Lobelia is a happy and attractive little plant with a ton of versatility. It comes in many varieties and colors and makes a great addition to garden spaces, containers, and hanging baskets.
Easy to grow and care for, lobelia is a plant for beginner and seasoned gardeners alike. Many gardeners love it because it’s one of only a few plant varieties to bloom with true-blue flowers.
If you’re thinking about adding this sweet flower to your garden, here’s how to grow and care for lobelia to keep it happy.
All About Lobelia
Lobelia is often thought of as a common, annual bedding plant, but it actually refers to a family of plants with over 400 different varieties.
There are several different species of lobelia, and each species now has many hybrids and cultivars. The most popular in the U.S. is Lobelia erinus, which is also known as edging lobelia or common annual lobelia.
Lobelia is a popular plant because it has hard to find true-blue flowers. Most often grown as an annual, there are also perennial varieties that come in a variety of colors.
If you buy your plants from a nursery, you’ll quickly find that the most popular color is blue. However, there are also cultivars with red, pink, white, and purple blooms.
Annuals vs. Perennials
Lobelia erinus is an annual (although it is hardy in USDA zones 10 and 11), but there are other species that are perennial in USDA hardiness zones 2-8.
Annual lobelias are low-growing plants, typically reaching 12-14 inches in height max. The perennial varieties are taller with some growing 2-3 feet high and others up to 4 feet in height. Several of the perennial lobelias are native wildflowers in the U.S.
The annual varieties are great for small spaces like window boxes, containers, and hanging baskets. They also make great edging and front of the border plants.
Perennial varieties tend to be taller, so they can be used further back in borders and make a perfect choice for wildflower or pollinator gardens.
Most lobelia species grow best in cool weather and will bloom the best in your garden in spring or early summer and in fall. They can tolerate partial shade and may need it in hotter climates.
Lobelia grows equally well in the garden and in containers, but does prefer locations with more moisture. However, you can find cultivars that are more tolerant of dry soil if those are the growing conditions you have.
Most varieties also prefer consistently moist soil conditions. Native lobelias can be found growing alongside ponds and in wetlands, so you’ll want to make sure they aren’t planted in a dry spot. They do, however, make perfect plants for growing around a water feature.
Lobelia does like richer soils. If your soil has normal to low fertility, mixing in some homemade compost before planting will make your plants much happier.
Best Varieties and Cultivars
With so many species to choose from, there’s sure to be a lobelia that will work in your garden. Here’s a look at the most used annual and perennial species:
- Lobelia erinus– As mentioned, this is probably the most popular annual species of lobelia. Plants tend to be compact and have tiny, true-blue flowers. You can also find cultivars that have white, rose, or purple blooms.
- Lobelia cardinalis– Also known as cardinal flower, this is likely the most popular perennial species. Plants grow 2-3 feet tall and bloom with spikes of scarlet colored flowers. Loves wet growing conditions.
- Lobelia siphilitica– Sometimes called blue cardinal flower, this species is also perennial and grows up to 3 feet tall. Plants will bloom with bright to deep blue flowers that are long-lasting.
There are several more species of lobelia, including L. inflata or Indian tobacco, which has medicinal uses. However, these three are the main ones used ornamentally, and most hybrid varieties come from crossing these species with one another.
White lobelia is a lovely cultivar that could be used in an all-white garden, mixed with blue lobelia, or grown with other plants in a border or containers.
Here are a few of the best specific cultivars to look for locally or by mail order:
- Laguna Dark Blue or Laguna Sky Blue (annual)– These are two Proven Winners cultivars that have better heat resistance and prefer drier conditions than most lobelias. ‘Dark Blue’ has true-blue flowers and ‘Sky Blue’ has paler blue to white flowers.
- ‘Crystal Palace’ (annual)– This is another blue cultivar that is very compact and great for small spaces, containers, and as a border or edging plant. ‘Crystal Palace’ only grows about 6 inches tall and has dark green leaves.
- ‘Rosamond’ (annual)- Another compact variety, ‘Rosamund’ has mauve flowers with white centers. It looks stunning when paired with blue lobelia and works especially well in window boxes, containers, and as a ground cover.
- ‘Snowball’ or ‘Hot Snow White’ (annual)– Both of these cultivars have pure white flowers and a compact habit. ‘Hot Snow White’ has better heat resistance, and blooms last longer in the summer.
