Common Cactus Terms & Definitions

Trichocereus bridgesii /
Bolivian Torch

Roots that grow from an unusual place on the plant, such as from a stem rather than from the main root system. In cacti, adventitious roots can appear when a cutting is trying to root, when a plant is stressed, or when a stem section is in contact with a suitable rooting surface.

Roots that grow above the soil line, usually from the stem. In cactus culture they are often a sign that the plant is searching for moisture, support or a place to root. A few aerial roots are not automatically a disaster, but they are worth reading in context: check humidity, watering, root health and whether the plant is leaning or trying to anchor itself.

A method of growing plants without soil, in which roots are suspended in air and sprayed with a nutrient-rich mist.

Chemical compounds found in some cactus species that have medicinal or psychoactive properties. (We do not entertain this subject at all, it is illegal).

Pigments that give some cactus flowers their vivid colors, ranging from pink to purple to red.

The pattern of areoles on a cactus stem, which can help to identify different species.

An areole is the small pad or cushion on a cactus where spines, flowers, pups and new growth can emerge. Areoles are one of the features that make a cactus a cactus. On a Trichocereus, they usually sit along the ribs in regular rows.

A small, dormant bud located in the axil, or angle, between a cactus stem and a branch or spine.

A disease that can affect cactus plants, caused by various types of bacteria that thrive in moist conditions.

Bolivian Torch is a common name for Trichocereus bridgesii, also known botanically as Echinopsis lageniformis.

Typical bridgesii plants are columnar and often slimmer than pachanoi, with a blue-green to glaucous skin, pronounced ribs and longer spines. They can look elegant, fierce and a bit wild compared with the softer, rounder look many people associate with San Pedro. As with most Trichocereus, appearance varies a lot between clones, seedlings and growing conditions.

The process of a cactus plant producing a tall, elongated stem in response to environmental stress or damage.

Protective scales that cover a cactus bud before it opens into a new growth point.

A callus is the dry, sealed surface that forms over a cut or damaged area. When rooting cactus cuttings, you normally let the cut end callus before planting. This helps reduce the risk of rot by giving the wound time to dry and seal.

The pigment that gives cactus plants their green color, and helps to absorb sunlight for photosynthesis.

A flattened stem that behaves a bit like a leaf. In Opuntia, for example, the flat pads are cladodes. They photosynthesise, store water and produce new growth, flowers and fruit from their areoles.

A genetically identical copy of a cactus plant, produced through asexual reproduction. In Trichocereus collecting, a clone usually means a known plant line that has been propagated by cuttings or grafts rather than grown from seed.

Shop our Trichocereus clones.

The first seed leaves produced by a seedling. In many cacti they are tiny and short-lived, but the term is useful when talking about seed germination and the earliest seedling stage.

Corking is the development of a tough, woody or cork-like layer on older cactus tissue. It often appears near the base of mature plants and can be completely normal, especially on older Trichocereus. Corking is usually firm and dry. Soft, wet, black or spreading tissue is more concerning and may indicate rot rather than age-related corking.

CAM is a water-saving form of photosynthesis used by many cacti and succulents. In simple terms, the plant opens its stomata mostly at night to take in carbon dioxide, then uses that stored carbon dioxide during the day while keeping water loss lower. This is one reason cacti are so well adapted to dry environments.

A crested cactus grows in a fan, wave or brain-like shape instead of forming a normal single growing point. This usually happens when the growing tip changes from a point into a line of growth. Crests can occur through mutation, damage or other disruption to the meristem. Crested Trichocereus can look dramatically different from normal columnar plants, so this is one of the best terms to show with a labelled photo.

Example: Tr. pachanoi f. Cristata Variegated TPCV.

Crown rot is rot affecting the top or central growing area of the plant. It can be caused by fungal or bacterial infection, often helped along by excess moisture, poor airflow, cold damp conditions or damage. If the crown turns soft, dark or collapses, act quickly: isolate the plant, keep it dry and assess whether clean tissue can be saved.

