Back to Glossary A - Z

Sand A soil mineral particle measuring 0.05-2.0 mm in diameter. (Nelson, 2003)

Sandculture The culture of plants in a root substrate consisting exclusively of sand. (Nelson, 2003)

Sashbar The bar to which glass is attached in a greenhouse. (Nelson, 2003)

Senescence The process of growing old; aging. (Nelson, 2003)

Sepal One of the components of the calyx. (Nelson, 2003)

Shatter When used to describe a floral condition, this term refers to the dropping or abcission of petals. (Nelson, 2003)

Short-night plant A plant that undergoes a photoperiodic response, such as flowering, only when the night length is less than a critical length. (Nelson, 2003)

Sill The portion of the greenhouse that rests on the curtain wall and to which the side wall sash bars are attached. (Nelson, 2003)

Silt A mineral component of soil that’s consiting of particles measuring 0.002-0.05 mm in diameter. (Nelson, 2003)

Slab-side (also known as cling-side) A flower that has failed to open symmetrically. The petals on part of the circumference are still straight up, while the remaining petals have opened in a normal fashion. (Nelson, 2003)

Sleepiness A condition in flowers in which petals curve upward, giving the appearance of a wilted condition. It is commonly caused by ethylene gas after harvest. (Nelson, 2003)

Soil The upper, heavily weathered layer of the earth's crust that supports plant life. It is a mixture of mineral and organic materials. (Nelson, 2003)

Soil Structure The combination of primary soil particles into secondary aggregate particles. (Nelson, 2003)

Solenoid valve An electrically activated valve that controls the flow of gases or liquids. Such valves can be activated by a time clock to control the flow of water in automated greenhouse watering systems. (Nelson, 2003)

Solstice The two times of the year when the sun is farthest from the equator (closest to the poles). In the Northern Hemisphere, the summer solstice occurs about June 22 and the winter solstice about December 22. (Nelson, 2003)

Split A flower having a split calyx, in which the petals protrude from the split. It is a common problem of carnations. (Nelson, 2003)

Spore The reproductive unit of fungi consisting of one or more cells; analagous to the seed of green plants. (Nelson, 2003)

Sporophore A hypha or fruiting structure bearing spores. (Nelson, 2003)

Spreader-sticker See surfactant.

Standard chrysanthemums Cultivars of chrysanthemum customarily grown with on large flower on each stem. (Nelson, 2003)

Sterilization The destruction of all living organisms. Greenhouse tools and growing containers are periodically sterilized to eliminate harmful organisms including pathogenic diseases, insects, nematodes, and weeds. (Nelson, 2003)

Strap leaves Leaves whose margins are partially or completely missing such that the leaf is narrower than normal, often resembling a strap. (Nelson, 2003)

Strut A support member of the greenhouse frame that is under a compression force. (Nelson, 2003)

Surfactant A chemical used to alter the surface properties of liquids. Surfactants are added to pesticide sprays to reduce the surface tension over the plant leaf surface. Without a surfactant, complete coverage of the leaf surface often is not achieved. Surfactants used for this purpose include spreader-stickers, wetting agents, and detergents. Surfactants are also used to enhance the initial wetting of root media containing relatively dry peat moss, which tends to be waxy and water-repellant. (Nelson, 2003)

Symphillid A small translucent to white, many-legged arthropod that ranges up to 1/4 inch (6 mm) in length and feeds on the roots of plants. (Nelson, 2003)

Systemic Spreading internally throughout the plant body. Some pesticides are systemic, as are some pathogens. (Nelson, 2003)