Glossary

Soil with a pH below 7, suited to ericaceous plants like rhododendrons and camellias, which can't take up nutrients properly in alkaline conditions.

Soil with a pH above 7, often chalky; unsuited to ericaceous plants unless grown in a pot with adjusted compost.

A plant that completes its whole lifecycle, from germination to seed, within one growing season, then dies.

A small sap-sucking insect (greenfly or blackfly) that clusters on soft growth, weakening it and sometimes spreading plant viruses.

The bud at the very tip of a stem; its growth suppresses side shoots until it's removed by pinching.

A plant in the arum family (Araceae), such as Monstera or peace lily; usually needs airy, free-draining compost.

A plant sold with soil removed from its roots, typically a deciduous tree, shrub, hedging plant or rose, planted while dormant.

A plant grown for a single season of temporary display, then removed or discarded once flowering finishes.

A plant completing its lifecycle over two growing seasons, usually flowering and setting seed only in its second year.

When a plant flowers and sets seed prematurely, usually triggered by stress such as heat, drought or overcrowding.

A modified, often colourful leaf surrounding a flower; the showy 'petals' of Cornus kousa and poinsettia are actually bracts.

A fungal condition, often following leafhopper egg-laying damage, that causes flower buds to brown and fail to open.

Cutting back late-summer perennials by around a third in late spring, to delay flowering and produce a bushier, sturdier plant.

Encouraging seed potatoes to sprout short shoots in a light, cool place before planting them out.

Yellowing of leaves, often between the veins, caused by a nutrient deficiency, commonly from unsuitable soil pH.

A small clear cover placed over young plants to protect them from cold and encourage earlier growth.

Decomposed organic matter used to improve soil structure and fertility, distinct from potting compost used in containers.

A swollen underground stem base (e.g. crocosmia, crocus) that stores energy, functioning similarly to a bulb.

The point where a plant's roots and top growth meet, usually at or just below soil level.

A plant variety produced through cultivation and selection, shown in single quotes after the species name.

A fungal disease that kills seedlings at soil level, usually caused by overwatering, overcrowding or poor airflow.

Removing spent flowers to prevent seed formation and, in many plants, encourage further flowering.

A plant that drops all its leaves at the end of the growing season, typically in autumn.

Having separate male and female plants of the same species; sometimes both are needed for the female to produce berries.

Removing some flower buds to direct a plant's energy into fewer, larger blooms.

Propagating a plant by splitting an established clump into smaller, separately rooted sections.

A resting state, usually over winter, when a plant's growth slows or stops almost completely.

How freely water passes through soil or compost; poor drainage causes waterlogging and root rot.

Describing acid-loving plants, or the lime-free compost formulated specifically for growing them.

Pale, stretched, weak growth caused by insufficient light, as a plant reaches towards a brighter source.

A plant's aspect and light/wind conditions at a site, typically described as sun, part shade or shade.

A lightweight, breathable fabric used to protect plants from frost and cold wind without excluding light or air.

Encouraging a plant, often a bulb, to flower earlier than its natural season, usually with extra warmth.

Early pruning of a young tree or shrub to establish a strong, well-shaped branch framework.

A low-lying area where cold air collects, making frost more likely and more severe than on surrounding ground.

A taxonomic grouping of related species; the first word in a plant's Latin name (e.g. Rosa).

A propagation method joining the stem of one plant onto the root system of another, common in roses and fruit trees.

A fast-growing crop sown to cover and improve bare soil, then dug in before it sets seed.

Able to survive most winters outdoors in mild areas or with protection, but vulnerable to hard frost.

Gradually acclimatising a plant raised indoors or under cover to outdoor conditions before planting it out.

The RHS H1a–H7 scale describing the minimum temperature a plant can be expected to survive.

Able to survive outdoors year-round in the local climate without protection.

A non-woody plant whose top growth typically dies back to the ground each year.

The dark, stable organic matter in soil formed from decomposed plant and animal material, improving structure and fertility.

A plant resulting from crossing two different species or varieties.

A standardised loam-based potting compost formula, available in different nutrient strengths for different growth stages.

The average dates marking the end of spring frost risk and the start of autumn frost risk in a given area.

Compost made purely from decomposed leaves, valued as a soil conditioner and seed-sowing ingredient.

Describing weak, elongated, sparse growth, usually caused by insufficient light.

A well-balanced soil type containing a mix of sand, silt and clay, considered ideal for most plants.

A small area with growing conditions distinct from the surrounding district, such as a sheltered courtyard.

A layer of material spread over soil to retain moisture, suppress weeds and moderate soil temperature.

A general-purpose growing medium suited to most everyday potting and sowing tasks.

The point on a stem where a leaf, bud or shoot arises.

The nitrogen, phosphorus and potassium ratio shown on fertiliser packaging, indicating its balance of plant nutrients.

A small plantlet produced naturally at the base of a parent plant, which can be detached and grown on separately.

Describing compost made without peat, in line with the UK's move away from peat extraction for horticulture.

A plant that lives for more than two years, typically flowering repeatedly each year.

Removing the soft growing tip of a stem to encourage bushier, more branched growth.

Describing a plant whose roots have filled and circled its pot, needing a larger container or root loosening.

Moving a plant into a larger pot as it outgrows its current one.

Transplanting seedlings from a crowded seed tray into individual pots or wider spacing.

Creating new plants from an existing one, by seed, cuttings, division or other methods.

Replacing a plant's pot and often its compost, whether moving up in size or refreshing at the same size.

A thickened underground stem that grows horizontally, storing energy and producing new shoots along its length.

The root system and lower stem onto which a different variety is grafted.

A circular cluster of leaves radiating from a central point, typical of succulents like Echeveria.

Browning or crisping of leaf tissue caused by too much sun, wind, heat, cold or chemical strength.

A plant's tendency to drop seed that germinates freely nearby without deliberate sowing.

Propagation cuttings taken from young flexible growth, partly firmed growth, or fully mature dormant growth respectively.

A large modified leaf or bract surrounding a flower spike, typical of aroids like anthurium and peace lily.

A plant trained with a clear stem topped by a rounded head of growth, such as a standard rose.

A shoot arising from a plant's roots or rootstock, often below a graft union, and usually removed.

Replacing the top layer of compost in a large pot with fresh material, without full repotting.

A cluster of flowers or fruit borne on a single stalk, as in rhododendrons or tomatoes.

A swollen underground stem or root (e.g. dahlia, potato) that stores energy and can produce new shoots.

Irregular colouring or patterning on leaves, often white or yellow alongside green, from a genetic or occasionally viral cause.

Soil or compost saturated with water for a prolonged period, depriving roots of the oxygen they need.

A young, unbranched, single-stemmed tree, typically sold bare-root, planted to be trained into shape.

A hedge, fence or screen used to reduce wind speed and its damaging or drying effect on plants.