Classification, origin and description
Common name: Sansevieria.
Etymology: the correct name should have been Sanseverina (and some authors call it that) since the Neapolitan botanist Vincenzo Petagna, discoverer of the genus, asked the Swedish naturalist C.P. Thumberg, to whom he sent the first observed specimen, to dedicate its name to the count of Chiaromonte, P. A. Sanseverino, creator of a garden of rare plants in southern Italy. Due to an error by Thumberg, perhaps endorsed by the fact that a count of Sansevero actually existed, the genus was given the name of Sansevieria, which it still preserves today.
Origin: almost all the species come from Africa, with the exception of S. zeylanica which is native to Ceylon.
Genre description: includes about 60 species of herbaceous, evergreen, perennial, leathery plants, with rhizomatous root system (which develops just below the soil surface), with solitary or rosette-shaped caulinary leaves, narrow and thin, flat or cylindrical ( S. cylindrica), with a leathery consistency, which in some cases can be thickly imbricated one to the other to form a short caule arranging itself in a fan or a stem with guaining leaves. A species S. parva emits stolons at the apex of which new seedlings are born. Some species in spring-summer produce white or greenish-white flowers, inconspicuous, but sometimes very fragrant.
Sansevieria trifasciata variety Laurentii (photo website)
Species and varieties
Sansevieria cylindrica: this rhizomatous species, with an erect bearing, has leaves up to one meter long, almost cylindrical in shape, rigid and about 2,5 cm thick. Dark green in color, they are crossed by a narrow central furrow. It produces pinkish flowers that bloom in spring-summer.
Sansevieria asta: this species, originally from Africa, has leathery and light green leaves with dark green and slightly curved edges.
Sansevieria grandis: this epiphytic species has oval green leaves, with dark green streaks and red edged margins, which reach the size of 20-25 cm. in length and 10-15 cm. wide. They are arranged to form a main rosette from which hanging stolons that carry other rosettes of leaves. It is a species suitable for growing in hanging baskets.
Sansevieria hahnii o S. trifasciata "Hahnii": this dwarf species, considered by some to be a mutation of S. trifasciata, has leaves 6-7 cm wide. and 10 cm long, ovate-triangular in shape, concave, sometimes wavy, dark green in color, with yellow, gray-green or whitish transverse streaks, arranged in a spiral, one after the other towards the center, to form a rosette. It is a species that easily hatches. The variety "Golden Hahnii" has leaves with variegated margins of yellow or creamy white.
Libyan Sansevieria: this species, characterized by ensiform, rigid, erect leaves, which reach 60 cm. in length and crossed by wide white bands edged with red, it produces, in spring-summer, a long ear that collects thick clusters of white flowers.
Sansevieria scabrifolia: species characterized by gray-green leaves arranged to form narrow rosettes 15 cm high.
Sansevieria thyrsifolia: native to Africa, this species has leaves about 40 cm long, erect and wide, with a green leaf with darker edges.
Sansevieria trifasciata: native to Africa, this rhizomatous species has erect caulinary leaves, leathery in consistency, linear in shape, slightly concave and dark green in color with transverse and irregular gray or whitish green streaks. In nature it reaches considerable heights and is used to obtain textile fibers; in pot it remains small (about one meter). The flowers, when they appear in spring-summer, are white-greenish and bloom united in little showy inflorescences that at night give off a pleasant scent. Among the most common varieties we find: "Laurentii", with leaves 30-45 cm high. with white, yellowish or golden yellow margins. Many cultivars have been obtained, among which we remember: "Craigii", with long and slightly obovate leaves and "Goldiana", with cream yellow margins and irregular streaks in the center of the foil.
Sansevieria cylindrica "Skyline" (website photo)
Environmental requirements, substrate, fertilizations and special precautions
Temperature: the minimum winter temperature should not be lower than 10-13 ° C, but they can also tolerate lower temperatures if kept dry.
Light: good and widespread, away from direct sunlight. They also tolerate moderate light, but in this case the variegated leaf varieties will lose their streaks, to return to a single color.
Watering and environmental humidity: space the waterings in spring-summer, so that the soil dries between the one and the other (generally it is sufficient once every two weeks, a little more often if it is very hot); thin out even more in the autumn-winter period. They are plants subject to radical rot, if you water too much. They have no particular needs in terms of environmental humidity, but washing of the foliage will contribute to the well-being and beauty of the specimens.
Substrate: mixture based on garden compost, leaf and peat compost, with the addition of sand.
Special fertilizations and tricks: repotted in March-April, if necessary. If you do not proceed with repotting, it is a good idea to replace 2.5 cm. of substrate surface with new soil. Administer liquid fertilizer, in spring-summer, every 3-4 weeks.
New specimens can be obtained by division of the tufts, separation of suckers and leaf cutting. The first two methods can be used for species at least 15 cm high. and for the 5 cm high rosette ones. and they are the only ones capable of ensuring the maintenance of the typical streaks of some varieties. They are practiced in spring, before the vegetative restart, extracting the plant from the pot and separating the earth from the roots. Then the rosette plants must be divided, making sure that each portion of the rhizome has at least one rosette developed by the stolons of the main rhizome; those with vertical growth instead must be multiplied by cutting the rhizome so that each portion has at least one bud and an adequate portion of roots. The leaf cutting, about 10 cm long, must be planted, in summer, with the apex facing upwards, in pots filled with peat and sand, at a depth of about 5 cm. and at a temperature of 20 ° C. Before proceeding, however, wait about a week for the callus to form. The new shoots take enough time to appear and during this period care must be taken to avoid rotting or drying.
Diseases, pests and adversities
- Leaves with brown spots and which begin to rot at the base: excessive watering with risk of rotting of the roots. We must remove the plant from the pot and remove the part of the rotten rhizome. Let the rhizome dry for at least a week. Discard the rotted leaves. Treat the cut parts with a fungicide product. Finally, repot the plant and water in more moderation.
- Variegated or mottled leaves that turn totally green: not very bright exposure.
- Cotton mealy bugs: can attack plants, especially in hot and dry climates. You have to remove them, treat the plant with an anticoccidic product and raise the level of environmental humidity (the spraying and the washing of the leaves allow to eliminate the cochineals in the larval state). As an alternative to the chemical, the affected parts can be rubbed with a cotton swab wet with water and alcohol.
- Brown mealybugs: they occur with the formation of brown growths (determined by the small "shell") and giving the plant a blackish and sticky appearance (due to the production by the plant of sugary substances that make it subject to attack by fungi and fumaggini). They are fought by removing them and treating the plant with an anticoccidic product or by rubbing the affected parts with a pad soaked in water and alcohol.