My Favorite Rocks

A Great 2003 to one and all! I really want to start this new year with a big bang. What better way than to begin the year with a feature on my favorite cactus group – the ariocarpus or "Living Rocks." This genus is one of the most highly prized of all cacti today for several reasons. First, their unique appearance. Ariocarpus aren’t your typical-looking cactus plants. For one, none of them have spines. And their shapes and forms are also very different from the rest of the cactus kingdom. Many of the species look literally like rocks and rough gravel with the generally hard, shell-like texture and fissures on their outer skin. In fact, these plants are quite difficult (impossible at times) to find in their natural habitats because these blend so well with their gravelly surroundings. This is the reason for their famous nickname, Living Rocks. Some are almost covered with stones and soil, with only the tips of their tubercles sticking out. The only way to spot them in the wild is if these are flowering, and my, what beautiful flowers they have – from shades of pink to white, yellow and deep magenta.

A second reason for their appeal (and some growers might not find this quite appealing) is the challenge which Living Rocks present in growing them well. These are really not the easiest plants to culture well, particularly in our hot, humid environment. In their native situations, these come from hot, dry climates with cool nights. Many are found in elevations of 500 to 1,000 meters and above. They are also quite slow growers, with some species taking five or more years to grow an inch in diameter. Their slow growth and limited range in their natural habitats, mainly in Mexico with a few outliers in Texas, have contributed to their rarity in collections today. Mature plants like the ones pictured here are, at least for me anyway, really sights to behold and appreciate, and seeing them leads one to marvel at God’s artistic creations. It is precisely this challenge that beckons serious collectors to give these plants a try.

I have always been attracted to these Living Rocks, ever since I got seriously afflicted with the cactus bug as a teenager. I remember the first time I owned my first Living Rock. I was a high school student at Xavier. I remember a group of friends and my family going to Baguio; on the trip down, we made a stop in Dau, Pampanga when there were some nice PX offerings there. I happened to chance upon an old house that had a few odd cacti displayed outside. When I knocked, the caretaker showed me to an amazing array of cactus plants for sale inside, not the types of plants one would see at the old Farmer’s Garden in Cubao, but rarer plants that one only saw in cactus books. I was told that the owner of the collection (I did not actually meet her) obtained her plants from the nearby Clark Airbase, then still the largest US airbase outside the US. It seems she had a contact with one of the airmen, who would bring these exotic plants in for her.

Anyway, to my luck, she was selling a few of her plants. One which immediately caught my eye was a five-inch diameter Ariocarpus retusus with very narrow and numerous tubercles. The price for the plant was the princely sum of P500. At that time more than 20 years ago, P500 was a hell lot of money. But I did not give it a second thought and snapped up the plant. I had the plant for quite a few years before I left for graduate school in the US. I entrusted the care of my small collection to our household help then. When I returned, the A. retusus was gone, a victim of overzealous watering.

Since that first Rock, I’ve had the chance to grow quite a number of all the known species. I’ve grown some quite well even if these are reluctant to flower in our humid environment. But I’ve also killed my share, always a heartbreak for me, but a learning experience nevertheless. Whenever one of these rarities succumbs under my care, I always ask myself what I did wrong, so that I can avoid doing the same in the future. I think I’ve had some success in this respect, as the Rock mortality rate with me has diminished significantly.

Depending on which botanist you talk to, there are generally seven accepted species of ariocarpus, with several varieties and forms. Most of these varieties and forms are not recognized by the strict botanist as these plants have a certain degree of variability in form and structure. But to the collector, these variations are in some cases worth noting and preserving via the recognition of a unique scientific name representing the special variants. The species vary in size from the giants in the group, A. retusus and A. trigonus (the latter regarded by some to be a sub-species of the former) with forms growing up to 10 inches or so in diameter. A. retusus generally has white to cream-white flowers, although some have pinkish white flowers as well. The flowering specimen depicted in the photo happens to be a hybrid of some kind, as the flowers here are a deep pink/magenta. A. retusus has one recognized variant, v. furfuraceus, used to distinguish A. retusus plants with prominent areoles (those little tufts of wool) sticking at the tips of the plant’s tubercles. A. trigonus, which is the only ariocarpus which I have yet to see flowering "in the flesh," has beautiful yellowish flowers. It has forms with wider, thicker, longer and slimmer tubercles.

