Gardening Glossary: Jargon in Plain English

Gardening has a lot of jargon, but most of it is handy shorthand once you know what it means. This glossary explains the words you’ll find on seed packets, plant labels and feed boxes in one plain line each, with a typical UK example.

Use it as a quick reference while you garden. If you’re just starting out, the guide to gardening for beginners walks you through your first season step by step.

Why does gardening have so much jargon?

Gardening words pack a lot into a few letters. “Prick out into 9cm pots when seedlings have two true leaves” is a whole instruction in one line. The trouble is that seed packets and labels assume you already know the code.

Seed packets pack a lot of jargon into a few lines. Once you know the words, the instructions are simple.

The terms below are grouped by job: sowing, pruning, soil, planting and problems. Each table gives the word, what it means and an example.

Sowing and propagation terms explained

These words cover the journey from seed packet to a plant ready for the garden.

Hardening off: trays go out by day and back under cover at night until the plants are used to outdoor life.

Term	What it means	UK example
Germination	A seed sprouting into life.	Tomato seed coming up in a warm propagator
Seed leaves	The first pair of leaves a seedling shows, which look different from the rest.	The round first leaves on a courgette
True leaves	The leaves that follow, shaped like the adult plant’s.	The jagged leaves that follow on a tomato
Pricking out	Moving seedlings from a shared tray into their own pots or modules.	Cosmos seedlings moved into module trays
Potting on	Moving a plant into a bigger pot as it grows.	Tomatoes moved from 9cm pots to larger ones
Module tray	A tray divided into small cells, one plant per cell.	Lettuce and leeks sown in modules
Propagator	A covered tray, often heated, that keeps seeds warm and humid.	Starting chillies in February
Hardening off	Getting indoor-raised plants used to outdoor life over a few weeks.	Bedding plants out by day in May
Direct sowing	Sowing seed straight into the ground where it will grow.	Carrots and parsnips in a drill
Drill	A shallow groove in the soil for sowing seed in a line.	A 1cm drill for radishes
Chitting	Letting seed potatoes sprout in a light, cool place before planting.	Early potatoes on a windowsill in February
Cutting	A piece of stem or root used to grow a new plant.	Lavender cuttings taken in summer

Pricking out, potting on and hardening off do most of the work. The guide to sowing seeds indoors shows the whole journey, and the hardening off guide gives a simple day-by-day plan.

Pricking out in practice: ease the roots up with a dibber and hold the seedling by a leaf, never the stem.

What do pruning terms mean?

Pruning words describe either a cut or the part of the plant you’re cutting. Once you can tell a leader from a lateral, pruning instructions make far more sense.

Term	What it means	UK example
Deadheading	Removing faded flowers so the plant makes more flowers instead of seed.	Roses and sweet peas in summer
Pinching out	Nipping off a soft growing tip so the plant bushes out.	Sweet peas pinched when about 10cm tall
Stopping	Removing the main tip to stop upward growth.	Outdoor tomatoes stopped after four or five trusses
Leader	The main central stem of a tree or shrub.	A young apple tree’s main upright stem
Lateral	A side shoot growing from a main stem.	Side shoots removed from cordon tomatoes
Spur	A short, stubby shoot that carries fruit buds.	Spur-pruned apples in winter
Coppicing	Cutting a shrub or tree close to the ground so it regrows with new stems.	Hazel cut down every few years
Pollarding	Cutting back to a permanent framework at head height or above.	Willows and limes on streets
Crown	The branch framework of a tree, or the point where stems meet roots on a perennial.	Planting a peony with its crown shallow
Water shoots	Fast, upright, sappy shoots that sprout after hard pruning.	A thicket of shoots on a hard-cut apple

Knowing when to prune each plant matters more than the cut itself. The year-round pruning calendar gives the right month for common garden plants.

Cut just above an outward-facing bud with a slight slope, so the new shoot grows out rather than into the middle.

What do NPK, ericaceous and tilth mean?

Soil words are the densest jargon in gardening, and the most worth learning. These cover what soil is, what you add to it and what the feed box is telling you.

Term	What it means	UK example
Loam	Soil with a good balance of sand, silt and clay.	Crumbles in the hand, neither sticky nor gritty
Tilth	A fine, crumbly soil surface ready for seed.	Raked down before sowing carrots
pH	How acid or alkaline soil is, with 7 as neutral.	Most veg like it slightly acid to neutral
Ericaceous	Lime-free, for acid-loving plants and the compost they need.	Blueberries and rhododendrons
Organic matter	Anything once living, added to feed and improve the soil.	Manure, compost, leaf mould
Mulch	A layer spread over the soil to hold moisture and smother weeds.	Bark chips round shrubs in spring
Leaf mould	Crumbly soil improver made from rotted leaves alone.	Bagged autumn leaves, ready in a year or two
Green manure	A crop grown to cover and feed the soil, then dug in or cut down.	Phacelia sown after early potatoes
NPK	The amounts of nitrogen, phosphorus and potassium in a feed.	Tomato feed is high in potassium
Top dressing	Adding compost or feed to the surface without digging it in.	Fresh compost on top of pots in spring
Liquid feed	Fertiliser mixed with water so plants take it up quickly.	Weekly tomato feed once flowers appear
No-dig	Leaving soil undisturbed and adding compost on top instead.	A layer of compost spread each autumn

To find out what your own soil is like, try the simple tests in the guide to UK soil types.

The jam-jar test: shake soil with water and let it settle. Sand sinks first, then silt, with clay settling last on top.

