A crested cactus grows as a flat fan or a folded, brain-like ridge. A monstrose cactus grows as a lumpy cluster of short, knobby stems. Both are unusual growth forms of ordinary cactus species, and both are kept going by cuttings and grafts.
The short version
- A crest forms when the growing point at the tip of a stem stretches into a line, so the stem grows as a fan or a wavy ridge. A monstrose plant forms when that tip stops early and growth breaks out from many areoles (the small felted pads that carry the spines) at once.
- Care follows the plain plant, meaning the ordinary form of the same species. Water only when the mix is dry all the way to the bottom of the pot, check the folds of a crest for pests, and protect a monstrose plant from cold at least as early as the plain plant, and sooner if its product page gives a higher temperature.
- Both forms tend to grow more slowly and rot more easily than the plain plant.
- Either form can revert, meaning it puts out a normal stem. Cut that stem off and root it if you want to keep the form, or leave it if you like both.
- A named crested or monstrose plant is usually a clone, kept going from cuttings or grafts of one original plant.
- Monstrose stems root from cuttings. Crests may be grafted onto a rooted column, which can help them grow well.
- For any one plant the cause is usually unknown. A crest that comes from a mutation, frost or injury does not spread to other plants.
What you have
Every crested or monstrose plant is a form of an ordinary species, the plain plant. The label usually gives that species name followed by cristata (crested) or monstrosa (monstrose).
Crested and monstrose forms turn up in many kinds of cactus. Growers find them in many members of the Trichocereus group (San Pedro and its relatives), among them crested and monstrose forms of San Pedro and of the Bolivian torch. Another example is the monstrose Peruvian apple, sold as Cereus repandus, with thick, twisted, knobbly stems of a muted gray-green (see the monstrose Peruvian apple cutting page). Crests also appear on wild saguaros.
Care differences
Start from the care of the plain plant. Growers often find that both forms grow more slowly than the plain plant and rot more easily, so lean toward drier and more careful.
Water only when the mix is dry all the way to the bottom of the pot. In cool months, when the plant is making no new growth, give little or no water. Watering cactus covers how to check the mix.
Mealybugs and scale tend to hide in the folds of a crest, where they are hard to spot. Look into the folds each time you water, and see cactus pests if you find any.
Monstrose forms may take less cold than the plain plant. Start protecting at 28 to 30 F, earlier for pots and in wet winters. A monstrose plant may need protection sooner; if its product page gives a lowest safe temperature, go by that. Winter care covers how to protect a plant.
Give the same light as the plain plant, and bring a new plant into direct sun gradually (sun acclimation).
A large crest can be top-heavy. Use a pot wide or heavy enough that it will not tip, and firm the mix around the base.
If the base of either form turns soft or dark, it may be rotting. Follow cactus rot.
Keeping the form
A plant that has crested or gone monstrose keeps that trait in the cuttings and grafts taken from it. That is why a named form is usually a clone. How strongly the form shows depends on growing conditions, so 2 pieces of the same clone can look different.
Both forms can revert. A crest may send up a normal, rounded column, and growers also see monstrose plants put up a normal stem. A normal stem grows up from a single tip, with the even ribs and spines of the plain plant. Some growers find that a crest kept in too little light, or one that has been stressed or damaged, is more likely to revert.
If you bought the plant for its form, cut the normal stem off where it joins the crested or monstrose growth, and root it as a separate plant. If you are happy to have both, leave it. A reverted section may crest again later.
Wear cactus gloves. Wipe off any sap and dirt, then wipe the blade with 70% isopropyl alcohol so it stays wet for at least 30 seconds. Let it air dry. Take the cut, then dry and root the piece as in taking cuttings from your own plant.
Making more plants
Monstrose stems root from cuttings like any column, and the Peruvian apple roots easily. Cut a stem, let the cut end dry until it is firm and sealed, then root it as in how to root a cactus cutting, which also covers how to tell it has rooted. Give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks.
Crests may be grafted: a piece of the crest is joined onto a rooted column, called the stock, whose roots then supply it. Grafting is one way to keep both forms growing well. A plant may grow faster on a graft than on its own roots, and its shape can differ between the two. Growers sometimes take a crest off its stock later and root it. Cactus grafting explains how a graft works, and caring for grafted cacti covers taking a plant off its stock.
