Lobelia sp.

Zone: 3 to 9

Soil: loam

Light: Part sun

Bloom colour: Blue and Red

Bloom period: August to September

Height: 2 to 5 feet

Moisture: Medium to moist, well drained.

Attracts: Bees and hummingbirds

Notes: While the species of Lobelia typically sold in nurseries like moist soil, they do not do well in clay. I have tried twice in two different locations and neither species was able to make it through a winter. Great blue lobelia is highly attractive to bumblebees and anthophorine bees, which have tongues long enough to reach the base of the flower. Even though the flower colour is not even close to red, hummers will also frequent this plant to obtain nectar. Great blue lobelia is typically two to four feet tall. Initially the plants will not look that tall and may be hidden behind other plants. However, the flowerheads just grow and grow as more flowers come into bloom. It will thrive in full sun as long as it is watered regularly. The plants themselves do not occupy a large area and it will be necessary to plant several together in order to attract the attention of pollinators. Great blue lobelia should be placed in the middle or the back of the border. The intensity of the blue is strong enough that they need white or yellow flowers to complement them. White phlox, tall coreopsis or a mid-summer sunflower are excellent choices that will be in flower at the same time. It is more tolerant of shade than the cardinal flower and also self-seeds in these conditions.

The cardinal flower is typically found next to streams and ponds. It is a popular garden plant although it is short-lived. If you do not mulch, there is a chance that it can self-seed, otherwise you can divide it. You can grow specimens in sandy soil, but you must ensure that the soil never dries out with frequent watering. It is one of the most eye-catching flowers in the garden. Hummers adore this plant and will spend time visiting each individual flower. During the winter, ensure that the basal rosettes are not smothered by leaves. The cardinal flower is quite shade tolerant when first planted, but it will have great difficulty making into the following spring when the old leaves wither away. For new growth to appear, it needs several hours of sunshine. To avoid going back to the nursery for more plants, it is recommended to collect the dried seedheads and shake out the seed onto a tray of soil. Keep the tray in cold storage over the winter and expose it to sun and moisture in the spring. It is easy to raise these plants from seeds.

Spiked lobelia is a much smaller plant than the other two species and it needs to be planted en masse towards the front of the border to be noticed. The plants appear as almost white, but on closer inspection are a pale lavender. Spiked lobelia is the most drought tolerant of the species mentioned here and requires a loam or sandy soil to do well. I combine my plants with Verbena simplex, which I place just in front. The smaller flowers of Lobelia spicata do not attract bumblebees, but they do get visited by smaller bees and the odd butterfly. Spiked lobelia is difficult to get, even from native plant nurseries. If you manage to obtain some, collect seed from your own plants and follow the advice given above for cardinal flowers.


Lobelia silphilatica - Great blue lobelia
Lobelia with bumblebee
A bumblebee grips the outside the of plant while it sticks its head in to collect the pollen. The pollen collected is being stored on the hind legs using a corbicula.
Lobelia with phlox
David's phlox make a great background companion plant for blue lobelia
Lobelia cardinalis
Lobelia cardinalis - Cardinal
Lobelia spicata
A close-up of the small flowers of Lobelia spicata (spiked lobelia) shows the pale lavender petals.
Lobelia spicata
Lobelia spicata - Spiked Lobelia
Lobelia with Rudbeckia
Some great blue lobelia plants actually have white flowers. These specimens combine well with the blue flowers and yellow coneflowers.