What the red actually is
Breeders have never produced a scarlet Lobelia erinus. The colour sold as red is magenta, cerise or carmine-pink, often with a pale eye, which reference lists group under magenta ("red"). 'Rosamund' is the classic cultivar, a bright carmine that is still grown, and 'Riviera Rose' pushes towards pink. If you want a flame-red lobelia you are thinking of the tall cardinal flower, Lobelia cardinalis, which is a different plant for a wet border.
Using a strong colour
Cerise lobelia can look harsh next to orange but sits happily with white, pale blue and silver. It makes a lively edge for a bed of grey-leaved plants or a strip beside a path.
- Mix it with white lobelia in a basket to soften the intensity.
- Pair it with deep blue forms for a bold, jewel-like contrast.
- Keep it clear of orange and yellow marigolds.
Growing notes
Like every Lobelia erinus it is a half-hardy annual, so keep it under cover until the last frost has passed. It does well in sun or light shade and needs steady moisture; a small basket on a windy gable can dry out within a day. Feed regularly while it blooms.
A mid-season haircut after the first flush keeps it neat and often brings more flowers in late summer.
Handling and pets
All lobelias contain alkaloids, including lobeline. The ASPCA lists the cardinal flower as toxic to dogs, cats and horses, so do not let animals chew the plant. Wear gloves if your skin is sensitive, and keep the National Poisons Information Centre in mind if a child swallows any.
