"Cactus" ID?


Jan 29, 2013
I bought this plant almost 8 years ago at Walmrt. Its the only plant I've ever managed to not kill and it went three years without water at one point, any idea what it is and how large it could get?
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May 9, 2011
Looks more like some sort of euphorbia imo
Have to agree.. look like a euphorbia. There are so many, it may be difficult to narrow it down further. \

Be careful not to to over water now (if you're giving it TLC)--the base being yellow sometimes is how rot looks when it starts. Also a dehydrated plant but, the top looks good. Also, water from the bottom (ie soak in tub, not pour it--this can help prevent rot and ensure 100% of the roots get water... doing this in the morning (so it doesn't get cold/rot) 1x a month would be good.. not that you wanted any care tips, just couldnt help myself :)

Stan Schultz

Old Timer
Jul 16, 2004
I bought this plant almost 8 years ago at Walmrt. Its the only plant I've ever managed to not kill and it went three years without water at one point, any idea what it is and how large it could get? ...
Most species relatively small, less than 6" or 8" tall.

No, it is definitely not a Euphorbia (family Euphorbiaceae). It's a true cactus (family Cactaceae) and probably belongs to the genus Mammillaria or a closely allied genus. Members of this genus are very common in the American southwest, throughout Mexico, and into Central and South America. Also, very popular house plants.

To get them to flower, you need to give them ample but not searingly hot light almost all year long. During the warm, growing season you water them a lot, but never allow them to sit in water. I grew mine in sandy soil in flower pots setting directly on a concrete sidewalk in open shade so the excess water flowed away almost instantly. They got good morning and very late afternoon sunlight, but were shaded during the middle (hottest part) of the day.

In the fall, remove them to a place where they receive very bright light, but where the temperature drops quite low. They need temperatures near freezing. Stop watering them except once a month.

In the spring as soon as they show signs of beginning to grow again, or as soon as all danger of a killing frost is past (whichever comes first), set them outside or on a brightly lit window sill and begin watering them as per above. You can give them a light fertilizing with a balanced fertilizer once or twice during the beginning of their growing season, but no more and no later.

Here are a couple of photos I took of closely related species I found just north of the Big Bend National Park in west Texas last year. (Click or right-click the thumbnails to see larger images.)

As you found out, very hardy plants. Can live for decades, even outlive you!


Oct 6, 2011
Agreed, suspect Mammillaria as well- see how it looks somewhat like "nipples" with spines coming out? Cacti are notoriously difficult to key out without reproductive material. Definitely 100% not Euphorbia. Two characters telling you that, one screaming it from this image- Euphorbia have paired spines that are formed directly from the cuticle of the plant, not whorls of spines that are coming out of the node on the plant (remember in Cactaceae these "spines" are modified leaves and as such come out of nodes just like real leaves on the average plant- Euphorbia actually have leaves, albeit often very reduced and only on the newest growth... an exception to that rule in Cactaceae are Pereskia species that actually do have leaves as well, but they are primitive and it is not the norm at all). Also, something you can't see on this photo, Euphorbia will have milky sap when cut/injured. This plant will definitely not.

To add to what Stan said about distribution, your true cactus genera harken from the NW whereas all your other odd succulents with spines are OW. The only exception I know of are weedy Rhipsalis species which have recently spread as invasive exotics. Otherwise, cactus are (natively) NW.


Mar 23, 2013
You're right. Thank you for the clarification. My expertise with cacti doesn't go far beyond a few species. Thank you.