Broccoli companion plants: the 12 that actually help (and 3 that don't)

Broccoli is a heavy feeder that sits in the garden for 60–100 days — long enough for aphids, imported cabbageworm, and cabbage loopers to find it and cause real damage. Companion planting is not a magic shield, but the right neighbors can reduce pest pressure, attract beneficial insects, and in a.

—- title: "Broccoli companion plants: the 12 that actually help (and 3 that don't)" slug: broccoli-companion-plants hub: care category: "Companion planting" description: "Which plants genuinely benefit broccoli by repelling pests or improving growth — and which three common choices are a mistake. Sourced from Extension research." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 9 release_after: 2026-06-25 —-

Broccoli is a heavy feeder that sits in the garden for 60–100 days — long enough for aphids, imported cabbageworm, and cabbage loopers to find it and cause real damage. Companion planting is not a magic shield, but the right neighbors can reduce pest pressure, attract beneficial insects, and in a few cases improve soil conditions for the main crop.

The research on companion planting is thinner than garden writers often imply. Much of what circulates as "proven combinations" is anecdote. This guide sticks to what Extension services and peer-reviewed research actually support.

Why companion planting matters more for brassicas than most vegetables

Broccoli (Brassica oleracea var. italica) is a brassica. As a group, brassicas are host plants for a narrow range of specialist insects — imported cabbageworm (Pieris rapae), cabbage looper (Trichoplusia ni), diamondback moth (Plutella xylostella), and harlequin bug in warmer regions. These pests locate host plants primarily by volatile chemical signals (glucosinolates) released by the leaves.

Per NC State Extension, intercropping with aromatic plants can partially mask these volatiles, making it harder for pests to locate broccoli rows. The effect is not elimination — it's dilution and delay.

The companion planting table

The 12 companions that actually help

1. Dill (Anethum graveolens)

Dill flowers are among the most effective attractors of parasitic wasps in the vegetable garden. Per UC IPM, Aphidius and Braconid wasps that parasitize cabbage aphids and caterpillars are strongly attracted to umbellifer flowers. Plant dill within 10–15 feet of broccoli rows and allow it to flower. The catch: mature dill planted directly beside tomatoes is allelopathic — but that concern does not apply to broccoli.

2. Cilantro (Coriandrum sativum)

Like dill, cilantro in flower provides nectar and pollen for parasitic wasps. Per Cornell Cooperative Extension, sowing cilantro in succession near brassica beds maintains a flowering presence throughout the season, which keeps beneficial insect populations higher than bare-soil or mulched paths would.

3. Sweet alyssum (Lobularia maritima)

Sweet alyssum flowers attract syrphid flies (hoverflies), whose larvae are active predators of aphids. Per Oregon State Extension, planting alyssum at the edges of vegetable beds or as a living mulch beneath tall crops like broccoli has been shown in field trials to increase syrphid fly presence and reduce aphid populations. It also suppresses weeds between rows.

4. Nasturtium (Tropaeolum majus)

Nasturtiums work as a trap crop — aphids, particularly black bean aphids and cabbage aphids, prefer nasturtium to broccoli and will aggregate on it. Per Clemson HGIC, the trap crop strategy requires monitoring: once nasturtiums are heavily infested, remove and destroy the plants rather than letting the aphid colony move on to broccoli.

5. Thyme (Thymus spp.)

Per Penn State Extension, thyme's aromatic volatile compounds have been shown in some studies to reduce host-plant location by cabbage moths. Plant thyme as a border between rows. It is also deer-resistant and drought-tolerant, making it a low-maintenance edge plant in most zones.

6. Sage (Salvia officinalis)

Sage is cited in multiple Extension publications as a potential deterrent for imported cabbageworm adults (Pieris rapae). Per Missouri Botanical Garden, culinary sage interplanted between brassica rows has a long tradition in kitchen gardens. The mechanism is presumed to be volatile masking, though controlled studies are limited.

7. French marigold (Tagetes patula)

French marigold's reputation for repelling nematodes is real but requires context. Per UMass Extension, the nematode suppression effect of Tagetes patula requires planting it densely as a cover crop and tilling it into the soil — not just placing a few plants near the row. As a companion in the same-season bed, marigolds attract beneficial insects and may have some above-ground pest deterrence. Do not confuse French marigold (T. patula) with African marigold (T. erecta), which does not share the same nematode-suppression chemistry.

