Lobelia: profile, flowering & hardiness

Lobelia is versatile and has a long flowering period, provided that the location is suitably warm and sunny.

The pretty and low-growing trailing lobelia (Lobelia erinus) finds its use in the flower bed or on the balcony and terrace. In our continuing article we explain everything about planting and caring for garden lobelia. Here, first of all, we will talk about the characteristics and the different varieties of the beautiful flower perennial.

Garden lobelia: characteristics and origin

Lobelia erinus, also known as blue lobelia, is originally from Southern Africa and belongs to the bellflower family (Campanulaceae). Depending on the variety, lobelia either develops an upright and bushy habit or is more pendulous. Hanging garden lobelia varieties are wonderful to showcase in hanging baskets. Trailing lobelia reaches a maximum height of about 25 cm, and the shoots of hanging varieties sometimes grow up to 1 m long. The delicate leaves of lobelia are ovate and dark green. Depending on the variety, you can admire the different flower colours from June to September. They range from blue to purple or even white. The flowers are five-toothed and zygomorphic in structure, which means that they consist of two mirror-image halves. After fading in autumn, capsule fruits form that open when seeds are ripe, releasing very small, brown seeds.

Is lobelia perennial?

Lobelia erinus is actually a perennial. In our country, however, trailing lobelia is mainly cultivated as an annual, as it dies quite quickly at the first frosts and overwintering is not always successful.

Tip: Related species such as blue cardinal lobelia (Lobelia siphilitica) are also hardy in our area. However, during bare frosts this species should be covered with brushwood or similar.

Is lobelia bee friendly?

Yes, although lobelia does not provide a large supply of nectar, the intensely coloured flowers still attract bees. Combined with other bee-friendly flowering plants that provide abundant nectar, an ecologically valuable planting arrangement can be created.

The most beautiful varieties

Due to the wide colour spectrum of trailing lobelia varieties, there is something for every colour arrangement:

• ‘Bella Rosa’ grows up to 20 cm tall and charms with delicate pink flowers from May to October.

• ‘Kaiser Wilhelm’ blooms royal blue from June to September. This variety reaches a height of max. 25 cm.

• ‘Laguna Sky Blue’ grows to 30 cm tall and blooms in a delicate shade of blue.

• ‘Pendula Sapphire’ is often used as a hanging basket plant. This variety shows dark flowers with white eyes and grows up to 10 cm high.

• ‘Richardii’ has charming blue flowers with white coloured throats. This variety also reaches a maximum height of 20 cm and has a drooping habit.

• ‘Red Cascade’ enchants with pink to red flowers from June to October. This variety reaches a height of up to 30 cm.

• ‘White Lady’ displays white flowers from June to October and grows up to 15 cm tall.

Tip: Lobelia erinus is often offered as a colourful mixture, consisting of different varieties. An example is the mixture ‘Color Cascade‘ with white, pink-red and blue flowers.

Is lobelia hardy?

No, trailing lobelia is not hardy in our area. Plants that have been planted in the flower bed are usually taken out in autumn and composted. Potted plants can be overwintered in bright but cool winter quarters, for example, in cold greenhouses. To do this, the plant should be cut back by one-third. Make sure the temperature is cool but at least 10 °C. During the dormant period, the plant should be watered less but it should not dry out. Feeding can be completely stopped. After the last frosts in spring, the perennial can then be placed outside again. Temperatures should be at least 5 °C.

Propagation

Lobelia erinus is self-sterile and thus requires pollen transfer by a pollinator, such as bees. Therefore, if pollination fails to occur, no seeds are formed. Pollination can be done by hand, although the small flowers require some dexterity. To do this, take a small brush, carry off the pollen on the male pistil and pollinate the female plant with them. Alternatively, the seeds can be purchased in specialised stores. In our dedicated article about planting and caring for lobelia we explain how to make sowing a success.

Alternatively, lobelia can be propagated by cuttings. To do this, cut off a shoot at least 5-10 cm long, from which remove the lower leaves. After that, the cutting is put in potting soil. Keep the cutting moist but not too wet and bright but not too sunny in a warm location. If new foliage leaves are formed, you can assume that the propagation has worked.

Is lobelia poisonous?

Yes, trailing lobelia is toxic to us humans as well as pets. The plant parts of Lobelia erinus contain alkaloids, especially the alkaloid lobeline. As a result, keep children and pets away from the beautiful plant. Here it is recommended to use lobelia, for example, out of reach as a hanging plant.