Table of Contents

Gardening Glossary

Last updated: May 2026

Gardening writing uses a substantial technical vocabulary, much of it unintuitive to the new gardener. This glossary defines the terms you will most often encounter on Explore Your Garden and in gardening writing more broadly. Definitions aim for usefulness over botanical perfection; where a term has a more precise scientific definition, we say so.

A–C

Annual: A plant that completes its full life cycle — germination, flowering, seed production, death — in a single growing season. Examples: marigolds, lettuce, basil, sunflowers (in temperate climates).
Bare root: A plant supplied without soil around the roots, usually during the dormant season. Roses, fruit trees, and many shrubs are commonly sold bare-root in winter; cheaper than container-grown and usually establish well if planted promptly.
Biennial: A plant with a two-year life cycle: vegetative growth in year one, flowering and seed production in year two, then death. Examples: foxglove, parsley, carrots (when grown for seed).
Bolt: When a plant prematurely produces flowers and seeds, usually in response to heat or stress. Lettuce that “bolts” becomes bitter and inedible; coriander bolts within weeks of warm weather.
Cold frame: A low, glazed enclosure used to protect plants from cold and to extend the growing season at both ends. Effectively a small unheated greenhouse at ground level.
Companion planting: The practice of growing different species near each other for mutual benefit — pest deterrence, pollinator attraction, soil improvement. Some claims are well-supported; others are folkloric. We try to distinguish in articles.
Compost: Decomposed organic matter, usually produced from plant waste, that improves soil structure and provides slow-release nutrients. The single most useful soil amendment for most gardens.
Crop rotation: The practice of growing different plant families in a given bed in successive seasons, to reduce soil-borne pest and disease pressure and to balance nutrient demands.
Cultivar: A “cultivated variety” — a plant variety that has been selected and propagated for specific traits and that retains those traits when reproduced. “Sungold” is a tomato cultivar; “tomato” is the species.

D–F

Damping off: A fungal disease of seedlings, in which the stem collapses at the soil line and the seedling dies. Triggered by over-wet conditions, poor air circulation, and contaminated containers. Prevent with clean trays, fresh seed-starting mix, and disciplined watering.
Deadheading: Removing spent flowers to encourage further blooming and prevent the plant from putting energy into seed production. Useful for many flowering annuals and perennials.
Direct sow: Sowing seeds directly into the soil where the plants will grow, rather than starting them indoors and transplanting later. Standard for root crops and beans; possible for many other crops in suitable climates.
Drainage: The rate at which water moves through soil. Good drainage is the property of soil that holds water long enough for roots to take it up but does not remain saturated.
Drip irrigation: A watering system that delivers water slowly through emitters at the soil level, reducing evaporation and avoiding wet foliage. Useful in dry climates and in row crops.
F1 hybrid: A first-generation hybrid produced by crossing two specific parent lines. F1 hybrids are typically vigorous and uniform but their saved seed does not reliably reproduce the same characteristics.
Frost date: The average date of the first or last frost for a given location. The last spring frost date determines when warm-season crops can safely go outdoors; the first autumn frost determines the end of the warm-season window.

G–L

Germination: The process by which a seed begins to grow into a seedling. Different seeds have different optimal germination conditions (temperature, moisture, light or dark).
Greenhouse: A glazed structure used to extend the growing season, protect tender plants, or cultivate species not suited to the outdoor climate. Heated greenhouses provide more control; unheated “cool” greenhouses extend the season at both ends.
Hardiness zone: A geographic zone defined by typical winter low temperatures, used to predict whether a perennial plant will survive the winter outdoors. The USDA system is used in North America; the RHS system is used in the UK and parts of Europe.
Hardening off: The process of gradually acclimatizing indoor-raised seedlings to outdoor conditions before transplanting, by increasing exposure to outdoor sun, wind, and temperature over a week or two.
Heeling in: Temporarily covering the roots of bare-root or potted plants with soil to keep them alive until they can be planted in their final location. Useful when ground conditions delay planting.
Heirloom: An open-pollinated cultivar with a long history of cultivation, typically pre-dating modern industrial breeding. Heirlooms can be saved-from-seed reliably (unlike F1 hybrids).
Humus: Stable, decomposed organic matter in soil, distinct from compost (which is in the process of decomposition). Humus contributes to soil structure and water retention.
Loam: A balanced mix of sand, silt, and clay, generally considered the most workable garden soil texture. Most amendments and improvements aim toward loam.