8. Garlic and onions (Allium spp.)

The evidence for alliums deterring aphids is mixed. Some field observations suggest sulfur compounds from alliums confuse aphid orientation. Per Texas A&M AgriLife Extension, interplanting broccoli with garlic or onions is low-risk and potentially beneficial, though the evidence for meaningful pest reduction is anecdotal at the scale of a home garden.

9. Celery (Apium graveolens)

Celery is traditionally paired with brassicas in European kitchen gardens. The volatile scent is thought to confuse white butterflies. Evidence is largely historical and observational rather than experimental. It is a compatible companion in terms of spacing and soil needs.

10–12. Neutral companions worth planting (spinach, lettuce, beets)

Spinach, lettuce, and beets grow beneath the broccoli canopy without competition and without documented pest interaction. They improve bed utilization in spring, when broccoli spacing leaves substantial bare ground. Per Cornell Cooperative Extension, interplanting low-growing crops under tall brassicas is a practical way to suppress weeds without allelopathic risk.

The 3 companions to avoid

Fennel

Fennel (Foeniculum vulgare) is allelopathic to nearly every vegetable in the garden. Per NC State Extension, fennel produces compounds from its roots and decomposing plant tissue that inhibit germination and growth of neighboring plants. Keep it in a container or a dedicated corner of the garden, away from all vegetable beds.

Concentrated brassica blocks

Growing cabbage, cauliflower, kale, and broccoli in a solid block concentrates glucosinolate volatiles in one area, creating what is effectively a beacon for specialist brassica pests. Per Oregon State Extension, mixed plantings that alternate brassicas with non-host crops reduce pest pressure compared to solid brassica blocks. Rotate all brassica family members together as a group, but space individual brassica crops within the season by interplanting non-hosts between them.

Mature mustard

Mustard (Brassica juncea, B. hirta) belongs to the same family as broccoli and hosts the same pests. A small mustard planting at the bed edge can work as a trap crop for diamondback moth, but once established, mature mustard plants attract and retain the same insects that damage broccoli. This is particularly problematic for harlequin bugs in the South, which overwinter in mustard and move to spring brassica crops.

Spacing and arrangement

Per Rutgers NJAES, effective companion planting requires physical proximity — plants more than 20–30 feet from the target crop provide minimal benefit. For a standard 4-foot wide raised bed, plant fragrant herbs (thyme, sage) at the edges of each bed, or in the paths between beds. Tall companions like dill and cilantro should be placed where they won't shade the broccoli, typically on the north side of east-west rows.

Frequently asked questions

Does companion planting eliminate the need for pest control in broccoli? No. Per NC State Extension, companion planting is one component of an integrated pest management strategy, not a replacement for monitoring and physical controls. Hand-picking caterpillars, using floating row cover for cabbageworm prevention, and applying Bacillus thuringiensis (BT spray) (Bt) when populations are high remain important tools regardless of companion planting.

Can I plant two different brassicas next to each other? Technically yes, but it amplifies pest attractant signals and concentrates host plants for specialist insects. Per Oregon State Extension, alternating brassicas with non-host crops (even just marigolds or lettuce between plants) reduces pest load more than planting brassicas continuously.

Is there evidence that marigolds protect broccoli from above-ground pests? The soil nematode evidence is solid when marigolds are grown as a full-bed cover crop and tilled in. The above-ground pest deterrence is less well-documented. Per Clemson HGIC, marigolds in a vegetable bed are beneficial but should not be relied upon as primary pest management.

What is the best use of nasturtiums near broccoli? As a trap crop planted upwind of broccoli. Aphids and whiteflies tend to colonize nasturtiums preferentially. Monitor weekly. Remove infested nasturtium plants once aphid colonies are dense, before they migrate. Per Clemson HGIC, this strategy works best when the nasturtium is more attractive than the main crop, which requires planting nasturtiums before or at the same time as transplanting broccoli.

Sources

1. NC State Extension — Brassica Companion Planting
2. UC IPM — Biological Control in the Home Garden
3. Cornell Cooperative Extension — Vegetable Gardening
4. Oregon State Extension — Companion Planting in the Vegetable Garden
5. Clemson HGIC — Companion Planting
6. UMass Extension — Marigolds and Nematode Management
7. Texas A&M AgriLife Extension — Companion Planting
8. Penn State Extension — Thyme
9. Rutgers NJAES — Companion Planting
10. Missouri Botanical Garden — Salvia officinalis