the glossary

Terminology

A page dedicated to explaining the horticultural terminology you are likely to encounter in your quest to grow your own at home!

Seeds, Bulbs & Tubers

Vegetables are commonly grown from seed, bulb or tuber. Seeds range in size from tiny dots you can barely see, such as Rocket, to substantial vessels like a Broad Bean. Bulbs tend to be more substantial than seeds, garlic is a good example of a bulb. Tubers tend to be larger again, potatoes are a good example (although perhaps slightly confusingly, they are often sold as 'seed potatoes' as opposed to 'tubers').

Germination & Propagation

Germination refers to the process by which a seed begins to grow and sprout roots and shoots in order to produce a new plant. The term can also be applied to bulbs and tubers.

Propagation is simply the process of producing new plants from existing ones. The most common methods are to grow from seed/bulb/tuber, by taking cuttings from a parent plant, or by dividing a mature plant into several pieces.

Plug Plants & 'Starts'

In the UK we call these plugs, or plug plants, but you may also come across the use of the term 'starts' which is how they're referred to in the USA and Canada. They are the same thing; seedlings (baby plants) that have been grown in a small container (often a module tray, or small pot) ready to be transplanted into the ground or a larger container.

Transplanting & Potting On

This describes the act of moving a plant from one location to another. Typically in vegetable gardening, we are referring to transplanting a seedling from a module tray into a raised bed, or from a seed bed into its final growing location.

Whilst potting on does fit the wider definition of transplanting, it is used as a more specific term for moving a plan from it's current container (pot!) into a larger one.

Module Trays & Seed Trays

Seeds are often sown into seed trays or module trays to enable them to be brought undercover (e.g. greenhouse, coldframe, house, shed) and allow seedlings to germinate and start growing (usually for a period of several weeks) in a more controlled environment where there are no pests such as slugs and snails, and where conditions (such as the temperature) are generally more favourable.

Seed trays differ from module trays in that module trays contain a module/compartment for each individual plant (or clump of plants if multisowing - sowing multiple seeds together), whereas seed trays provide an undivided space for seeds to germinate and seedlings grow.

Pricking out

If a seed tray is used, the seedlings will need pricking out in order to separate them and provide them each with more space to grow. Traditionally, the growing medium (usually seed compost) is loosened with a small tool called a dibber, and the seedlings are lifted individually by gently lifting them by one of their leaves (not the stem, to avoid damaging it which would likely kill the seedling). A dibber is not strictly necessary - a plant label or pen/pencil can also be used to achieve the same result. The small seedling (it's best to do this whilst they're very small) is then transplanted to a location where it has some space to grow on.

Seedlings grown in module trays do not require pricking out; they can just be lifted from their module/cell to be transplanted.

Seed Beds

An alternative to germinating seeds in a module tray or seed tray; seeds can be sown into a bed, or part of a bed, dedicated to raising seedlings. Seeds are sown in the same way as a seed tray and then pricked out and transplanted to grow on to maturity.

Direct Sowing

Some seeds, such as parsnips and carrots, grow best without having their roots disturbed (root vegetables such as these tend to fork if their tap root is disturbed, so you don't end up with a typical carrot shape once grown). Direct sowing is a good option for plants such as these as it simply means they are sown in-situ where they will grow on and mature.

Succession Sowing, Interplanting & Companion Planting

Succession sowing refers to the practice of planting the same crop at intervals throughout the growing season, rather than planting all of the seeds at once. This allows for a steady supply of fresh produce over a longer period of time.

Interplanting, also known as intercropping, is the practice of planting different crops in the same space at the same time. This can be done by planting different crops in alternate rows, or by interspersing different crops in the same bed. The idea behind interplanting is to make the most efficient use of the available space, by using different crops that have different growth habits and requirements. The result is also referred to as a polyculture, as opposed to a monoculture where a single crop is grown in the space.

Companion planting is essentially intercropping, but where at least one of the plants is specifically intended to help the other in some way. For example, marigolds are often planted next to tomato plants with the primary goal of deterring whitefly which is a pest that tomato plants frequently attract.

Dibber, Trowel & Hoe

A dibber is a gardening tool used for pricking out seedlings, and for making holes in the soil or compost for planting seedlings or bulbs.

A trowel is a small hand-held 'spade' with a pointed, scoop-shaped blade and a handle used for digging and planting.