- ‘Fountain’ (annual)– This is actually a series of several differently colored varieties that all have a trailing habit and will spill gracefully out of window boxes, hanging baskets, and containers. You can choose from blue, rose, red, lilac, and white flowers.
Some cultivars have paler blue flowers, sometimes with a white center. You can find a variety of lobelia to go with pretty much any color scheme.
- ‘Starship Deep Rose’ (perennial zones 6-10)– This is a stunning cultivar that grows about 2 feet tall and wide. Flowers are large and a lovely rose-pink, and the foliage has a unique bronze cast to it. Plants prefer moist conditions and blooms are excellent as cut flowers.
- ‘Starship Scarlet’ (perennial zones 6-10)– Same as ‘Starship Deep Rose’ except with bright scarlet flowers. This is a standout in beds and borders and attracts hummingbirds with its red blooms.
How to Grow Lobelia
Lobelia is an easy to grow plant and requires little care beyond regular watering. You can either buy transplants at your local nursery or garden center, or you can start lobelia from seed.
Starting from Seed
Both annual and perennial lobelias share the same method for starting from seed. You can either sow indoors (the recommended method) or outdoors into your garden.
To start seeds indoors, you’ll need flats or cell packs filled with a seed starting mix that has already been mixed with water until it’s damp. Sow seeds 8-12 weeks before your last frost.
Lobelia seeds are tiny and don’t need to be covered with soil to germinate. Just sprinkle the seeds on top of the soil mix and gently press them down into the soil. Water them gently so that you don’t wash any away.
Lobelia is a fairly easy plant to grow from seed. Be sure to sow seeds on top of the soil and leave uncovered so that they can germinate properly.
Place your seeded trays somewhere warm (65-75°F) and keep the soil moist during the germination period. The seeds will start germinating in 14-20 days, so just keep an eye on them until you see seedlings start to emerge.
Once the seedlings have popped up, place the trays under fluorescent lighting or a spot in your house that gets lots of sunlight. If you use lights, keep them on for 14-16 hours a day and make sure plants get at least an 8 hour dark period.
After a few weeks or when seedlings have 2-3 pairs of leaves, you can transplant them from their small cells to larger 3-4 inch pots.
It’s a good idea to run a small fan on your seedlings a few times a day. This helps prevent damping off and other plant conditions that are caused by poor airflow and too much dampness.
About one week before you’re ready to plant outdoors, harden off your plants by taking them outside during the day and bringing them back in at night. Transplants can go in the ground after all danger of frost has passed.
Sowing Seeds Outdoors
Lobelia will get a slower start if you sow seeds outdoors, but it can be a good method if you don’t have the supplies to start seeds indoors.
You’ll want to sow seeds in early spring but after all danger of frost has passed. Get your beds or planting area ready by working the soil to break up clumps and loosen hard soil. You can add in some homemade compost to provide nutrients for seedlings when they sprout.
Plants like to grow in soil that’s rich in nutrients. To give plants a boost, you can amend your soil with compost or other organic materials like leaf mold or well-rotted manure.
Once again, sow seeds lightly on top of the soil. You can press seeds into the soil so that they’re less likely to wash or blow away, but don’t cover them.
Water seeds gently and keep the area damp but not soaking wet while they germinate. In the cooler temperatures of spring, it can take seeds 20+ days to germinate.
Once seedlings come up and start growing, you can thin them to 4-6 inches for annual lobelias or 6-12 inches for perennial varieties.
Lobelia should be planted in the cool weather of early spring, after all danger of frost has passed. Perennial varieties can also be planted in the fall.
Pick a spot for your lobelia plants that’s in full sun or partial shade. If you live somewhere with very hot and dry summers, part shade will be better.
Work the soil by breaking up clumps and adding in compost or other organic materials as needed to give better drainage and more nutrients. Most varieties prefer slightly acidic soil and moist conditions, although there are several hybrids that need drier conditions.
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Spacing for your plants will depend on which variety you have. Compact annual lobelia only needs to be spaced 4-6 inches apart. Many of the perennial varieties get larger and will need up to 1 or 2 foot spacing.
Dig holes for your plants that are slightly wider than the root balls. Gently loosen the roots of each plant before setting it in its hole.
