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Accepted Scientific Name: Mammillaria polythele Mart.
Hort. Reg. Monac. (1829) 127, nomen; et in Nov. Actorum Acad. Caes. Leop.-Carol. German. Nat. Cur. 16(1): 328, pl. 19 328 1832. Mart. & Schrank
Origin and Habitat: Querétaro, Guanajuato, Hidalgo, Mexico
Altitude range: 1700-2250 metres above sea level.
Mammillaria polythele Mart.
Hort. Reg. Monac. (1829) 127, nomen; et in Nov. Actorum Acad. Caes. Leop.-Carol. German. Nat. Cur. 16(1): 328, pl. 19 328 1832.
- Mammillaria polythele Mart.
- Mammillaria crocidata Lem.
- Mammillaria dolichocentra Lem.
- Mammillaria galeottii Scheidw.
- Mammillaria dolichocentra var. galeottii (Scheidw.) Salm-Dyck ex C.F.Först.
- Mammillaria obconella var. galeottii (Scheidw.) Backeb.
- Mammillaria obscura var. galeottii (Scheidw.) Salm-Dyck ex C.F.Först.
- Mammillaria tetracantha var. galeottii (Scheidw.) Borg
- Neomammillaria galeottii (Scheidw.) Britton & Rose
- Mammillaria hidalgensis J.A.Purpus
- Neomammillaria hidalgensis (J.A.Purpus) Y.Itô
- Mammillaria hoffmanniana (Tiegel) Bravo
- Neomammillaria hoffmanniana Tiegel
- Mammillaria kewensis Salm-Dyck
- Neomammillaria kewensis (Salm-Dyck) Britton & Rose
- Mammillaria neophaeacantha Fritz Schwarz
- Mammillaria tetracantha Salm-Dyck
- Mammillaria xochipilli Repp.
Mammillaria polythele subs. durispina (Boed.) D.R.Hunt
Mammillaria Postscripts 6: 7 7 1997
- Mammillaria polythele subs. durispina (Boed.) D.R.Hunt
- Mammillaria kelleriana F.Schmoll ex R.T.Craig
- Mammillaria subdurispina Fritz Schwarz
- Neomammillaria subdurispina (Backeb.) Y.Itô
Mammillaria polythele subs. obconella (Scheidw.) D.R.Hunt
Mammillaria Postscripts 6: 7 7 1997
- Mammillaria polythele subs. obconella (Scheidw.) D.R.Hunt
- Cactus obconella (Scheidw.) Kuntze
- Mammillaria obconella Scheidw.
- Neomammillaria obconella (Scheidw.) Y.Itô
- Mammillaria ingens Backeb.
- Mammillaria polythele cv. Stachellos hort.
Description: Mammillaria kewensis is one of the innumerable forms of Mammillaria polythele which is one of the most widespread and morphologically variable taxon. In the past there were a number of names amongst Mammillaria polythele (at least 11 varieties), but all this varieties merge gradually one with another through a continuous series of transitional forms and it is almost impossible to tell them apart, and now the names Mammillaria kewensis is not accepted by many botanists that treat it as synonym, but it still has a value for a collector because they identify plants with particular characters.
Stem: Globose to cylindric, 3 to 4 cm. in diameter.
Tubercles: Short, terete, when young short-woolly in the axils and at the areoles. Axils of tubercles bearing crisp hairs.
Central spines: Looking like radials and often confused with them, sometimes only 2 at first and pointing up and down, of which the lowermost longer, later 3 to 6, somewhat spreading, brown with dark tips, 4-17 (rarely to 25) mm long.
Radial: Absent or rudimentary.
Flowers: About 15 mm long, reddish purple; perianth-segments lanceolate, acute; stigma-lobes 5, reddish.
Subspecies, varieties, forms and cultivars of plants belonging to the Mammillaria polythele group
- Mammillaria ingens Backeb.: has solitary stems up to 40 cm tall and 15 cm in diameter. Distribution: Biosphere Reserve of Barranca de Metztitlán, Hidalgo, Mexico.
- Mammillaria kewensis Salm-Dyck: has 3 to 6 spine, somewhat spreading, brown with dark tips. Distribution: Querétaro, Guanajuato, Hidalgo.
- Mammillaria polythele Mart.: (subsp. polythele) has stems 8-10 cm in diameter and only 2 spines at first, later 3-4. Distribution: Hidalgo, Guanajuato, and Queretaro.
- Mammillaria polythele subs. durispina (Boed.) D.R.Hunt: has stems 5-6 cm in diameter and 6-8 radiating spines that vary in length to 15 mm. Distribution: Guanajuato and Queretaro.
- Mammillaria polythele subs. obconella (Scheidw.) D.R.Hunt: has stems up to 15 cm in diameter and 4 unequal spines arranged like a cross c. 2 cm long, ± equal, somewhat recurved, yellowish at first, later grey. Distribution: Barranca de Venados and near Metzquititlan, Hidalgo.
- Mammillaria polythele cv. Stachellos hort.: has a blue-green pinecone like, stem up to 8-10 cm in diameter, 30-40 cm tall. Tubercles Prominent, globular conical clothed in white wool with few or no spines.
Bibliography: Major references and further lectures
1) Nathaniel Lord Britton, Joseph Nelson Rose “Cactaceae: Descriptions and Illustrations of Plants of the Cactus Family” vol. 4 The Carnegie Institution of Washington, Washington 1923
Cultivation and Propagation: In good conditions with careful application of water and excellent ventilation Mammillaria kewensis grows without difficulty.
Growing rate: It is a slow growing species that rewards the patient grower with a beautiful displays of flowers since from an early age.
Soil: Requires good drainage provided by a very permeable open cactus soil (With not less than 50% grit content). Reduce the use of peat or other humus sources in the potting mixture.
Repotting: Repot every 2-3 years. Use small sized pots.
Feeding: During the beautiful season enrich the soil using a fertilizer rich in potassium and phosphorous, but poor in nitrogen, because this chemical element doesn’t help the development of succulent plants, making them too soft and full of water.
Watering: Water should be carefully applied and only when the soil is dry to the touch. Allow soil to drain thoroughly before watering again. Additionally, water should not be applied from above, as the feathery spines will retain water and add to rotting problems, but in good conditions with excellent ventilation, in bright light, it usually grows without particular difficulty. Do not water in the winter.
Light: Outside full sun or afternoon shade, inside it needs bright light, and some direct sun. Direct sun encourages flowering and heavy spine production.
Hardiness: Protect from frost. But it's hardy to -5°C if kept dry. A winter rest that allows the plant to shrivel (perhaps losing up to 25% of its summer height) will encourage flowering and long time survival.
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 misting the vulnerable plants every day
- Mealy bugs: occasionally they 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: it 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.
Propagation: Direct sow after last frost. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants!
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