Cosmos
Cosmos bipinnatus Cav.
Botanical family: Asteraceae
Cosmos bipinnatus, a tall Mexican annual with feathery foliage and wide, open pink, mauve or white flowers from summer until the frosts. An easy, generous border flower, much visited by the garden's small folk.
Full sun
Ordinary to poor, well-drained (soil too rich gives leaves at the expense of flowers)
Moderate, drought-tolerant once established
Frost-tender annual, killed by frost, it self-seeds year after year
An annual killed by frost in your zone
Open flowers pollinated by insects
Role in permaculture
A first-rate insectary plant: its open flower offers easily accessible nectar and pollen and draws both pollinators (bees, butterflies) and beneficial insects (hoverflies, lacewings, tiny parasitoid wasps) whose larvae keep aphids in check. Sow it along borders or in a flowering strip near vulnerable crops, in poor soil, too much nitrogen gives leaves and few flowers.
Companions
No companion planting is documented for this plant: no recommended neighbour, no neighbour to avoid.
Insects attracted or useful
Seasons & availability
A frost-tender annual flower: sown in spring, in March under cover or in April and May in place after the last frosts, it flowers from summer until the first frosts, July to October, and feeds bees, bumblebees and hoverflies in the kitchen garden. Cut the flowers for the vase, or let a few heads run to seed for next year.
Available: July, August, September, October.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Plants For A Future, « Cosmos bipinnatus » (pfaf.org/user/Plant.aspx?LatinName=Cosmos+bipinnatus)
- Missouri Botanical Garden, « Cosmos bipinnatus » (plantfinder.mobot.org/PlantFinderDetails.aspx?taxonid=277181)
Family behaviour: Asteraceae
In general, Asteraceae are a family rich in flowers appreciated by pollinators and beneficials (pot marigold, yarrow, chamomile). It is very scattered, from the mildest lettuce to the allelopathic sunflower.
Understanding families means learning one rule per family rather than every pairing one by one. Learn more →
Species & varieties
The best-known species and varieties in France.
Species
Common varieties
Keep in mind
Attracting beneficials is a helping hand, not a guarantee of pest control: the effect depends on garden pressure, weather and surrounding diversity. Specific cosmos–vegetable "companion" pairings are mostly garden folklore; the solid role is functional (a nectar-rich flowering strip). A frost-tender annual in mainland France, cosmos nonetheless self-seeds readily. Sources: RHS, “Cosmos bipinnatus, cosmea”; USU Extension, “Cosmos in the Garden”; Hicks et al. 2016, PLoS ONE (DOI 10.1371/journal.pone.0158117).
A note on rigour: many companion pairings are gardening folklore; this note sums up what the sources say, where there are any.
Key takeaways
- • Prefers full sun exposure.
- • Ideal soil: ordinary to poor, well-drained (soil too rich gives leaves at the expense of flowers).