Glossary

A

aerial root: A root that leaves the stem above ground, to grip a trunk and to drink. A cutting taken with one attached establishes faster. More on this
air-filled porosity: The fraction of a pot still filled with air once it has finished draining. It is the number that actually decides whether roots rot, and aroid mixes are built to keep it high. More on this
anthocyanin: The pigment class behind red, purple and pink in leaves and flowers. A plant missing it entirely is green where it should be red, which is what an albino sundew or a green-stemmed philodendron is.
Award of Garden Merit: An RHS mark given to plants that perform reliably in ordinary conditions. It is about growing well, not about rarity.

B

basionym: The name a plant was first published under, when it has since been moved to another genus. The original author stays in brackets in the new name, which is what those brackets mean.

C

calcium oxalate: Needle-shaped crystals carried through the tissue of most aroids. They are the whole of the toxicity to cats, dogs and children: painful rather than poisonous.
CAM: Crassulacean acid metabolism: opening the leaf pores at night, storing the carbon dioxide as acid, and running photosynthesis by day with the pores shut. It costs growth and saves water.
chilling injury: Cold damage with no frost involved — wilting, water-soaked patches, blackening days later — in tropical plants below roughly 10 to 12 °C. Distinct from the chilling a temperate plant needs before it will flower.
chimera: A plant built from cell layers of different genetics, one carrying a mutation and one not. Most stable variegation is a chimera, which is why it cannot be grown from seed.
chloroplast: The compartment inside a plant cell that does photosynthesis. White leaf tissue has none that work, which is why it cannot pay its own way.
clone: Every plant propagated by cutting or division from one original, and so genetically identical to it. Most named cultivars are a single clone.
coir: Coconut husk fibre, used in place of peat. It holds water well and drains better than peat does. More on this
corm: A short swollen underground stem that stores food between seasons. Much of what the hobby calls an Alocasia corm is really a rhizome.
cultivar: A plant selected and propagated by people rather than described from the wild. Written in single quotes after the species — Monstera deliciosa 'Thai Constellation' — and never italicised.

D

dormancy: A rest, not a decline. In a cool, dark winter some plants drop their leaves and live off an underground stem until warmth returns. Watering one as though it were sick is how it dies. More on this

E

endemic: Found naturally in one place and nowhere else.
epiphyte: A plant that grows on another plant, taking nothing from it — perched in bark and leaf litter rather than rooted in soil. It is why so many houseplants want an airy mix rather than compost.
epithet: The second word of a botanical name — the deliciosa in Monstera deliciosa. It belongs to the species, and it never stands on its own.
explant: The piece of a plant a tissue-culture lab starts from — a petiole, a leaf disc, a shoot tip. Which tissue it is taken from decides what grows back, which is why some variegation cannot survive the process.
extension service: The public advisory arm of a land-grant university in the United States. Their factsheets carry a lot of what is actually known about growing things, written by people who tested it — which is why they are cited so often here, and why two of them disagreeing is worth mentioning.

F

far-red: Light just past the red a human eye can see. It is what reaches the forest floor after the canopy has taken the rest, and some understorey plants have photosynthetic machinery tuned to eat it.
fenestration: The holes and splits in a mature Monstera leaf. They are cut by cells dying on schedule inside the furled bud, not torn later, so a leaf never gains one after it opens. More on this
foot-candle: A unit of light on a surface, one lumen per square foot, still the everyday unit in horticulture. About 10.8 lux. Bright indirect light starts around 1,000 of them. More on this
frass: Insect droppings. On a leaf it shows as tiny black varnish-like specks, and it is often how an infestation is found. More on this

G

genus: The rank above species: a group of species close enough to share a name. Monstera and Philodendron are genera; the first word of a botanical name is the genus.

H

hemiepiphyte: A plant that lives half its life on the ground and half up a tree: it germinates on the forest floor, climbs a trunk, and may lose its ground roots entirely.
heterosporous: Making two sizes of spore — a few large ones and many small ones — rather than one. It is the clean way to tell a spikemoss from a fern, most of which make one size.
homonym: The same botanical name published twice for two different plants. The later one is illegitimate and has to be replaced, whatever its merits.
hybrid vigour: The tendency of a cross to outgrow both its parents. Not a rule — plenty of hybrids, including some here, grow more slowly than either.
hydrophobic: Dried so far that it repels water instead of absorbing it. Peat and coir both do this, and water then runs down the sides of the pot rather than into the mix. More on this

I

ICRA: An International Cultivar Registration Authority: the body that registers cultivar names for one group of plants. Most genera have none, which is why so many trade names are unregistered.
IPNI: The International Plant Names Index. It records where and when a name was published, without ruling on whether it is the accepted one — that is POWO's job.

