Lobelia Care Guide: How To Grow Edging Lobelia

A lovely herb plant with bright blue to purple blossoms, the trailing lobelia flower is a perfect choice for filling in around garden beds, driveways and borders. It’s easy to grow and, depending on your zone, can be an annual or perennial.

Purple Lobelia Flowers
lobelia 1
(Image credit: kn1)

Edging Lobelia Care: How To Grow Trailing Lobelia Plants

A fast-growing, trailing herb, lobelia flowers are small, colorful blossoms that make lovely edging plants along borders, paths, patios or driveways with rich green foliage.

There are hundreds of species of Lobelia flower. Most can be found growing in tropical regions or those with warm, temperate climates. Common “edging” lobelia can be grown as a perennial in frost-free regions, but in cooler zones, is commonly grown as an annual.

Lobelia grows and blooms quickly, and can fill in the borders and edges of hardscape and garden beds, as well as being a lovely addition to containers. 

Quick Facts:

Botanical name: Lobelia erinus

Height: 6-9 in. (15-23 cm.)

Spread:  6-12 in. (15-30 cm.)

Sun exposure:  Full Sun, Part Sun

Soil requirements: Slightly Acidic

Hardiness zones: USDA Zones 10-11

When to plant:  Early Spring

Caring For Lobelia

Soil & Fertilizer Needs 

Though it is somewhat adaptable, lobelia enjoys growing in soil that’s slightly acidic. Good drainage is also important, as the plants will not tolerate excessively wet or waterlogged soil. Insufficient drainage is among the most common concerns for lobelia, and can lead to various fungal diseases as well as stem and root rot. 

Applying a well-balanced fertilizer monthly will help keep your lobelia plants looking their best. When the plants stop flowering, stop fertilizing them. 

Water & Light Requirements 

Lobelia plants appreciate consistent irrigation throughout the growing season. Cool, moist soil  helps them continue to produce flowers through even the hottest portion of the summer. 

The amount of sunlight each plant receives plays a role in helping the plants flourish. Lobelia performs best in a location that receives full sun throughout the day. In warmer growing zones, most lobelia plants benefit from some afternoon shade to shelter them from the midday heat. 

Basic Lobelia Care 

Lobelia plants can be difficult to start from seed, but are often available as bedding plants in very early spring. This makes them a good choice for ornamental beds that need seasonal color, as well as hanging baskets and containers. Beyond consistent watering, lobelia plant care is relatively simple. 

You may want to deadhead or prune the plant. Note that lobelia is considered to be quite toxic. Proper research before planting is essential so that gardeners and visitors are safe from its effects.

Problems, Pests, & Diseases 

Proper irrigation is vital to the health of lobelia plants. As the flowers are unable to tolerate dry conditions; scheduled watering is often necessary as a means to avoid wilting, yellowing, and other foliar diseases. Lobelia plants seldom have problems with pests. However, it’s good to remain vigilant for damage caused by common garden insects, like aphids or mites. Lobelia plants have proven themselves resistant to most browsing wildlife, including both rabbits and deer.

Pruning Lobelia

efficiently drop spent flowers without the need for deadheading. Provided that temperatures remain cool, gardeners can expect an impressive period of bloom from lobelia plants. 

As the weather warms, it’s not uncommon for the plants to stop flowering completely and the plants may begin to die back or start to lose their attractive appearance. Prune the plants back near to the ground to encourage new growth, which will begin with the arrival of more hospitable weather nearing autumn. 

Trailing Lobelia Varieties

The following is a short list of the most popular varieties of trailing lobelia.

Blue Cascade Lobelia

Blue Moon Lobelia

Cambridge Blue Lobelia

Riviera Blue Eyes Lobelia

Regatta Midnight Blue Lobelia

Tonya Barnett

Tonya Barnett has been gardening for 13 years. Flowers are her passion. She has trasformed her backyard into a cut flower garden, which she regularly chronicles on her YouTube channel http://www.youtube.com/@tonyawiththeflowers.