How the forms arise
At the tip of every stem is a growing point, a small zone of dividing cells called the apical meristem. On a column cactus it sits at the top of the stem. Growth comes from that single point, which is why a normal stem grows round. As the stem lengthens, the growing point lays down ribs, and the areoles sit along them. Each areole holds a dormant bud of its own, which is where new stems start. How a cactus works covers areoles and ribs.
In a crest, the growing point stretches into a line. The whole ridge acts as one growing point and adds stem along its full length, so the plant widens sideways into a flat fan, a wavy ribbon or, once the folds crowd together, a brain-like mass. The botanical term is fasciation, and cacti are among the plant families where it is most common.
In a monstrose plant, the tip of each stem quits early, after only a few areoles. Growth then breaks out from areoles here and there with no pattern, so the plant builds a cluster of short, knobby stems instead of one column.
What causes them
Fasciation in plants can start with a random mutation, with injury to the growing point from frost, insects, animals, chemicals or knocks, or with some infections. For any one cactus the cause is usually unknown, and often there is no clear trigger. In wild crested saguaros, a mutation, a hard freeze and lightning are all possible causes.
A crest that comes from a mutation, frost or injury does not spread to other plants.
Variegated plants
Variegation is a separate change: patches of yellow or other pale colors where the stem has little or no chlorophyll, the green pigment a plant uses to feed itself. Brightly colored forms with no chlorophyll at all cannot feed themselves and live only on a graft. Collecting unusual columns covers them alongside crests.
Sources
Modifications to Shoot Apical Meristems. J. D. Mauseth, University of Texas at Austin. https://web.biosci.utexas.edu/mauseth/researchoncacti/Apical%20meristems.htm
Fascinating Fasciation. Susan Mahr, University of Wisconsin-Madison Extension. https://hort.extension.wisc.edu/articles/fascinating-fasciation/
Fasciation in Plants: What It Means. Royal Horticultural Society. https://www.rhs.org.uk/problems/fasciation
Fasciation. Jay W. Pscheidt and Melodie Putnam, Pacific Northwest Plant Disease Management Handbook, Oregon State University, reviewed 2023. https://pnwhandbooks.org/node/24371
Stem fasciation in cacti and succulent species: tissue anatomy, protein pattern and RAPD polymorphisms. A. N. El-Banna, M. F. El-Nady, Y. H. Dewir and M. E. El-Mahrouk, Acta Biologica Hungarica 64(3): 305-318, 2013. https://d-nb.info/1218946474/34
Cereus uruguayanus (Cactaceae) and its naturalised occurrence in Queensland, Australia. P. I. Forster and M. Schmeider, Austrobaileya 5(4): 671-677, Queensland Herbarium, 2000. https://ia903202.us.archive.org/27/items/biostor-257061/biostor-257061.pdf
The Crested (Cristate) Saguaro. Saguaro National Park, U.S. National Park Service. https://www.nps.gov/sagu/learn/nature/the-crested-saguaro.htm
TOWT Carnegiea gigantea forma cristata. University of Arizona Campus Arboretum. https://arboretum.arizona.edu/towt-carnegiea-gigantea-forma-cristata
Cereus repandus. Martin landscape plant library, Arizona State University Library. https://www.asu.edu/lib/camartin/plants/Plant%20html%20files/cereusrepandus.html
Pachycereus schottii. Martin landscape plant library, Arizona State University Library. https://www.asu.edu/lib/camartin/plants/Plant%20html%20files/pachycereusschottii.html
Cereus repandus (L.) Mill. Plants of the World Online, Royal Botanic Gardens, Kew. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:130627-1
Studies on Inter-generic Grafting Compatibility of Ornamental Cacti. R. Perumal, M. Prabhu, M. Kannan and S. Srinivasan, International Journal of Current Microbiology and Applied Sciences 9(11): 2133-2144, 2020. https://www.ijcmas.com/9-11-2020/R.%20Perumal,%20et%20al.pdf
Grafting Types, Cactus Grafting. Plant Propagation, University of Florida IFAS. https://propg.ifas.ufl.edu/06-grafting/02-graftingtypes/05-grafting-cactus.html
Plant Disease Pointers, January 2022: Decontaminating Your Way to Healthier Plants. Plant Disease Diagnostics Clinic, University of Wisconsin-Madison, 2022. https://pddc.wisc.edu/2022/01/27/january-2021-decontaminating-your-way-to-healthier-plants/