Lobelia

( loh - BEEL - ee - uh )

At-A-Glance Information

Lobelia is a genus containing perennial and annual flowering plants that are commonly planted in containers and hanging baskets as well as in flower borders and beds. All species in the genus have simple, alternate foliage and tubular, two-lipped flowers with five lobes. Blooms are intensely colored and profuse, making Lobelia a very popular ornamental for many different landscape styles. The flowers will attract butterflies and hummingbirds to the garden. Use Lobelia plants as trailing spillers for container arrangements, in mixed beds and borders, and to complete color schemes in the garden. Perennial species make great additions to water features and rain gardens, native or pollinator gardens, or when added to woodland or meadow landscapes. Take care when planting these flowers in the landscape, as plant parts are highly toxic to humans and pets (including horses) if ingested.

Lobelia Species and Varietals

The genus Lobelia is a member of the plant family Campanulaceae and includes 415 species. The plants in this genus are closely related to those in Campanula (Bellflower). Species in the former genus Pratia are now included in the genus Lobelia. The best growing zones for Lobelia vary depending on the species. For more information, see the following descriptions. To find your zone, click here: Zone Map.

Lobelia anatina (Apache Lobelia, South Western Lobelia, Mountain Lobelia)
These plants are native to southwestern North America, and form small shrubby plants. Flowers are blue to violet in color, and form on upright spikes in July through October. Plants reach up to 32 inches tall when in bloom, and are perennial herbaceous plants that are typically grown as annuals, especially in cooler climates. Best in USDA hardiness zones 6-9.

Lobelia anceps (Trailing Lobelia, Angled Lobelia, Swamp Lobelia)
These upright to scrambling plants reach up to a foot tall and have variable green leaves. Flowers are violet to deep blue, typically paler at their bases. These plants are native to Queensland, where their bloom time is from November through July. Trailing Lobelia grows well in USDA hardiness zones 9 and 10.

Lobelia angulata (Pratia angulata) (Pānakenake, Lawn Lobelia, Creeping Pratia, Pratia)
This species is a semi-evergreen to evergreen creeping, wide-spreading herbaceous plant that reaches up to three feet wide. It forms a nice mat that can be used to naturalize in moist areas of the garden or between stepping stones. Flowers are white, and stems are typically green, though they sometimes will have purple to maroon edging and mottling. Individual plants can reach up to 1-4 inches tall and 6.5 feet wide. Lawn Lobelia grows well in USDA hardiness zones 6a-9b.

Lobelia browniana (Toothed Lobelia, Humped Lobelia)
This annual species can be erect and succulent to semi-succulent, typically reaching a height of 20 inches at maturity when in bloom. Flowers are blue and bloom from November through February in the plant's native range in eastern Australia. Toothed Lobelia grows well in USDA hardiness zones 9-11.

Lobelia cardinalis (Lobelia fulgens) (Cardinal Flower, Scarlet Lobelia, Indian Pink)
This perennial species grows well in USDA hardiness zones 3-9 or Sunset growing zones 1-7 and 14-17 and is native to the eastern United States as well as scattered areas in the mountains of the southwestern United States and Mexico. It produces a single stem topped with a spike of red flowers in summer. It is naturally a bog plant, and loves rich, moist soil and can take full sun or partial shade. Cultivars include 'Queen Victoria' (4-5 feet tall with purple-red foliage and scarlet flowers), 'St. Elmo's Fire' ('Elm Fire'; with bronze foliage and scarlet flowers), 'Black Truffle' (with near-black spring foliage that matures to maroon), and 'Mini' (a compact variety mainly used in aquariums).

Lobelia chinensis (Asian Lobelia, Chinese Lobelia, Herba Lobellae Chinensis, Ban Ban Lian, 半边莲)
This species is native to China, and forms a small perennial herbaceous plant up to about a foot wide. It grows well in USDA hardiness zones 6-10. Although it is an herb commonly used in traditional Chinese medicine, the FDA has banned its use in the United States due to its toxicity. This species is considered invasive in the Mid-Atlantic region of the United States.

Lobelia columnaris (Giant Lobelia)
These plants are native to Cameroon and Equatorial Guinea. They naturally grow in subtropical and tropical dry forests, and reach between 2 and 5 feet tall when mature and in bloom. Flowers are borne on large terminal spikes and are white to bluish. Foliage is green, and leaves are largest at the base of the plant. Giant Lobelia grows well in USDA hardiness zones 10-12.

Lobelia deckenii (Lobelia keniensis) (Gin-and-Tonic Lobelia, Giant Lobelia, Tree Lobelia)
Endemic to Tanzania's mountain ranges, these plants prefer moist areas. Each plant can produce multiple rosettes of foliage that grow for several decades before producing a single large inflorescence that bears hundreds of thousands of seeds. The mother plant then dies. Individual plants usually form between one and eighteen rosettes which are connected underground.

