Lobelias are worth looking out for in the Highlands

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The blue flowered bedding Lobelia, Lobelia erinus, is often planted in hanging baskets, window boxes and at the front of bedding schemes, it is neat and tidy, easy to grow and flowers for a long period in the summer months and rightly so is a popular garden plant.

There are about 415 species of Lobelia in the world, found in such diverse places as the Hawaiian Islands, Mexico and the mountains in East Africa.

Here in Scotland we have only one species, the Water Lobelia, Lobelia dortmanna, but ours is a special one as it is an aquatic plant. It is only found growing wild in lochs and ponds with acid water and low levels of nutrients, which makes it very susceptible to water enrichment and sedimentation.

It is widespread and common in the Highlands growing in both stony and earth substrate in water up to one metre deep where it forms a rosette of short stubby leaves only 2-4cm tall.

As it is underwater it cannot capture carbon dioxide from the atmosphere like normal land plants with their leaves in the air but obtains its CO2 from the rooting zone.

When it flowers it sends up a simple, leafless stem which extends up above the water surface for 15 to 30cm, producing a few elegant white, or very pale blue or pale pink flowers and making the flowers available for pollination by flying insects.

This is a special and beautiful plant and well worth looking out for when on holiday in the Highlands. The ones in the photograph were in Loch Gynack near Kingussie. Outside Scotland it can be found in Northern Europe and across northern North America.

In complete contrast several species grow between 3,300m and 4,600m (10,800-15,100 feet) on the high mountain slopes and valleys in the lofty East Africa Mountains. These are Giant Lobelias, some species grow 3m (10 feet) tall, either from a single giant rosette or branched with the rosettes connected by underground stems. After many decades a rosette will reach flowering size, the flowers are pollinated by birds, then produce hundreds of thousands of seeds before the rosette will die.

The giant rosette acts as a water reservoir holding water at the leaf bases, at night this water freezes and the freezing process is enough to protect the growing point from severe frost.

If for some reason a rosette looses its water reservoir then it is very susceptible to frost damage.

Another species often cultivated in our gardens is Lobelia cardinalis and its hybrids. This is native to The Americas.

In our gardens this herbaceous perennial prefers a moist, rich soil, sending up a stout spike to about 1m tall, the leaves are dark maroon and the tall, erect flower spike produces many vibrant cardinal red flowers. In its native habitat it is pollinated by Ruby-throated Hummingbirds.

These exotic species are quite a contrast to our little aquatic Scottish native plant.