You can then fill in around each plant with soil so that the top of the root ball is just covered. Firm the soil with your hands and be sure to water all your new plants thoroughly.
Growing Lobelia in Containers
Annual lobelia makes an excellent plant for a container garden. It stays compact or trails beautifully over the sides of containers depending on which varieties you choose.
With a range of colors, you can match lobelia with pretty much any color scheme. Plant it in small masses in front or around the sides of your containers with plants of increasing height in the center for an eye-catching display.
You can also do smaller containers of just lobelia (maybe in different shades) and arrange them with other containers.
Many varieties of lobelia are compact and grow well in containers. The one thing to remember is that container gardens are more likely to dry out and need more water than plants in the ground.
To grow lobelia in containers, make sure your pots have drainage holes drilled in the bottom. Cover the holes with a square of old fabric to keep the soil from washing out when you water.
Fill your containers with a good quality potting mix. If you don’t want to fertilize very much over the summer, choose potting soil that has a slow-release fertilizer already mixed in. Get the soil damp but not dripping wet before putting it in the containers.
Plants can go a little closer together in pots, but still space them at least a few inches apart. Water plants in well and continue to water regularly, especially during dry spells.
Caring for Lobelia
All varieties of lobelia are low maintenance, which is a huge benefit. The biggest way you need to care for them is by routinely watering, especially during hot and dry spells.
There are several cultivars that prefer dry conditions (so be sure to check the label or seed packet that goes with your plants), but otherwise you’ll need to provide them with plenty of water. Also, keep in mind that containers dry out quickly and may need watered daily.
You can put a light layer of mulch around plants to help keep moisture in and weeds down. Be sure that you keep mulch about 1 inch away from the stem to prevent rotting.
Annual lobelias do not need to be deadheaded. Most varieties will bloom profusely at the beginning of summer and slow down once hot weather comes. After the first big bloom, you can cut plants back by ⅓ – ½ to encourage profuse blooming again in the fall.
Lobelia works with many other plants including petunias. Plant it with like colors for a cool scheme or with warm colors for a contrast.
Perennial lobelias can be deadheaded throughout the season to encourage more flowering. They should also be divided every 2-3 years to keep plants vigorous.
You can fertilize annual lobelia every four weeks with an all-purpose fertilizer or liquid plant feed. Or you can mix in a slow-release fertilizer while planting and reapply every few months.
Perennial varieties typically don’t need as much fertilizer. You can add a layer of compost or a light fertilizer each spring.
Lobelia is typically not bothered by pests. Older annual varieties may not be tolerant of heat, and plants can start to fade or die from the center in extreme heat. If you’re finding this to be a problem, look for heat resistant cultivars.
Sometimes perennial lobelia will have problems with rust, leaf spot, or root rot. Spacing plants properly and removing infected plants immediately can help control these plant diseases.
Fortunately, lobelia is a deer resistant plant and is usually avoided by rabbits as well.
Plants are considered deer-resistant and usually aren’t bothered by many other pests either. The biggest threat to lobelia is usually overly dry or hot weather, which can cause it to stop blooming or die out.
What to Plant With Lobelia
If you’re wondering where to plant lobelia in your garden or what to plant it with, here are a few ideas:
- Plant perennial lobelia in places that are wet and difficult for other plants to grow in. They make a great addition to a pollinator garden and will attract butterflies, hummingbirds, and beneficial insects.
- Lobelia works great as a border plant. You can use the annual varieties at the front and the perennial varieties in the middle or back.
- Planting masses of lobelia can have a stunning effect (just remember that the display of blooms will likely decrease in hotter weather). You can do all one color or mix different colors together like blue, mauve, and white.
- Depending on which colors you choose, lobelia can complement or contrast plants like sweet alyssum, marigolds, phlox, and verbena. If grown in a shadier spot, try pairing with hostas or ferns.
- In both containers and the garden, lobelia works well with other spring-summer bloomers. Try it with pansies, petunias, geranium, snap dragons, or dusty miller.
As you can see, lobelia is a very versatile plant that’s easy to add to any garden. You don’t have to be a master gardener to grow it, and there are many varieties to choose from.
If you’re interested in lobelia as a plant that attracts pollinators, check out growing guides for other pollinator-friendly plants like bee balm, butterfly weed, and purple coneflower.