Rare Leaf Glossary
Houseplant glossary
Node, chimera, reversion, LECA… The terms you meet in care guides and plant swaps, explained simply.
- acclimation
- Gradually adjusting a plant to new conditions, such as lower humidity after shipping or after coming out of tissue culture. Sudden changes in light or humidity often cause leaf drop.
- aerial root
- A root that grows from the stem above the soil, usually at a node. Climbing aroids use them to cling to supports and take up moisture; cuttings with an aerial root tend to root faster.
- air layering
- Rooting a section of stem while it is still attached to the parent: wound it lightly at a node, wrap with moist sphagnum and plastic, then cut and pot it once roots form.
- anthocyanin
- Water-soluble plant pigments that give tissue red, pink or purple tones. They are behind the reddish new leaves and dark coloring of many philodendrons.
- bright indirect light
- Plenty of light without direct midday sun hitting the leaves, such as near an east window or set back from a south window behind a sheer curtain. Most aroids and variegated plants prefer it.
- callus
- Wound tissue that forms over a cut surface. Succulent cuttings are left to dry and callus before planting so they do not rot.
- cataphyll
- A modified, bract-like leaf that wraps and protects a newly emerging leaf in philodendrons and other aroids. Once the leaf unfurls it usually dries and falls off, though some species keep it on the stem.
- chimera
- A plant made of genetically different cell layers, such as green tissue and tissue without chlorophyll. Chimeral variegation does not come true from seed, is kept only by vegetative propagation, and can shift or disappear unpredictably.
- coco coir
- Fiber and pith from coconut husks, used as a peat alternative. It holds moisture well; some products contain salts and are best rinsed before use.
- corm
- A swollen underground stem base that stores food. Alocasia produces small corms (cormlets) among its roots, which can be grown into new plants.
- cultivar
- A plant form selected and maintained in cultivation for distinct traits, such as Monstera deliciosa 'Thai Constellation'. Cultivar names go in single quotes and are not translated.
- cutting
- A piece cut from a plant, most often a stem section with a node and a leaf, that grows into a new plant. It is genetically identical to the parent, which is how cultivars and variegated plants are propagated.
- division
- Splitting a clumping or rhizomatous plant into several pieces, each with its own roots and leaves. Best done at repotting time.
- dormancy
- A period of slowed or halted growth, usually in winter with less light. Alocasias may drop their leaves and survive as a corm; reduce watering and stop fertilizing.
- drainage
- How well a pot and its mix let excess water escape. A drainage hole is essential; water sitting around the roots starves them of oxygen and leads to rot.
- fenestration
- Holes or splits in the leaf blade, best known in Monstera. They appear on mature leaves; juvenile plants and plants in low light often produce solid leaves.
- fungus gnats
- Small black flies that hover around pots. Their larvae live in moist potting mix, feed on organic matter and fungi, and can damage the tender roots of cuttings; letting the surface dry out helps.
- growth point (apical meristem)
- The actively dividing tissue at the tip of a shoot that produces new leaves. Pinching it out usually makes the plant branch from buds at the nodes below.
- humidity
- The amount of water vapor in the air, given as relative humidity in percent. Tropical aroids and calatheas in dry, heated rooms get brown leaf edges and are more prone to spider mites.
- hybrid
- A plant produced by crossing two different species or cultivars. An interspecific hybrid is marked with × in its botanical name, as in Alocasia × amazonica.
- integrated pest management (IPM)
- An approach that combines prevention, regular monitoring, physical and biological controls, and uses pesticides only as a last resort. For houseplants that means quarantine, sticky traps, predatory mites and targeted treatment.
- internode
- The section of stem between two nodes. Unusually long internodes with small leaves often signal that the plant is stretching for more light (etiolation).
- leaching (flushing)
- Running a large volume of water through the pot to wash out salts built up from fertilizer and hard water. A white crust on the soil or pot and brown leaf tips are signs of salt buildup.
- leaf blade (lamina)
- The flat, photosynthetic part of a leaf, excluding the petiole. Variegation pattern, fenestration and sinus shape are all judged on the blade.
- LECA (expanded clay)
- Lightweight expanded clay aggregate: fired clay balls used as a drainage layer, a mix additive, or on their own in semi-hydroponics, where roots draw water from a reservoir.
- lux / foot-candle
- Units of illuminance, the amount of light falling on a surface. Lux is metric, foot-candles are US units; 1 foot-candle equals about 10.76 lux. Measure with a light meter or, roughly, a phone app.
- mealybugs
- Sap-sucking insects covered in white, cottony wax. They cluster in leaf axils and on roots and excrete sticky honeydew that sooty mold grows on.
- mottled (marbled) variegation
- A fine, scattered pattern of flecks and streaks across the whole blade rather than large solid blocks. Pothos 'Marble Queen' is a typical example.
- node
- The point on a stem where a leaf, an axillary bud and, in aroids, often an aerial root emerge. A cutting needs at least one node to grow a new shoot.
- NPK (fertilizer ratio)
- The three numbers on a fertilizer label give its nitrogen (N), phosphorus (P) and potassium (K) content. Nitrogen drives leaf growth; feed houseplants mainly during active growth, diluted per the label.