Cuttings are pieces of cactus removed and rooted to make new plants. A good cutting should be cleanly cut, allowed to callus, then rooted in a suitable dry or lightly moist medium depending on species, season and conditions. With Trichocereus, cuttings are one of the most common propagation methods.

Browse current cactus cuttings.

a fine powder made from the fossilized remains of diatoms. It is often used as a natural insecticide and to improve soil drainage.

Damping off is a disease problem that affects seedlings, often causing them to collapse at soil level or turn mushy. It is usually associated with excess moisture, poor airflow, contaminated media or weak seedlings. In cactus seed growing, clean conditions, sensible moisture and ventilation help reduce the risk.

Referring to cactus plants that lose their leaves or stems seasonally, often in response to dry or cold conditions.

A genus of cactus plants that have long, columnar stems with dense spines and showy flowers.

The process of arid environments, such as deserts, expanding and becoming more dominant due to factors such as climate change and human activity.

Referring to cactus plants that are adapted to survive in dry environments by conserving water and storing it in their tissues.

A genus of cactus plants that have large, spherical or cylindrical stems with prominent ribs and spines.

A genus of cactus plants that have showy, trumpet-shaped flowers and cylindrical or spherical stems.

Referring to a plant or animal species that is native to a specific region or area, and found nowhere else.

The outermost layer of a cactus stem or leaf, which helps to protect against water loss and damage.

A plant that grows on another plant, but is not parasitic, commonly found in some cactus species.

Etiolation is stretched, weak growth caused by insufficient light. A cactus may become thinner, paler and more elongated as it reaches for stronger light. On columnar cacti this often shows as a narrow, skinny section at the top of otherwise thicker growth. Once a section has grown etiolated, it will not fatten back up to match the older growth, but future growth can improve if the plant is moved into better light gradually.

A genus of cactus plants that have large, barrel-shaped stems with prominent ribs and spines.

Chemical compounds found in some cactus species that have anti-inflammatory and antioxidant properties.

A developing bud on a cactus plant that will eventually open into a flower.

A genus of cactus-like plants that have thick, succulent leaves and showy flowers.

A taxonomic rank used to group closely related cactus species together.

Glaucous means blue-grey, grey-green or waxy-looking. On cacti it usually refers to the natural bloom or coating on the skin that gives some plants a soft blue cast. This coating can rub off, so avoid handling glaucous plants more than necessary if you want to preserve the look.

Browse plants tagged Glaucous.

Grafting is joining one cactus to another so they grow as a single plant. The top piece is the scion and the rooted bottom piece is the rootstock. Growers graft to speed up growth, save weak seedlings, propagate rare material, support plants that struggle on their own roots, or create novelty plants.

For a deeper walkthrough, see our Grafting Cactus 101 guide.

Example: Tr. peruvianus Sharxx Blue clone graft – whole plant.

A genus of cactus plants that have small, spherical or cylindrical stems with colourful flowers.

Chemical compounds found in some cactus species that are carcinogenic and may increase the risk of cancer.

Chemical messengers that regulate growth and development in cactus plants, such as auxins and cytokinins.

Trichocereus pachanoi (San Pedro)

A plant produced by crossing two different cactus species, varieties or cultivars. In Trichocereus, hybrids can show a mix of traits from both parents, including spine character, colour, rib shape, growth rate and flower features.

Shop Trichocereus hybrid cultivars.

A genus of cactus-like plants that have thick, succulent leaves and showy flowers.

A method of propagation in which cactus plant tissue is cultured in a nutrient-rich medium to produce new plants.

A natural, non-toxic pesticide made from soap and water, often used to control pests on cactus plants.

The space between two areoles on a cactus stem, which can vary in length depending on the species.

The process of cactus plants evolving in different ways due to being separated by physical or environmental barriers, leading to the development of new species.

A branch or side shoot that emerges from a cactus stem or spine.

A genus of cactus-like plants that have thick, leaf-like structures that resemble stones or pebbles.

A genus of cactus plants that have small, cylindrical or spherical stems with dense spines and colourful flowers.

Mealybugs are small white sap-sucking insects that hide in areoles, creases, roots and other awkward places. They can weaken plants and spread surprisingly quickly through a collection. The white fluff is often the first thing people notice. If you find them, isolate the plant and treat promptly.

