Asparagus plant care: watering, fertilising & more

Edward
Edward
Edward
Edward

With a passion for growing installed at an early age, I have always been happiest outdoors in nature. After training as a professional gardener and horticultural therapist, I currently run horticultural therapy and community kitchen gardens in the UK, helping others access the many physical and mental health benefits of growing vegetables, fruit and plants.

Favourite fruit: apples and pears
Favourite vegetable: asparagus

Asparagus is not only found in delicatessens and restaurants but in many home gardens as well. Learn all about how to water, fertilise and care for asparagus plants.

An asparagus plant being fertilised
Fertilise asparagus to get the best harvest [Photo: Jomyoothphoto/ Shutterstock.com]

Asparagus (Asparagus officinalis) has to be one of the most rewarding vegetables to grow as nothing quite beats the taste of freshly picked asparagus from the garden. With a short but much-awaited harvest period, you will want to do everything you can to ensure a plentiful supply of tasty spears in late spring. Read on to find out how to care for asparagus plants to make sure they remain healthy, strong and ready for harvest time.

Asparagus plant care: watering

Watering asparagus is essential for it to thrive and crop well, come spring. Asparagus plants require a moist but well-drained soil or bed and need adequate moisture during the active growing season, especially whilst establishing.

When growing asparagus, it is best to water the asparagus plants weekly during the growing season for at least the first 2 years and then as necessary. However, it is important not to overwater, especially if the soil is not light and free draining, as this can lead to the crowns rotting. To test if asparagus needs watering, check the top layer of soil with your finger down to 5cm deep. If it is dry, give the asparagus a slow, thorough watering.

Where possible, use harvested rainwater, although mains water at room temperature will suffice if required.

An asparagus spear growing
Asparagus prefers a moist but well-drained soil [Photo: VVVproduct/ Shutterstock.com]

When the harvesting period comes to an end, the spears are allowed to mature into tall feathery stems that are cut back to ground level when they die back in winter. As summer progresses, watering can be reduced and stopped in autumn when the plant goes dormant until the following spring.

Tip: to keep the soil moist, especially during the summer months, seep or soaker hoses can be used to provide regular moisture to the base of the plants.

Fertilising asparagus

Asparagus plants are fairly heavy feeders and benefit from an annual mulch and feed to ensure the best crop.

Asparagus thrives in a rich and fertile soil. On planting and annually thereafter in late winter, apply a layer of organic matter or well-rotted manure to help conserve moisture, suppress any annual weeds and enrich the soil by providing food for underground microorganisms.

Asparagus spears growing through mulch
A layer of mulch can help conserve moisture and suppress weeds [Photo: VVVproduct/ Shutterstock.com]

In early spring before the harvest season starts, a general organic fertiliser can be applied. For example, you can use our Plantura All Purpose Plant Food for fertilising asparagus plants, as it contains all the key nutrients, especially nitrogen to encourage strong growth. Plus, as it is a slow-release fertiliser, it will feed the asparagus plants for up to 3 months.

All Purpose Plant Food, 1.5kg
All Purpose Plant Food, 1.5kg
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(4.8/5)
  • Perfect for a variety of plants in the garden & on the balcony
  • Promotes healthy plant growth & an active soil life
  • Long-lasting fertiliser that is free from animal products - child & pet friendly
£12.99

Pruning asparagus plants

Asparagus plants require pruning or cutting back annually at the end of the year. Once spears have been left to grow into large feathery stems over the summer months, they can be cut down to ground level using a clean and sharp pair of secateurs. However, this must only be done once the asparagus crowns have been replenished and the foliage has turned yellow and died back.

yellow asparagus foliage in winter
Once the asparagus foliage turns yellow and dies back, cut it back to ground level [Photo: Iker Zabaleta/ Shutterstock.com]

Do not add the died-back foliage to your home compost system due to potential contamination by pests and disease, but rather carefully dispose of it in your household waste bin.

Common pests and diseases

Once established, asparagus generally grows trouble free and crops reliably every spring. However, there are some asparagus pests and diseases that can result in poor yields:

  • Asparagus beetle: present in North America and Europe including the UK, the asparagus beetle (Crioceris asparagi) eats the foliage and can subsequently reduce harvest yields the following year. The adults are 6mm to 8mm long, with a colourful red head and six yellow markings on their back, making them easy to identify. The eggs and larvae are less obvious, but on closer inspection the tiny black beetle eggs can be seen sticking out horizontally off the spears. The eggs turn into black-brown larvae up to 10mm in length. Smaller numbers can be tolerated with little damage or controlled by picking off by hand or encouraging predators, such as ground beetles. Larger infestations may need to be sprayed with a natural pyrethrin insecticide.
An asparagus beetle on foliage
Asparagus beetles eat the foliage and stems, which can result in a poor crop the following year [Photo: Tomasz Klejdysz/ Shutterstock.com]
  • Stemphylium purple spot: asparagus purple spot is a fungal disease caused by Stemphylium vesicarium that affects both the asparagus spears and foliage. Most common in cool and wet summers, Stemphylium purple spot can lead to defoliation and reduced harvests the following year. Identifiable by its oval purple marks on the stems, which if spread, can cause the needles to turn brown and drop. If purple spot is suspected, all affected stems and debris need to be removed at the end of the growing season and disposed of carefully.
  • Rust: asparagus rust (Puccinia asparagi) is a fungal disease identified by orange or brown lesions on the stems and foliage. Often present during wet summers, asparagus rust can cause dieback and reduced harvests. Prevention measures that can help avoid rust taking hold include planting rust resistant cultivars such as the Jersey varieties, planting at the recommended spacing, and planting any new asparagus plants in a separate bed away from any rust affected plants. If asparagus rust is identified, any affected stems must be removed and destroyed, and any debris cleared from around the growing site.
  • Slugs and snails: causing damage to young asparagus plants and seedlings, slugs and snails can wipe out an entire sowing overnight if undeterred. Feeding off the leaves and stems, these gastropods can often be identified by their slime trails and feeding holes they leave behind. Control measures include encouraging predatory wildlife into the garden, placing barriers around susceptible plants and removing by hand.

Here in the UK, we tend to mainly grow asparagus that produces green spears, but for something even more eye-catching, why not try a purple or even white variety. Find out more in our article on the best types of asparagus to grow at home.

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