Gardeners' glossary A-Z

Cold frame

A frame covered in glass or plastic used to protect outdoor plants and seedlings. The transparent sides admit sunlight and trap warmth that would otherwise escape at night.

Column/columnar

Describes the shape of branches/trees that are erect and close together. Having the shape of a column.

Companion plant

Plants that work well together, either aesthetically, because their colours are complementary or they flower at different times, or functionally, because they benefit one another, with one plant perhaps repelling pests that prey on the other.

Compost

The aerobically decomposed remnants of organic matter used to enrich soil.

Peat-free composts commonly consist of composted bark, wood fibre and coir, with added nutrients. Using peat-free composts has considerable environmental benefits for peatlands, which are now threatened habitats.

Loam-based composts from the John Innes range, are soil based, rather than peat based, with good moisture and nutrient-retentive qualities.

Additional soil conditioners include vermiculite and perlite. Vermiculite is a mineral that forms spongy, lightweight kernels that enable the soil to hold more water. They're also useful in preventing the compaction of soil and in loosening heavy soil. It's also used as a medium in which to root cuttings. Perlite is a lightweight aggregate made from an amorphous volcanic or other vitreous rock. Totally inert and sterile, it's useful in opening cavities in the soil and enabling water and air to reach roots. It's often used in potting soil.

Compound

Leaves having two or more similar parts, or being divided into two or more leaflets.

Cone

A seed-bearing conical fruit on conifer plants, comprising overlapping scales surrounding a central axis.

Conifer

A cone-bearing tree of the pine family, usually evergreen.

Container grown

Refers to plants grown and marketed in containers ranging in size from one to five gallons. May be planted all year round.

Contractile

Refers to roots that shrink vertically, drawing the plant down into the soil, especially in time of drought. They help position the plant at an appropriate level in the ground.

Coppice

A thicket or copse of small trees.