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Like lots of others out there, I was wondering what the differences were between Old Man Cactus and Old Lady Cactus. I can imagine that the “old” part of the name refers to the white hairy spines they both have, as old people tend to have white wispy hair also – but other than that, how can you tell them apart?
Both the Old Man and Old Lady Cacti are common varieties of cacti that people like to grow in their homes. They both have white hairy spines, but the Old Lady cactus’ stem is round and grows to 10”, while the Old Man cactus’ stem is cylindrical and can grow up to 3’ in pots or 20-40’ in the wild.
If you’re as curious about the differences between these two cacti as I was, then I have a few more differences (as well as some similarities) that I learned about these peculiar-looking cacti.
Differences Between Old Man and Old Lady Cactus
The Old Man cactus, Cephalocereus senilis, and the Old Lady cactus, Mammillaria hahniana, are both native to Mexico and are drought tolerant plants. They are both covered in a soft-looking wooly covering, giving them a similar appearance (at least when they are small), but what are the differences between them?
Their Spines are Similar, but With Some Differences
As Mentioned before, they both have white, hairy spines that give them a soft appearance. It appears to me that the hairs on the old man cactus have a more “wispy” appearance– or a slightly more unkempt look than what you would generally see on the old lady cactus.
The tufts of hair on the old lady cactus appear to have a more symmetric look than those of the old man cactus, but there are some exceptions, so looking at the hairy spines isn’t the best way to tell them apart.
Fun Note: The hairs on both of these serve the purpose of protecting them from sun, heat, and cold of their harsh, native environment.
Differences in Their General Shape
The biggest differences I can easily see between these two plants is in their shape.
The old man cactus is cylindrical in shape, even as a young plant but as it ages, it can grow to be much taller than a man.
The old lady cactus has a rounded, spherical shape and tends to keep a more rounded shape even as it grows larger. It does become more elongated as it ages, but still keeps an overall rounded appearance.
Their Growth is Very Different
The old man cactus is very slow growing. It can take as much as 10-20 years before it even starts to bloom. It can grow up to 20 feet in height in the wild. When they are in pots and grown indoors, they grow up to around 3 feet in height.
The old lady cactus also grows slowly, but will not get as large as the old man cactus. It usually grows to be about 4 inches in height but can reach as high as 10 inches in height after many years.
Differences in Their Flowers
The old man cactus puts out tubular shaped flowers. These flowers range in color from a light pink to a reddish-pink or even sometimes, yellow in color. These large flowers form from the sides of the stems and they bloom at night.
Old lady cactus flowers form around the top of the cactus’ stem in a circle, giving it the appearance of a crown. The fuschia-pink colored flowers are funnel shaped and are much smaller than those on the old man cactus.
We have an article here called How to Get an Old Lady Cactus to Bloom and another, here, on How to Get an Old Man Cactus to Flower. Check them out If you’re interested!
Where Can You Buy an Old Man or Old Lady Cactus?
With all that being said, if you are interested in buying one of these plants for your own home, they can be easily found at any local garden center.
You can also check these out on Amazon. This one is an old man cactus that I would recommend, or if you want an old lady cactus, this can be a good choice.
Here’s a table comparing the two types of cacti:
| Old Man Cactus | Old Lady Cactus | |
| Scientific Name | Cephalocereus senilis | Mammillaria hahniana |
| Origin | Mexico | Mexico |
| Lifespan | Up to 200 years | 10 to 200 years |
| Height | 20-40’ | Usually 3.5- 4” but up to 10” |
| Diameter | Up to 1 foot” | Usually 4” but Up to 8” Likes to grow in clusters |
| Growth Rate | slow | slow |
| Sunlight | Full sun | Full to partial sun |
| Watering | Drought-tolerant, needs occasional watering | Drought-tolerant, needs occasional watering |
| Flowers | Large, reddish-pink, tubular shaped flowers | Small fuschia-pink, funnel shaped flowers |
| Spines | White hair-like spines | White hair-like spines |
Note: The information in this table is general and may vary somewhat depending on the specific growing conditions of the plants.
Do Old Man and Old Lady Cactus Plants Have Sharp Spines?
The wooly, hair-like covering that covers the stems of old man and old lady cactus plants gives them such a soft appearance that we might even wonder if they have any sharp spines at all.
Both old man and old lady cactus plants look very soft since they are covered with hair-like spines, but underneath their soft-looking exteriors are some very sharp spines. Don’t be deceived by the soft exterior of these cacti; their spines will hurt you if touched.
Conclusion:
After looking into the similarities and the differences of these two types of cacti, it seems that other than their coating of soft hair-like spines, they are very different in how they look and grow.
Even with those differences, they both would be great plants to have and grow. They certainly would add an interesting “touch” to my indoor succulent garden.
Take a look at this Youtube video to get a better idea of how these two cacti look like when side by side:
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