There are very few flowers that can match the true blue of Lobelia. For connoisseurs of blue there’s even a choice between sky blue, midnight blue, marine blue, blue splash, and blue eyes! These grow anywhere; plant anytime annuals are the quintessential edging plant.
They grow in full sun or semi shade and like loose, gritty soil. When nothing else seems to grow in July, punnets of seedlings can still be planted out, provided the area does not receive heavy frost.
Conventional growing wisdom says they should be spaced about 20 cm apart, but why not break the rules and plant them even closer together for quick, maximum impact? Once the seedlings have settled in, about two weeks after planting, give them a boost with a liquid fertiliser like Margaret Roberts Supercharger, Nitrosol or Sheer Blue.
Although they flower best in spring and autumn, you can expect blooms throughout the year. Cut back when the flowers begin to go to seed and they will be encouraged to send out new flowers in a month or two. The dwarf, upright growing varieties, like the ‘Riviera’ series, only grow 7-10 cm high and stay compact and mounded while flowering prolifically. All the different blues form part of the ‘Riviera’ series, as do shades of lilac, rose and white.
A particularly attractive variety is the ‘Midnight Blue’, which has bronze foliage. ‘Blue Eyes’ has a distinct white eye that adds an extra sparkle to the blue. There are also two very attractive mixes – the ‘Springtime Blues’ mix consists of a designer mix of blue shades with a touch of rose while the ‘Riviera’ mix includes all the colours in the series.
A new arrival in the seed packet series is the Lobelia ‘Emperor William’. The seed is extremely fine and care must be taken when sowing. Sow fairly thickly in spring or autumn and transplant in clumps when the small seedlings are large enough to handle. This indigenous variety is also perfect for edgings, rockeries, containers and window boxes.
There are also trailing Lobelias, which have a more cascading habit. These are suitable for hanging baskets, window boxes and for softening edges of raised beds and rockeries. The ‘Fountain’ series has light blue and white blooms as well as a mix, which includes ‘Sapphire Blue’.
A beautiful recipe for a hanging basket is to combine trailing blue Lobelia with white Alyssum, scented Geraniums (small pink flowers) and Lavender. A super winter into spring window box can be made up of Pansy Evita, Lobelia ‘Sky Blue’ and red or yellow Tulips.