Plant glossary

Acclimate

Gradually getting a plant used to a new spot - especially more light - over a week or two, so it doesn't shock and drop leaves.

Aerial root

A root that grows above the soil, used by climbers like monstera to grip surfaces and take up moisture from the air.

Annual

A plant that completes its whole life cycle - germinating, flowering, setting seed and dying - within a single growing season. Many vegetables and bedding plants are annuals.

Aroid

A plant in the arum family - monstera, philodendron, pothos, anthurium. They like chunky, airy soil and bright indirect light.

Biennial

A plant that takes two growing seasons to complete its life cycle - leaves in the first year, then flowers and seed in the second. Foxgloves and some vegetables are biennial.

Bolting

When a plant rushes to flower and set seed prematurely, usually triggered by heat or stress. It turns leafy crops like lettuce and rocket bitter and tough.

Bottom watering

Standing a pot in a tray of water so the soil draws moisture up from below, encouraging deeper roots and even soaking.

Bulb

An underground storage organ made of fleshy leaf layers, holding food for the plant - onions, garlic, tulips and daffodils all grow from bulbs.

Chlorosis

Yellowing of leaves from a lack of chlorophyll - often caused by overwatering, poor light or a nutrient shortage.

Cotyledon

The first leaf or pair of leaves a seedling produces, part of the seed itself. The 'true leaves' that follow look like the mature plant's.

Cutting

A piece of stem or leaf taken to grow a new plant - the basis of propagation.

Damping off

A fungal disease that rots seedlings at soil level, making them keel over. It is caused by overwatering and poor airflow; clean tools and sowing thinly reduce the risk.

Deadheading

Removing faded flowers before they set seed, which encourages many plants to keep producing more blooms rather than putting energy into seed.

Dormancy

A natural rest period, usually in autumn and winter, when growth slows or stops. Water and feed much less during it.

Epiphyte

A plant that grows on another (or on bark) rather than in soil, taking moisture from the air - orchids and many ferns.

Etiolation

Pale, stretched, leggy growth caused by too little light, as the plant reaches for a brighter source.

Fertiliser (NPK)

Plant food. The three numbers are nitrogen (leaves), phosphorus (roots/flowers) and potassium (overall health).

Germination

The moment a seed sprouts and begins to grow, given the right warmth, moisture and sometimes light. Different seeds need different conditions to break dormancy.

Hardening off

Toughening up an indoor-raised plant before it goes outside, by exposing it to outdoor conditions a little at a time.

Humidity

The moisture in the air. Many tropical houseplants like it higher than a typical centrally-heated room provides.

Hydroponics

Growing plants in water and nutrients rather than soil.

Leggy

Stretched, sparse growth with long gaps between leaves - almost always a sign of too little light. See etiolation.

Loam

The ideal garden soil: a balanced, crumbly mix of sand, silt and clay that holds moisture and nutrients while still draining freely.

Mulch

A layer of material - compost, bark, straw or gravel - spread over the soil to lock in moisture, suppress weeds and protect roots.

Node

The point on a stem where leaves, buds or roots emerge. Cuttings need at least one node to root.

Peat-free

Compost made without peat, whose harvesting damages important carbon-storing bog habitats. Peat-free mixes based on bark, coir and wood fibre are the sustainable choice.

Perennial

A plant that lives for several years, often dying back in winter and regrowing each spring. Most houseplants and many garden flowers are perennials.

Perlite

Lightweight white volcanic granules added to soil to improve drainage and air flow around the roots.

pH (soil)

A measure of how acidic or alkaline soil is, on a scale of 0 to 14. Most plants prefer around 6 to 7; some, like blueberries, need acidic soil to thrive.

Photoperiod

The length of day and night a plant experiences, which triggers processes like flowering. 'Short-day' and 'long-day' plants respond to changing daylight through the year.

Photosynthesis

How plants turn light, water and carbon dioxide into the sugars they grow on. No light, no food.

Pinching out

Nipping off the growing tip of a stem to make a plant branch and grow bushier rather than tall and leggy. Common with herbs, tomatoes and many houseplants.

Propagation

Making new plants from cuttings, division, offsets or seed.

Pruning

Trimming a plant to shape it, remove dead growth, or encourage bushier new growth.

Repotting

Moving a plant to a new pot with fresh soil, usually one size up, when it outgrows its current home.

Rhizome

A thickened underground stem that stores energy and sends up new shoots - snake plants and ZZ plants grow from them.

Root-bound

When roots have filled the pot and started circling, leaving little soil. A sign it may be time to repot.

Soil mix

The blend a plant is potted in. Different plants want different mixes - airy for aroids, gritty for succulents.

Succulent

A plant that stores water in thick leaves or stems - cacti, aloe, echeveria. They want sun and infrequent watering.

Top dressing

A fresh layer of soil, compost or decorative material added to the surface of a pot.

Transpiration

The way plants release water vapour through their leaves - part of how they move water up from the roots.

Tuber

A swollen underground stem or root that stores energy, such as a potato or a dahlia. New plants sprout from its buds or 'eyes'.

Variegation

Patches of white, cream or other colours on leaves where there's less chlorophyll. Variegated plants often need more light.

Vermiculite

A spongy mineral added to soil to hold moisture and nutrients - often used for seed-starting.

Wilting

Drooping, limp growth. Usually thirst (perks up after water) but can also mean overwatering and root rot.

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