Plants

Trailing Lobelia

Lobelia erinus

Ulrike Hanninger Ulrike Hanninger

Trailing lobelia blooms for months on end with proper care and is covered over and over again by a multitude of small flowers. Here, you will find all that you need to know to cultivate the popular balcony flower.

Growth type
  • Perennial plant
  • one year old
Growth height (from)
from 15.00cm to 35.00cm
Growth width (from)
from 0.00cm to 0.00cm
Growth characteristics
  • hanging
  • upright
  • tight
Flower color
  • purple
  • blue
  • white
  • multicolored
Flowering time (month)
  • May to September
Flower shape
  • tight
  • small
Leaf color
  • green
page format
  • lancéolées
Fruit shape
  • Capsule
Light
  • sunny to semi-shade
Soil type
  • sandy to loamy
Soil Moisture
  • moderately humid to humid
Lime compatibility
  • lime-tolerant
Nutrient requirements
  • nutrient-rich
Humus
  • rich in humus
Decorative or utility value
  • Flower Decoration
  • picturesque growth
Toxicity
  • non-toxic
Use
  • Flowerbeds
  • ground cover
  • Borders
  • Planters
  • Underplanting
  • Rebates
Garden style
  • Flower garden
  • Roof Garden
  • Pot garden

Origin

Trailing lobelia (Lobelia erinus), also known as Blue Lobelia or Lobelia for short, belongs to the bellflower family (Campanulaceae) and is originally native to the Cape region of South Africa.

Growth

The growth pattern of the Trailing Lobelia is very compact and dense. Both upright and hanging varieties are available, which we usually cultivate as an annual. The upright Lobelia varieties reach heights between 5.90 and 13.77 inches, the hanging variety develop shoots that can be up to a 3.28 feet long.

Leaves

The leaves of the Lobelia are arranged alternately, lanceolate and about 0.78 to 1.18 inches long. Their color ranges from green to dark green.

Flowers

Trailing lobelia forms a multitude of small flowers and blooms from May to September. The flowers are zygomorphic, so they consist of two perfectly symmetrical halves. They are usually found in a pronounced shade of blue, but they are also available in purple and with or without a white eye in the middle.

Lobelia blossoms

If you mirror the flowers of the Trailing Lobelia along an imaginary axis of symmetry, you get two exactly identical halves

Fruits

After flowering, small capsule fruits are formed which release seeds as soon as they open.

Location

Although Trailing Lobelia also thrives in partial shade. More sun means more flowers. Hanging Lobelia varieties are best kept in hanging baskets, but can also be used as understory plants. Trailing Labelia that grow upright are better off in the balcony box, in the pot or in the bowl.

Substrate

You can use commercially available humus-rich potting soil as a substrate for your Lobelia.

Watering

Planting Lobelia

Expanded clay ensures good drainage in the balcony box

Always keep the Trailing Lobelia uniformly moist. Especially when growing in pots, the substrate should never dry out completely. To prevent waterlogging we recommend adding a made of expanded clay or similar, at the bottom of the planting container.

Fertilizing

The frequent bloomers have a high nutritional requirement, therefore, regular fertilization is a must. Fertilize the Trailing Lobelia every two weeks with a little low-dose composite fertilizer after watering it. Important: Use only fertilizers with a low nitrogen content. Nitrogen promotes plant growth, but at the same time inhibits flower formation.

Additional care

To have the flowering period last until fall, the Trailing Lobelia is pruned by a third after the first main flowering at the end of July.

Overwintering

Wintering is only possible in very few Trailing Lobelia varieties. The ‘Richardii’ variety, for example, can be placed in a bright winter quarters between 50 and 59 degrees Fahrenheit before the first frosts. When placed there, water it moderately and put it back outside after ice saints. As a rule, however, it makes more sense to collect the seeds in fall and sow the lobelia again next spring.

Where to plant

Hanging basket with Trailing Lobelia

The Trailing Lobelia looks quite attractive in a hanging basket

Most often you can find the Trailing Lobelia in the balcony or terrace. Tried and tested companion plants are nastriums or pelargoniums (geraniums). Tone-on-tone plants with, for example, blue daisies ensure a continuous sea of flowers. In the garden, lobelia are often used as ground cover, for bed borders or sunny flower beds.

Varieties

Numerous cultivars and varieties of the Trailing Lobelia are available in stores. They differ in leaf and flower shape as well as in their growth. Upright and rather small, at a height of around 3.93 inches, are for example:

  • “Blue pearl”: bright blue flowers
  • “Cambridge Blue”: light blue flowers
  • ‘Kaiser Wilhelm’: light green foliage and cornflower blue flowers.
  • “Rosamunde”: intense red flowers with white eyes
  • “Snowball” and “Regatta White”: pure white
  • “Pumila Splendens”: dark blue with white eye
White Trailing Lobelia

In white, too, Trailing Lobelia is an absolute eye-catcher

The Trailing Lobelia varieties are hanging plants:

  • “Cascade Mix”: Mixture of blue, white and purple flowers; the shoots are up to 15.74 inches long
  • "Sapphire": dark blue flowers with white eyes; the shoots are up to 19.68 inches long
  • “Richardii”: Flowers in light blue; the shoots are up to 39.37 inches long

Propagation

Trailing Lobalia are propagated by sowing. From March, sow the seeds under glass at 60.8 to 64.4 degrees Fahrenheit. Since they are light-dependent germinators, the seeds are only covered with a thin layer of substrate. The seedlings are then picked out in individual groups so that small, compact plants emerge. From May - as soon as the ice saints are over — the plants can move outdoors and to their final place on the balcony, terrace or in the garden.

The above-mentioned lobelia variety “Richardii” can only be propagated using cuttings. Prune it in November.

Diseases and Pests

Note: Trailing lobelia is prone to mold (gray rot). With the right choice of location (nice and airy) and a suitable substrate (low in nitrogen and permeable) you can prevent the fungal disease — however, hundred percent protection cannot be guaranteed. You should therefore regularly check for infestation and remove the affected parts of the plant immediately. There is a high risk of infection, especially in balcony boxes.

Frequently Asked Questions

What do Trailing Lobelia look like?

The Trailing Lobelia is a compact growing shrub that is usually cultivated as an annual. As a balcony flower, it is available as both an upright plant and a hanging plaint. The blue flowers have a special feature because they consist of two halves that are absolutely symmetrical. The center of the flower often has a white eye.

How big is the Trailing Lobelia?

Upright Lobelia can reach heights of between 5.91 and 11.81 inches, depending on the variety. The shoots of the hanging varieties, on the other hand, can develop an incredible length of up to 39.37 inches.

When can you plant the Trailing Lobelia?

Before you can plant the trailing Lobelia outdoors, you should wait until the Ice saints (mid May).

When does the Trailing Lobelia bloom?

The Trailing Lobelia blooms between May and September.

How often must you water the Trailing Lobelia?

The substrate of the Trailing Lobelia should always be kept moist — especially when growing in pots.

How must one care for the Trailing Lobelia?

The Trailing Lobelia needs fertilization about every two weeks. You can also encourage re-flowering by trimming the flowers at the end of July.

Is the Trailing Lobelia winter-hardy?

The Trailing Lobelia is not a winter hardy shrub. However, some varieties can be overwintered in a 50 to 59 degree Fahrenheit warm quarter.

What goes well with the Trailing Lobelia?

Trailing lobelia is a popular balcony plant, which goes well with perlagoniums, nastriums or blue daisies.

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