Groundcover Lobelias
Groundcover plants are important in all environments. They provide a living mulch. By preventing sunlight penetrating beneath their leaves they supress weeds, lower soil temperature and so reduce soil water evaporation. The roots of these low-growing, dense plants bind the soil, protecting it from erosion. This is important if the yard is sloping or if the soil is poor and thin and nutrients are rapidly lost by rain. Groundcovers are useful for bare areas of the garden that are difficult to maintain, such as banks. They are excellent for filling in spaces between taller shrubs and trees and enhance that aesthetic value of gardens. As groundcover plants grow and die, they add organic matter to the soil. This is broken down by soil microorganisms in the process of nutrient cycling. The end result is the release of nutrients – soil fertility is improved. Since these plants provide habitats and food sources for a variety of fauna, such as beneficial insects and birds, they improve biodiversity in urban environments. This creates a healthy balance between predator and prey species which in turn helps to control pest species.
Lobelia is a very diverse and widespread genus with 415 species found in different areas of the world. There are 39 Australian native species (more are still being described) seven of which are found in S.E. Queensland,. They vary in habits, shapes, sizes, flower structure and colours and fruit although typically the flowers are bilaterally symmetrical with fused anthers. Three native Lobelia species that are groundcovers are L. trigonocaulis, l. pednculata and L. anceps.
The forest lobelia (L. trigonocaulis) is a creeping herb found in moist forest areas of New South Wales and Queensland. It has heart-shaped leaves and pretty, small mauve-blue flowers throughout summer and autumn. Each flower is composed of 3 larger and 2 smaller lobes. The anthers are fused together to form a cup around the female parts. The matted pratia (Lobelia pedunculata, synonym Pratia pedunculata) grows on damp ground, margins of rivers and lakes and in wet sclerophyll forests in filtered sunlight. This vigorous evergreen perennial forms a mat of tiny, saw-toothed oblong to roundish leaves to 2 cm tall. The delicate star-like flowers, with 5 lobes connected to a short tube and stalk, are produced in summer. They are either white or blue-mauve in colour and are unisexual. The angled lobelia (Lobelia anceps – formerly Lobelia alata) is a prostrate plant growing to 30 cm high with narrowly elliptical leaves that are angled at the base. Small light blue- flowers, with the two upper petals smaller than three lower ones, are mainly produced in summer and autumn. Unlike the forest lobelia and matted pratia, this species will grow in dense shade. As it is a frog habitat plant, the angled lobelia would be ideal to grow beside shaded ponds.
All three lobelias grow in moist but not waterlogged soil and filtered sunlight. They prefer a slightly acidic soil, but will adapt to most kinds of sandy or loam soils and they will tolerate light frosts. Grown as borders or between shrubs, they make an attractive as well as functional addition to the garden. Due to their trailing growth, they create a cascading effect in hanging baskets and window boxes, or surrounding a centrepiece in a patio container.
