Reference

Plant-growing glossary

Plain-English definitions of the terms you'll meet growing plants indoors — the light, watering, soil and propagation jargon that's rarely explained. 68 terms, grouped by topic.

Light

Bright indirect light: A spot that's well lit but where the sun's rays don't land directly on the leaves, like a few feet back from a bright window or beside one with a sheer curtain. Most popular houseplants want this, and it's the safest default if you're unsure.
Dappled light: Light broken up into patches of sun and shade, like sunlight coming through leaves or a slatted blind. It mimics the conditions under a forest canopy that many houseplants evolved in.
Direct sun: Sunlight that falls straight onto the plant with nothing in the way, usually right on a sunny windowsill. Edibles like tomatoes, basil, and peppers need several hours of it, but many leafy houseplants will scorch in it.
Grow light: An electric lamp that gives plants the light spectrum they need to grow indoors. Useful in flats with dark rooms or short winter days, and it lets you grow herbs or seedlings away from a window.
Low light: A spot far from windows or one that only gets weak, filtered daylight. Few plants truly thrive here; most labelled "low light" only tolerate it, so growth slows and edibles generally won't produce.
North-facing window: A window facing north (in the northern hemisphere) that gets steady but indirect light and no direct sun. Good for shade-tolerant foliage plants, too dim for most fruiting edibles.
South-facing window: A window that faces south (in the northern hemisphere) and gets the most direct sun through the day. It's the brightest spot in most homes and the best place for sun-hungry edibles.

Water

Bottom watering: Watering by sitting the pot in a tray of water and letting the soil soak it up through the drainage hole. It encourages roots to grow downward and avoids splashing the leaves or compacting the surface.
Drainage hole: The hole in the bottom of a pot that lets excess water escape. Without one, water pools at the bottom and rots the roots, so it's the single most important feature to check when buying a pot.
Drought-tolerant: Describes plants that cope with dry soil and infrequent watering, like cacti, succulents, and snake plants. A good fit if you travel or tend to forget watering.
Humidity: The amount of moisture in the air. Many tropical houseplants want higher humidity than a typical heated or air-conditioned flat provides, which can show up as crispy leaf edges.
Misting: Spraying a fine mist of water over the leaves, often done to raise humidity. The effect is brief and minor; a humidity-loving plant does better with a humidifier or a pebble tray than with misting.
Overwatering: Giving a plant more water than it can use, so the soil stays wet and the roots suffocate or rot. It's the most common way beginners kill houseplants, and the fix is usually watering less often, not more.
Waterlogged: Soil so saturated that water fills the spaces roots need for air. It usually comes from watering too often or a pot with no drainage, and it leads to root rot.

Soil

Coco coir: A growing medium made from coconut husk fibre, sold as bricks that expand in water. It's a peat-free way to hold moisture and is common in seed-starting and houseplant mixes.
Mulch: A protective layer spread over the soil surface, such as bark, gravel, or compost. It slows water loss and keeps roots steadier in temperature, useful for pots that dry out fast.
Perlite: Small white volcanic-glass granules mixed into potting soil to keep it loose and airy. It creates pockets for air and drainage, which helps prevent the soggy soil that causes root rot.
Potting mix: A bagged blend made for growing plants in containers, lighter and more open than garden soil. Don't use soil dug from outside in pots, as it compacts and drains poorly indoors.
Repotting: Moving a plant into a new pot, usually one size larger, with fresh mix. Most plants need it every year or two as they outgrow their container or use up the soil.
Root-bound: When a plant's roots have filled the pot and started circling the edges with little soil left. Signs include roots poking out the drainage hole and soil that dries out very quickly; it means the plant needs repotting.
Top dressing: Adding a layer of material such as compost, grit, or bark to the soil surface in a pot. It can feed the plant slowly, improve the look, or help keep moisture in.
Vermiculite: A spongy mineral added to soil to hold moisture and nutrients. It's often used for starting seeds because it keeps the mix evenly damp without becoming waterlogged.
Well-draining soil: A potting mix that lets water flow through quickly instead of staying soggy, so roots get air and don't rot. You improve drainage by adding perlite and always using a pot with a hole in the bottom.

Plant parts

Bulb: A rounded underground storage organ made of layered leaves, as in onions and garlic. It holds enough energy for the plant to sprout and grow on its own.
Crown: The point where a plant's stems meet its roots, usually at soil level. Burying the crown too deep or keeping it wet can cause rot, so it's worth keeping it at the surface when potting.
Etiolated: The technical word for the pale, stretched, weak growth a plant puts out when it lacks light. It's the more extreme version of leggy and is fixed by giving more light.
Internode: The length of bare stem between two nodes. Long, stretched internodes are a sign a plant isn't getting enough light.
Leaf node: The spot on a stem where a leaf attaches and new growth can emerge. When taking a cutting, you cut just below a leaf node because that's where roots will form.
Leggy: When a plant grows long, thin, and sparse with wide gaps between leaves, usually because it's reaching for more light. Moving it somewhere brighter and pinching it back helps it bush out.
Node: The point on a stem where leaves, buds, or roots grow from. It matters for propagation, since most cuttings only root if they include at least one node.
Offset: A small baby plant, also called a pup, that grows at the base of a parent plant. Once it has a few roots you can separate it to grow on its own.
Rhizome: A thickened stem that grows horizontally underground and sends up new shoots, as in ginger and many ferns. You can cut a piece with a bud to start a new plant.
Rosette: A circular, ground-hugging arrangement of leaves growing from a central point, as seen in succulents and lettuce. Water aimed at the centre can collect and cause rot.
Runner: A stem that grows sideways along or above the soil and sprouts new plantlets at its tip, classic in strawberries and spider plants. You can pin these down or pot them to make free new plants.
Tuber: A swollen underground stem that stores energy, like a potato. It can sprout new plants from its "eyes," which is why a potato regrows from scraps.
Variegation: Patches of white, cream, or other colours on leaves where green pigment is missing. Variegated plants often grow more slowly and need brighter light to keep their markings.

