Lobelia siphilitca (Great Blue Lobelia) — perennial

Overview

Lobelia siphilitca is a perennial in the genus Lobelia, part of the Campanulaceae family. Lobelia siphilitca grows best in full sun and partial shade, and tolerates most soils. Suggested uses include wildlife gardens, rain gardens, naturalized areas and borders. It is native to Ontario.

About

Lobelia siphilitca is a species in the genus Lobelia (family Campanulaceae) that bears the two-lipped, tubular flowers characteristic of the group. It has simple, alternate leaves and the five-lobed floral structure seen across Lobelia. Flowering occurs from June to September. Members of the genus commonly produce abundant displays of flowers, a trait reflected in this species.

About the genus

Lobelia is a genus of flowering plants in the family Campanulaceae comprising 444 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions. They are known generally as lobelias.

Wikipedia contributors, "Lobelia", CC BY-SA 4.0 — Lobelia

In the garden

Lobelia siphilitca belongs to the genus Lobelia within the Campanulaceae and shares the structural features that define the group: simple alternate leaves and two-lipped, tubular flowers with five lobes. The genus has a wide, subcosmopolitan presence, occurring mainly in tropical to warm-temperate regions with a few species extending into cooler temperate zones. Species within Lobelia take many forms, including annuals, perennials and shrubs, so L. siphilitca should be considered in that wider context when planning planting. Look to the species’ origin and nursery labelling when deciding siting and winter protection, because Lobelia species vary from tender to fully hardy. Many plants in the genus produce prolific blooms and the floral structure suits insect pollinators; selecting a position where flowers are visible to pollinating insects will make the most of that trait. Regular observation during the season will show when plants are at their peak and when any pruning or thinning is required. Where space allows, select a spot where the flowering spikes can be appreciated from paths or seating; the two-lipped flowers provide architectural detail in mixed herbaceous schemes. For gardeners tracking seasonal interest, note that Lobelia siphilitca flowers in the UK from June to September, making it useful for summer display and late-summer continuity.

Growing conditions

Best soil and position for Lobelia

Sunlight: full sun, partial shade
Soil type: moist, rich, well-drained
Soil moisture: moist, wet

Plant details

Lobelia siphilitca size, habit and characteristics

Plant type: perennial
Suggested uses: wildlife gardens, rain gardens, naturalized areas, borders
Native to: Ontario
Toxicity: Toxic if ingested

Care notes

Pruning and caring for Lobelia siphilitca

Cultivation: Prefers moist to wet soils, often found in wetlands and along stream banks. Tolerates partial shade but flowers best in full sun.
Pruning: Remove spent flowers to encourage prolonged blooming; cut back in late fall or early spring.
Propagation: Seed, division