Mammillaria karwinskiana (subsp. nejapensis) (Syn. Mammillaria nejapensis)-Silver Arrows

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) after I brought it home on 9-21-18, #510-7.

Silver Arrows, Royal Cross

Mammillaria karwinskiana

mam-mil-AR-ee-uh  kar-winz-kee-AH-na

Syn.

Mammillaria karwinskiana subsp. najapensis

Syn.

Mammillaria nejapensis (var. longispina)

Synonyms of Mammillaria karwinskiana (45) (Updated on 12-11-20): Cactus fischeri (Pfeiff.) Kuntze, Cactus geminatus (Scheidw.) Kuntze, Cactus karwinskianus (Mart.) Kuntze, Cactus pyrrhocephalus (Scheidw.) Kuntze, Cactus subpolyedrus Kuntze, Cactus virens (Scheidw.) Kuntze, Mammillaria beiselii Diers, Mammillaria closiana Roum., Mammillaria confusa (Britton & Rose) Orcutt, Mammillaria confusa var. centrispina R.T.Craig, Mammillaria confusa var. conzattii (Britton & Rose) R.T.Craig, Mammillaria confusa var. robustispina R.T.Craig, Mammillaria conzattii (Britton & Rose) Orcutt, Mammillaria fischeri Pfeiff., Mammillaria geminata Scheidw., Mammillaria jalappensis Pfeiff., Mammillaria jozef-bergeri Wojn. & Prajer, Mammillaria karwinskiana subsp. beiselii (Diers) D.R.Hunt, Mammillaria karwinskiana var. flavescens Zucc. ex Pfeiff., Mammillaria karwinskiana subsp. nejapensis (R.T.Craig & E.Y.Dawson) D.R.HuntMammillaria karwinskiana var. virens (Scheidw.) Salm-Dyck, Mammillaria karwinskii Lawr., Mammillaria malletiana Cels, Mammillaria malletiana var. pyrrhocephala (Scheidw.) Schelle, Mammillaria multiseta C.Ehrenb., Mammillaria nagliana Repp., Mammillaria nejapensis R.T.Craig & E.Y.Dawson, Mammillaria nejapensis var. brevispina R.T.Craig & E.Y.Dawson, Mammillaria nejapensis var. longispina R.T.Craig & E.Y.DawsonMammillaria neomystax Backeb., Mammillaria parmentieri Link & Otto, Mammillaria polygona Zucc. ex Pfeiff., Mammillaria pyrrhocephala Scheidw., Mammillaria pyrrhocephala var. confusa (Britton & Rose) Borg, Mammillaria pyrrhocephala var. donkelaerii Salm-Dyck, Mammillaria pyrrhocephala var. malletiana (Cels) Borg, Mammillaria strobilina Tiegel, Mammillaria subpolyedra Salm-Dyck, Mammillaria tropica Repp., Mammillaria virens Scheidw., Neomammillaria confusa Britton & Rose, Neomammillaria conzattii Britton & Rose, Neomammillaria karwinskiana (Mart.) Britton & Rose, Neomammillaria pyrrhocephala (Scheidw.) Britton & Rose, Neomammillaria subpolyedra (Salm-Dyck) Britton & Rose

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.

Plants of the World Online by Kew lists 164 species of Mammillaria (as of 12-11-20 when I am updating this page). It is in the plant family Cactaceae with 144 genera. Those numbers could change as updates are made.

Mammillaria karwinskiana is a variable species and there were several recognized varieties. Even though they are not currently recognized, the variations still exist in this species so that needs to be considered when trying to identify unlabeled plants. This particular plant in my collection was likely Mammillaria nejapensis var. longispina (1948) which was also a synonym of Mammillaria karwinskiana subsp. nejapensis (1997). Well, heck, there are 60 synonyms so it was given a multitude of names. It would be hard to tell at this point which ones were for this plant or the other variations. Personally, I think the variations should still be accepted names instead of them being considered just synonyms of the species. The variations exist and should be recognized.

THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 9-21-18, #510-8.

I brought this plant home from Lowe’s on September 21, 2018. The label said it was a Mammillaria nejapensis but upon research, I found that name is a synonym of Mammillaria karwinskiana. The label further 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 measured approximately 1 7/8” tall x 2 3/16” wide without the spines and was growing in a 4 oz. (2 1/2″ diameter pot.

