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Classification, origin and description
Common name: Primula del Capo.
Etymology: from the Greek "streptos", twisted and "karpos", fruit, due to the spiral shape of the seed capsules.
provenance: Eastern and Southern Africa, Asia and Madagascar.
Genre description: includes about a hundred herbaceous or suffruticose species, evergreen, delicate, caulescent or acauli, with many leaves joined at the base of the plant to form a small head or with a single large horizontal or hanging leaf. All species share the presence of a dense silky hair and the tubular shape of the flowers, which are isolated in the acauli species and gathered in bunches in the caulescent ones. They are used as flowering indoor plants. S. rexii is particularly widespread as a houseplant.
Streptocarpus (photo www.aggs.org)
Streptocarpus wendlandii (photo www.hydrotip.de)
Species and varieties
Streptocarpus caulescens: this caulescent species has ramified and tomentose stems, which bear opposite, rounded and oval leaves. From July to December it produces small pale blue flowers gathered in axillary inflorescences. It grows up to 30 cm. about.
Streptocarpus dunnii: single leaf species, curved downwards, almost one meter long, oblong-lanceolate in shape. In May-June it produces hanging pink-vermillion flowers and gathered in round inflorescences. It is suitable for growing in a greenhouse.
Streptocarpus holstii: native to East Africa, this bushy species has stems that grow up to 50 cm. (with prostrate posture, later erect) and bear small, dark green, opposite, oval-shaped leaves with evident ribs. From June to September it produces flowers, similar in shape to violet and blue in color with purple reflections and white throat.
Streptocarpus x hybridus: this hybrid, mainly derived from S. rexii, has tufts of bright green leaves and tomentose. From May to October it produces flowers, similar to those of the foxglove, white or purple red, 3-6 cm long, gathered in short racemes. Among the most common varieties we find: “Constant Nymph”, with blue-purple flowers with evident veins in the throat; "Diana", with purple flowers with white throat; "Merton Blue", mauve blue flowers with a white throat; "Mexican White", with white flowers with a yellow throat.
Streptocarpus kewensis: this species has only two or three large leaves with a bright, oval and elongated green leaf. The flowers, 4-5 cm long, bloom in bunches of 6-8 at the top of the numerous flower stems. They can be white, red or purple, with dark purple variegations in the throat.
Streptocarpus polyanthus: acaule and rhizomatous species, which has one or two tomentose leaves and an oval or heart shape (10 cm wide and 30 cm long). In autumn-winter it produces flower scapes, 30 cm long, which carry blue-lilac flowers with wavy petals at the edges.
Streptocarpus rexii: this bushy species, native to southern Africa, has 20 cm long leaves. and 6 cm wide, ribbon-shaped, dark green in color, tomentose, with evident ribs on the lower page and arranged to form a rosette. Numerous slender, reddish and tomentose flower stems form from the base of the leaves, practically all year round, bearing a large pale blue flower streaked with purple. in height. S. x hybridus derives from this species.
Streptocarpus saxorum: native to East Africa, this suffruticose species is suitable for growing in hanging baskets, due to its ability to form large tufts (20 cm high and 50 cm wide) with semi-prostrate and expanded growth habit. The leaves, oval and fleshy, are tomentose and vary in color from bright green to dark green. From April to October, it produces pale mauve violet-like flowers.
Streptocarpus watsonii: single leaf species that produces numerous stems, each carrying up to 16 pink-purple flowers with white throat streaked with red.
Streptocarpus wendlandii: 30-80 cm high. perhaps it represents the most ornamental species, with its only large leaf, curved downwards, wavy, oval-rounded and dark green on the upper page and purple on the lower one. The blue-violet flowers with white speckles bloom in large spikes, carried by sturdy stems.
Environmental requirements, substrate, fertilizations and special precautions
Temperature: the minimum winter temperature must not be lower than 10 ° C. They do not tolerate sudden changes or excess temperatures. From April to October it should not rise above 15-18 ° C. The environment should be ventilated, but not subjected to drafts.
Light: very good, but widespread, away from direct sunlight.
Watering and environmental humidity: water regularly in spring-summer; thinning doses in autumn-winter. Single leaf species should be watered in moderation. Raise the environmental humidity by placing the plants on terrines containing wet pebbles.
Substrate: an acid pH mixture based on leaf earth, moorland and peat, with the addition of sand and shredded charcoal.
Special fertilizations and tricks: the bushy species are repotted annually, in March. Administer liquid fertilizer every fifteen / twenty days. Withered flowers must be removed (unless you want to get the seed for reproduction), to obtain an abundant and lasting flowering. Be careful not to raise atmospheric humidity without ensuring adequate air exchange: you risk the development of mold or other fungal diseases.
The acaulous and bushy species, as well as the hybrids, are sown in January. The seeds are very small. As soon as the size of the seedlings allow it, they must be transplanted into pots containing the same substrate suitable for adult plants. The plants thus obtained will be able to bloom, from June to October of the same year. Single-leaf species, on the other hand, require two transplants and protection from direct sunlight. They will bloom all winter. The bushy species can also be multiplied by division of the tufts in March, on the occasion of repotting. Another method used to obtain new specimens is that of leaf cuttings. These take root between May and June, in a peat and sand substrate kept humid, in a protected environment and at a temperature of 18-21 ° C. The small leaves are used whole, while the large ones must be cut into pieces at least 6-7 cm long. and rooted with the base in the substrate. The new seedlings (which should appear within six weeks) will have to be transplanted into 8 cm pots. in diameter and subsequently in containers of adequate size for plant growth.
Diseases, pests and adversities
- Appearance of a gray mold on the leaves: high humidity without air exchange. Remove the affected parts and treat the plant with fungicide products.
- Aphids: attack leaves and flowers. They suck the sap and make the plant sticky. They are eliminated by washing the plant and treating it with specific insecticides.