- offset (pup)
- A young plant that forms at the base of the parent plant. Once it has its own roots, it can be separated and potted up on its own.
- orchid bark
- Coarse chunks of bark, usually pine. In aroid mixes it creates large air pockets, similar to the conditions of plants that climb tree trunks in the wild.
- perlite
- Lightweight white granules of volcanic glass that has been heated until it puffs up. Mixed into potting media to improve aeration and drainage; it contains no nutrients.
- petiole
- The stalk that attaches the leaf blade to the stem. Many aroids have long petioles, and variegation can show on them before it shows on the leaf.
- pH
- A measure of how acidic or alkaline the potting mix is, on a 0–14 scale where 7 is neutral. Most houseplants prefer slightly acidic conditions; at the wrong pH some nutrients become less available.
- phytosanitary certificate
- An official document from the exporting country's plant protection authority confirming a shipment meets the importing country's plant-health rules. Since December 14, 2019, virtually all plants for planting entering the EU from outside it need one, even small quantities for personal use.
- plant passport
- An official EU label for plants for planting that confirms plant-health requirements are met and allows tracing. It is not needed for direct sales to final users, but it is required for distance sales such as online orders.
- potting mix (substrate)
- The medium a potted plant roots in, such as potting soil, bark, perlite and coco coir. Aroids do best in chunky, airy mixes that drain quickly after watering.
- predatory mites
- Beneficial mites released for biological pest control. Phytoseiulus persimilis hunts spider mites, while Neoseiulus (Amblyseius) cucumeris is used mainly as a preventive against thrips.
- pumice
- A porous volcanic rock used as a mineral component of potting mixes. It is heavier than perlite, less likely to float to the surface, and does not break down.
- quarantine
- Keeping a newly bought plant away from the rest of your collection for several weeks while you check it for pests. It stops thrips, spider mites or mealybugs from spreading.
- reversion
- When a variegated plant starts producing plain green growth. Green shoots are more vigorous and can take over, so they are usually cut back to where they arise.
- rhizome
- A horizontal stem growing underground or along the surface, with roots and shoots emerging from its nodes. Rhizomatous plants such as ZZ plants and calatheas are usually propagated by division.
- root bound
- When roots fill the whole pot, circle the edges and grow out of the drainage hole. Water runs straight through, and the plant needs repotting into a slightly larger pot.
- root rot
- Root decay caused mainly by waterlogging and fungal or water-mold pathogens such as Pythium. Affected roots are brown, mushy and smelly, and the plant wilts even though the soil is wet.
- rooted vs. unrooted cutting
- A rooted cutting already has its own roots and is ready for potting; an unrooted cutting is just a stem piece with a node that still has to root. Unrooted cuttings are usually cheaper but riskier.
- rooting hormone
- A powder, gel or solution containing synthetic auxins (such as IBA) that the base of a cutting is dipped into. It speeds up and evens out root formation, especially in harder-to-root plants.
- scale insects
- Sap-sucking insects that sit under a protective shell on stems and leaves. Soft scales excrete sticky honeydew, armored scales do not; the shell protects them from many sprays.
- sectoral variegation (half-moon)
- Variegation in large solid blocks, where a whole section of the leaf is white or pink. The extreme case is a "half-moon", where exactly one side of the midrib lacks chlorophyll.
- sinus
- The notch at the base of a leaf blade where the petiole attaches, typical of heart- and arrow-shaped leaves. Its shape helps tell related species apart, for example among Alocasia.
- spadix
- A fleshy spike densely covered with tiny flowers, characteristic of the arum family (Araceae). It is paired with a protective spathe.
- spathe
- The bract that wraps or backs the spadix in the inflorescence of aroids. In peace lilies and anthuriums it is the showy white or colored part people usually call the flower.
- species
- The basic unit of botanical classification, written as genus plus species epithet in italics, e.g. Epipremnum aureum. When botanists reclassify a plant, the old name becomes a synonym (Calathea orbifolia is now Goeppertia orbifolia).
- sphagnum moss
- Dried moss that holds a lot of water while staying airy. It is used for rooting cuttings, air layering and moss poles.
- spider mites
- Tiny mites (most often Tetranychus urticae) that feed on leaf undersides. Leaves get fine yellow stippling and, in heavy infestations, fine webbing; they thrive in warm, dry air.
- stolon (runner)
- A slender stem that grows out from the parent plant and forms a new plantlet at its tip. Spider plants (Chlorophytum comosum) are the classic example; plantlets can be rooted while still attached.
- thrips
- Tiny, slender insects with fringed wings that suck out leaf cell contents. They leave silvery patches and black specks of excrement, and on aroids often hide in unfurling leaves.
- tissue culture
- Propagating plants from tiny pieces of tissue on a nutrient medium under sterile lab conditions. It produces large numbers of genetically identical plants, which is why once-rare cultivars become cheaper.
- variegation
- Leaf patterning in green plus white, cream or yellow, where some tissue lacks chlorophyll. It can be genetic, chimeral or virus-induced; the pale areas do not photosynthesize, so variegated plants grow more slowly.
- water propagation
- Standing a cutting with its node in water until roots form, then potting it into soil. Change the water regularly; water-grown roots need a little time to adjust to soil.