Lobelia syphilitica (Great Blue Lobelia) — perennial

Overview

Lobelia syphilitica is a perennial in the genus Lobelia, part of the Campanulaceae family. Lobelia syphilitica grows best in full sun and partial shade, and tolerates most soils and acidic and neutral pH. Its UK hardiness is rated H5. Suggested uses include borders, water gardens and meadows. It is native to Ontario.

About

Lobelia syphilitica is a perennial in the Campanulaceae valued for its blue flowers that appear from June to September. It originates from Ontario and favours consistently moist, rich soil. Plants suit full sun or partial shade and will tolerate sheltered or exposed positions. The species is toxic, so handle and site it with care.

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 syphilitica is a perennial native to Ontario that performs best where soil remains reliably moist. Flowering runs from June to September, producing noticeably blue blooms that suit damp planting situations. Plant into moist, rich, loamy soil with an acidic to neutral pH and position where it receives full sun or partial shade; the species accepts north, east, south or west aspects and will tolerate both sheltered and exposed sites. It carries a UK hardiness rating of H5, which translates as hardy in most UK gardens. Use it at the back of borders, on pond margins or within meadow-style, moisture-retentive schemes where the soil does not dry out. Because the plant is toxic, avoid sowing or planting where small children or curious animals might ingest foliage or seed, and label it clearly in mixed beds. Do not add large quantities of cut material to compost heaps; treat and dispose of clippings with caution because of the plant's toxicity.

Growing conditions

Best soil and position for Lobelia

Sunlight: full sun, partial shade
Soil type: moist, rich, loamy
Soil pH: acidic, neutral
Soil moisture: moist
Aspect: north, east, south, west
Exposure: sheltered, exposed
UK hardiness: H5

Plant details

Lobelia syphilitica size, habit and characteristics

Plant type: perennial
Suggested uses: borders, water gardens, meadows
Native to: Ontario
Toxicity: toxic

Care notes

Pruning and caring for Lobelia syphilitica

Cultivation: Prefers moist, rich soils and can tolerate wet conditions; best grown in full sun to partial shade.
Pruning: Cut back after flowering to encourage fresh growth.
Propagation: Seed, division

Frequently asked questions

How do I grow Lobelia syphilitica?

Prefers moist, rich soils and can tolerate wet conditions; best grown in full sun to partial shade.

Where is the best place to plant Lobelia syphilitica?

Lobelia syphilitica prefers full sun and partial shade. It suits sheltered and exposed positions.

What soil does Lobelia syphilitica need?

Lobelia syphilitica is adaptable and grows happily in most soil types, including moist, rich and loamy. It prefers acidic and neutral soil. Aim for soil that stays moist.