A hoe is a tool consisting of a long handle with a flat blade fixed perpendicular to it at the end. There are many different types of hoe with different functions, but the most common use for a hoe in the UK is weeding.

Compost, Soil & Leafmould

There are many different types of compost made from different materials and intended for different purposes. For example, seed compost is intended specifically for the purpose of sowing seeds and is deliberately low in nutrients. In essence though, compost is an organic matter made from decomposed material, broken down by bacteria and fungi over time. Ingredients may or may not include animal manures, and other natural materials. The best compost is rich in nutrients and full of beneficial microorganisms.

Soil is the natural loose material that covers the surface of the earth and is composed of various materials including stones, mineral particles and living organisms. Note that in the USA, compost is often referred to as soil, or potting soil.

Leafmould is a type of compost made specifically from fallen leaves. The decomposition process for leaves is a much more fungally dominant process than the bacterially dominant process of many composting processes. Leafmould is also much lower in nutrients.

Mulch

Mulching involves placing a layer of material on top of your growing medium. The material may be organic, such as woodchip, compost, straw, or grass clippings for example, or inorganic such as gravel, or even man made materials such as a weed membrane/landscape fabric.

Sheet mulching refers specifically to the application of a sheet material to serve as a mulch, and may or may not be covered with a further mulching material. For example, cardboard may be used as the sheet mulch layer and then covered with woodchip to create a pathway, the cardboard will decompose over time. Alternatively, a landscape fabric may be laid in place temporarily to create a site for a new raised bed, held down only with pegs or stones.

Different types of mulch serve different purposes dependent upon the materials used, but the common functions of a mulch are to suppress weed growth, retain moisture in the underlying growing medium, and to feed soil microorganisms, adding to fertility and soil/plant health.

Heirloom | Hybrid | GMO

Heirloom plants are varieties of plants that have been passed down through generations and are considered to be "open-pollinated." This means that the seeds of an heirloom plant will produce plants that are true to the original variety. Heirlooms are often considered to be more flavorful and nutritious than hybrid or GMO plants, and they are also considered to be important for preserving plant genetic diversity.

Hybrid plants are created by crossing two different varieties of a plant. The resulting plant will have characteristics from both parents. They are created to combine the desirable traits of each parent, such as disease resistance, yield, or taste. Hybrids can be created naturally or through human intervention. They are often considered to be more productive and disease-resistant than heirloom plants, but the seeds from a hybrid plant will not produce plants that are true to the original variety.

GMO, stands for Genetically Modified Organism, it refers to plants that have been genetically modified in a lab using genetic engineering techniques. This process allows scientists to introduce specific traits into a plant, such as resistance to pests, disease, or herbicides. GMOs are often created to improve crop yield, or to make farming more efficient. They have been a topic of great debate and concern due to potential risks to human health, the environment and the loss of biodiversity.

Annuals | Perennials | Biennials

Annual, biennial, and perennial are terms used to describe the life cycle of a plant.

Annual plants are those that complete their entire life cycle, from seed to flower to seed, in one growing season. Annuals have to be regrown from seed every year. Examples include tomatoes, peppers, cucumbers and lettuce.

Biennial plants have a two-year life cycle. In the first year, they grow leaves, stems and roots, but they don't produce flowers. In the second year, they produce flowers, seeds and then die. Examples include onions, carrots, leeks and beetroot.

Perennial plants are those that live for more than two years. They go through a period of growth, followed by a dormant period and then re-emerge to grow again. Perennials can live for many years, and they come back year after year from their root systems. Examples include asparagus, blackberries, raspberries and strawberries.

Raised Beds

Wake up, it's not that sort of bed! A raised bed is a growing area that has been raised above the level of the immediately surrounding ground. Raised beds may have sides constructed from wood, metal, or other material, or it may just be mounded earth/compost with no sides at all. If they have sides, they can be made much taller for accessibility and further improved drainage.

Row Covers | Netting | Mesh | Fleece

Netting, fleece and mesh are all types of row cover; lightweight fabrics used to cover growing areas (rows or raised beds) to protect plants from pests or from the elements. Fleece is helpful to warm the soil, protect plants from wind, and provide a more sheltered microclimate. Different types of mesh and netting are designed to keep specific pests, such as carrot root fly or cabbage white butterflies, away from your crops.

