The label says this plant is a Mammillaria nejapensis but, according to Plants of the World Online by Kew, Mammillaria nejapensis is a synonym of Mammillaria karwinskiana.
Mammillaria karwinskiana Mart. is now the correct and accepted name for this species. It was named and described by Carl (Karl) Friedrich Philipp von Martius in Nova Acta Physico-Medica… in 1832.
The synonym, Mammillaria nejapensis R.T.Craig & E.Y.Dawson, was named and described by Robert T. Craig and Elmer Yale Dawson in Allan Hancock Foundation: Occasional Papers in 1848.
I bought this plant from Lowe’s on clearance on September 21, 2018. The label says:
“Native to Oaxaca, Mexico, forms globular stems with silvery white spines, dense wool at the areoles. Becomes slightly columnar, branching to form large clusters. Flowers are pale yellow with reddish midstripe. Water thoroughly when soil is dry.”
The plant is growing in a 4 oz. (2 1/2” diameter x 2 1/4” tall) pot. The plant measures approximately 1 7/8” tall x 2 3/16” wide without the spines.
Origin: Central and Southwest Mexico and Guatemala
Zones: USDA Zones 9b-11 (25-40° F)
Size: Hmmm… Maybe up to 8” or so tall.
Light: Sun to light shade. If grown inside over the winter, you should gradually increase the amount of light gradually when you put them outside.
Soil: Very well-draining soil. Potting soil amended with grit and price or perlite.
Water: Average during the summer and very seldom during the winter. Allow to dry out between watering
Mammillaria karwinskiana is one of only a few Mammillaria species commonly referred to as “Owl Eye Cactus” known for their dichotomous branching. I think this means the plant (stem) divides into two parts. Then the two become 4 and so on… I haven’t experienced this yet, be but could get interesting.
I moved the potted plants inside for the winter on October 10 because the weather forecast said we would be having an “F” in a few days and the evening temperatures were going to be dropping. I always measure the cactus and some of the succulents when I move them inside to see how much they have grown in the past year. I didn’t measure this plant then because I only had it for a short time and it hadn’t grown.
November 29 was a nice spring-like day, so I took the cactus to the back porch for a photo shoot. I was working on a post to show the difference between the cactus in my collection.
Mammillaria karwinskiana differs from the four subspecies (which aren’t accepted names at the moment) because it lacks a central spine. Even though the photo looks like there are five radial spines there are actually six (I counted to make sure). The description of this plant on Llifle taught me a lot of new words… I looked up the words on the CactiGuide Glossary of Cacti Terms then looked at the plant to figure out what it was talking about. 🙂 Then I realized I have been spelling the website name wrong for FIVE years.
Anyway… It says, “The Axil is very woolly, with tufts of white hair and long white bristles.” This is talking about the top of the plant. I think the “bristles”, which are stiffened hair (according to CactiGuide), become the radial spines. Not sure, though, because I didn’t notice any long white bristles on this plant. Maybe with age… It also says the tubercles are, “Firm, pyramidal, arranged spirally with 13-21 parastichys.” Hmmm… According to the glossary of terms, a parastichy is a secondary spiral in phyllotaxis. GEEZ! What is a phyllotaxis? It says, “Phyllotaxis is a mode of arrangement of leaves in relation to axis.” WHAT? LEAVES?!?! WHAT LEAVES? The tufts of hair between the tubercles are interesting, though, as is the wool on the tips of the nipples. WHOOPS! I mean tubercles…
I will continue adding more photos and information as time goes by. This one will be interesting to watch and see how long it takes the stem to split. 🙂
I hope you enjoyed this page and maybe found it useful. If you have any comments, questions or suggestions, I would like to hear from you. Please click on “like” if you visited this page. It helps us bloggers stay motivated. 🙂 You can check out the links below for further reading. The links take you directly to the genus and species of this plant.