Plants
Lobelia
Lobelia erinus · Campanulaceae
Hardly any balcony flower delivers such a rich, true blue as lobelia: the low cushions and trailing varieties cover themselves from May into September with hundreds of small lipped blooms. In German folk speech it is called Männertreu — men's faithfulness. We buy our bedding stock compact and full of buds at the Veiling Rhein-Maas.
- Light
- Sunny to part-shaded, no scorching midday heat.
- Watering
- Regular — evenly moist, check daily on hot days.
- Care level
- Easy
- Botanical
- Lobelia erinus
Lobelia erinus comes in two growth habits: compact cushion varieties of ten to fifteen centimetres for bed edges and box foregrounds, and trailing Pendula types with shoots up to forty centimetres for hanging baskets. Classics are the deep blue Crystal Palace with dark foliage and the cascading Sapphire.
Its strength is blue — a rare colour in the summer range. In box plantings we like lobelia as a cooling contrast to white bacopa, red geraniums or yellow million bells; the blue-white-red trio has been a balcony classic for generations.
Unlike many South Africans, lobelia does not want it bone-dry: it needs evenly moist, humus-rich soil and quickly answers a dry root ball with browned cushions. In the blazing midday sun of hot spots, light part shade is often the better choice.
The most important care trick is the summer cut: when the first flush fades around the turn of July, cut the cushions back by about half, feed and water well — two to three weeks later a second, often equally lavish bloom follows into autumn.
Worth knowing: like all species of the genus, lobelias contain alkaloids, above all lobeline, and are no snacking plant. For normal balcony culture this is uncritical, but nibbling pets and small children should not get at the plant.
Is Lobelia toxic to children and pets?
- Children
- Toxic
- Cats
- Toxic
- Dogs
- Toxic
Lobelias contain pyridine alkaloids (including lobeline) and are toxic to cats, dogs and children. The small balcony plants contain lower amounts than wild species, but should still be kept out of reach of pets and small children.
Typical symptoms: After ingestion: drooling, vomiting, diarrhoea, abdominal pain; with larger amounts heart rhythm disturbances and tremors.
In an emergency:call the German poison control centre in Bonn on +49 228 19240 (24/7) — for pets, contact an emergency vet directly. This information does not replace medical or veterinary advice.
Overview: toxic & non-toxic plants for cats, dogs and children
Care
- 01A sunny to part-shaded spot; light shade is preferable in hot positions.
- 02Keep evenly moist — a dry root ball browns the cushions.
- 03Feed moderately every one to two weeks.
- 04After the first flush in July, cut back by half for a second bloom.
- 05Plant out only after the last spring frosts; lobelias are frost-tender.
- 06Do not place within reach of nibbling pets.
Frequently asked
- Why is lobelia called Männertreu in German?
- The folk name — men's faithfulness — is a wink at the flowers' staying power: depending on the reading, the long, faithful flowering stands for constancy, or the quick fading of each single bloom for the opposite. In the language of flowers, blue lobelia stands for loyalty either way.
- Is lobelia toxic to cats or dogs?
- Yes. All lobelias contain alkaloids such as lobeline, which can cause vomiting, diarrhoea and, in larger amounts, cardiovascular symptoms in cats and dogs. Hang baskets out of reach, keep pets from nibbling boxes, and see a vet if ingestion is suspected.
- Why has my lobelia stopped flowering in high summer?
- That is the normal summer pause after the first flush, often intensified by heat and drought. Cut the cushions back by half, water and feed well — the plant will regrow and flower a second time from August into autumn.
- Is lobelia perennial?
- Balcony lobelia (Lobelia erinus) is grown as an annual here and dies with the frost. There are, however, hardy perennial lobelias such as Lobelia cardinalis and Lobelia siphilitica for beds and pond edges — though these are even more toxic than the balcony form.