Ariocarpus fissuratus v. fissuratus and its variant lloydii represent the "middle of the road," with diameters up to seven or eight inches. This species derives its name from its extremely fissured and weathered appearance. It so mimics the surrounding rocks and terrain around it that hikers and trekkers have been known to trample them underfoot! But the plants are quite tough and are perfectly fine even after an experience like this. The variety fissuratus is the only known ariocarpus which is found outside Mexico, in the Big Bend area in Southwestern Texas, USA. The rest are endemic only to Mexico, where these inhabit limestone hillsides and flats in compacted sandy clay soils. The variety lloydii is a bigger-growing form with smoother tubercles. Ariocarpus, if well-cared for, can live for a very long time. The big lloydii pictured here is well over a foot in diameter and is well over a hundred years old. A. fissuratus has beautiful pink/magenta flowers as shown in the flowering specimen.

Then there are the smaller growing species – the smallest being the A. kotschoubeyanus complex, which can attain a size of less than an inch to about four inches in diameter. Along this size spectrum are the different varieties, from v. macdowellii, which is the smallest in size with individual heads just barely reaching an inch in diameter, to v. elephantidens, the "elephant" of the species attaining up to four inches or so. A. kotschoubeyanus has pink to magenta colored flowers, although one variant, v. albiflora, has pinkish white flowers. There is an interesting true story about A. kotschoubeyanus. This plant achieved what is probably the highest price ever paid for a single cactus plant, but this has to be verified with the Guinness Book of World Records. In 1840, the traveler/collector Karwinsky is said to have brought the first three plants of this species to Europe. One of these plants was purchased by Prince Kotschoubey for the kingly sum of 1,000 francs, and another plant sold for $200 in 1840 prices! As a reward for the price he paid, the plant was named after him, hence the strange scientific name "kotschoubeyanus."

Ariocarpus agavoides is a very unique looking plant with its long, green tubercles. Mature plants attain a size of under an inch to four inches in diameter. This plant was discovered in 1941 and was thought to be a monotypic species as the only member of the genus Neogomesia. It was correctly transferred into ariocarpus in 1962. In their native habitats in Tamaulipas, Mexico, it is said that the local children chew this plant as candy. Boy, if one of my kids chewed my agavoides, I’d go ballistic! It’s actually amazing that these rare plants have managed to survive in the wild even with their habitats being converted into agricultural land, or the local kids eating them up! With me, ariocarpus flowers are always a premium, although I think I do manage to grow them well vegetatively. One of my frustrations with A. agavoides is that year in and year out, I always manage to produce flower buds on my plants, but these don’t develop into flowers, and eventually just wither away. Again, my oft-repeated phrase – we just don’t have the balance of hot days and cool nights needed by these plants for flower production. Oh, well, I’d much rather strive for healthy vegetative growth anyway.

Ariocarpus scaphirostris (used to be called scapharostrus) is one of the rarest in the genus, is slow-growing like the rest of the group, and is very difficult to spot in its natural habitats. It attains a size of up to four inches in diameter, although plants of this size are well over 20 to 25 years old. It has beautiful magenta flowers like most in the genus. One of its unique aspects is its boat-shaped tubercles, as pictured in this old four-inch specimen. Occasionally one sees a multi-headed plant of this species. The one pictured used to be grafted. The graft has since been removed and the specimen is now growing on its own roots. It took me well over a year to get these "own" roots to grow and take hold, and I was quite pleased with the result. With this as well as the rest of these Rocks, one has to be extra-patient and not force the plants with excessive watering and fertilizing, formulas for quick disaster with this group.

