The Lobelia (Loh-beel- ee-uh) plant is a favorite garden addition in early spring when the weather is still cool, and its abundant bright flowers help shake off the drear of winter. Lobelia is named after the Flemish botanist most associated with the genus, Matthias de L’Obel (1538-1616).
Today, thanks to hybridization, there are over 400 varieties of Lobelia, both annual and semi-perennial, herbaceous perennial and woody. It‘s easy to find just the right variety to brighten up your yard, garden, porch or balcony.
In this article, we will discuss the care of these cheery plants and recommend some popular varieties. Read on to learn more.
Lobelia Plant Growing Guide
Origin: Lobelia is native in most parts of the world except for Near Eastern and Central Asia
Common Names: Cardinal flower, Indian Tobacco, Edging Lobelia, Asthma Weed, Vomitweed, Pukeweed
Height: Perennials can grow to be four feet high. Annuals reach a maximum height of about fourteen inches.
Hardiness: Annual: USDA zones 1-10. Perennial: USDA zones 2-10. [source]
Uses: Edging, Trailing, Hanging baskets, Window boxes, patio or deck railing planters, Folk medicine.
Life Cycle: Half-hardy annual or perennial.
Light: Full sunlight to partial shade. Older varieties of lobelia do not tolerate heat well and should be planted in partial shade.
Temperature: About 70 degrees Fahrenheit is ideal.
Soil: Well-drained soil, slightly moist, hummus rich soil with a pH of 6-7.5.
Water: Water regularly to keep the soil lightly and evenly moist. A twice-weekly watering is recommended for garden plants. Daily watering is recommended for potted plants.
Fertilizer: Work plenty of compost and organic matter into the soil before planting. Twice-monthly fertilizing using a water-soluble liquid fertilizer high in phosphorus is recommended.
Grooming: Deadhead frequently to encourage more blooms. Keep tips pinched back bushier growth. After the first flowering, prune the entire plant back by about half an inch to encourage more flowering. [source]
Flowers: Produces abundant 5-lobed, asymmetrical blossoms in shades of white, blue, red and purple throughout the summer months.
Foliage: The small, lance-shaped leaves are almost hidden by the blossoms. Leaf color ranges from medium green to very deep green. Some varieties have bronzed edges.
Pests: Lobelia is susceptible to red spider mite infestation, which causes leaves to change colors and fall. Prevention is the best approach. Frequent misting with cold water will keep red spider mites from setting up shop. Add a few drops of horticultural Neem oil insecticide to the water for greater effect.
Problems: If allowed to become too dry, plants may stop flowering during the summer months. If this happens, a good pruning followed by a deep watering should remedy the situations. Be sure to keep soil evenly moist going forward to prevent further problems. Covering the surface of the soil with a couple of inches of organic mulch helps keep moisture in.
Miscellaneous: Lobelia plants are rabbit and deer resistant with very attractive flowers hummingbirds and butterflies love.
Grow Your Own Lobelia Seeds and Cuttings
Propagation by seed: Plant Lobelia seeds indoors early in the spring, or sow directly into the moist soil outdoors after all danger of frost has passed. Germination time is 14 days at consistently warm (70 degrees Fahrenheit) The seeds can germinate at lower temperatures, but it can take quite a long while. If sowing indoors, allow a couple of months for seedlings to become mature enough to be transplanted outdoors several weeks after the last frost.
Propagation by cuttings or division: If you have a lobelia plant that you are especially fond of, you may wish to try growing more by cuttings or division. If the parent plant is growing outdoors, relocate it to a cool, protected spot indoors early in the autumn. It should receive lots of light but sparse watering through the winter.
In February, move the Lobelia seedlings to a warmer setting. Continue watering and watch for new growth. When it appears, take cuttings and plant them into small pots containing sandy soil or pure sand. They should develop roots shortly. When this happens, move your cuttings to more permanent containers with good quality soil.