M–P

Mulch: A layer of material (organic: compost, bark, straw, leaf mold; inorganic: gravel, fabric) applied to the soil surface to suppress weeds, reduce evaporation, regulate temperature, and (for organic mulches) gradually improve soil.
NPK: Nitrogen, Phosphorus, Potassium — the three main macronutrients in fertilizers. Fertilizer labels list the percentages as three numbers (e.g., 10-10-10). Different plants and growth stages have different ideal ratios.
Organic gardening: A broadly defined approach that avoids synthetic fertilizers and pesticides, emphasizes soil health, and works with biological cycles. Specific certifications have stricter definitions.
Perennial: A plant that lives for more than two years. Some perennials are short-lived (3–5 years); some are long-lived (decades to centuries for trees).
pH: A measure of soil acidity or alkalinity on a 0–14 scale, with 7 being neutral. Most vegetable crops prefer pH 6.0–7.0. Some plants (blueberries, rhododendrons) need acidic soil; some tolerate alkaline.
Pinching out: Removing the growing tip of a plant to encourage branching and bushiness. Common with herbs (basil) and tomatoes (removing side shoots in indeterminate varieties).
Pollination: The transfer of pollen from male flower parts to female flower parts, enabling fertilization and seed/fruit production. Some plants are wind-pollinated, most are insect-pollinated, and a few are self-pollinating.
Potting on: Moving a young plant into a larger container as it outgrows its current one, so that root development can continue.
Propagation: The production of new plants, by seed, cutting, division, layering, grafting, or tissue culture. Different plants propagate best by different methods.
Pruning: The selective removal of branches or shoots to control plant size, shape, productivity, or health. Different plants need pruning at different times of year and in different ways.

R–X

Raised bed: A garden bed elevated above the surrounding ground level, often framed with timber or stone. Provides better drainage, easier access, and a clean break from poor underlying soil.
Rootball: The mass of roots and surrounding soil of a plant, especially as it appears when the plant is removed from a container or lifted from the ground for transplanting.
Self-seeding: When a plant produces seeds that drop and germinate to produce new plants without intentional sowing. Some annuals self-seed reliably year after year (calendula, foxglove, nasturtium).
Side dressing: Applying fertilizer or compost in a strip alongside an established row or plant, rather than mixing it into the soil at planting time.
Soil amendment: Any material added to soil to improve its physical or chemical properties — compost, leaf mold, sand, lime, gypsum, manure, biochar.
Sucker: A shoot arising from the base or roots of a plant, often vigorous and undesired (suckers from tomato plants are removed; suckers from grafted roses originate from the rootstock and produce different flowers).
Top dressing: Applying compost or fertilizer to the surface of soil around an established plant, allowing it to wash in gradually with watering.
Transplant: To move a plant from one location to another — from a seed tray to a larger pot, from a pot to the ground, or from one part of the garden to another.
True leaves: The leaves a seedling produces after the initial seed leaves (cotyledons). True leaves resemble the adult plant’s foliage and are the signal that the seedling is ready to be transplanted or thinned.
USDA hardiness zone: The North American hardiness-zone classification system, dividing the continent into zones based on average annual minimum winter temperature. See the official USDA map.
Vermicompost: Compost produced by worms (typically red wigglers) processing organic matter. Higher in plant-available nutrients than standard compost.
Xeriscaping: Garden design that minimizes water requirements, typically by selecting drought-tolerant plants and using mulches and water-efficient irrigation. Practical in arid and semi-arid regions and increasingly relevant elsewhere as climate patterns shift.

For broader gardening orientation, see our Beginner’s Gardening Guide. For specific terms not covered here, the Royal Horticultural Society’s online resources are an excellent reference. If a term you have encountered on our site is missing here, email info [at] exploreyourgarden [punto] site with the suggestion.

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