Lobelia dortmanna (Dortmann's Cardinalflower, Water Lobelia)
These plants form stolons and are considered to be aquatic plants, forming underwater basal leaf rosettes and flower stalks that rise above the surface. Individual flowering stems are hollow and can stretch up to 40 inches to emerge from the water's surface. Blooms are white to pale pink or pale blue. Leaves are evergreen and lack stomata. These plants occur naturally in shallow water on lakeshores and in wetlands. Water Lobelia grows well in USDA hardiness zones 3-8.

Lobelia erinus (Edging Lobelia, Garden Lobelia, Trailing Lobelia, Blue Lobelia)
This annual species grows well in all zones and is native to South Africa. It is a popular and widely-grown ornamental species of Lobelia, with bronze-green to pure green foliage. Blooms persist from early summer to the first frost of the year and are blue with white or yellow throats in the straight species. These plants need rich, moist soil to perform well in the garden. Cultivars are listed and described below:

'Cambridge Blue'
Clear, soft blue flowers on 4-6 inch plants.

'Crystal Palace'
Upright cultivar with bronze-green foliage and intense deep blue blooms.

'Laguna' Series
Including 'Dark Blue', 'Cloud White' and 'Ultraviolet'. To 6-12 inches tall and 12-24 inches wide.

'Monsoon'
With cobalt-blue flowers and darker foliage than the species.

'Rosamunde'
Carmine-red flowers with white centers.

'Sapphire'
Ornamental trailing form with purple-blue blooms with white eyes.

'Snowball'
With pure white blooms.

'Techno' Series
With great heat tolerance in a variety of bloom colors.

Lobelia hypoleuca (Kuhi'aikamo'owahie, Opelu, Liua, Mo'owahie)
This species is endemic to Hawaii, and is cultivated elsewhere as a garden ornamental. These large, woody shrubs can reach up to 11 feet tall when mature. Leaves are green and shiny and white and wooly on the undersides. Each plant produces 3-7 flowering stalks up to 16 inches tall. Flowers are blue.

Lobelia inflata (Indian Tobacco, Puke Weed, Bladder-Pod Lobelia)
This species is native to eastern North America and is an annual or biennial plant that reaches between 6 and 40 inches tall. Leaves are green, and flowers are violet, tinted yellow on their interiors. The common names for this plant refer to its historical use as a tobacco substitute and emetic. Indian Tobacco grows well in USDA hardiness zones 3-9.

Lobelia laxiflora (Mexican Lobelia, Sierra Madre Lobelia, Mexican Cardinalflower, Looseflowers Lobelia, Drooping Lobelia)
This perennial Lobelia grows best in USDA hardiness zones 7-10 or Sunset growing zones 7-9 and 12-24 and is native to Arizona and Mexico. It reaches 3 feet tall and 3-6 feet wide. Stems are erect and clothed in narrow leaves, topped with open clusters of orange-red flowers over a long season in summertime. Can withstand aridity and neglect, and persists in abandoned gardens. Needs little water and can take full sun to partial shade. Cultivars include 'Candy Corn' (with striking purple stems to 5 feet tall with bright orange and yellow blooms) and 'Helen Ewart' (upright, dense clumper with red flowers that have gold-orange interiors). Individual plants can spread aggressively via underground rhizomes. This species is considered an invasive garden weed in California.

Lobelia nicotianifolia (Wild Tobacco, Ran Tambakhu, रान तंबाखू , Kadahogesoppu, Kaat Pukayila, Dhawal, धवल)
These perennial plants are commonly called Wild Tobacco due to the shape of their leaves. They are commonly grown across India and Sri Lanka, and produce a spike of white flowers in December. These plants can reach up to 5 to 10 feet tall when mature and in bloom. Wild Tobacco is well-suited for USDA hardiness zones 10-12.

Lobelia pedunculata (Matted Pratia, Trailing Pratia, Blue Star Creeper)
With profuse shows of sky blue flowers, these Australian natives are garden knockouts. They can spread via underground stolon, and has the potential to be a nuisance if not kept in check. Individual plants reach up to 1-3 inches tall and 12-24 inches wide. These plants do well in USDA hardiness zones 6-10 and are considered invasive and persistent lawn weeds in California and Oregon in the Untied States, Belgium, Germany, Great Britain and Ireland.

Lobelia polyphylla (Tabaco del Diablo, Tupa del Littoral Many-Leaved Tupa, Devil's Tobacco)
These plants are native to northern and central Chile. They are commonly called Devil's Tobacco due to the fact dried leaves have narcotic and hallucinogenic effects when smoked. Flowers are dark red and foliage is green. Individual plants reach up to 5 to 6.5 feet tall and 2 to 3 feet wide when mature. Devil's Tobacco grows well in USDA hardiness zones 8a-10b.

