Record — updated 2026-07

Sweet Alyssum Companion Plants

Entry No. 056

Lobularia maritima · mustard family family · rotation group: brassica

The best companion plants for sweet alyssum are Lettuce, Broccoli, Aphid-Prone Crops Generally, Squash, and Strawberry. Of the 5 pairings recorded here, 4 are supported by published research and 1 is 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 sweet alyssum

Companion plants for sweet alyssum — 4 research-backed, 1 traditional
Plant	Claimed benefit	Evidence	What the evidence actually shows
Aphid-Prone Crops Generally	A border of alyssum raises beneficial insect numbers and suppresses aphids across the bed.	Research-backed	UC Davis reported aphid suppression extending up to 50 feet from the alyssum planting, with parasitic wasps, lacewings and hoverflies as the responsible predators. Source: Aphid Relief from Sweet Alyssum, UC Davis
Broccoli	Strip-intercropped alyssum supplies floral resources for aphid predators in broccoli.	Research-backed	USDA-ARS found broccoli outcompetes alyssum, so bed sections planted with alyssum alone are recommended for all-season flowers, with additive intercropping used for early-season bloom. Source: Brennan, E.B. (2016), Agronomy of strip intercropping broccoli with alyssum for biological control of aphids, Biological Control 97:109-119
Lettuce	Alyssum interplanted with lettuce attracts hoverflies whose larvae suppress lettuce aphids.	Research-backed	The best-evidenced pairing in this entire dataset. Alyssum has been used as a commercial insectary plant in California organic lettuce for over 20 years, and USDA-ARS work established intercropping layouts that deliver the aphid benefit without sacrificing marketable lettuce yield. Source: Brennan, E.B. (2013), Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids, Biological Control 65(3):302-311
Squash	Alyssum planted with squash increases the natural enemies of aphids.	Research-backed	Independently confirms the lettuce and broccoli results in a third crop; UMN Extension lists this among its research-supported companion pairings. Source: Companion planting in home gardens, University of Minnesota Extension
Strawberry	Alyssum is grown in strawberry beds as a low insectary ground cover.	Traditional	Used commercially alongside the lettuce and broccoli systems, but the published trial evidence is strongest for lettuce. Source: Lobularia maritima, NC State Extension Gardener Plant Toolbox

The honest verdict

Of everything gardeners recommend planting alongside sweet alyssum, 4 pairings have been tested properly: Lettuce, Broccoli, Aphid-Prone Crops Generally, Squash. Those are the ones worth planning your bed around.

The remaining 1 pairing on this page is 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.

Other recorded effects

Effects that aren't about a neighbouring plant — what sweet alyssum does for (or to) the garden around it, and the caveats attached to the popular versions of those claims.

Recorded effects and caveats — Sweet Alyssum
Effect	The claim	Evidence	What the evidence actually shows
Lettuce (field verification)	Alyssum plantings measurably reduce aphids inside lettuce heads.	Research-backed	Important nuance from the UC IPM trial: hoverfly counts were similar across treatments, yet fields with sweet alyssum alone had fewer aphids on traps and inside lettuce heads. Notably, mixing alyssum with cosmos and cilantro performed no better than no insectary plants at all. Source: Del-Pozo-Valdivia confirms the benefit of insectary plants in lettuce, UC IPM (2019)
Parasitic Wasps and Flies	The tiny open flowers are accessible to short-tongued parasitoids and predatory flies.	Research-backed	Clemson Extension names sweet alyssum specifically as a small-flowered plant that attracts parasitic flies and wasps which feed on the nectar. Source: Ballew, J. (2022), Attracting Beneficial Insects to Your Vegetable Garden, Clemson HGIC
Container and Bed Edging	Low spreading habit makes alyssum a living mulch at bed and container edges.	Traditional	Practical: 3-10 inches tall with a 6-12 inch spread and good drought tolerance once established. Source: Lobularia maritima, NC State Extension Gardener Plant Toolbox
Brassica Crop Rotation	Alyssum is a neutral flower that can go anywhere in the rotation.	Traditional	Genuinely important and widely missed: sweet alyssum is in the Brassicaceae, so it belongs in the brassica rotation group and can host brassica pests and diseases rather than breaking their cycle. Source: Lobularia maritima, NC State Extension Gardener Plant Toolbox
Mixed Insectary Plantings	Mixing several insectary flowers beats planting alyssum alone.	Not supported	Contradicted by trial: fields with alyssum plus cosmos and cilantro showed no aphid benefit over fields with no insectary plants, while alyssum alone did reduce aphids. Source: Del-Pozo-Valdivia confirms the benefit of insectary plants in lettuce, UC IPM (2019)
Production Space	Insectary alyssum is free to add.	Research-backed	It does cost land: USDA-ARS work exists precisely because alyssum displaces crop plants, and the recommended additive layouts are designed to recover that loss. Source: Brennan, E.B. (2013), Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids, Biological Control 65(3):302-311

Growing sweet alyssum: the numbers

Field data — Sweet Alyssum
Sun	Full sun (6+ hours)
Water	Low once established
Spacing	8 in apart · 12 in between rows · 4 per square foot
Mature size	about 6 in tall
Soil pH	6–7.5
Days to maturity	42–56 days
Frost tolerance	Hardy — takes hard frost
Containers	Yes — 1 gallon minimum
Common pests	flea beetles, aphids
Common diseases	downy mildew, stem and crown rot

When to plant sweet alyssum

Zone 6b shown

Start indoors Sow / transplant outdoors Harvest

Start seeds indoors: Feb 13 – Feb 27 — 6–8 weeks before your last frost

Transplant outdoors: Mar 27 – Apr 9 — 2 weeks before last frost

Direct sow outdoors: Mar 27 – Apr 9 — 2 weeks before last frost

Expected harvest: May 8 – May 22 — 42–56 days from planting

Fall planting: Sep 1 – Sep 14 — 8 weeks before your first fall frost

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

Varieties worth knowing

seeds

Snow Princess — vegetatively propagated and sold as plants, not seed; heat and cold tolerant with no midsummer stall
Carpet of Snow — classic low white seed-grown carpeting type
Easter Bonnet — compact and early flowering; seed grown
Royal Carpet — purple seed-grown selection

Variety names link to seeds 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 sweet alyssum next to something recorded as a bad neighbour, the square turns red and tells you why.

Records for the plants named above:

Lettuce Broccoli Strawberry Squash

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

Arugula Bok Choy Broccoli Brussels Sprouts Cabbage Cauliflower

Sweet Alyssum companion planting questions

What should not be planted next to sweet alyssum?

We have no well-evidenced antagonists on file for sweet alyssum. The reliable rule is to avoid crowding it with anything in its own family (mustard family), which shares its pests and diseases and makes rotation harder.

How far apart should sweet alyssum be planted?

Space sweet alyssum about 8 inches apart in the row, with 12 inches between rows. In a square-foot bed that works out to 4 plants per square foot.

Does companion planting with sweet alyssum actually work?

Partly. 4 of the pairings on this page are backed by published research — Lettuce, Broccoli, Aphid-Prone Crops Generally, Squash. 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 sweet alyssum?

Start seed indoors 6–8 weeks before your last frost. Transplant outdoors 2 weeks before last frost. In zone 6b that means roughly Mar 27 – Apr 9. 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.