Description & Interesting Facts:
The genus Lobelia has more than 360 species with a cosmopolitan distribution that is especially rich in tropical and sub-tropical regions. It belongs to the beautiful bellflower family (Campanulaceae), which contains many beloved garden ornamentals. Lobelia secies in this genus are flowering annuals, perennial herbs, or small shrubs, with flowers in shades of blue, purple, pink or white.
Although only 69 species occur in South Africa, the genus is found throughout the country and grows in a variety of habitats from sheltered to exposed rocky slopes, sand dunes, sandy flats, as well as shady, damp, coastal mountain slopes and forest floors.
Lobelia flowers achieve cross-pollination by being ‘protandrous’ i.e. the male reproductive organs mature first with the style pushing through and producing the pollen. After the style has emerged completely, the female stage of the flower begins when the stigmatic lobes separate from the style and are receptive to pollen from another plant. The flowers will attract many insect pollinators, including a variety of bees, butterflies and other pollinators.
Their long flowering period, ease of cultivation, and stunning flowers have made many Lobelia species popular in the horticultural industry.
Lobelia erinus
This lobelia is the most widely cultivated species in the genus, and has been grown in gardens since the seventeenth century. It never goes out of fashion and remains popular with gardeners worldwide. Lobelia erinus has several common names, including: Edging Lobelia, Garden Lobelia and Trailing Lobelia. It is native to southern Africa and extends from Malawi, Mozambique, Zambia and Zimbabwe, south to Botswana, Namibia, Eswatini, Lesotho and South Africa.
This little annual herb or short-lived perennial can reach heights between 15 to 20cm with a 20 to 25cm spread , forming dense mounds of small flowers. Some varieties have bronzy foliage and others sport bright green leaves. The cascading varieties produce billowing masses of flowers up to 30cm long and are favourites to mix with other plants in hanging baskets and containers.
The wild form is known for its beautiful sky-blue and white flowers, but breeders have been hard at work on this little beauty and today gardeners are spoilt with flowers that often feature a tiny white "eye" in each bloom and come in various shades of blue, purple, lilac, pink, and pure white. The fruit is a capsule, 5 to 8mm long.
Riviera Mixed Lobelia. Picture courtesy Ball Horticultural Company In the Garden:
Lobelia is a popular choice for gardeners due to its variety of uses. This reliable little plant can be tucked into just about any plant combination to fill in the gaps in garden beds or pots, or to add a bit of trailing interest.
While lobelia can handle semi-shade to full sun if planted in autumn for winter and spring colour, when planting in spring for summer colour, in our hot climate its best to site lobelias where they will receive semi-shade, and especially during the hottest time of the day. Therefore, the companions you select to plant with them will vary according to the planting season.
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For a winter and spring flowering garden, along with annuals like Primroses, Pansies and Violas, English Daisies and Alyssum, Lobelias are a favourite to plant between bulbs like Daffodils, Tulips, Anemones, Dutch Irises, Freesias and Cyclamens to create a living carpet beneath them.
The root system of Lobelia is generally quite small compared to other annuals, making it easy to tuck into empty spots of the garden. Try planting it in the cracks and crevices of a stone wall, or along a set of stairs to cascade over the edge. Its trailing habit will gently soften any hard edges.
Lobelias and other small annuals look lovely planted underneath winter dormant or evergreen Roses, along with other shallow rooted plants.
In summer lobelias grow well with other shade lovers like Coleus, shade-loving Impatiens, Bedding & Cascading Begonias, Aquilegia, Flowering Tobacco, Forget-me-not, and Foxgloves.
Because lobelia thrives in consistently damp soils, it pairs best with other water-loving shrubs like Fuchsia, Hydrangea, Azalea and Rhododendron, and smaller plants like Ferns and Hostas.
Lobelia makes an excellent edging plant for flower beds, and is excellent for boggy areas or near water features.
It is especially lovely in hanging baskets and window boxes, planted with other flowering and trailing plants.
Lobelias are good in wildlife gardens as they attract many pollinators like bees and butterflies to the garden.
Cultivation:
Regatta Mixed Lobelia. Picture courtesy Ball Horticultural CompanyDespite its delicate appearance, lobelia does not require a lot of maintenance.
What climate is best for growing Lobelia?
Although Lobelias grow in very diverse climatic conditions they thrive in a cool to moderate climate and are considered a premier cool-season flower which blooms best during spring and autumn when the temperatures are ideally between 15 and 24°C.
In frosty regions of South Africa lobelias are often planted out in early spring to flower in summer, but they will often sulk a bit during the hottest months, only to spring back and bloom profusely again in autumn. In our winter rainfall regions lobelias are a favourite to establish in the garden in late summer, just before the first rains arrive.
Is Lobelia hardy to frost and cold?
While they love cool weather, Lobelia is tender to all but occasional light frosts, and in cold winter regions it is generally grown as a summer annual which is planted out in spring after all danger of frost is over, and discarded at the end of its bloom time.
Does Lobelia like sun or shade?
If grown in spring, in our hot climate lobelias do best where they receive semi-shade to sun. In very hot regions they require shade during the hottest time of the day. If grown during the cooler winter months they will take semi-shade to full sun.
What soil type is best for growing Lobelia?
Lobelias like fertile soil that is loose and gritty, with perfect drainage. Good drainage is especially important when growing lobelias in containers.
How much water do Lobelias require?
Consistent moisture is essential, so try to keep the soil evenly moist, but not soggy. For this reason lobelias are wonderful water-wise flowers for our winter rainfall regions.
In areas with regular rainfall, you may not need to provide extra water. In drier areas be prepared to water your lobelia every few days through the summer, and even more often if the weather is exceptionally hot.
Supplemental watering will be necessary when growing Lobelia under shrubs. When possible, use drip irrigation or soaker hoses to keep the roots consistently moist.
Fertilising Lobelias
Because lobelia flowers so profusely it does best when fertilised regularly during the growing season with a feeder for flowering plants. Feeding is especially important for potted plants.
Pruning Lobelias
Lobelias do not need to be deadheaded because the plant self-cleans its small spent flowers. However, it won’t harm the plants if you give them a light trim, and if your area has hot summers and the plants stop flowering, trim them back by about 1/3 and they will rebound and bloom again in late summer when temperatures cool down.
Growing lobelia from seed?
Seeds can be sown in seedling trays in spring or autumn when the soil temperatures are between 21 and 25°C. They need light to germinate, so do not cover them with soil. Germination will take up to one week and the plants will bloom within 9 to 14 weeks, depending on temperatures.
Caution:
Some sites state that Lobelia 'Erinus' has no toxic effects reported, while others report that it is mildly toxic to cats and dogs, potentially causing drooling, vomiting, or diarrhoea. Large doses of lobelia may cause serious toxic effects including sweating, convulsions, fast heartbeat, and very low blood pressure.
It is always advised that parents supervise children in the garden, and discourage pets from chewing on plants.