How to Grow Lobelia Erinus Successfully

Last Updated on April 16, 2024 by Real Men Sow

Lobelia erinus, an annual herb that blooms in spring and continues to bloom throughout the summer, is beautiful. Lobelia is the best choice if you want your garden’s colors to change from white and blue to purple, red, pink or pink. This flower is not only attractive but also low-maintenance. This flower adds color to your garden in any climate.

Blue flowers are rare in the world of plants. Blue is known for its ability to increase calmness, morale, and lower blood pressure. Your garden will be a tranquil oasis of relaxation if you select the cobalt Lobelia variety.

Growing Lobelia Erinus

The majority of Lobelia species thrive in cooler temperatures. They are tolerant to partial shade, but may require it in warmer climates. To get maximum flowering, it is best to plant it in partial shade if you live in the South. Choose a sunny location in the North and water it as needed.

Lobelia can be grown in both containers and garden beds. However, most varieties prefer high moisture areas. Native Lobelias can be grown alongside other pond plants. They thrive in wet areas so it is best to keep them out of direct sunlight. These plants are great for growing around water features. However, there are cultivars that can tolerate dry conditions better. Make sure you check the seed packet or label.

Lobelia erinus can be self-cleaning, so it doesn’t need to have its head cut. It is also deer-resistant and can be avoided by rodents such as rabbits. Too much sun can cause lobelia to become brittle in summer heat. You can revive your lobelia by trimming it back and giving it water regularly. Radical pruning can encourage new growth. By fall your plants should be fully blooming again. You can also pinch back plants if you want a bushier appearance.

Planting Lobelia Erinus

Lobelia erinus should only be planted after frost danger has passed. However, it is best to plant them in the spring when the weather remains cool. Perennial varieties can be planted in the fall. Dig holes slightly larger than the root ball of your perennial plant. To provide nutrients and drainage, break up any clumps. The soil should be slightly acidic for most Lobelia varieties.


Because they grow larger, perennial varieties should be spaced between 1 and 2 feet (30-60 cm). You can space compact annual Lobelias at 4-6 inches (10-15cm) apart. Each plant should be covered with soil until the top of its root ball touches the ground. To firm the soil, use your hands to water it.


To retain moisture and stop weeds growing, we recommend adding a thin layer of mulch. To prevent rot, keep the mulch 1 inch (2-5 cm) from the stem. For perennial varieties, a spring fertilizer or compost application is enough. An annual plant needs to be fertilized more often. To help them through the growing season, you can use a continuous-release fertilizer.

Growing Indoors

A potting mix that is rich in organic matter should be used if you grow Lobelia erinus indoors. You can also combine Lobelias with other moist-loving flowers, such as sweet alyssum or balsam, that can tolerate shade. For an eye-catching display, place Lobelias in small groups around the container and add taller plants in the middle.

Propagating Lobelia Erinus

Even though perennial Lobelias can only live for a short time, it is possible to propagate the plants from seed. This is easy even for beginners. 

You can start both perennial and annual Lobelias from seeds. It is better to sow indoors than outside in your garden. You will need a seed starter mix and cell packs to start seeds indoors. It is best to sow seeds 8-12 weeks before the last frost in your region.

Because the seeds of Lobelia are so small, you don’t have to cover them with soil in order to get them to germinate. Place the seeds on top of this mixture and press down gently with your fingers. Make sure to water them well so they don’t dry out. The tray should be kept in a warm place with temperatures between 18-24°C.

The seeds will begin germinating in 14 to 20 days. For the next few weeks, ensure that the seedlings receive lots of sunlight. Once they have at least two pairs of leaves, you are able to move them into larger pots. Start leaving the seedlings outside for a week and bring them inside at night to harden. After the danger of frost is over, plant the seedlings in the ground.

General Care Guide for Lobelia Erinus


Lobelia doesn’t need to be in direct sunlight. It can grow in any shade or full sun location. If your summers are very hot, you might want to plant lobelia in a spot that gets direct sunlight in the morning, and shade or partial shade in the afternoon. To get maximum flowering in areas with mild summers, you can grow it in full sunlight (as long it is tended to and watered regularly).


Lobelia loves well-drained, rich soil. Root rot can be caused by soggy soil. Good potting soil is essential to keep lobelia blooming throughout the year, whether it’s in a pot or hanging basket.


The soil should be kept moist but not soggy. You might not need to water your soil if there is regular rainfall. However, lobelia in drier regions may need to be watered more frequently during the summer.

Temperature and Humidity

Annual lobelia thrives in moderate temperatures and moderate humidity. It can survive in any climate, provided you give it a little extra attention. Planting lobelia in a place that is shaded from the afternoon sun can prevent it from scorching or even dying. 

The plant will thrive if it is given enough moisture. However, if the environment is extremely dry, it might become shriveled. The plant can often be revived if you quickly use the watering can or hose. The annual lobelia is not able to withstand freezing temperatures and should be discarded in winter.


Because lobelia is both a prolific flowerer and a heavy feeder, fertilize it every two weeks using a liquid fertilizer that’s specifically designed for flowering plants. They are usually higher in phosphorus and potassium than they are in nitrogen or potassium because phosphorus encourages more flowers.

Use the package directions to mix the fertilizer and water. Apply the fertilizer to the base of your plant. To keep your lobelia flowering, fertilize it every other week throughout the summer.

Real Men Sow
Real Men Sow

Hello, I’m Pete and I’m currently based in the west of Scotland, in a small place called Rosneath, where I’m exploring my garden adventures. I personally started gardening around 6 years ago and initially, I started out by growing my favorite fruits and berries, such as strawberries, Raspberries & Gooseberries. Since then I’ve added a lot of vegetables and working closely with my neighbor, it’s been a lot of fun.