Lobelia Species and Recommended Varieties
Lobelia aberdarica (ab-er-day- rik-uh) – This species calls Kenya, East Africa home, needs a sheltered location where it can reach 6 feet tall and displays French-blue flowers arranged atop 4-foot spikes.
Lobelia cardinalis (kar-din-nai/- liss) – Commonly known as the Cardinal-flower due to its striking flower spikes of cardinal-red flowers. This perennial grows 3 to 4 feet where it blooms in late summer. Cardinalis does well when planted in light shade in moist to wet soil conditions.
Lobelia siphilitica (sif-fil-/it-ik-uh) – Strong-grower perennial reaching near 3 feet. In late summer, Lobelia siphilitica produces deep blue flowers in late summer.
Lobelia tenuior (ten- yew-ee-or) – This annual from Australia produces slender stems with large bright blue flowers. Not found in most nurseries but worth more attention.
Lobelia erinus (er-n/e-nuss) – The annual varieties tend to be smaller and are a good choice as edging plants. The trailing types are useful for hanging baskets and window boxes.
They do very well in the sort of rocky soil found in their native South Africa. For this reason, these compact annuals are great for adding color to rock gardens.
Compact Lobelia Varieties
There are many compact varieties. Among the best choices are:
- Kaiser Wilhelm: As the name would indicate, this is an old and established variety. It is hardy, tried and true, very compact and sports mounds of bright blue flowers.
- Crystal Palace: This variety only grows to be about six inches high. With its dark green leaves and deep blue flowers, it is a lovely choice as a border plant.
- Mrs. Clibran: This compact variety also has blue flowers, but white centers add a touch of dazzle.
- Rosamond: Couple this compact variety with Mrs. Clibran to create a very patriotic Lobelia patch. Its flowers are deep red with white centers.
- Snowball: As its name indicates, this compact beauty produces mounds of pure white flowers.
Trailing and Cascading Lobelia Varieties
Cascading and trailing Lobelia varieties are great for hanging baskets and window boxes. Their stems may tumble over container edges to a length of twenty inches. Some good varieties to choose from include:
- Sapphire: This is an excellent choice for a hanging basket, window box or balcony planter. Its pretty, trailing stems produce massive amounts of bright blue blossoms with white centers.
- Fountain Blue: This variety produces large (1″ across) azure-blue blossoms from late in the spring until mid-summer. It may not bloom during the hottest summer months but will bloom again in the late summer and autumn if well-cared-for. The deep green leaves make a pretty addition to the garden during its hiatus.
Heat Resistant Hybrids
Heat-resistant hybrids are an excellent choice for very hot climates:
- Bella Cielo has pretty, sky-blue blossoms that bloom from spring to autumn. It is very compact at about ten inches high and wide.
- Hot Water Blue is another sky-blue choice that produces copious amounts of lovely blossoms even during the hottest weather in either full sun or partial shade. It grows to be eight or twelve inches high and wide.
- Bella Aqua Lobelia produces bright blue blossoms throughout the springtime, summer, and autumn. It has a tidy, mounding growth habit and grows to be about a foot tall and a foot wide.
- Hot Snow White has superior heat resistance qualities. It makes a pretty, dazzling white edging plant at only ten inches high and wide.
- Techno Heat Upright Light Blue can tolerate extreme heat throughout the springtime and the summer. It has an upright growth habit, standing about ten inches high with a spread of about sixteen inches.
How To Choose Lobelia
If you are starting out with vigorous seedlings, spring is the best time to buy Lobelia. Visit your local nursery or garden center and look for plants with a compact shape, healthy leaves, buds, and flowers.
Because these plants bloom continuously through the spring, summer and into the fall, you don’t need to worry purchasing a plant in bloom and assuming it will offer nothing but leaves after the flowers fade. A plant in healthy bloom will continue to perform well for as long as you take good care of it.
All-in-all, lobelia is an easy-care plant that will bring lots of color and happiness to your garden, porch or patio.