Cambridge Blue Lobelia is a dainty, popular plant; it has many fans who love its soft, subtle, light blue flowers on branching stems with tiny leaves. Its light green foliage is not often seen because of the abundance of flowers which bloom from spring to autumn.
A versatile plant that is perfect in a pot, a rock garden, a border, a hanging basket, or anywhere a touch of colour is needed.
Lobelia erinus is a compact, bedding variety of Lobelia, which forms dense, brilliant mounds about six-inches tall. It is ideally suited for use as a ground cover, an edging plant along sunny or partially-shaded pathways, tucked into rock gardens, or artfully blended together in lush masses of mixed colours. Blur your vision while looking at such a planting and you’ll think you’ve slipped into a Monet canvas.
Lobelia 'Cambridge Blue' has been awarded the prestigious RHS Award of Garden Merit (AGM).
Timing: Sow indoors in late winter to late spring.
Sowing to flowering is about 16 weeks; they will flower happily until the first signs of winter. To get the most from your plants, sow early in the year. However, Lobelia erinus have such a long flowering period, so long as temperatures are around 15 to 20°C (60 to 70°F) while they germinate they can be sown up to late spring.
Fill a seed tray or pot with moist seed compost. Stand the tray in water until completely moist and then drain off the excess water.
Sow seeds as thinly as possible over the surface of the compost. The finer you sow them, the easier pricking out will be. Mixing the seeds with silver sand may help a more even distribution of seeds. Lightly press the seeds into the compost. Do not cover them with soil as they need light to germinate. Place in warmth 15 to 20°C (60 to 70°F), and keep moist at all times.
Germination will take 10 to 14 days. Keep the seedlings in a light position, but shade from bright sun. When large enough to handle (usually after 5 to 6 weeks) transplant 5cm (2in) apart into trays of potting compost. It is easier to transplant little clumps of Lobelia seedlings than to try to transplant single seedlings.
Gradually accustom plants to outside conditions for 2 to 3 weeks before planting out when danger of frost has passed, usually from the end of May. The plants will spread so allow 15cm (6in) between plants.
Lobelia erinus will grow best in a cool spot with partial shade. Before planting, add some organic matter or a controlled release fertiliser into the soil.
It does not like hot, dry weather; in midsummer they can be rejuvenated by cutting them back by half their height, which also will help them become bushier. Reapply fertilizer and water them well. Keep plants moist at all times, if the plant does dry out it will die back, if this happens cut it back and it should produce a second flush of growth.
City/Courtyard Gardens, Cottage/Informal Garden, Flowers Borders and Beds or Patio/Container Plants. Trellis and screens. Edging plants, tubs, baskets and window boxes.
The genus Lobelia is made up of as many different species as there are days in the year. The species erinus is native to southern Africa: from Malawi and Namibia south to South Africa. The ancestor of the garden lobelia was a plant that grew to around 25cm (10in tall), but nurserymen nowadays would be mortified if their labours produced a plant that high. In fact, this doesn't happen, since cultivated varieties today are very compact or have a trailing habit.
Lobelia is a genus of about 370 species of annuals, perennials (even some aquatics) and shrubs. In their native habitat they may be found along riverbanks, wet meadows, marshes, woodlands, mountain slopes and deserts. They often have bright, tubular flowers with five lobes, the upper two lobes often are erect and the lower three are fan-like.
Since they originated from the tropics, many are not hardy in our area and these we tend to treat as annuals.
The genus Lobelia was described in 1753 by Linnaeus who named it in honour of a Flemish nobleman, Matthias de L'Obel (1538-1616), a botanist and physician to King James 1.
The species name erinus is the genus name of another plant - Erinus alpinus. Erinus comes from Greek er meaning 'spring', for the time when this plant blooms. Used in this manner, as the species name it simply means 'like the plant Erinus'.
Lobelia erinus is divided into two separate groups
- The first group is referred to as compacta, more precisely as the Lobelia erinus Compacta Group. The plants have a compact upright habit and form green tufts 10 to 15cm (4 to 6in) high. They are highly suitable for flower-beds, containers, and edging purposes, but may also be planted in the centre of a hanging basket.
- The second group, Lobelia erinus Pendula Group, often referred to as pendula ultimately acquire a trailing habit. As young plants, trailing and upright lobelias are almost indistinguishable from one another. It is not until they start growing vigorously that trailing lobelias reveal their true nature by arching over the rims of window-boxes, pots, and hanging baskets and concealing them with a mass of green-leafed stems and numerous small flowers.
Trailing lobelias are, in fact, also suitable for flower-beds and borders, where they will cover the soil with their creeping stems.
- Additional Information
Packet Size 200mg Average Seed Count 5,000 seeds Family Campanulaceae Genus Lobelia Species erinus Cultivar Cambridge Blue Synonym Lobelia compacta Common Name Edging Lobelia, Garden Lobelia Hardiness Half Hardy Annual Flowers June onwards Height 15cm (6in) Spread 25cm (12in) Position Prefers a sunny position Soil Moist but well drained Notes Time to plant seeds: Late Winter to early Spring