The Lobelia cardinalis is a perennial aquatic herbaceous plant native to North America, belonging to a genus of which there are numerous perennial and annual ornamental plants cultivated in our gardens. This species appears as a compact rosette of large dark green leaves, in spring from the rosette grows a stem of red, fleshy, very branched, which easily reaches 100-120 cm in height, on which there are numerous bright red buds; the latter bloom starting from the base of the rosette, revealing beautiful carmine-colored flowers, with the low trilobate petal and the one higher up bilobed; the stamens are gathered to form a tube.
The leaves of the Lobelia cardinalis are oblong and lanceolate in shape with a serrated edge and have long petioles.
In late summer it produces woody capsules full of seeds that guarantee the multiplication of this plant.
To promote the growth of this plant it is important to avoid the lobelia cardinalis emit a main stem by pruning the tips. In this way the establishment of a main stem is avoided and the growth is distributed over the whole plant with the emission of lateral jets.
After pruning you will have a plant with a more globular habit and more valuable from an ornamental point of view.
It prefers sunny positions, but develops without problems even in partial shade, as long as it is placed in a bright place. It does not fear the cold, even if in places with very cold winters it is advisable to repair the basal rosette from too persistent frosts; in summer it is preferable to shade it on particularly hot days. Optimum temperatures for Lobelia cardinalis range between 10 and 25 ° C with optimal conditions that settle at temperatures around 18 ° C.
The aquatic lobelia is a plant that likes very wet soils, on the banks of streams or basins; if desired, it can also be grown far from the water, both in the ground and in the pot, remembering that it needs large amounts of water, and therefore it must be watered abundantly and often, without ever allowing the soil to dry.
In spring it is possible to sow lobelias, in a mixture of peat and sand in equal parts, remembering to keep the soil always moist; cultivate new plants in pots for at least a year and plant them the following spring. In spring and autumn it is possible to divide the heads of basal rosettes, obtaining new seedlings, which must be made to winter in a sheltered place, before being planted the following year.
An alternative to sowing is the division for tufts, easy to make if the plant is lush and abundant. To multiply the aquatic loblia with this technique it will in fact be sufficient to divide the "mother" head with a decisive cut and obtain a new seedling which, taking root, will give life to a new plant.
Aquatic lobelia - Lobelia cardinalis: Pests and diseases
Among the parasites and diseases that can attack Lobelia cardinalis we sometimes point out aphids and cochineal, which can ruin the plant, leaves and flowers.
There lobelia cardinalis can suffer too sunny exposure and usually in these conditions it is a plant that becomes stunted and grows in a very reduced way.