Lobelia, a member of the Campanulaceae family, is a perennial flowering plant that thrives in wet, marshy environments. It’s easy to grow and has many uses, from culinary to medicinal.
It has many different health benefits and can also be grown in your garden without much trouble. There are many ways to grow lobelias including planting it from seed, propagating using cuttings or division, or transplanting an old plant into new soil with a container.
Let’s take a look at how to grow lobelia.
What is Lobelia?
Lobelia is an annual herb that is known for its beauty in the backyard garden. Its common name shares the same name as the botanical one, making it easy to reference and find.
There are many lobelia flower varieties to choose from, including those that are biennial. An easy-to-grow plant, lobelia is a summertime bloomer that will offer flowers all the way up to the first frost.
A compact plant, lobelia generally grows only three to five inches tall, making it an excellent choice as a groundcover. However, there are some varieties that can grow up to three feet in height.
The colors vary but generally include pink, white, red, and blue. Violet-blue, though, is the most common color you will find. Lobelia is the perfect plant to grow along a pond or creek, in a border, as a groundcover, or even in a container like a hanging basket.
You will hear this plant referred to by many other names in addition to lobelia, such as cardinal flower, Indian tobacco pukeweed, vomit weed, asthma weed, edging lobelia, and more. It is generally grown as an annual or half-hardy perennial and can be used for folk medicine, an edging plant, in a trailing fashion, in a hanging basket or window box, or even on a deck or patio railing.
Growing Lobelia Plant
Lobelia grows best in full sun or partial shade. While newer cultivars can be grown in intense heat, older ones cannot tolerate any amount of heat and therefore prefer being grown in the shade. On average, you’ll do well when growing lobelia plant in locations where temperatures average 70 degrees Fahrenheit.
The plant requires soils that are moist and fertile, ideally with a pH of around 6 to 7.5. You will need to make sure the soil is well-draining – otherwise, soil requirements do vary a bit among different lobelia species.
How to Plant Lobelia
You can plant annual lobelia seeds just about anywhere, sowing them directly in the garden. This can be done as soon as the danger of frost has passed but if you want to get a jumpstart on the growing season, sow seeds indoors about ten to twelve weeks prior to the last first date.
Seeds should be sown in moist, rich soil. Spread them thinly on top of the soil and water thoroughly. Put the tray of seeds in a well-lit area that’s warm and free from drafts.
Your seedlings should appear within a week or two. Then, you can begin thinning out the plants. Put them in the garden when they are at least two to three inches tall, spacing them four to six inches apart.
Water deeply, then sit back and relax! Once these plants are established, they require little maintenance.
Of course, if you don’t want to plant seeds, you can always purchase plants that were already started in containers at your local nursery or garden supply store. Plant these at the same depth they were planted in within the container, again, only after the risk of frost has passed.
Caring for Lobelia Flower
Ready to start growing lobelia plants in your garden? Once you’ve planted your lobelia seeds or plants, you can follow these tips for caring for lobelia plants in the garden or in a container.
Lobelia flower, like many common garden flowers, requires soil that remains lightly and evenly moist. It’s best to water about two times per week for garden plants. If you’re growing in a container, daily watering is more ideal, particularly if you live in a hot environment or plan on growing your lobelia in full sun.
A note on watering – if the soil in which you are growing your lobelia plants becomes too dry, your plant will have a hard time producing flowers during the summer. Therefore, regular pruning followed by a deep watering will be necessary to reverse the issue. To prevent it, make sure the soil always stays moist. You can add a layer of mulch (about two to three inches thick) to help the soil conserve moisture, too.
Fertilizing your lobelia plants is essential if you want them to set lots of colorful, healthy blooms.
Ideally, the soil should be amended with plenty of compost or other organic matter before you plant. You can also fertilize twice per month by using a water-soluble liquid fertilizer with high amounts of phosphorus.
While nitrogen and potassium, the other two ingredients in most commercial fertilizers, are also necessary for lobelia to grow, it is phosphorus that will be most beneficial in helping the plant set flowers.
Maintaining the Plants
Like many other flowering plants, lobelia flower grows best when it is deadheaded on a regular basis. Deadheading will encourage the plant to continue to set flowers until the first frost.
To do this, just pinch the tips back after they’ve started to wilt to encourage a bushier growth and additional flowering.
Once the initial flowering of the season has occurred, you can prune the entire plant back, cutting by about half an inch. This will encourage more flowering.
Throughout the summer, your lobelia plant should produce large quantities of asymmetrical, five-lobed flowers in shades like red, white, purple, violet, and blue. These often conceal the leaves, which are tiny and shaped like lances. They can be pale green to dark green or even edged with bronze!
Pests and Diseases
Lobelia is a tough plant that doesn’t suffer from very many pest or disease problems. However, you will want to keep an eye out for spider mites, particularly if you are growing lobelia indoors or in a container, spider mites will cause the leaves to change color and eventually fall from the plant.