J

jasmonate: A plant hormone best known for wound and defence responses. Carnivorous plants reuse it to run digestion: it is what tells a sundew leaf to curl around something it has caught.

L

LECA: Lightweight expanded clay aggregate — fired clay pebbles, reusable and inert, used for semi-hydroponics or as a chunky component. More on this
lux: The metric unit of light on a surface, one lumen per square metre. Roughly a tenth of a foot-candle. More on this
lycophyte: A member of the older of the two surviving lineages of vascular plants, separated from ferns and seed plants for roughly 410 million years. Spikemosses and clubmosses are lycophytes; nothing sold as a fern is.

M

montane: Of the cool, humid forest belt on a mountainside, above the lowland tropics. Plants from it dislike hot dry rooms.

N

naturalised: Growing and reproducing outside cultivation in a place it is not native to, without help. Three plants in this collection are naturalised somewhere, and banned there for it.
node: The point on a stem where a leaf attaches and new roots and shoots can form. A cutting without one is a leaf on a stick: it cannot grow. More on this

O

offset: A young plant thrown up from the base of a mature one, already rooted and separable at repotting. More on this
orchid bark: Graded pine bark chips. The coarse structural part of an aroid mix, holding it open so roots get air. More on this
osmotic: To do with water moving across a membrane towards the saltier side. Feed too strongly and the gradient reverses, pulling water out of the roots — which is what fertiliser burn is. More on this
ovule parent: The parent that carried the seed in a cross — the mother, by convention written first.

P

perlite: Volcanic glass popped like corn into light white granules. It holds no water and takes up space, which is how it keeps air in a mix. More on this
petiole: The stalk that carries a leaf. Length, colour and texture often tell species apart when the leaves do not.
photoperiod: Day length, as a plant measures it. Several plants here take their cue from it rather than from temperature, which is why a warm windowsill can defeat a dormancy or a flowering they would manage outdoors.
plant patent: A US patent on a plant that can be reproduced without seed, lasting twenty years and barring propagation. Searching for one is how this site checks whether a cultivar's origin was ever documented.
pollen parent: The parent that supplied the pollen in a cross — the father, by convention written second.
POWO: Plants of the World Online, Kew's database of accepted plant names and native ranges. Where a scientific name on this site comes from unless another authority is named.
primordium: A leaf at its earliest stage, a millimetre or two of tissue in the bud. A Monstera's holes are already decided at this size.
programmed cell death: Cells dying on a schedule as part of normal development rather than from injury. It is how a Monstera leaf gets its holes.
pumice: Porous volcanic rock. Heavier than perlite and it holds a little water, so it does the same job without floating to the top of the pot. More on this

R

rhizome: A thickened stem that creeps along or under the surface, storing food and putting up leaves as it goes. It is a stem, not a root.
RHS: The Royal Horticultural Society. Its plant register and its Award of Garden Merit are among the few horticultural authorities worth citing.

S

sector: A block of tissue descended from one group of cells — the whole-half-leaf kind of variegation, as opposed to an even speckling.
self-heading: A philodendron that grows as a crown of leaves from a short upright stem rather than climbing. The opposite habit to a vining one.
skototropism: Growing towards darkness rather than light. A seedling on the forest floor heads for the darkest part of the horizon, because that is where the nearest trunk is.
sphagnum: Bog moss, dried and used as a growing medium. It holds many times its own weight in water while staying open enough for roots to breathe. More on this
sport: A shoot that appears on a plant carrying a mutation the rest does not have. Propagated on its own, it becomes a new cultivar.
subspecies: A population within a species, distinct enough to name and consistent enough to recognise, but still able to interbreed with the rest.
sunfleck: A patch of direct sun that moves across the forest floor as the canopy shifts. Much of an understorey plant's light budget arrives in these brief flecks.
synonym: A botanical name that is no longer the accepted one for a plant, usually because the same species was described twice. Old books and plant labels are full of them.

T

tissue culture: Growing plants from a few cells in sterile jars of nutrient gel. It is how a rare cultivar becomes a supermarket plant, and why prices for some of them collapse.
tospovirus: A group of plant viruses spread by thrips. There is no cure, which is the real reason thrips are worth taking seriously. More on this

U

understorey: The layer beneath the forest canopy: dim, still and humid, lit mostly by sunflecks. It is the habitat nearly every houseplant comes from.

V

variegation: Patches of leaf with little or no chlorophyll, so they read as white, cream or yellow. The pale tissue cannot feed itself, which is why a variegated plant grows more slowly than a plain one.