Lobelia rhombifolia (Tufted Lobelia)
This annual is native to southern Australia, and reaches between 2 and 12 inches tall Flowers are violet to blue with a white mark in the center, and sit atop thin, erect stems. Flowers bloom from September through February in their native range. This is considered a rare species on Tasmania.

Lobelia siphilitica (Great Blue Lobelia, Great Lobelia, Blue Cardinal Flower)
Best in USDA hardiness zones 4-9 or Sunset growing zones 1-9 and 14-17, this native of the eastern United States grows 2-3 feet tall and a foot wide at maturity when in bloom. Flowers are blue and present on plants in summer. These plants need ample amounts of water and part shade to thrive in the garden. Cultivars include 'Alba' (with white flowers), 'Mistassinica' (compact variety), and 'Blue Selection' (with intense blue flower spikes on sturdy stems).

Lobelia x speciosa (Lobelia gerardii) (Cardinal Flower, Hybrid Cardinal Flower, Hybrid Lobelia)
This group of hybrids was derived from Lobelia cardinalis and Lobelia siphilitica. They are perennials and grow well in USDA hardiness zones 6-10 or Sunset growing zones 2-9 and 14-17. Individual plants can reach 5 feet tall and a foot wide at maturity when in bloom. Hybrid Cardinal Flowers need rich soil and ample water for best performance and full sun to partial shade. Cultivars are listed and described below:

'Compliment' Series
With intense bloom colors on upright spikes. To 1-3 feet tall and 12-18 inches wide.

'Fan' Series
With large flowers on compact plants with bronze foliage.

'Hadspen Purple'
Velvet-rich deep purple flowers and violet-toned foliage.

'Starship' Series
Compact plants with a variety of bloom colors. Dark foliage and stems.

Lobelia telekii (Cousin Itt Lobelia, Giant Lobelia, Teleki's Lobelia)
These interesting monocarpic plants are native to alpine zones in East Africa. They typically produce a single rosette of foliage that grows for several decades before flowering and then dying. In ideal growing conditions, these plants are able to produce more than one rosette connected by underground tuber roots. Individual plants can reach up to 10 feet tall at maturity (when in bloom). Individual leaves can be 3 feet long.

Lobelia tupa (Devil's Tobacco, Tabaco del Diablo, Chilean Lobelia)
This species grows best in USDA hardiness zones 7-10 or Sunset growing zones 4-9 and 14-24. It is native to Chile and has a tropical look to it. Plants grow to 6 feet tall and 3-4 feet wide, have red stems and green leaves. Flowers are a rich, warm red and form in clusters, attracting hummingbirds in droves. Needs a sunny, sheltered placement and rich, well-draining soil. Easy to propagate via division; needs regular water.

Caring for Lobelia

Take care when planting these flowers in the landscape, as plant parts are highly toxic to humans and pets (including horses) if ingested. Lobelia plants are considered easy-care additions to the garden (most species are, anyway) and they can thrive in a spot that receives full sun to partial shade. The more sun these plants get, the better they will flower and the less leggy they will be. If summers are hot, it is best to provide Lobelia plants with a little afternoon shade during the warmest hours of the day. In mild areas, they can be grown in sun all day long. They enjoy a rich, well-draining soil with a pH of between 60 and 7.0 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Water newly planted Lobelia regularly to help it develop a strong root system. At maturity, these plants prefer to have their soil kept moist but not soggy. Most species of Lobelia cannot take standing water (with a few exceptions). As a general rule of thumb, water whenever the top inch or two of soil feels dry to the touch, and make sure all additional water can drain out from the root zone.

Fertilize yearly in early springtime with a application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Perennial species will die back to the ground in most temperate zones each winter, and re-sprout in the next. Trailing Lobelias can be pinched back as they put on new growth in early spring to encourage a bushier habit. After flowers fade, trim or shear the plant to encourage more foliage and blooms to form. Annual species of Lobelia are pulled at the end of the growing season and composted, replaced in the next year with new plants. Perennial species can last in the garden for between 3 and 4 years on average before needing to be replaced. These plants will freely re-seed in the garden, and can also spread via creeping stems and underground roots, providing flowers for the garden indefinitely.

Caring for Lobelia in Containers
Lobelia flowers are wonderful accents in the ground, but can also be grown in containers, where they are commonly used as filler or spiller plants. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Lobelia plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Propagation

Lobelia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Lobelia, follow the instructions below:

Propagating Lobelia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 3-4 inch softwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new plant.

Propagating Lobelia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods on Lobelia plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-3 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Lobelia seed pods form where flowers once bloomed.

Lobelia seeds.

Problems and Pests

Certain species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Lobelia plants can be susceptible to developing issues with the following pests and diseases in the landscape: