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Origin and Habitat: Frailea atrobella grows around San Jose Chiquitos in the Chiquitos province, departement of Santa Cruz, Bolivia.
Altitude range: c. 300-360 metres above sea level.
Habitat and ecology: This species usually grows on very shady spots in a dense forest, partly under the leaves littier. The eastern Bolivian province of Santa Cruz is the home of several other cactus species, such as Frailea chiquitana Cardenas (Cardenas 1951) Gymnocalycium chiquitanum Cárdenas (Cárdenas 1963), Frailea larae R. Vasquez (Vasquez 1994) and Frailea camera Hauser Prestlé (Prestlé 2002).
- Frailea atrobella Diers, Krahn & R.Vásquez
Description: Frailea atrobella is a nice frailea species superficially similar Frailea mammifera subsp. angelesiae, but smaller in size with a larger number of ribs, tubercles with smaller, weaker spines, shorter flowers, red berries and conspicuously flat stemmed seedlings.
Derivation of specific name: Lat. atrobella = freely translated as black beauty.
Stem: Up to 25 mm in diameter, epidermis shiny dark green to violet at the base.
Ribs: 18 to 22 ribs broken down into tiny little tubercles carrying the areoles, beneath each tubercles there is a dark purple-brown semicircle.
Radial spines: Short (2-5 mm long) flat, reddish brown to black.
Central spines: One directed obliquely upwards, the other down.
Flowers: Light to bright yellow opening only with high temperature and adequate humidity of the substrate. They are self-fertile.
Bibliography: Major references and further lectures
1) Diers, Krahn & R.Vásquez "Frailea atrobella (Cactaceae) – eine neue Art aus Ostbolivien" Kakteen Sukk. 62(6): 156 (155-162; figs.). 2011 [Jun 2011]
2) Diers, W. Krahn, R. Vasquez “Új faj Bolíviából, a Frailea atrobella” in: 47 HRLEVÉL 2013 augusztus Magyar Kaktusz és Pozsgás Társaság Közhasznú Egyesület Internetes Újságja
Cultivation and Propagation: Frailea atrobella is a summer grower species relatively easy to grow. It is sometime seen as a grafted plant but grows very well on its own roots too. Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too.
Growth rate: Fraileas are relatively short-lived plants, only lasting few years (rarely more than 10-15 years in cultivation) and, possible annuals in habitat! In fact they reseed readily around the base of the mother plant if kept reasonably moist during warm weather. It is a good idea to keep restarting them from seed; what looks like a healthy big plant may suddenly die of old age without warning.
Soil: Use mineral well permeable substratum with little organic matter (peat, humus), plants may become too elongated if compost is too rich.
Repotting: Re-pot every 2 years. Use pot with good drainage.
Fertilization: It grows much faster with a low nitrogen content fertilizer in spring and summer. Potassium helps maintaining the plants compact and healthy.
Watering: Requires careful watering to keep plant compact. Water sparingly from March till October, the thin, fibrous roots suffer if there is humidity, therefore the plant should be watered only when the surrounding terrain is dry. Keep dry as soon as the temperature starts dropping in October and keep it perfectly dry in winter at temperatures from 5 to 15 degrees centigrade.
Hardiness: They need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous if kept on the dry side prior to, and during, cold weather). It tends to rot in winter during the resting phase, if kept wet. In the rest period no high atmospheric humidity!!
Sun Exposure: Light shade to full sun, its colour tends to richer and darker when grown in light shade. In a shaded position the plants grow faster, but are not flat shaped and dark coloured.
Uses: It is an excellent plant for container growing. It always looks good and stays small.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the infested plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Scales: Scales are rarely a problem.
- Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much. To prevent rottenness it is also advisable to surround its root neck by very rough sand or grit, this help a fast water drainage.
Propagation: With fresh harvested seeds or (rarely) by grafting. Fraileas set seed (when well grown) and grow easily from seed. Seedlings dislike strong light and dry conditions and need to be repotted frequently during the first few years. However, old plants become senile and have a tendency to succumb to disease and a weak root system. At this stage, as is well known, they die suddenly. So, after they reach about 4-5 cm in diameter grow them slowly, and adopt a new repotting period, using intervals of every 3-4 years. Additionally grow them under drier conditions or with stronger sunlight. But plants are sometine grafted to accelerate growth, but the grafted plants are typical rather tall growing, compared with plants on their own roots that are usually more flat to the ground.
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