Please see our Cactus Pests & Treatment blog post for tips on how to treat / prevent these little assholes from ruining your day.

The meristem is the active growing tissue of the plant. On a columnar cactus, the main apical meristem sits at the growing tip. Changes or damage to the meristem can affect how the plant grows, and unusual growth forms such as crests are linked to changes in normal meristem behaviour.

Chemical compounds found in cactus plants that play important roles in metabolism and defence against pests and disease.

A type of flowering plant that has a single cotyledon, or embryonic leaf, and parallel veins in the leaves.

Monstrose growth is irregular, mutated growth that does not follow the normal shape of the species. Instead of neat ribs and a regular column, the plant may produce lumpy, bumpy, segmented or unpredictable forms. Trichocereus bridgesii monstrose, often shortened to TBM, is one of the best-known examples in cultivation.

Monstrose growth is irregular and distorted; crested growth is usually fan-like, wavy or comb-shaped.

Browse plants tagged Monstrose.

Mycorrhizae are beneficial fungi that form relationships with plant roots. They can help plants access water and nutrients, especially in living soils. In cactus growing, mycorrhizal products are sometimes used during potting, rooting or transplanting.

We do offer Xtreme Gardening – Mykos Pure Mycorrhizal Inoculum by tub or single use.

A small, round or oval bump on a cactus stem or root, often associated with the presence of nitrogen-fixing bacteria.

Noid means “no ID”. It is used when a plant has lost its label, arrived without reliable identification, or cannot be confidently identified. In Trichocereus collecting, a noid plant can still be beautiful and worth growing, but it should not be sold or shared as a named clone without solid provenance.

A genus of cactus plants that have flat, paddle-shaped stems with spines and showy flowers.

A large cactus species that has multiple stems and produces white or pink flowers.

The process of cactus plants entering a period of dormancy during the winter months, typically characterized by reduced growth and water consumption. In the UK, overwintering is mostly about keeping plants cool, bright, dry enough and protected from freezing wet conditions.

See our guide on how to protect your cacti over winter.

The production of fruit without fertilization, often seen in some cactus species.

• Trichocereus peruviana
• Echinopsis peruviana

Shop Trichocereus peruviana

PC – Predominant Cultivar or Predominant Clone (The previous is more the accepted term). It is the most common variety of T. pachanoi (or pachanot) found all over the United States, particularly in the Southwest, where numerous cactus nurseries have been cloning this strain for decades.

I get asked fairly often if I sell pachanois as PCs, not I don’t. As it is pretty much a US thing, it is actually quite rare to find PC’s this side of the pond. I had to seek out and import a PC.

A genus of cactus plants that have leaves and showy flowers, making them appear more like typical non-cactus plants.

The thick, outer layer of a cactus fruit that provides protection and helps with seed dispersal.

The process by which cactus plants use sunlight to convert carbon dioxide and water into glucose, providing energy for growth and development.

Chemical compounds found in cactus plants that have potential health benefits, such as reducing inflammation and improving immune function.

The act of removing the tips of new growth on a cactus plant, typically done to encourage branching and fuller growth.

The transfer of pollen from the male reproductive organ of a cactus flower to the female reproductive organ, resulting in fertilization and the production of seeds.

The soil or other material used to plant cactus in a container. A good cactus potting mix should balance drainage, aeration, mineral content and enough organic matter for the plant and growing style. Trichocereus generally appreciate a free-draining mix that does not stay wet and stagnant around the roots.

It will always be cheaper in the long run to make your own, but for convenience we do offer cactus substrate here.

A fruit-like structure that forms from a cactus flower, but is not derived from the ovary like a true fruit.

A genus of cactus plants that have flattened, wing-like stems with spines and showy flowers.

A pup is a new side shoot or offset produced by the cactus. Pups may emerge from the base, from an areole, or from near a damaged growing point. Once large enough, some pups can be removed and rooted as cuttings, while others are left to form a multi-headed plant.

A genus of cactus plants that have thin, elongated stems and small, inconspicuous flowers.