Preventing a spider mite infestation is far easier than treating one once it arises. You will want to regularly spray your plant with cold water to prevent the pests from coming near the plant and forming their webs. You can also use a few drops of neem oil to keep the pests at bay.
You shouldn’t have to worry about animals like rabbits and deer nibbling on your lobelia, but you will instead be rewarded by the presence of countless hordes of hummingbirds and butterflies. Both of these species are attracted by the beautiful, fragrant flowers.
There are few diseases that plague lobelia – in most cases, you can prevent the likelihood of disease by keeping your plants healthy and following the tips mentioned earlier in this article for care.
Proper watering is the most essential tip when maintaining lobelia plants. While diseases are uncommon, the ones you might encounter with this plant include damping off, root rot, and leaf blight, all of which are fungal diseases that can be prevented with proper attention to watering and airflow.
Do not allow the soil to become overly saturated or dried out and make sure your lobelia plant is grown in an environment that provides the ideal amount of sunlight or shade depending on the species you’ve selected.
Types of Lobelias
There are quite a few different varieties of lobelia flower, though there’s just a handful that are seen in the home garden. These include L. inflata (sometimes referred to as Indian tobacco), L. siphilitica, and L. cardinalis (Cardinal flower).
Lobelia flower hasn’t always been grown solely for its ornamental value. In fact, L. inflata was once smoked by Native Americans as a treatment for asthma! It was also prescribed by doctors to induce vomiting in instances of accidental poisoning – which makes the plant’s other lesser-known nickname, pukeweed, make a lot more sense.
One of the most common species of lobelia that you can grow in your garden is Lobelia erinus, a species that is native to South Africa and frequently referred to as the trailing lobelia. It’s beloved for its attractive violet and blue flowers and its trailing fashion. It can be grown as a hanging basket flower, with flowers produced in loose clusters.
These flowers grow best (and most vibrantly) during cold weather. While violet and blue are the most common flower colors supported by this plant, you may occasionally also find it with flowers in shades of white pink, and reddish-purple. These flowers are tubular and accompanied by long, narrow green leaves. The plant only grows to about six to nine inches tall and performs best in hardiness zones 10 to 11.
Lobelia siphilitica is another popular variety. Referred to as both the great blue lobelia and the great lobelia, this popular perennial is native to North America and is best known for its tall spikes of vibrant blue flowers that sit atop lance-shaped foliage.
This plant has long-lasting flowers that generally blossom from late summer until mid-fall. It is an upright plant that is low-maintenance and extremely hardy. The flowers do require pollination.
Otherwise, this plant is easy to care for, with the ability to grow up to three feet tall and 18 inches wide. It grows in clumps and can tolerate wetter soils, making it a good choice for settings like woodland borders or even alongside ponds and streams.
Lobelia cardinalis is the lobelia species that we most commonly refer to as the cardinal flower. A popular native bellflower plant, it also grows in clumps and is an upright perennial with massive profusions of spiked, scarlet-red flowers. A hardy, low-maintenance plant, the cardinal flower has the potential to self-seed and grows up to four feet tall.
One final lobelia species to mention to help you on your hunt for the perfect plant is Lobelia x speciosa ‘Vedrariensis’. This perennial grows in an upright fashion and produces lovely dark purple flowers and dark green leaves. What’s truly unique about this plant, however, is that as midsummer and early fall approach, the dark green leaves turn a vivid shade of purple!
It can add a ton of vertical value to a landscape with the ability to grow to up to four feet tall and three feet wide. It performs well in both partial shade and full sun and can tolerate dry or wet soils.
How to Find the Perfect Lobelia Plant
It’s no secret that there are dozens of gorgeous lobelia plants for you to choose from – so how do you find the perfect one for your garden?
It might help to look for lobelia plants that are native to and hardy in your local area. This will help you grow a plant with minimal care required. Check in with your local garden center or nursery to find the best options for your needs.
You will also want to keep an eye out for plants that have certain features that may prove to be helpful to you as you are designing the ideal garden. For example, you might consider lobelia plants that grow in a more compact fashion or those that produce flowers in a certain color.
Either way, the best time to plant lobelia will be in the springtime. Don’t assume that you need to choose a lobelia plant that has already bloomed – if you’re buying plants early in the spring, choosing a plant that has already bloomed is not necessary. The plant will bloom later on as long as you care for it properly.
When all is said and done, know that no matter what kind of lobelia you choose, you’ll be rewarded with a plant that is easy to care for and beautiful to behold. These flowers are the perfect choice for gardeners who want to add a touch of color and beauty to their homes – with minimal care required.
Lobelia: Cornell University http://www.gardening.cornell.edu/homegardening/scene3417.html
Cardinal flower, Lobelia cardinalis: University of Wisconsin-Madison https://hort.extension.wisc.edu/articles/cardinal-flower-lobelia-cardinalis/
Plant of the Week: Lobelia, Edging: University of Arkansas Extension https://www.uaex.edu/yard-garden/resource-library/plant-week/lobelia-edging-1-25-08.aspx
*image by MartinaUnbehauen/depositphotos