Mammillaria spinosissima ‘Un Pico’ (Bald-Headed Irishman)

Mammillaria spinosissima ‘Un Pico’ after I bought it home at 1 1/2″ tall x 1 5/8″ wide on 4-3-21, #899-8.

Mammillaria spinosissima ‘Un Pico’

Red Headed Irishman, Spiny Pincushion Cactus

Mammillaria spinosissima

mam-mil-AR-ee-uh  spin-oh-SIS-ee-muh

Plants of the World Online by Kew lists 108 synonyms of Mammillaria spinosissima which you can see HERE. I didn’t want to add the whole list on this page…

Mammillaria spinosissima Lem. is the accepted scientific name for this species of Mammillaria. It was named and described as such by Antione Charles Lemaire in Cactearum Aliquot Novarum in 1838.

There were several infraspecific taxa for Mammillaria spinosissima but now they are listed as synonyms of the species… 

The genus, Mammillaria Haw., was named and described as such by Adrian Hardy Haworth in Synopsis Plantarum Succulentarum in 1812.

As of 12-10-22 when this page was last updated, Plants of the World Online lists 139 species in the Mammillaria genus. It is a member of the plant family Cactaceae with 150 genera. Those numbers could change as updates are made on POWO.


Mammillaria spinosissima ‘Un Pico’ on 4-3-21, #788-9.

I brought this cactus home from Wagler’s Greenhouse (one of three Amish-owned local greenhouses) on 4-3-21 labeled Mammillaria spinosissima ‘Un Pico’. Actually, I saw about 40 or so of these plants on Thursday but  I wasn’t sure if I possibly already had one. I knew I didn’t have one by that name, but you know how plant names change, and I have several that looked similar. I wrote down the name to double-check to make sure it wasn’t a synonym of a species I already had. When I found out I didn’t have this one, I went back on April 2 and found out that they had been moved. When I did find them, they were in a different location and there were only a few left. Unfortunately, it was Good Friday so they were closed. One of Mrs. Wagler’s granddaughters hid one I selected and I picked it up the next day.

The species Mammillaria spinosissima is a highly variable and VERY spiny species of cactus. The cultivar ‘Un Pico’, however, is a selection of a stable genetic mutation that only produces one long central spine and some may have none. The particular plant I brought home, however, has a few areoles with more than one spine. Time will tell if it is actually a Mammillaria spinosissima ‘Un Pico’ because it has some growing to do… Common names for the species include Bald-Headed Irishman and Spiny Pincushion Cactus. “Un Pico’ should be called the Bald-Headed Irishman (even though the species is a native of Mexico).

When I brought this plant home, it measured 1 1/2” tall x 1 5/8” wide. It was in a 4 1/4” diameter x 3 1/3” tall pot. I re-potted it and put it in a mixture more suitable for cactus and check its roots for a plug wrapper. I don’t like my plant’s roots having to try and grow through the wrapper…

Mammillaria spinosissima ‘Un Pico’ (Bald-Headed Irishman) at 3″ tall x 1 7/8″ wide on 8-18-21, #827-22.

I measured the plants on the front porch on 8-18-21 instead of waiting to do them all as I bring them inside for the winter in October. I didn’t have them inside until October 28 in 2021 because there wasn’t an “F” in the forecast until then. The Mammillaria spinosissima ‘Un Pico’ did very well over the summer and grew to 3″ tall x 1 7/8″ wide. It doubled in height in only three months.


Even though this plant did very well, it didn’t make it through the summer in 2022…

Family: Cactaceae
Origin: The species is native to Guerrero and Morelos in Mexico.
Zones: USDA Zones 10a-11(30 to 40° F/-1.1 to 40° C)
Size: Slowly to about 10-12” x 4” diameter.
Light: Sun to part shade.
Soil: Fast-draining. Good quality potting soil amended with pumice (50/50) or additional perlite and chicken grit (2-1-1).
Water: Average during the summer, barely if at all during the winter.

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 re-pot it right away. It is advisable to re-pot them in a better potting soil more suitable for cactus and succulents.

There isn’t much online about the species or ‘Un Pico’ except for online stores. I will continue adding more photos and information as time goes by. 

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. If you see I have made an error, please let me know in a comment or email me at




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