joints by cleaning them out, and then filling them with mortar left projecting slightly from the interstice, or with a fillet of putty or lime.

tufa A porous limestone that holds moisture and is usually gray. It is often used in masonry construction and sometimes used for cultivating alpine plants.

tuff or volcanic tuff A porous low-density rock of volcanic particles.

tufted Grasses with spike-like foliage or grasses that have a fine texture with upright leaves originating at a basal clump and growing upward and outward without much arching or weeping. An example is Blue fescue. (Compare with mounded (2), upright grasses, upright divergent grasses, upright arching grasses, and arching.)

tufted grasses tufted grasses tumbled A metal or stone that has been finished by rotating in a drum.

tump 1. A British term for a mound. 2. A clump of any vegetation.

tundra A rolling treeless region usually in the arctic or subarctic climates where the subsoil is never fully thawed and the prevalent vegetation is moss, lichens, herbaceous plants, and low shrubs.

tungsten steel A gray to white, heavy, hard steel containing 5 to 24% tungsten and 0.4 to 2% carbon.

tunic In botanical terms, an enclosing or covering membrane or tissue such as around a seed, or the papery or fibrous membrane around a bulb or corm.

tunicate Covering or sheathing made up of leaf bases that form concentric circles when viewed in cross section like the bulb of an onion.

turbidity Water clarity or opaqueness determined by the amount of sediment suspended in the flow.

turbinate A botanical term meaning top-shaped or shaped like the top of an inverted cone.

turbulent flow A vigorous, fast water flow, usually caused by steepness of grade and bumps or projections (boulders, bedrock) underneath or to the sides of the flow. A turbulent flow in a water feature serves to aerate the water, assisting in control of algae growth, and providing air for aquatic plants and fish.

turbulent flow emitter In drip irrigation, an emitter of water droplets having a small tortuous path for the water to flow through that controls the amount of water emitted by dissipating energy in friction against the walls of the water passage and between the water particles themselves. Elevation differences and friction loss in pipe distribution can affect the output of emitters. These emitters are not highly sensitive to pressure or temperature variations. See also emitter.

turf A thick cover of grass that is usually maintained by mowing.

turgid Full of water; distended. Plant tissues that are naturally and normally swollen to a firmness and not limp, especially after watering.

turgor The normal state of plant cells when receiving sufficient water to provide a firmness instead of being limp.

Growing Soilless

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