Blue Lobelia

Blue Lobelia flowers for shade gardens in late summer

Blue Lobelia is herbaceous and perennial, with toothed alternate leaves, growing to about 1.5 metres in height.

The stems are erect, though frequently branched.

The flowers are quite interesting; with blue irregular two lipped flowers, appearing in lengthy terminal racemes.

The corolla is slit on both sides close to the base. When the seeds appear, they are contained in double celled capsules, each containing many seeds. These capsules have a lobe shaped base. Great Blue Lobelia has deep blue flowers in late summer for 3 to 4 weeks.

Care of Lobelia

Lobelia is very easy to take care of and flowers in late summer for around a month. This makes it a very useful plant for colour later in summer when other flowers have died off these lovely Lobelia flowers will bring a touch of color to a garden just before fall / autumn.

Lobelia plants prefer to be moist most of the time but they don’t like to stand with their roots in water.

Lobelia flowers are tolerant to shade and the plant itself requires little care. It will self-sow most of the time so you do not really have to worry about Lobelia propagation, but you are still advised to divide the plants every 2 to 3 years as this practice tends to make the plant grow more vigorously.

You should grow Lobelia in rich soil, especially in soil that is rich in organic matter like humus.

If you live in a reasonably temperate climate, rosettes on your plant will stay green through the winter. If you live in a temperate climate, you must be careful not to mulch this plant as when the temperature rises above and then falls below freezing point your plants roots may become water logged resulting in rot.

In cold climates where the weather stays frozen, mulching is probably a good idea – this will protect the plant through the harsh cold of winter, though you should remove the mulch the moment temperatures rise above freezing to prevent rot.

Lobelia Propagation

Like most other plants, Lobelia Blue Splendens plant is best propagated in the spring. What you have to do is to remove the rosettes, discarding the remains. Then plant the latest rosette in organically enriched soil.

Generally, the Lobelia will not need propagation for at least two years. The great Blue variety can grow up to three feet in height and nearly a foot wide.

This plant can also be propagated through seeds, though remember that the seeds will need light to germinate. Sow them in fine grain pit in a flat box, keeping the seeds moist and under lights.

In a few weeks the seeds will put out little green shoots which are ready for transplanting in around four to six weeks.

At this point you should put them into pots using the same soil mixture and adding fertilizer every second week or so to aid growth. Now they are ready to put into your garden planting them about a foot apart.

Lobelia plants require a lot of fertilizer to grow well.


Every experienced gardener knows that soil is not merely mud. The content of the soil whether it is clay like, loamy or sandy, can be crucial.

Just as important is how much water is retained in the soil, or even the Ph. factor of the soil, whether it is alkaline or acidic. Moist but well drained soil is absolutely necessary.

Soil for Lobelia must also be rich in organic matter so that it simulates that of shady woodland.

  • Humus rich well drained soil is a must.
  • Keep the plant moist but not wet and divide every 2 to 3 years.
  • Remember in milder climates do not mulch.
  • In colder climates remove the mulch when the temperatures rise above freezing in order to preserve the rosettes.


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