Lobelia
By Andrea Peck UCCE Master Gardener
Common name of plant: Lobelia
Scientific name: Lobelia erinus
Planting area: Perennial in USDA zones 10-11 during winter. Annual in other zones.
Size: 5” - 9” Tall and 5”-12” Wide
Bloom Season: spring to fall
Exposure: full or partial sun
Pruning needs: none
Water needs: Consistent, moist watering particularly in hot, dry weather.
Snapshot:
Best known for its electric blue flowers and trailing habit, Lobelia erinus is a welcome jolt of energy to any garden. It is a low, climbing type plant extending 5-9” tall and spreading only up to 12.” Lobelia grows as a perennial in Zones 10 and 11, but in other zones it is generally considered an annual. It prefers slightly acidic soil---in the pH range of 5.5 to 6.5. Soil that is rich in organic matter---leaf mold, compost, or well-rotted manure---will do much to provide this plant with nutrients and retain moisture during drier months. Keeping this plant moist is important after planting, but it is a consideration during the remainder of the year as well. In areas of significant summer heat, it may be best to place your Lobelia in a shady section of your garden and plan on consistent irrigation. An all-purpose feeder assists its growth during the summer months. Light pruning encourages a bushier shape and deadheading will increase flower growth.
Lobelia is at its best in rock gardens, along pathways---anywhere a burst of color is needed. They are the quintessential cottage plant and are quite showy when planted en masse. They are commonly used in containers, such as hanging baskets and window boxes especially where they are allowed to overflow and add a softening effect to harder surroundings. Though the blue varietal is popular, Lobelia does come in other colors such as white, lavender, pink, and even red. Hummingbirds and a number of butterfly species are attracted to the flowers. Given the right circumstances, the flowers do sow themselves and you may, if you are very lucky, see diminutive Lobelia plants pop up during the following year.
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