Companion planting
10 Broccoli Companion Plants (and What to Keep Apart)
Sweet alyssum, thyme, onion, and nasturtium have the strongest evidence behind them for broccoli, from a trap-crop trial and an Oregon State study on parasitoid wasps. Keep broccoli away from tomatoes, strawberries, pole beans, and a tight block of other brassicas.
The short answer
The best broccoli companions are sweet alyssum for its parasitic-wasp boost, the thyme-onion-nasturtium trio that cut caterpillar damage in an Iowa trial, and flea beetle trap crops like arugula or mustard. Keep broccoli apart from tomatoes, strawberries, pole beans, and a tight cluster of other brassicas. Crop rotation and spacing matter more than any single neighbor.
Broccoli's companion charts online repeat the same short list of herbs and flowers, but few of them link to an actual study. This guide checks each pairing against a real source and rates it research-backed, traditional, or anecdotal, so you know which ones are worth bed space.
Cabbage aphids, cabbage loopers, imported cabbageworms, and flea beetles are broccoli's main pests. The companions that hold up are the ones tied to those specific pests, not a general "keeps bugs away" claim.
Two things stand out once you check the sources. First, the strongest results come from planting several species together, not one magic neighbor: the thyme-onion-nasturtium trio beat any of the three planted alone, and the flea beetle trap crops work as a border, not a single companion tucked next to one plant. Second, even the best-documented pairing, sweet alyssum, only proved out one part of the story. It raised beneficial-wasp activity, but the researchers didn't see fewer aphids in the same trial. That gap between "helped one measurable thing" and "solved the pest problem" is worth remembering for every row in the table below.
10 companion plants for broccoli
Research-backed means a study or trial supports the pairing. Traditional means an extension service lists it as a companion or documented practice, without a controlled test of the benefit. Anecdotal means it's garden lore with no source behind it.
| Plant | Why it helps | Evidence |
|---|---|---|
| Sweet alyssum | Its flowers feed hoverflies and parasitic wasps; an Oregon State trial found parasitism of cabbage aphids nearly doubled in broccoli interplanted with alyssum | Research-backed (Oregon State University) |
| Thyme | Part of an Iowa trial combo (with onion and nasturtium) that cut cabbage looper and imported cabbageworm damage on broccoli | Research-backed (University of Minnesota Extension) |
| Onion | Same Iowa trial combo; also roots at a different depth so it doesn't compete for space | Research-backed (University of Minnesota Extension) |
| Nasturtium | Trap crop that draws aphids and cabbage white caterpillars onto itself; also part of the Iowa trial combo | Research-backed / traditional (Utah State University Extension) |
| Arugula or mustard | Sacrificial trap-crop border planted 2-4 weeks before broccoli to pull flea beetles off the main crop | Research-backed (Utah State University Extension) |
| Bunching (green) onions | Listed with dill and marigold as companion crops used for flea beetle management | Traditional (Utah State University Extension) |
| Dill | Aromatic herb extension services list as a cabbage-family companion; its flowers can feed pest-eating insects generally | Traditional (West Virginia University Extension) |
| Marigold | Used alongside green onions in flea beetle management, but the evidence for marigold on its own is thin and mixed | Traditional, mixed evidence (Utah State University Extension) |
| Lettuce | Quick, shallow grower that fills bare soil around young broccoli before the plants need the room | Anecdotal (garden-space logic) |
| Beets | Same low, fast-growing space-filler role as lettuce | Anecdotal (garden-space logic) |
The pattern: the strongest picks either feed broccoli's pest predators or pull pests onto themselves. Lettuce and beets are fine choices, just don't credit them with pest control they've never been tested for.
Bad companion plants for broccoli
Now the avoid list, with an honest note on how solid each reason is.
| Keep apart | Why (and how solid the reason is) |
|---|---|
| Tomatoes | Extension-listed. West Virginia University Extension names tomatoes as a poor neighbor for the cabbage family. |
| Strawberries | Extension-listed. Same WVU Extension list flags strawberries for the cabbage family. |
| Pole beans | Extension-listed. Also on WVU Extension's do-not-plant-near list for the cabbage family. |
| Other brassicas, clustered (cabbage, cauliflower, kale) | Well supported. They share broccoli's pests and its heavy nitrogen appetite. Iowa State Extension says to grow cole crops in the same spot only once every three to four years, and packing the family together works against that. |
The rotation point deserves the most weight here. Iowa State University Extension recommends planting cole crops in a given area only once every three or four years. A tight block of broccoli, cabbage, and cauliflower elbow to elbow undoes that rotation and concentrates the pests you're trying to avoid.
