How the Old Man Cactus Got Its Fuzz


Old man cactus (Cephalocereus senilis). Photo: Manzel Pumpkin,

One popular cactus that rarely receives much more than a passing mention is the old man cactus (Cephalocereus senilis). It’s usually sold without a label, mixed in with other cacti and succulents, but still, it’s quite easily identified: a columnar cactus completely covered with long white hairs. Obviously, this fuzzy white covering suggested the unkempt white hair of an old man: even the botanical name says so. Cephalo means head (cereus refers to candle, a reference to its columnar shape) and senilis means old. 

The woolly covering of this cactus almost seems to invite you to give it a bit of a hug, but that would be a mistake. Under the fuzz there are sharp outward pointing spines. Ouch! 

Since most other cactus have stems that are pretty much hairless, you might wonder why this one has a full head of hair. And there is a good reason.

The hairy covering protects against extreme sun and cold. Photo:

Where it grows in the wild, in the mountains of Mexico, thus at high altitudes, the old man cactus is subject to extremely intense sun and heat during the day, yet temperatures down to just below freezing during winter nights. The hair helps protect it from both. During the day, it keeps dangerous ultra-violet rays from burning the fragile young cells while the fuzz traps a layer of air between the spines and stem, keeping heat at bay. During the winter, the same air layer traps heat during the day and thus provides insulation from cold winter winds.

On mature specimens, the lower hairs eventually fall off, leaving only the top part covered in fuzz. This type of hairy upper growth is called a cephalium. 

Growing Your Own

I first grew an old man cactus when I was just a boy… and soon lost it to rot. I’d put it in a terrarium where it’s hard to give more than medium light, yet this desert plant prefers full, blazing sun. I had more luck when I grew a second specimen on its own in front of a sunny window. I kept it for about 7 years, until I moved away to study, and when I got back, it was gone. My guess is that, top-heavy as it was, it had toppled over and broken its pot, and no one in my family would have wanted to try repotting such a spiny plant.. At any rate, it had by then become big and unwieldy, not something I’d want to take to university with me.

Rule one with this plant is to give it full sun or as close to full sun as you can. It simply won’t accept anything less. As for watering, keep it on the dry side. Water it abundantly, completely soaking the potting mix, then wait until the soil is essentially bone dry before watering again. If you have spot that is cool to cold but above freezing in the winter (which it will appreciate), it may need no watering at all from late fall through spring. Under warmer conditions, do water it a few times during the winter.

Old man cactus outdoors in a mild climate. Photo: World of Succulents

Theoretically, it can take a light freeze… but yours will do much better if you keep it above 50˚F (10˚C) indoors. (Outdoors, it will adapt to arid climates in USDA hardiness zone 9 and above.)

You’ll need to repot every few years or so, using bigger and bigger and heavier and heavier pots to keep this top-heavy plant upright. A cactus potting mix, which theoretically drains better than regular potting mix, would seem ideal, but, quite honestly, it does fine in most houseplant mixes. 

Either don’t fertilize it or do so only very lightly, maybe once or twice a year from spring through summer at one quarter the recommended rate.

If the hairs become dingy, apparently you can clean them by dipping an old toothbrush in soapy water and combing through them. I’ve never found that to be necessary on my plants.

Flowers (when they appear!) grow from the cephalium at the top of the plant. Photo:

Don’t expect flowers from this cactus. It can take decades to bloom, even in the wild. I’ve never seen the pinkish white flowers, not even in public greenhouses.

Your cute little old man cactus will eventually become a monster (in the wild, it can reach up to 50 feet/15 m tall with a stem up to 18 inches/45 cm in diameter, although that can take a century!). It never branches and most plants remain solitary, but some specimens may eventually form offsets at the base. However, that too is decades away.

When it becomes too big (and again, that won’t be for many, many years, as it’s a very slow-growing plant), cut it back to near ground level, which will force it to produce offsets you can then root and pot up individually. You could also root the top (leave the cut end exposed to the air for several weeks until it has fully healed over). 

Other Fuzzy Cactus

Silver torch cactus (Cleistocactus strausii). Photo: World of Succulents

There are other cactus covered in white hair, most growing under the same extreme mountain conditions as the old man cactus.

The Peruvian old man cactus (Espostoa lanata) is quite similar in its youth, but with golden spines that clearly peek out from the white hair. Grow it much like the regular old man cactus.

The silver torch cactus (Cleistocactus straussii) is a sort of smaller version, with narrower, clustering stems and white hair that is not as long or dense. Faster growing, it will bloom fairly readily indoors, with curious tube-shaped red flowers, but only after 15 years or more.

And you’ll find many other “old man” type cactus offered through specialist growers.

The old man cactus: slow but steady, practically thriving on neglect, it might be just the plant you need to complete your cactus and succulent collection.