Determinate & Indeterminate (Tomato Plants)

Determinate and indeterminate tomatoes are two different types of tomato plants that have distinct growth habits and characteristics.

Determinate tomatoes are also called "bush" tomatoes, they are usually smaller plants that have a more compact and bushier growth habit. They typically grow to a pre-determined height and then stop growing taller. They produce fruit all at once (usually during a 2-3 week period) then the plant dies.

Indeterminate tomatoes, also called "vining" tomatoes, are larger plants that continue to grow and produce fruit throughout the growing season. They are taller and less compact than determinate tomatoes, and need support such as staking or caging to keep them upright. They will need stopping at some point (pinching the top of the plant off) and generally produce fruit more continuously throughout the growing season.

Staking, Supporting and Training

Some plants require support to prevent them from snapping or falling over. Staking involves inserting a wooden or metal stake into the ground/growing medium next to the plant that requires support, then tying the plant to the stake to provide enough support to keep it upright.

Supporting is similar to staking, it involves using a structure to support the plant, but may be more elaborate than a single stake, such as a cage, trellis, teepee, or even a living support such as a tree or other plant. This method is often used for plants that are naturally climbing, such as climbing beans, peas, and cucumbers.

Training is the process of shaping or directing the growth of a plant. This can be done by pinching off side shoots, tying stems to supports, or training a plant to grow along a trellis or other support.

Greenhouses, Polytunnels & Coldframes

These are all structures used to extend the growing season; allowing you to start growing earlier in the year, and finish later. They help to protect plants from the elements and provide a more controlled environment for plant growth.

There are some plants that don't grow well or produce a harvest without the additional heat and protection offered by one of these options. However, that applies only to plants originating in hotter climates which don't enjoy the British weather, such as the most chilli plants, melons, aubergines and sweet peppers. Some varieties of tomato and cucumber will also only thrive when grown undercover. However, there are absolutely loads of things that will grow outdoors very happily, so these structures are a nice to have but are certainly not essential!

In terms of key differences between the 3, a cold frame is smaller, lower to the ground structure that you can't walk into but instead lift a lid and place plants within it. Greenhouses are larger and can accommodate the grower as well as the plants, although you won't want to hang around in there for too long on a warm day - it's called the greenhouse effect for a reason! Both greenhouses and coldframes use either glass or polycarbonate (a rigid plastic) to allow light through to the plants. Greenhouses are made from either a wooden or metal frame which supports the glazing. Coldframes are usually made out of wood or bricks.

Polytunnels are similar to greenhouses but are made from a series of metal hoops which then have a transparent polythene cover (plastic sheeting) stretched over them. They are cheaper to purchase but generally don't last as long as a greenhouse, they also don't retain heat quite as well overnight.

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Grow Lights, Heat Mats & Propagators

Grow lights are artificial lights which attempt to mimic the spectrum of natural sunlight, they are typically used indoors to provide plants with the ability to photosynthesize where there is no, or insufficient quality of, natural light for them to do so. These can be really useful for helping seedlings to get growing early in the season where it's too cold for them to be out in the elements but not light enough on a windowsill for them to grow strongly. Note that almost all vegetable seeds do not require light to germinate so there is no need to provide them with any light until they have sprouted.

Warmth, however, is a key ingredient for germination. Different seeds require different amounts of warm, although generally the acceptable range for germination is sufficiently broad as to suit a wider variety of different seeds to enable multiple plants to be germinated concurrently in the same conditions. A heat mat is useful in this regard; particularly if starting seeds outside of a heated house, such as in a shed, garage, greenhouse, coldframe or polytunnel where warmth can be in short supply. Heat mats are electrically heated pads that are placed under seed trays or pots to provide bottom heat to the roots of plants, this is a fairly efficient way of targeting the warmth where you need it, rather than attempting to heat a large structure.

Propagators are a useful partner; these are devices used to create optimal conditions for seed germination and to root cuttings. In their simplest form, they comprise a clear plastic dome, which sits atop a tray holding the seed tray, module tray or pots. They are used to trap warmth and moisture to provide an optimal environment for germination and rooting. They are often used in conjunction with heat mats to help retain the heat generated and maximise efficiency. They also reduce the frequency of watering required because less of the moisture from the plants and growing medium can escape.