Which companion helps with which pest
Match the companion to the actual pest broccoli has, not a vague "repels bugs" claim.
| Pest | Companion tactic | Source |
|---|---|---|
| Cabbage aphid | Interplant with sweet alyssum to raise parasitic wasp activity; note the one trial didn't see lower aphid counts that season, likely due to timing | Oregon State University |
| Cabbage looper, imported cabbageworm | Thyme, onion, and nasturtium planted together (as a trio, not one plant alone) | University of Minnesota Extension, citing an Iowa trial |
| Flea beetles | Trap-crop border of arugula or mustard, planted 2-4 weeks ahead of the broccoli | Utah State University Extension |
| Flea beetles | Bunching green onions, dill, and marigold as companion crops | Utah State University Extension |
The flea beetle trap crop works on timing as much as plant choice. Utah State University Extension says to plant the trap crop two to four weeks before the cash crop, so it's already larger and more established by the time flea beetles arrive, which makes it the more attractive target.
Note
Cabbage root fly and harlequin bug don't have a documented companion-plant fix in the sources checked for this guide. Floating row cover and monitoring do more for those two than any companion pairing.
A sample bed layout
Picture a 4x8 ft raised bed. Set broccoli down the center on 18 to 24 inches of spacing, which fits two rows with room to spare. The plant spacing calculator works out the exact count for your bed size.
Run a ribbon of sweet alyssum or dill along one edge so the flowers are within reach of the whole bed. On the opposite edge, a border of arugula or mustard sown two to four weeks before the broccoli goes in acts as the flea beetle trap crop. In the gaps between young broccoli plants, tuck in lettuce or beets, since they'll be harvested before the broccoli fills the space. Keep tomatoes, strawberries, and pole beans in a different bed entirely.
Pro tip
Sweet alyssum's benefit showed up in wasp activity, not fewer aphids, in the one trial behind it. Plant it because it's cheap, low-maintenance, and feeds beneficial insects all season, not because it guarantees an aphid-free crop.
It applies to the whole brassica family
Broccoli, cabbage, cauliflower, kale, and Brussels sprouts share the same pests and the same three-to-four-year rotation rule, so most of what's here carries over. If cabbage is the crop in question, cabbage companion plants covers it with cabbage-specific sources. Growing Brussels sprouts in the same bed? When to harvest Brussels sprouts covers the bottom-up signs that tell you sprouts are ready.
Broccoli is a heavy feeder
Companion planting won't fix an underfed plant. University of Maryland Extension lists broccoli among the heavy feeders that need about 3 pounds of nitrogen per 1,000 square feet, more than the average vegetable. Iowa State University Extension also calls for fertile, well-drained soil with a pH between 6 and 7, plus at least six hours of direct sun a day. Feed the bed well and give plants full spacing first, since good soil and airflow protect broccoli more than any companion can.
Common mistake
Packing broccoli, cabbage, and kale into one dense block. They share pests and pull the same heavy dose of nitrogen from the soil, so crowding them together concentrates both problems. Space the family out and rotate it to a new spot every three to four years.
Expecting marigold alone to control pests. Utah State University Extension lists marigold as part of a companion-crop mix for flea beetles, not a standalone fix, and the evidence for marigold by itself is thin. Use it for the flowers, and lean on row covers or handpicking for real pest control.
Get the spacing right first
None of these companions matter much if broccoli is crowded to begin with. Crowded plants compete for light and trap humid air around the leaves, which invites disease regardless of what's growing nearby.
Space broccoli 18 to 24 inches apart in the row, with 24 to 30 inches between rows, per Iowa State University Extension. The how far apart to plant broccoli guide has the full spacing table by method, when to plant broccoli covers timing for spring and fall crops, and when to harvest broccoli covers the bud signs that say it's ready.
For the same evidence-versus-folklore approach on other crops, see onion companion plants and lettuce companion plants.
