Record — updated 2026-07

Asparagus Companion Plants

Entry No. 002

Asparagus officinalis · asparagus family family · rotation group: other

The best companion plants for asparagus are Tomato, Basil, Parsley, Dill, and Sweet Alyssum. Avoid planting asparagus near Onion, Garlic, Potato. Of the 10 pairings recorded here, 0 are supported by published research and 10 are traditional practice with no controlled evidence behind them.

Research-backed tested in controlled research Traditional long practice, untested Not supported tested and not supported

What to plant with asparagus

Companion plants for asparagus — 0 research-backed, 7 traditional
Plant	Claimed benefit	Evidence	What the evidence actually shows
Basil	Basil interplanted with asparagus is said to repel asparagus beetle by scent.	Traditional	Found only in gardening media. UMass Extension's common asparagus beetle fact sheet lists no companion plant among its controls. UMN Extension does note that a few studies show basil can reduce thrips on tomato, but nothing links basil to asparagus beetle. Source: UMass Extension — Common Asparagus Beetle
Dill	Dill left to flower near the asparagus row is said to bring in beneficial insects that attack asparagus beetle.	Traditional	Same logic and same gap as parsley — the beetle's main natural enemies are a tiny egg parasitoid wasp plus lady beetle larvae and other predators (UMN), and flowering umbels are a standard nectar source for parasitoids, but no trial has tested dill in asparagus. Source: University of Minnesota Extension — Asparagus beetles
Nasturtium	Nasturtium is said to act as a trap plant for aphids around the asparagus bed.	Traditional	No asparagus data. UMN Extension cites research for nasturtium reducing squash bug in squash, but aphids are a minor asparagus problem compared with asparagus beetle, rust and fusarium, so even a real trap effect would change little. Source: University of Minnesota Extension — Companion planting in home gardens
Parsley	Parsley grown among asparagus is said to deter asparagus beetle and improve spear vigor.	Traditional	Untested. There is a plausible route worth naming honestly: parsley left to bolt produces umbels that feed small parasitoid wasps, and UMN reports the wasp Tetrastichus asparagi can kill up to 70 percent of asparagus beetle eggs. Nobody has measured whether parsley actually raises parasitism in an asparagus bed. Source: University of Minnesota Extension — Asparagus beetles
Rhubarb	Rhubarb makes a good permanent-bed neighbour at the end of the asparagus row.	Traditional	This is a siting recommendation rather than a pest or yield effect. NDSU Extension states that 'the end of an asparagus row is a suitable location' for rhubarb because both are full-sun perennials that must sit outside the tilled part of the garden. Nothing has been measured about one benefiting the other. Source: NDSU Extension H61 — Rhubarb and Asparagus (revised April 2024)
Sweet Alyssum	A low border of sweet alyssum is said to support hoverflies and parasitoids that suppress asparagus pests.	Traditional	Insectary strips have decent general support for boosting natural enemies, but UMN Extension's companion-planting review stresses that specific pairings usually lack crop-level evidence, and no asparagus study was found. Alyssum also stays low enough not to compete, which is the main practical reason to use it here. Source: University of Minnesota Extension — Companion planting in home gardens
Tomato	Asparagus and tomato are said to protect each other — asparagus roots deterring root-knot nematodes on tomato, and tomato deterring asparagus beetle.	Traditional	Half of this has real chemistry behind it and half has nothing. Takasugi et al. (1975) isolated asparagusic acid from asparagus roots, showed it is nematicidal at 50 ppm against several plant-parasitic nematodes and inhibits Heterodera egg hatch, and measured at least 35 ppm in the roots. But no field trial shows that growing asparagus beside tomato lowers root-knot damage on the tomato — the compound is a root defense for asparagus itself, not a demonstrated neighborhood effect. The tomato-repels-asparagus-beetle half is pure tradition: neither UMass nor UMN asparagus beetle guidance mentions tomato or any companion plant, recommending instead prompt harvest, fall fern removal, handpicking and the egg parasitoid Tetrastichus asparagi. Source: Takasugi et al. 1975, Chemistry Letters 4:43 — Identification of Asparagusic Acid as a Nematicide Occurring Naturally in the Roots of Asparagus