Ribs are the raised vertical sections running along the stem of many columnar cacti. They give the plant structure and allow it to expand and contract as it stores or loses water. On Trichocereus, rib count, shape and spacing can also be useful descriptive features.

The rootstock is the lower, rooted cactus used in a graft. It provides the root system and much of the growing power for the scion above it. Common rootstocks are chosen because they are vigorous, resilient and compatible with the scion.

For a practical example, see the Grafting Cactus 101 guide.

A cluster of leaves or stems that grow in a circular pattern, typically seen in some cactus species.

San Pedro is a common name most often used for Trichocereus pachanoi, though in collector conversations it is sometimes used more loosely around related columnar Trichocereus species such as pachanoi, peruviana and bridgesii. For clarity, it is best to use the botanical name where possible, especially when selling, labelling or comparing plants.

• Trichocereus pachanoi
• Echinopsis pachanoi

A plant that obtains nutrients from dead or decaying organic matter, often found in some cactus species.

The scion is the top part of a graft: the cactus piece being attached to the rootstock. The scion is usually the plant the grower wants to propagate, speed up, rescue or display.

For a practical example, see the Grafting Cactus 101 guide.

A genus of cactus plants that have small, cylindrical stems with spines and showy flowers.

A genus of cactus-like plants that have thick, succulent leaves and showy flowers.

A cactus species that has long, snake-like stems and small, inconspicuous flowers.

The portion of a cactus plant that grows above the ground, typically consisting of stems, leaves, and flowers.

A genus of cactus plants that have small, round stems and showy flowers.

A spine is a modified plant structure that grows from a cactus areole. Spines can protect the plant, provide shade, reduce moisture loss and help with identification. They are not the same as thorns in the strict botanical sense, even though most people use the words casually.

A type of plant that stores water in its leaves, stems, or roots, often seen in cactus plants.

A single, thick root that grows deep into the soil, providing stability and water absorption for a cactus plant.

A plant that grows in soil or on the ground, as opposed to an epiphytic plant that grows on other plants.

 A genus of cactus plants that have small, cylindrical stems with spines and showy flowers.

A genus of epiphytic plants that are often called “air plants,” as they do not require soil to grow and absorb nutrients from the air.

Topdressing is the layer of grit, gravel, pumice, lava rock or decorative stone placed on top of the potting mix. It can make pots look tidy, reduce soil splash, help keep the plant base drier and discourage fungus gnats. Avoid burying soft green tissue under heavy topdressing, especially on young or rot-prone plants.

A genus of cactus plants that have columnar stems with showy flowers.

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Turgor pressure is the internal water pressure that helps plant tissue stay firm. When a cactus is well hydrated, the stem often feels plump and firm. When water is low, the plant may wrinkle, soften slightly or pull inward between the ribs. Always read this alongside season, temperature and root health before watering heavily.

Variegation is a pattern of reduced or missing chlorophyll that creates yellow, cream, white or lighter green areas on the plant. Variegated cacti can be beautiful, but heavily variegated sections may grow more slowly or be more sensitive because they have less green tissue for photosynthesis. Fully non-green plants often need grafting to survive.

Browse plants tagged Variegated.

Watering cacti is about timing, conditions and substrate, not just adding a little splash now and then. In active growth, many cacti prefer a proper watering followed by a chance to dry down. In cold, dark or dormant conditions, water use drops sharply and wet roots become risky. Pot size, substrate, airflow, temperature and season all matter.

A type of landscaping that uses drought-tolerant plants, such as cactus, to conserve water in arid climates.

A xerophyte is a plant adapted to dry conditions. Cacti are classic xerophytes because many store water in their stems, reduce leaves, use spines and waxy skin, and rely on water-saving processes such as CAM photosynthesis.

The tissue in a cactus plant responsible for transporting water and nutrients from the roots to the rest of the plant.

The amount of fruit or seeds produced by a cactus plant, typically measured by weight or volume.

A common name for the Christmas cactus, a type of cactus plant that produces showy flowers in the winter months.

The cell formed by the fusion of a male and female reproductive cell, leading to the development of a cactus seed.