Growing

Bolting: When a leafy plant like lettuce or basil suddenly shoots up a flower stalk and goes to seed, often in heat. The leaves usually turn bitter, so harvest before it happens or pinch off the flower stalks early.
Cutting: A piece of stem or leaf removed from a plant and rooted to grow into a new one. Many herbs and houseplants root in a glass of water on the windowsill.
Deadheading: Removing faded or spent flowers from a plant. It tidies the plant and often pushes it to produce more blooms instead of setting seed.
Division: Splitting one mature plant into two or more, each with its own roots and shoots. It's the easiest way to multiply clumping plants and to tidy one that's outgrown its pot.
Hardening off: Gradually getting an indoor-raised plant used to outdoor conditions over a week or two before planting it out. Skipping this step shocks the plant with sudden sun, wind, and cold; relevant if you have a balcony or windowsill that opens out.
Pinching: Nipping out the soft growing tip of a stem with your fingers to make the plant branch and grow bushier. It keeps herbs like basil full and stops them getting straggly.
Potting up: Moving a plant into a slightly bigger pot to give roots more room to grow. Going up one size at a time avoids leaving the roots sitting in a large mass of wet, unused soil.
Propagation: Making new plants from an existing one, by cuttings, division, seed, or offsets. It's a cheap, satisfying way to fill a small space without buying more plants.
Pruning: Cutting back stems or leaves to control a plant's size and shape or remove damaged growth. Light pruning keeps a plant manageable in a small space and can encourage fuller growth.
Succession sowing: Sowing small batches of seed every couple of weeks instead of all at once. It gives you a steady supply of salad or herbs rather than a glut followed by nothing, which suits a small windowsill.
Thinning: Removing some young seedlings so the remaining ones have room to grow. Crowded seedlings compete for light and water and stay weak, so it feels wasteful but pays off.

Edibles

Companion planting: Growing certain plants near each other in the belief they help one another, such as basil beside tomatoes. Some pairings help with pests or pollinators; the evidence is mixed, so treat it as a guideline rather than a rule.
Cut-and-come-again: A way of harvesting leafy crops by snipping the outer leaves and leaving the centre to keep growing. Lettuce, spinach, and many herbs let you pick repeatedly from one plant for weeks.
Days to harvest: The rough number of days from sowing or planting until a crop is ready to eat, usually printed on seed packets. It helps you plan and set expectations, though indoor conditions can make it slower.
Microgreens: Young, edible seedlings harvested within a week or two of sprouting, when they're a couple of centimetres tall. They grow fast on a windowsill in a shallow tray and are one of the easiest indoor edibles for beginners.
Regrow from scraps: Growing new food from kitchen offcuts, like sprouting spring onion roots or lettuce bases in water. It's a fun, free experiment, though yields are usually small.

Problems

Aphids: Tiny soft-bodied insects, often green or black, that cluster on new growth and suck sap. They multiply fast but wipe off easily with a damp cloth or a spray of soapy water.
Chlorosis: Yellowing of leaves while the veins often stay green, caused by a lack of nutrients, poor drainage, or wrong soil. It's a signal to check watering and feeding before assuming the worst.
Damping off: A fungal problem that makes seedlings suddenly collapse and rot at the base of the stem. It's brought on by overly wet, stagnant conditions, so good airflow and not overwatering help prevent it.
Fungus gnats: Small black flies that hover around houseplants and breed in damp soil. They're mostly a nuisance rather than a serious threat, and letting the top of the soil dry out between waterings breaks their cycle.
Leaf scorch: Brown, dry, or bleached patches on leaves caused by too much direct sun or heat. Moving the plant out of harsh midday sun usually stops it spreading.
Mealybugs: Slow-moving pests that look like small blobs of white cotton-wool tucked into leaf joints. Dab them with cotton dipped in rubbing alcohol and check nearby plants, as they spread.
Nutrient burn: Damage from too much fertiliser, showing as brown, crispy leaf tips or edges. Feed at the recommended strength or weaker, since it's easier to add more than to undo an overdose.
Root rot: When roots decay because the soil has stayed too wet, usually from overwatering or poor drainage. Signs are wilting, yellowing, and a sour smell from the soil; it's the leading cause of houseplant death.
Spider mites: Minuscule sap-sucking pests that leave fine webbing and pale speckling on leaves, thriving in dry indoor air. Raising humidity and rinsing the plant helps keep them down.

General

Annual: A plant that completes its whole life in a single growing season, then dies. Many edibles like basil, lettuce, and tomatoes are annuals, so you resow them each year.
Biennial: A plant that takes two growing seasons to complete its life, usually leaves in the first year and flowers and seed in the second. Parsley and carrots are biennials.
Cultivar: A specific variety of a plant bred and selected by people for particular traits, like a sweeter tomato or a more compact basil. The name usually appears in quotes after the plant name on labels.
Hybrid: A plant created by crossing two different parent varieties, often labelled F1. Hybrids can be vigorous and uniform, but seed saved from them won't reliably grow the same plant.
Perennial: A plant that lives for several years, regrowing each season. Herbs like mint, rosemary, and chives are perennials, so one plant can keep producing for years.
Pollination: Moving pollen so a flower can develop into fruit or seed, normally done by insects or wind. Indoors you may need to help by gently shaking the plant or dabbing flowers with a small brush.
Self-fertile: A plant that can pollinate itself and set fruit without a second plant nearby. It's handy indoors, where pollinating insects are scarce, as with most tomatoes and chillies.