What not to plant with asparagus

Plants to keep away from asparagus
Plant	Claimed problem	Evidence	What the evidence actually shows
Garlic	Garlic is said to inhibit asparagus growth.	Traditional	Same folklore as onion, with the same absence of evidence. Treat it as a spacing issue: asparagus is a 15-plus-year planting that resents any root competition, so the reason to keep garlic out is bed management, not chemistry. Source: UMass Extension — Asparagus growing tips
Onion	Alliums are said to stunt asparagus and should be kept out of the bed.	Traditional	No test located, and no measured allelopathic mechanism. The documented problem is competition of any sort, not onions specifically: UMass Extension states that 'weeds shade asparagus, compete for water and nutrients, and reduce yield', which applies to an onion no more and no less than to any other plant sharing the row. Source: UMass Extension — Asparagus growing tips
Potato	Potatoes and other dug root crops are poor asparagus neighbours.	Traditional	Untested as a pairing but mechanically sound: Illinois Extension warns that asparagus roots 'spread out laterally for 5 feet or more over the years' and will compete with other crops for food and water, and crowns sit about 6 inches down — so any crop that requires digging the bed damages the planting. Source: Illinois Extension — Asparagus, Home Vegetable Gardening

The honest verdict

None of the companion pairings commonly recommended for asparagus have been confirmed in controlled trials that we could find. That does not make them harmful — it means the benefit is unproven, and you should plant for spacing, sun, and water compatibility first.

The remaining 7 pairings on this page are traditional practice. They circulate on every companion planting chart online, but we could not find controlled evidence testing them. They are not wrong so much as unverified — most cost nothing to try, and interplanting flowers and herbs has its own well-documented benefit of pulling pollinators and predatory insects into the garden.

Every row above links to the publication it came from. See how we grade evidence.

Growing asparagus: the numbers

Field data — Asparagus
Sun	Full sun (6+ hours)
Water	Moderate
Spacing	12 in apart · 48 in between rows
Mature size	about 48 in tall
Soil pH	6.5–7
Days to maturity	730–1095 days
Frost tolerance	Hardy — takes hard frost
Containers	Not well suited to containers
Typical yield	spears cut over a 6-8 week window each spring once the bed is established
Hardiness zones	2–9 (perennial)
Common pests	common asparagus beetle, spotted asparagus beetle, cutworm, aphids
Common diseases	asparagus rust, fusarium crown and root rot, needle blight

When to plant asparagus

Zone 6b shown

Start indoors Sow / transplant outdoors Harvest

Transplant outdoors: Mar 13 – Mar 26 — 4 weeks before last frost

Expected harvest: Mar 12 — 730–1095 days from planting

Those dates are for zone 6b. Get your own dates by ZIP code →

Varieties worth knowing

crowns

Millennium — All-male hybrid, very cold-hardy and long-lived; the top pick of UMN and NDSU for the Upper Midwest and Northern Plains. Planted as one-year-old crowns rather than seed, which is the normal home-garden practice.
Jersey Knight — All-male hybrid producing thick spears; UGA groups the Jersey hybrids as cold tolerant and resistant to rust and fusarium.
UC 157 — All-male hybrid bred for mild-winter regions and listed by UGA among the good male hybrids; the standard choice in the South and California.
Purple Passion — Purple-speared type recommended by UMN and NDSU; not an all-male hybrid, so it sets berries and volunteer seedlings and yields less than the Jersey/Millennium hybrids.

Variety names link to crowns on Amazon. As an Amazon Associate we earn from qualifying purchases. These are the varieties named in the extension sources for this crop, not a paid placement — where a source recommended a variety for a specific reason, that reason is the note beside it.

Put it in a bed

The garden planner checks every square against this ledger as you place crops — if you drop asparagus next to something recorded as a bad neighbour, the square turns red and tells you why.

Records for the plants named above:

Tomato Basil Parsley Dill Sweet Alyssum Nasturtium Rhubarb

Same rotation group (other) — don't follow one with another:

Celery Okra Rhubarb Sweet corn Sweet Potato Strawberry

Asparagus companion planting questions

What should not be planted next to asparagus?

Onion, Garlic, Potato. Alliums are said to stunt asparagus and should be kept out of the bed. No test located, and no measured allelopathic mechanism. The documented problem is competition of any sort, not onions specifically: UMass Extension states that 'weeds shade asparagus, compete for water and nutrients, and reduce yield', which applies to an onion no more and no less than to any other plant sharing the row.

How far apart should asparagus be planted?

Space asparagus about 12 inches apart in the row, with 48 inches between rows.

Does companion planting with asparagus actually work?

Partly. None of the pairings we found for asparagus have been confirmed in controlled trials. The rest are traditional practice: plausible, harmless to try, but untested. Treat the folklore as a starting point rather than a rule, and read what the evidence says about companion planting.

When should I plant asparagus?

Transplant outdoors 4 weeks before last frost. In zone 6b that means roughly Mar 13 – Mar 26. Get exact dates for your ZIP code →

Sources for this record

Record compiled 2026-07. Spot an error or a study we missed? Tell us and we'll correct the entry.