The newest species to be discovered and de-scribed are A. bravoanus and its sub-species, hintonii. The plants attain a diameter of be-tween two and four inches and produce pinkish magenta flowers. The species is named after the famed Mexican botanist Helia Bravo. The sub-species hintonii was originally classified as a variety of A. fissuratus because of its superficial resemblance to the latter. A. bravoanus is probably the rarest ariocarpus around, with a very restricted habitat locality in Mexico. This plant is only now starting to get introduced into cultivation in the form of seedlings and grafts.

Many books on the subject will tell you that ariocarpus are not for the beginner but for the experienced grower. I tend to have some disagreements with this statement. While true that ariocarpus are not the easiest of plants to culture, these can thrive vegetatively in our hot, humid environment if the grower has taken the effort to read up on them, understand something about their natural habitats, and maybe talk to some growers who have had some experience with these plant gems. In short, someone who is willing to take these plants seriously, beginner or seasoned grower, can have success with these plants. The following cultural regimen for Living Rocks is based on my personal experience and preferences, and has worked for me so far, with a few regrets here and there.

Growing Medium – I use only a mineral-based substrate, i.e., good garden loam, crushed brick, perlite and some course gravel. I don’t use any organic material as this may lead to root decay. In their native habitats, Living Rocks are found growing in limestone (calcium carbonate) and sandy-clay soils, and so experts have recommended adding limestone chippings into the medium. Unfortunately, I haven’t been able to find good quality limestone chippings so far (if anyone knows a source, please let me know via lifestyle@philstar.net.ph). Living Rocks have a thick taproot that stores a lot of water for the plant, hence, these are very sensitive to growing mediums which stay wet for a long time. The substrate must be very porous and quick-draining. Bearing in mind that I grow these plants in plastic pots (a challenge in our humid/wet environment since plastic pots dry out a lot more slowly than clay pots), I use a mixture of 30 percent garden loam (if you can get the clay-loam in Baguio, that might even be better), 35 percent perlite and 35 percent crushed brick, granite gravel, and marble chippings (the closest thing I’ve come to limestone).

Light and Ventillation – I try to give my plants as much direct sunlight as possible. In my greenhouse, which is beside my house, I have bright light year-round, but I don’t get direct sunlight in from mid-November through February, so I water a lot less during these months. These months also coincide with the natural resting period of these plants, when they should be given a lot less water anyway. But ideally, I would rather have direct sunlight into my greenhouses year-round. I also make sure that the greenhouses get as much air flowing in as possible given my location constraints.

Watering and Fertilizing – Living Rocks are actively growing from March through to early November, with a brief dormancy during the hottest times in mid-July to early August. These plants, however, flower at the end of their growing season, from end of August to early December. Bearing this in mind and remembering my greenhouse conditions, I water once every two weeks in March, then once every week to ten days from April to early October, then taper back to once every two to three weeks from end October to February. With this watering regimen, I make sure that the growing medium has thoroughly dried out before I water again. I only fertilize during the growing period, using 25 percent of the recommended dosage for a balanced 20-20-20 fertilizer every time I water the plants.

Pest Treatment – I have encountered two pests in Metro Manila. The white scale insect is the most prevalent, latching onto the tubercles and underneath the wool of the plants; the second is the root mealy bug which attacks the roots. I’ve noticed that the pesky scales start to occur when the direct sunlight into my greenhouse starts to disappear. Heavy infestations that go untreated will ultimately kill your Living Rock. I find the best treatment is to use systemic insecticides, mixed into the growing medium as granules. The poison is absorbed by the roots and filters through the plant. So when a pest sucker comes along and sucks the sap of your plant, it sucks in poison and dies. I have had excellent results using this method; unfortunately, it is not the safest means and all necessary precautions (i.e., read instructions carefully, use protective gloves and face masks, etc.) must be followed. I also spray the plants with malathion once or twice a year, in March and around November-December, or whenever I see an infestation build-up. But I always make sure the wife and kids are out of the house for at least a day before I do any of this monkey business.