Mammillaria karwinskiana (subsp. nejapensis) is native of a wide area around Oaxaca City in Mexico where it is found in tropical deciduous forests and shrubby dry areas. It initially grows as a solitary specimen and slowly divides dichotomously or branches out basally. I believe the species or some of the subspecies (GEEZ!) is found as far down as Guatemala. 

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) from the top on 9-21-18, #510-9.

Mammillaria karwinskiana is one of only a few Mammillaria species commonly referred to as “Owl Eye Cactus” known for their dichotomous branching. 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.

It is a globular shaped or cylindrical cactus that can be from blue-green to dark green in color that can grow to around 8” tall. One feature is all the long wool… My plant only had small threads when I first brought it home in 2018, but within a year it wasn’t recognizable as the same plant… 

Mammillaria karwinskiana is a very variable species, especially for the length of the spines. My particular plant, as I mentioned, is likely Mammillaria karwinskiana subsp. nejapensis, so this description is for that subspecies, even though it is currently listed as a synonym of the species.

As with basically all Mammillaria, its prominent tubercles are arranged in a spiral pattern. This (sub) species has 3-5 straight to slightly curved radial spines, kind of off-white color, some with brown tips. The upper spines on the areoles are shorter, the two on the sides being somewhat longer, and the lower one is much longer. As the plant has grown, the spines growing from the apex (top) of the plant are much longer, almost 1”. As the plant grows, those longer lower spines point downward. They are very thin and sharp! OH, when the plant was smaller, the areoles had small tufts of wool. As the plant grew larger and woolier, only the upper areoles have wool. 

The axils between the tubercles had small amounts of threads when the plant was smaller, but now it is downright wooly around the top of the plant. The wool looks like it spirals down the axils on the side of the plant about halfway down. The lower 1/3 appears to have none.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 10-10-18, #519-47.

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.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows)on 11-29-18, #534-19.

November 29 was a nice spring-like day, so I took the cactus to the back porch for a photoshoot. I was working on a post to show the difference between the cactus in my collection.

Mammillaria karwiskiana (subsp. nejapensis) (Silver Arrows) close-up on 12-1-18, #535-15.

In the above photo, you can see the areoles have small tufts of wool, five radial spines, and no central spines. The axils (the area between the tubercles) look like they are growing hair… In time, this hair gets longer and thicker making the plant look very wooly.

<<<<2019>>>>

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 6-22-19, #593-29.

The potted plants are enjoying being outside for the summer. Most of the cactus are on the back deck in full sun.

I was fairly busy during the summer so I wasn’t able to take a lot of photos. The cactus all did very well despite a little neglect.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) at 3 1/4″ tall x 2 3/4″ wide on 10-11-19, #639-61.

I had to move the potted plants inside for the winter on October 11 because an “F” was in the forecast. I always take photos of the plants when I bring them inside and measure the cactus and some of the succulents. The Mammillaria karwinskiana measured 3 1/4″ tall x 2 3/4″ wide. It was only 1 7/8″ tall when brought it home on 9-21-18 so it has grown a lot. The hair on this plant has become wool!

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) from the top on 10-11-19, #639-63.

The Mammillaria karwinskiana is fairly wooly, but not as much as the Mammillaria hahniana. I could not remember if there were buds when I brought the cactus inside or not. Kind of hard to tell what is under the wool. The top of cactus always looks neat. For sure, the wool on this cactus has gotten A LOT thicker. Maybe it is growing more for the winter. 🙂

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 11-11-19, #648-4.

The flowers were beginning to open when I took this photo on November 11. It is always interesting how the buds form and open facing the inside of the house first instead of the sunny side.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 11-11-19, #648-5.

I am really glad the flowers aren’t pink like several other Mammillaria in my collection. Information on Llifle says the flowers of this species are creamy-white to yellow with maroon midveins.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) flowers on 11-18-19, #653-1.

NICE!

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) flowers on 11-18-19, #653-2.

Well, that is just darn AWESOME!!!

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 11-18-19, #653-3.

There are more buds almost all the way around the plant.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 11-23-19, #655-4.

I took this photo when the flowers were fully open and some of the earlier ones are beginning to get a little droopy.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) on 11-14-19, #660-1.

There were eleven buds and flowers when I took the above photo on November 14. These buds are on the backside of the plant.

