Asparagus Companion Plants | Good and Bad

Asparagus (Asparagus officinalis) spears are a great addition to many culinary dishes. They have a short harvest season, and their dense root system takes up a fair amount of space. As such, beds containing only asparagus can have limited productiveness. 

By growing asparagus companion plants you’ll be able to utilize your growing space more effectively, help control common pests and attract pollinators. However, choosing the wrong companions can have negative effects on your plants. This article has all the key information to help you pick the perfect partner for your asparagus.

Companion Planting Explained 

Companion planting is the process of growing different plant species next to one another with the aim of them providing mutual benefits to one another. This growing technique was originally used to grow crop plants together as a natural way of increasing their yield. 

A well-known example of companion planting is called the “Three Sisters” method and is used to grow sweetcorn, beans and squash together. 

The tall sweetcorn provides a sturdy structure for the beans to climb up. The beans fix nitrogen into the soil which can then be used by the other plants to help them grow. The large leaves of the squash shade the soil which keeps it cool and moist and also suppresses the growth of weeds. 

Benefits

When practised correctly, companion planting brings about a lot of benefits. It’s a completely organic method that can improve biodiversity and enhance the size and yield of crop plants. Other benefits include: 

Pest Control: Companion planting capitalizes on the natural pest-repelling properties of certain plants, eliminating the need to use chemical-based pesticides. The scent of some plants repels insect pests or masks the fragrance of your main crop. Others attract predatory insects that will eat pests. 

Attract Pollinators: Fragrant and vibrant plants attract pollinators such as bees, butterflies and birds to your garden. They will boost plant productivity through pollination, improve the biodiversity of your garden and support the local ecosystem. 

Provide Shade: The large leaves and dense foliage of some companions will protect smaller plants from the sun. They will also cast shade upon the soil which helps keep it cool, moist and free of weeds. 

Considerations

Companion planting will only work if the chosen plants have similar growing conditions. For example, a plant that thrives in arid soil would suffer if grown alongside one that needs moist soil to thrive. 

Think about the characteristics of each plant. Do they both have deep root systems that will be competing for space? Will they be in competition for the same nutrients? If so, these are best avoided when it comes to sharing growing space.

You should also avoid planting species that are vulnerable to the same pests and diseases together as the likelihood of an attack will increase and can easily spread. 

Best Asparagus Companion Plants

Asparagus grows best in full sun and should be planted in well-draining soil with a pH between 6.5 and 7.0. They have extensive root systems so need deep soil. This hardy perennial is suitable for growing in USDA zones 2 to 11. 

Good companions will thrive under similar conditions and prevent asparagus from pest attacks. Examples of good asparagus companions include: 

Herbs

Dill: Tall growing asparagus fronds can provide dill with shade and cooler conditions whilst the dill flowers attract a variety of beneficial insects. 

Comfrey: This herb helps protect against fungal diseases and entices pollinators and beneficial parasitic wasps to your garden that will prey on asparagus beetles. These troublesome pests attack growing spears, causing browning and scaring.

Basil: This aromatic herb attracts beneficial insects whilst also repelling pests. Just like with Dill, the asparagus fronds will help protect the basil leaves from the sun. 

Cilantro: Unlike asparagus, cilantro has a shallow root system, so they won’t be in competition for resources. Cilantro flowers also entice beneficial insects to help keep pests at bay. 

Fruits and Vegetables

Strawberry: Strawberries make great groundcover plants in between asparagus rows. They also have a shallow root zone, so neither plant will be in competition with each other for resources.  

Eggplant: As a member of the nightshade family, eggplants contain a toxic alkaloid that acts as a natural pest repellent. Eggplants deter asparagus beetles from consuming the spears.

Lettuce: The feathery nature of asparagus fronds provide the delicate outer leaves of lettuce with shade and helps keep the soil moist and cool. Larger lettuce varieties will help to suppress the growth of weeds around the base of neighbouring plants.  

Horseradish: The compounds contained in horseradish can help to repel insect pests from eating your asparagus. Both plants also favour similar growing conditions making them ideal planting partners. 

Rhubarb: Rhubarb leaves contain oxalic acid which is a natural pest repellent. Once the rhubarb stalks have been harvested, I recommend using the large leaves as a weed-suppressing mulch. 

Tomato: The sweet scent of tomato leaves can help to ward off pests, including asparagus beetles. In return, asparagus deters nematodes that attack tomatoes. 

Spinach: Like asparagus, spinach is a cool season crop. The asparagus fronds help shade the spinach whilst the spinach leaves prevent weeds from growing. 

Peppers: Peppers contain capsaicin which wards off many garden pests. Their root systems are also great at retaining moisture in the soil. 

Flowering Annuals and Perennials

Petunia: The vibrant flowers of the petunia plant add a vibrant splash of colour which not only looks fantastic but can also attract pollinators to your garden. Petunias also help repel asparagus beetles. 

Marigold: The bright reds, oranges and yellows of marigold flowers add colour to your green asparagus bed. Marigold companion plants will also help to deter pests via their aroma. 

Nasturtium: These delicate flowers add aesthetic value, and the foliage helps to suppress the growth of weeds. Nasturtiums also attract pollinators and beneficial predatory insects. 

Worst Companions for Asparagus

Some plants you should keep far away from your asparagus are: 

Carrots: Like asparagus, carrots have long taproots so may compete with one another for growing space, water and nutrients. Additionally, carrots do not grow well with some asparagus companions such as dill. 

Potatoes: The extensive root system of potatoes are likely to compete with the roots of asparagus plants for water and nutrients in the soil. Asparagus can also stunt the growth of potatoes. 

Alliums: Alliums such as leeks, onions and garlic are slow growing and absorb a lot of nutrients from the soil. As such, they can hinder the growth of asparagus. 

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.