JERRY COLEBY-WILLIAMS explains common gardening and natural pest and disease terms that will make reading our magazine and other gardening information easier. It will also mean you can speak with more assurance when asking for products and plants at garden centers.

Glossary of terms

General gardening

Soil and cultivation terms

Acid soils have pH readings below 6.5 (see pH). Lime-hating (ericaceous or calcifuge) plants grow best in these conditions. Most Australian soils lean acidic, but you can improve them by cultivating and adding lime or dolomite.

Aerobic describes compost heaps where oxygen-dependent organisms drive the composting process.

Alkaline soils show pH readings above 7.4 and contain higher levels of lime. These soils suit lime-loving (calcicole) plants, including many vegetables like brassicas and onions. To reduce pH, you can add compost, pine needles, bark mulch, iron chelates or iron sulphate.

Anaerobic refers to composting conditions where organisms thrive in the absence or near-absence of oxygen.

Arborists specialise in tree care, including planting, pruning, diagnosing, and treating tree health issues. Don’t confuse arborists with tree loppers, who lack formal qualifications.

Bolting happens when a plant flowers early, often triggered by drought, poor nutrition, or heat stress.

Broadcasting involves scattering seeds (like salads) by hand across a prepared seedbed, then lightly raking or covering with soil or mulch before watering.

Bulbs store food underground and typically resemble a large bud enclosed in scales — for example, lily bulbs. People often misuse this term to describe corms, tubers and rhizomes.

Backfilling means returning soil to a planting hole after placing a plant in it.

Blanching keeps sunlight off selected food plants (like celery or cardoon), producing pale, tender and more palatable stems or leaves.

Catch crops, such as radish or salad greens, grow quickly in fallow soil between primary crops.

Compost comes from either home-decomposed garden waste or purchased ready-to-use. Look for certified organic composts at nurseries or hardware stores.

• Hot composting involves building a large heap (about one cubic metre) to generate heat, which kills weed seeds and pathogens.

• Cold composting allows materials to decompose at ambient temperatures — but won’t destroy seeds, bulbous weeds, or pathogens.

Compost tea is a liquid fertiliser made by steeping mature compost in water and filtering it. For best results, brew in an aerated container.

Cover crops like millet or barley protect bare soil from erosion and help suppress weeds.

Corms store food in a thickened stem base. Planted like bulbs, they produce new corms each season.

Crocks (broken terracotta pot pieces) cover pot drainage holes, reducing soil loss while maintaining drainage. Avoid using stones or bark, which can block drainage and cause root rot.

Culm refers to a bamboo stem — bamboo belongs to the grass family.

Cuttings are sections of root, stem or leaf taken to propagate a new plant.

Deadheading means removing spent flowers to tidy plants and prevent them from setting seed, which encourages prolonged blooming.

Division involves splitting or pulling apart a large clump of a plant into smaller parts to create new plants.

Deciduous plants drop all their leaves during dormancy. This may happen in winter or during dry seasons, as with strangler figs.

Espalier is a training technique that grows trees or shrubs flat against a support, creating a space-saving structure. Apples and pears are commonly espaliered.

Evergreens retain their leaves year-round. Some shed older leaves gradually; others drop and regrow their foliage with seasonal changes, like avocados.

Foliar feeding involves spraying diluted liquid fertiliser (e.g. seaweed) directly onto leaves, allowing plants to absorb nutrients efficiently. Use this method to feed plants growing under large trees.

Grafting joins two or more woody plants — typically a rootstock and a fruiting or flowering topstock — to create one productive plant. Grafts may fail over time if tissues don’t integrate fully.

Green manure crops (such as barley or lentils) improve soil by being dug in at a young stage to boost fertility or organic matter.

Grey water comes from household sources like sinks, baths, and laundry. You can reuse it in the garden if it’s free of fats, oils and harsh chemicals, but always check local regulations.

Gypsum (calcium sulphate) adds calcium and improves clay or sodic soils. It doesn’t affect pH.

Hardening off prepares plants grown under cover for outdoor conditions by gradually exposing them to wind, sun, and temperature changes.

Heirloom plants are varieties passed down for generations (often 50+ years). Gardeners prize heirloom tomatoes for their flavour and diversity.

Herbaceous plants have soft, non-woody stems. These perennials die back in winter and regrow in spring from buds near or below ground.

Inorganic substances, like synthetic fertilisers, don’t originate from once-living material.

Intercropping (or interplanting) grows two or more crops together, often mixing tall and short plants to boost productivity and diversity. Corn and beans are a classic combination.

Manure tea works like compost tea but uses aged animal manure steeped in water. Use a hessian sack or old pillowcase to contain the manure while soaking.

Micronutrients, or trace elements, support plant health in tiny amounts. Apply carefully — too much boron, for example, can harm plants as much as too little.

Mulch is a surface layer that retains moisture and controls weeds. Organic mulches (straw, bark, compost) enrich the soil; inorganic options (gravel, sand) don’t decompose but help suppress weeds.

Open-pollinated plants reproduce through natural means (e.g. bees, wind), producing offspring true to type. They’re generally more resilient and need less input than hybrids.

Organic gardening uses materials derived from living organisms and avoids synthetic chemicals. Always look for certification from an accredited body.

Permaculture combines traditional methods with modern sustainability practices. Founded by Australians Bill Mollison and David Holmgren, this holistic approach includes ethical food systems, urban gardening, and shared resources.

pH measures the acidity or alkalinity of soil or compost. The scale ranges from 0 (very acidic) to 14 (very alkaline), with 7 as neutral. Most plants thrive in slightly acidic soil (pH 6.5–7), where nutrients are most available.

Potting on/up involves moving a growing plant into a larger container to give its roots more room to expand.

Pricking out means carefully lifting and transplanting seedlings into separate pots or garden beds once they’ve sprouted.

Seedbed refers to a well-prepared garden bed for germinating seeds. It should be level, weed-free, and free from large clumps or debris.

Slow-release fertiliser provides nutrients steadily over time. Mineral rock dusts are a common example.

Tamping presses soil firmly around a newly planted plant to help support it and ensure good root contact.

Tilth describes finely crumbled, workable topsoil — ideal for sowing seeds.