draining and moist soil with a pH of 6.5 to 7.5, asparagus can struggle in heavy, compacted soil or soil that is prone to waterlogging. With this in mind, and as it is a large plant, asparagus is usually grown in its own dedicated bed rather than in pots or containers. However, asparagus can be grown successfully in raised beds, but only if the soil available is deep enough to support the plant and accommodate its deep roots.
If space is an issue, growing asparagus in pots or containers is possible, although this is not the preferred method as the lifespan and harvest potential of container grown asparagus is much reduced when compared to those grown directly in the ground.
Wherever you decide to plant your asparagus, it is wise to consider the location and conditions, as asparagus prefers to be grown in full sun but in a sheltered spot. Asparagus plants can tolerate some light shade, although for maximum spear quantity and quality a south facing site is recommended.
Tip: whether planted directly in the ground or in a raised bed, annual feeding in early spring is recommended to encourage a good harvest, promote plant health and help prevent asparagus diseases. A balanced fertiliser, such as our Plantura All Purpose Plant Food, is best because it slowly releases nutrients to the plants for the coming season, providing the key nutrients, especially nitrogen, required to encourage a good crop.
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Companion plants for asparagus
Asparagus plants are relatively heavy feeders and require a nitrogen rich soil for optimal growth. Some companion plants grow well alongside asparagus plants, but only if they do not compete for the same nutrients or encroach on the asparagus’s space.
Companion plants for intercropping with asparagus can include: lettuce (Lactuca sativa), which is a light feeder and quick cropping, beans (Phaseolus) because they fix nitrogen back into the soil, and strawberries (Fragaria), as they help provide ground cover and suppress weeds.
Once asparagus plants have come to the end of their natural life span, new asparagus plants should not be replanted in the same site, as the soil will be depleted of the essential nutrients. Hence, it is recommended to follow a spent asparagus bed with a crop rotation to promote the soil’s health and to grow only light to medium feeders. Some good crops to plant following asparagus include:
- Beans
- Garlic (Allium sativum)
- Kohlrabi (Brassica oleracea)
- Lamb’s lettuce (Valerianella locusta)
- Lettuce
- Radish (Raphanus sativus)
- Strawberries
Plants to avoid planting with asparagus
When it comes to companion plants for asparagus, there are also some plants that should not be grown together. Heavy feeders like broccoli (Brassica oleracea) should not be grown with asparagus, as they will both compete for the soil’s nutrients and limit each other’s growth. Jerusalem artichokes (Helianthus tuberosus) and potatoes (Solanum tuberosum) should also not be grown near asparagus, as both can encroach on asparagus’s roots underground. It is also advisable to avoid growing any alliums with asparagus, as alliums can stunt asparagus growth.
Step-by-step guide to planting asparagus
To grow asparagus from seed undercover, soak the seeds in water for 1 to 2 hours before sowing. Sow one seed 2cm deep per module in seed trays filled with a low nutrient seed compost, such as our Plantura Organic Herb & Seedling Compost. Water the seeds. Grow on at 14 to 16 °C, keeping the soil moist until they are large enough to harden off and plant out in June.
How to plant asparagus?
When it comes to planting out the strange-looking asparagus crowns, it can seem a bit daunting. Do not let this put you off; with the correct guidance, it is not too difficult:
- Remove any weeds and stones and work in a generous amount of well-rotted manure or garden into the soil to prepare the ground.
- Soak the bare root asparagus crowns in water for 15 minutes to rehydrate them before planting, as they tend to dry out if not planted immediately.
- Dig a 20cm deep and 30cm wide trench, add some organic matter and make a ridge along the middle.
- Plant the crowns on the ridge with their roots spread out evenly.
- Carefully backfill with soil until the growing tips are just visible at the soil’s surface.
- Water the crowns in slowly and thoroughly.
- Mulch with a layer of organic matter to conserve moisture and suppress weeds.
- Keep the soil moist after planting and especially during the first two growing seasons whilst the plants establish themselves.
- Avoid harvesting any spears for the first two growing seasons.
How deep should you plant asparagus?
If you are wondering how deep to plant asparagus crowns the answer can vary. Green asparagus is planted with the growing tips barely poking through the surface of the soil and its root extending down deep into the soil. On the other hand, the spears of white asparagus are cultivated completely under the soil, so they need to be planted slightly deeper with the spears always covered with earth as they grow. Either way, it is wise to plant your asparagus as recommended above, as if planted too shallowly, the plant may be short-lived. You can read more about the different asparagus varieties to grow in our dedicated article.
What is the recommended spacing for asparagus?
Asparagus plants require a lot of space. Planting your crowns too close together can cause thin growth and poor yields. To ensure that the crowns have enough room to mature over time, it is advisable to plant them in rows at a spacing of 30 to 45cm between the crowns and at least 50 to 60cm between rows.
Can you move asparagus?
Although asparagus plants can be moved, transplanting asparagus should be avoided, if possible, as it is not an easy process, and any future harvesting will be delayed by 2 to 3 years. However, if required, asparagus crowns can be transplanted in early spring to another prepared site. To move the plants, carefully lift their crowns and roots, taking care to not damage the growing tips or long roots. Replant as soon as possible to avoid them drying out.
Depending on the growing method, asparagus harvesting can begin in moderation after 2 to 3 years after planting. Learn more about how to harvest and store asparagus.
