Lobelia Plant Growing & Care Guide for Gardeners
Article by Dean Ravenscroft, Ph.D. - Updated 30th Oct 2023
In this Gardener's HQ guide, we'll explore cultivating Lobelia plants in your garden, indoor spaces, and other settings.
- Plant Characteristics: The Lobelia genus boasts vibrant tubular flowers in a spectrum of colors. These plants provide an elegant touch to gardens and attract pollinators to the garden.
- Ideal Growing Conditions: They thrive in well-draining soil and prefer partial shade to full sun. Use consistent moisture, but do not allow waterlogged conditions.
- General Care: Regular deadheading encourages prolonged blooming. Provide adequate watering to keep the soil moist during hot periods.
- Tips for New Gardeners: Ideal for beginners, providing a vibrant display with minimal fuss. However, be mindful of its moisture needs, especially in hotter regions. Overly wet soil can be detrimental.
Lobelia, Blue Cardinal Flower: Cultivation & Garden Use
Members of the Lobelia can be either half hardy annuals or perennials.
The height and flower type varies upon the variety. Perennials reach about three feet (90 cm), and have minute blue or yellow flowers on terminal spikes. Annual Lobelia are low growing plants of four to twelve inches (10 to 30 cm), and have massed blooms of purple, blue, or white flowers.
The annuals are ideal for growing in rock gardens and as edging plants, whereas perennial Lobelia are of great use for borders.
Some of the common names for Lobelia include Cardinal flower and Edging Lobelia.
Lobelia photograph by Daryl_mitchell; creative commons.
Lobelia spicata - Pale Spiked Lobelia by Gmayfield10.
How to Grow Lobelia
If growing Lobelia plant from seeds it is best to start them off indoors.
The seeds of annuals should be sown on the surface of vermiculite about seven weeks before due to be transplanted, a few weeks after the last frost of spring, they should be watered from below.
The perennial seeds should be prepared about 14 weeks in advance. First the seeds should be imbibed by placing the seeds (within soil) in a black bag, then placing in the fridge for three months.
Seeds should then be sown out in vermiculite at a temperature of 18 to 24 (64 to 75°F) degrees.
It should take about 3 weeks to germinate. Once growing they are susceptible to rotting so water from below.
The Lobelia seedlings should be transplanted with a spacing of 10 cm (4 inches; small Lobelia varieties) to 60 cm (2 feet; large Lobelia species) apart.
Lobelia can grow in either a sunny or partially shaded part of the garden. They prefer a moist humus rich soil that has a pH of between 6 and 7.5
Caring for Lobelia plants in the Garden
Once established in the garden Lobelia require a little bit of looking after; they should be watered regularly to keep the soil moist in dry spells.
It is best to remove the dead heads of Lobelia flowers when growing.
If you require more perennial Lobelia plants then you can take divisions or cuttings of the plants in spring or summer.
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Lobelia Growing and Care Guide
Common Names: Lobelia, Indian Tobacco, Pukeweed, Asthma Weed, Vomitweed, Cardinal flower. Lobelia: Edging; Trailing; Annual; Heath.Family: Campanulaceae.
Life Cycle: Half hardy annual. Half hardy perennial.
Height: Annuals: 3 to 14 inches (7 to 35 cm). Perennials: 24 to 48 inches (60 to 120 cm).
Native: Worldwide except Central and Near Eastern Asia.
Growing Region: Annual: zones 1 to 10. Perennial: zones 2 to 10.
Flowers: Summer.
Flower Details: Red, blue, purple, white. Asymmetric. Five lobes. Tubes. Often in racemes.
Foliage: Simple. Alternate. Lanceolate; Oval.
Sow Outside: Start indoors.
Sow Inside: Surface. Use vermiculite. Water from below. Prepare perennials by first mixing seeds in the vermiculite, placing in a freezer bag, keep moist, then stratify by refrigeration for three months. Germination time: two to three weeks. Temperature 70 to 75°F (21 to 24°C). Eight or nine weeks before expected last frost. Transplant outdoors a few weeks after the last frost; temperatures should not fall below 41°F (5°C). Spacing: annuals: 4 to 6 inches (10 to 15 cm); perennials: 10 to 24 inches (25 to 60 cm).
Requirements: Full sunlight or partial shade. Good drainage. Soil pH 6 to 7.5. Hummus rich soil. Moist soil. Regular watering to keep the soil moist. Deadhead. Propagate: divide or take cuttings in autumn (warm areas) or spring (cooler areas).
Common Questions
How many members does the Lobelia genus have?
The Lobelia genus contains more than 400 species.
Do members of Lobelia make a good garden or landscaping plant?
Yes, Lobelia can make great garden or landscaping plants. They are popular for their vibrant flowers and are excellent for borders, pots, or hanging baskets.
Which Lobelia species are most frequently grown by gardeners?
Commonly grown species include Lobelia cardinalis (Cardinal Flower) and Lobelia erinus (Edging Lobelia).
Are members of the Lobelia plant genus fragrant?
Lobelia plants are not typically known for their fragrance. However, their bright and attractive flowers more than make up for it.
What is the perfect location to grow Lobelia?
Lobelia prefers a location with full sun or partial shade, and moist, well-drained soil. Some species, like Lobelia cardinalis, thrive near water.
Is Lobelia invasive in the USA, if so in which states?
At present, no species of Lobelia are considered invasive in the USA.
How do I remove Lobelia plants from my garden?
To remove Lobelia, pull up the plant, making sure to remove all roots. Regular monitoring will be necessary to manage possible reseeding.
Summary
The Lobelia genus, belonging to the Campanulaceae family, consists of annual and perennial plants native to Americas. Known for their tubular flowers, which come in a variety of colours, these plants are often used in borders, containers, and hanging baskets.
Lobelia enjoys full sun to partial shade and moist, well-drained soil. Regular watering is necessary for optimal growth. Propagation is typically achieved through seeds, usually sown in the spring.
I hope that you enjoyed this guide on how to grow Lobelia plants. You may also enjoy the following Gardener's HQ growing guides: How to grow Trachelium, Petunia, and Jasione plants.
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