Your next step
Plant sweet alyssum or dill for the beneficial insects, add a trap-crop border of arugula or mustard for flea beetles, and tuck lettuce or beets into the gaps. Keep tomatoes, strawberries, pole beans, and a dense brassica block out of the same bed.
The biggest lever is still spacing and rotation, not the companion list. Set plants with real room using the spacing guide above, then time the crop right using the planting guide linked earlier.
Common questions
What should you not plant next to broccoli?
West Virginia University Extension lists tomatoes, strawberries, and pole beans as poor neighbors for the cabbage family, broccoli included. Also avoid packing broccoli tight against other brassicas like cabbage, cauliflower, and kale. Iowa State University Extension says to plant cole crops in the same spot only once every three or four years, and a dense brassica block works against that.
Do marigolds help broccoli?
Only as part of a mix, not on their own. Utah State University Extension lists bunching green onions, dill, and marigolds together as companion crops used for flea beetle management, but marigold alone has thin, mixed evidence behind it. Plant it for the flowers and treat any pest benefit as a bonus, not a guarantee.
How close can broccoli be planted together?
Iowa State University Extension recommends 18 to 24 inches between plants in the row, with rows spaced 24 to 30 inches apart. The [plant spacing calculator](/plant-spacing-calculator) works out exact plant counts for your bed size.
What is the 3-year rule for plants?
It's crop rotation. Iowa State University Extension says to grow cole crops (broccoli, cabbage, cauliflower, kale) in a given spot only once every three to four years, so the soil-borne diseases and pests that build up under one family don't have a home the following season.
Is broccoli companion planting backed by science?
Partly. An Oregon State University field trial found that interplanting broccoli with sweet alyssum nearly doubled parasitic wasp activity on cabbage aphids, though aphid counts themselves didn't drop that season. University of Minnesota Extension cites an Iowa trial where thyme, onion, and nasturtium cut cabbage looper and cabbageworm damage. Most other pairings on popular charts are undocumented, so treat this guide as a starting point, not a rulebook.
Sources
Agronomic claims in this guide are checked against these primary sources.
- Alyssum Attracts Predator Insects to Broccoli Fields — Oregon State University
- Companion planting in home gardens — University of Minnesota Extension
- Flea Beetles on Vegetables — Utah State University Extension
- Creating Sustainable School and Home Gardens: Companion Planting — Utah State University Extension
- Companion Planting — West Virginia University Extension
- Fertilizing Vegetables — University of Maryland Extension
- Growing Broccoli in the Home Garden — Iowa State University Extension and Outreach
- Companion Planting: Anecdotal or Tried and Tested? — University of Illinois Extension
Keep reading
13 Cabbage Companion Plants (and What to Avoid)
Good cabbage companions are quick, low crops like lettuce and beets, flowering herbs for pest-eating insects, and trap crops like nasturtium and arugula. Keep cabbage away from tomatoes, pole beans, strawberries, and other brassicas.
Read →Onion Companion Plants (and What to Keep Apart)
Good onion companions are carrots, beets, lettuce, and cabbage-family crops, mostly because onions are narrow and slow and fit between bigger plants. Keep onions away from beans and peas. The pest-repelling claims are mostly folklore.
Read →Lettuce Companion Plants (and What to Keep Apart)
Good lettuce companions are carrots, radishes, onions, chives, and tall crops like tomatoes or trellised cucumbers that throw afternoon shade. The real, evidence-backed win is shade that slows bolting in summer heat. Keep lettuce clear of fennel and avoid crowding.
Read →When to Plant Broccoli (Spring and Fall Timing by Zone)
Set broccoli transplants out 2 to 4 weeks before your last spring frost, once soil reaches about 40 F. For a fall crop, plant 6 to 10 weeks before the first fall frost. Timing by zone, soil-temp cues, and the common mistakes.
Read →12 Garlic Companion Plants (and What to Avoid)
Good garlic companions are low crops like beets, lettuce, and chard that share the bed while garlic grows through winter, plus tomatoes, strawberries, and carrots. Keep garlic away from beans, peas, and other alliums planted too soon after it.
Read →Zucchini Companion Plants (and What to Keep Apart)
Good zucchini companions are flowers like nasturtium and borage that pull in the bees zucchini needs to set fruit, plus beans and corn. Keep zucchini away from other squash and cucumbers, which share its pests. Most "avoid" charts are folklore.
Read →