Planting terms: what the label is telling you

A plant label squeezes a lot into a few words. These terms decode most of it, from how the plant is sold to whether it will survive winter.

Bare-root means no pot and no compost. Soak the roots and plant them while they’re dormant in winter.

Term	What it means	UK example
Hardy	Survives a UK winter outdoors without protection.	Most herbaceous perennials and native shrubs
Half-hardy	Damaged by frost, so it goes out after the last frost.	Dahlias and bedding, planted out in late May
Tender	Needs warmth and shelter, often all year.	Pelargoniums brought in for winter
Annual	Grows, flowers, sets seed and dies within a year.	Cosmos, sweet peas, courgettes
Biennial	Grows leaves in year one and flowers in year two.	Foxgloves and wallflowers
Perennial	Lives for three years or more, usually flowering each year.	Hardy geraniums
Herbaceous	Soft growth that dies down to the ground in winter.	Delphiniums vanishing in autumn
Deciduous	Drops its leaves each autumn; evergreen plants keep them.	Beech is deciduous, holly is evergreen
Bare-root	Sold dormant with no pot or soil, from late autumn to early spring.	Hedging plants and roses
Root ball	The mass of roots and compost that comes out of the pot.	Soak it well before planting
Pot-bound	Roots circling the pot because the plant has outgrown it.	Tease the roots loose when planting
Plug plant	A small young plant grown in a module and sold cheaply.	Bedding plugs in spring
Firming in	Pressing soil round a new plant to remove air pockets.	Gentle pressure with your hands or heel
Graft union	The bulge where a chosen variety joins a rootstock.	A rose’s graft union sitting at soil level

Hardy only describes frost tolerance. A hardy plant can still die from sitting in cold, wet soil all winter. The RHS rates hardiness from H1 (needs heated glass) to H7 (very hardy), and you’ll see these ratings on many labels and on the RHS website. The guide to planting bare-root trees covers what to do when a bare-root order arrives.

Problem terms: decoding what went wrong

Problem words matter because the diagnosis is in the word. Knowing that stretched seedlings are “leggy” tells you to give them more light.

That tall stem is bolting. The leaves turn bitter, so pick what you can and sow a fresh row.

Term	What it means	UK example
Bolting	A vegetable flowering and setting seed before you can harvest it.	Lettuce in a hot, dry July
Damping off	A disease that makes seedlings collapse at soil level.	Seedlings sown too thickly and kept too wet
Blight	A fungus-like disease that browns and rots potatoes and tomatoes in warm, wet weather.	Outdoor tomatoes in a muggy August
Rust	A fungal disease that leaves orange-brown spots on leaves.	Leeks after a damp summer
Canker	A sunken, dead patch on bark or stems that slowly spreads.	Apple canker on a branch
Chlorosis	Leaves turning yellow, often with green veins, from a nutrient shortage.	Acid-loving plants in limy soil
Leggy	Pale, stretched growth from too little light.	Windowsill seedlings leaning towards the glass
Biological control	Using a pest’s natural enemy instead of a chemical.	Nematodes watered on for slugs in spring
Systemic	A product the plant absorbs and moves around inside itself.	Glyphosate weedkiller works this way

Many problems are easier to prevent than cure. Moving crops to a new bed each year helps starve soil pests and diseases, and the crop rotation planner shows how.

Common mistakes when reading gardening jargon

• Assuming hardy means indestructible. Hardy only means frost-tolerant. Plenty of hardy plants die from cold, wet roots.
• Treating all compost as one thing. Seed compost, multipurpose, ericaceous and garden compost are different products. Blueberries struggle in ordinary multipurpose compost.
• Mixing up deadheading and cutting back. Deadheading removes faded flowers in summer. Cutting back removes whole stems, usually in autumn or spring.
• Skipping “harden off”. It’s the most skipped line on a seed packet, and the reason many trays of young plants struggle once they go outside.
• Confusing chitting with germination. Chitting is for seed potatoes. Germination is a seed sprouting in compost or soil.

Frequently asked questions

What does hardening off mean?

It means getting indoor-raised plants used to outdoor life gradually. Stand trays outside by day and bring them in at night for two to three weeks. Leave them out for longer each time, then overnight once frosts are over. Skipping it can leave plants scorched or stunted.

What is the difference between compost and mulch?

Compost is rotted organic matter; mulch is anything spread over the soil surface. Compost can be used as a mulch, but so can bark, gravel or straw. Mulch describes the job, not the material. A 5-7cm layer holds in moisture and smothers many weeds.

What does pricking out mean?

It means moving seedlings from a shared tray into their own pots or modules. Do it once they have their first true leaves. Hold each seedling by a leaf, never the stem, as a damaged stem rarely recovers.

What do the NPK numbers on fertiliser mean?

They show the amounts of nitrogen, phosphorus and potassium in the feed. Nitrogen feeds leafy growth, phosphorus helps roots, and potassium helps flowers and fruit. Tomato feeds are high in potassium, while lawn feeds are high in nitrogen.

What is bolting in vegetables?

Bolting is when a vegetable flowers and sets seed before you can harvest it. Lettuce, spinach, rocket and onions are the usual culprits. Heat, dry soil or a cold snap can trigger it. Bolted leaves turn bitter, so pick what you can and sow again.

What does bare-root mean?

Bare-root plants are sold dormant with no pot and no soil round the roots. They’re available from late autumn to early spring and are usually cheaper than potted plants. Roses, hedging and fruit trees are the usual bare-root buys. Plant them promptly so the roots don’t dry out.

Now the jargon makes sense, put it to work with the guide to starting a vegetable garden, or browse more how-to guides.