<<<<2020>>>>

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) at 3 5/8 tall x 3″ wide on 10-15-20, #747-69.

I had to move the plants inside for the winter on October 15 because an “F was in the forecast”. as always, I took photographs and measurements as I brought the cactus inside. The Mammillaria karwinskiana measured 3 5/8″ tall x 3″ wide.

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) with lots of wool for the winter on 7-15-20, #747-70.

The wool on the Mammillaria karwinskiana (subsp. nejapensis) looks like little tufts. Pretty neat, huh?

Mammillaria karwinskiana (subsp. nejapensis) (Silver Arrows) with flowers on 11-1-20, #754-2.

The Mammillaria karwinskiana started flowering shortly after I brought inside.

USEFUL INFORMATION:
Family: Cactaceae
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 perlite and grit or pumice.
***Water: Average during the summer and very seldom during the winter. Allow to dry out between watering

*During the summer, I keep most of my cactus on the back deck where they receive full sun. During the winter most cactus aren’t picky about the light because they are basically dormant. For several winters, mine were in front of the east-facing sliding door in the dining room so they didn’t get much light but they did great. I built a new shelf for the bedroom so now they are in front of a west-facing window. Most of the succulents are on a shelf in a south-facing window in a cool bedroom but a few are in my bedroom.

**When it comes to potting soil, finding the “sweet spot” is not exactly that easy when materials are limited. Cactus and succulent enthusiasts (and experts) do not recommend using peat-based commercial mixes but what choice is there for most of us. They say to use a loam-based mix… Hmmm… Our soil is loam, so do I just use dirt? Well, no because “dirt” is heavy and you need a “light” material. There is A LOT of cactus and succulent recipes online and some get pretty elaborate. Many say to use sand as an ingredient, but if you do that, it needs to be very coarse, like builders sand, because “ordinary” sand, like for sandboxes, is too fine and it clogs up the air space between the coarser ingredients. For MANY years I used 2 parts Miracle Grow or Schultz Potting amended with an additional 1 part of perlite and 1 part chicken grit. Schultz doesn’t seem to have as many large pieces of bark. Cactus and succulent enthusiasts recommended using pumice instead of perlite and grit so I checked it out… The “guy” at General Pumice (online) recommended using a 50/50 mix of potting soil and pumice. General Pumice has 3 different sizes to choose from depending on the size of the pot. SO, in 2018 I bought a bag of 1/8″ and mixed it 50/50 with Miracle Grow Potting Soil. I liked it pretty well. Then in 2020, since most of the cactus were in larger pots, I ordered the 1/4″ size. Pumice has a lot of benefits over perlite and has nutrients that are added to the soil when watering. Pumice is also heavier so it stays mixed in the soil instead of “floating” to the top. Still, there is the issue of the mix getting very hard once you stop watering the plants during the winter when you stop watering. I think this is because of the peat in the potting soil… SO, instead of re-potting the cactus and succulents in the spring, I started doing it during the fall and winter so their soil would be loose. Since you don’t water as frequently during the winter if at all, the timed-release fertilizer does not activate. I have not tried coir, but I am looking into it… 

I think a lot of growing tips online are written by people who never grew succulents and cactus. They just copy from one website and paste it to theirs. You have to sort of mimic the soil where species grow in their native habitat. For that, you almost have to go see for yourself… Typically, they grow in fairly rocky soil

***I water my cactus and succulents on a regular basis during the summer but barely ever in the winter (maybe a little in January) until close to time to take them back outside. 

You can read my Cactus Talk & Update and Cactus & Succulent Tips to get my opinion about growing cactus and succulents.

When you bring your new plants home from the store, you need to check their roots and the soil to see if they are wet. If so, you may want to repot it right away. It is advisable to repot them in a better potting soil more suitable for cactus and succulents.

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.

FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
WIKIPEDIA (GENUS)
LLIFLE (ENCYCLOPEDIA OF LIVING FORMS)
DAVE’S GARDEN
CACTUSGUIDE
MAMMILLARIAS.NET
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2 comments on “Mammillaria karwinskiana (subsp. nejapensis) (Syn. Mammillaria nejapensis)-Silver Arrows

  1. Hannah says:

    So happy I was finally able find out what type of cactus I had, and that it was normal for it to “split” into 2! Mine is five years old and has two heads, it almost looks like a heart.

    Liked by 1 person

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