50 Houseplants That Don’t Mind Dry Air


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Most houseplants just don’t do well in desert-dry air! Source:

Dry air is a major problem for houseplants in the winter… and indeed, any indoor plant (seedlings, cuttings, etc.). When the atmospheric humidity is less than 40%, certainly common enough in many homes, plants try hard to compensate by transpiring more heavily, that is, by releasing water to the air through their stomata (breathing pores). The drier the air, the more they transpire, and that can lead to their tissues losing water more rapidly than their roots can replace it. This can result in all sorts of symptoms of stress: wilting, flower buds turning brown, leaves curling under, brown leaf tips, even the death of the plant.

And if that weren’t enough, leaves stressed by dry air are also more subject to pest damage (red spider mites, whiteflies, thrips, etc.)

Some Plants Can Cope


Plants with thick, waxy leaves cope better with dry air than those with thin ones. Source:

That said, many plants, especially those native to arid climates or ones where they are exposed to long periods of drought, have developed ways of compensating for dry air. Cacti and succulents are usually very resistant to dry air and so are some epiphytic plants, like hoyas.

Some plants resist dry air by producing leaves with fewer stomata than normal, thus reducing water loss. Many have abandoned leaves altogether and breathe through their green stems (many cacti, for example). Others keep their stomata closed during the day, when the sun is hottest and water loss is greatest, breathing only a night. (This is called Crassulacean acid metabolism or CAM.) In other words, they essentially hold their breath 12 hours a day! Also, plants resistant to dry air often have extra-thick leaves or leaves coated with wax, powder or hair, all of which reduce evaporation.

Plants That Don’t Mind Dry Air

What follows are a few houseplants that don’t really mind it if the air in your home is on the dry side. Not that they will suffer if you increase the humidity to levels more acceptable to plants in general (most plants prefer a relative humidity of 50% or above) and that indeed is good for your health too, but if improving the atmospheric humidity something you just can’t do, at least these plants will pull through without a complaint!

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Aeonium arboreum ‘Atropurpureum’: one example of a plant that tolerates dry air. Source, Bernard Dupont, Wikimedia Commons

  1. Aeonium spp. (tree houseleek)
  2. Agave spp. (century plant)
  3. Aglaonema spp. (Chinese evergreen)
  4. Aloe spp. (aloe)
  5. Ananas comosus (pineapple plant)
  6. Aspidistra elatior (cast iron plant)
  7. Beaucarnea recurvata (ponytail palm)
  8. Cephalocereus senilis (old man cactus)
  9. Cereus peruvianus (Peruvian apple cactus)
  10. Ceropegia woodii (rosary vine)
  11. Clivia miniata (clivia)
  12. Crassula ovata (jade plant)
  13. Crassula spp. (crassula)
  14. Cryptanthus spp. (earth star)

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    The thick leaves of the dieffenbachia can generally cope quite well with drier air, but you can see just a bit of damage at the tip of this one. Source: Forest & Kim Starr, Wikimedia Commons

  15. Dieffenbachia spp. (dumbcane)
  16. Echeveria spp. (echeveria)
  17. Echinocactus grusonii (golden ball cactus)
  18. Epipremnum aureum (pothos, devil’s ivy)
  19. × Epicactus (orchid cactus)
  20. Euphorbia lactea (candelabra spurge)
  21. Euphorbia milii (crown of thorns)
  22. Euphorbia tirucalli (pencil cactus)
  23. Ficus elastica (rubber tree)
  24. Ficus lyrata (fiddle leaf fig)
  25. Gasteria spp. (ox tongue)
  26. Gymnocalycium mihanovichii friedrichii ‘Hibotan’ (red ball cactus)
  27. Haworthia spp. (zebra plant)
  28. Hippeastrum cvs (amaryllis)
  29. Hoya carnosa (wax plant)
  30. Kalanchoe (kalanchoe, panda plant)
  31. Ledebouria socialis (silver squill)

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    Few plants tolerate dry air as well as living stones (Lithops). Source: Dysmorodrepanis, Wikimedia Commons

  32. Lithops spp. (living stone)
  33. Mammillaria spp. (pincushion cactus)
  34. Opuntia spp. (bunny ears)
  35. Pachypodium lamerei (Madagascar palm)
  36. Pelargonium graveolens (rose-scented geranium)
  37. Pelargonium × hortorum (zonal pelargonium, zonal geranium)
  38. Peperomia obtusifolia, P. clusiifolia (baby rubber plant)
  39. Philodendron hederaceum oxycardium (heartleaf philodendron)
  40. Rhipsalis spp. (mistletoe cactus)
  41. Sansevieria trifasciata (snake plant)
  42. Schlumbergera (Christmas cactus)
  43. Sedum spp. (sedum, donkey’s tail)

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    The nearly round leaves of Senecio rowleyanus are designed to reduce evapotranspiration. Source: Forest & Kim Starr, flickr

  44. Senecio rowleyanus (string-of-pearls)
  45. Senecio serpens (blue chalksticks)
  46. Stapelia spp. (carrion flower)
  47. Streltizia reginae (bird of paradise)
  48. Syngonium spp. (arrowhead vine)
  49. Yucca elephantipes (spineless yucca)
  50. Zamioculcas zamiifolia (zeezee plant)20171227A