Acidic – A pH of less than seven. Acidic soils tend to be in areas of higher rainfall such as the eastern United States, and the coastal Pacific Northwest.

Alkaline – A pH of more than seven. Alkaline soils tend to be in arid climates of the western half of the United States.

Alluvial – Soil made up of materials left by the water from rivers and floods. It is typically loose and fast-draining.

Amendment (in soil) – Anything added to a soil, generally for biological and/or physical enhancement.

Anaerobic – Without oxygen.

Anti-siphon valve – Allows water to flow in only one direction. Prevents water from being sucked back into the water supply line.

Aqueduct – A manmade channel for moving water.

Atmospheric backflow preventer – Prevents backflow into water supply.

Bay Delta – A nickname for the Sacramento – San Joaquin Delta. A 1,100 square mile area in Northern California from which our watershed gets most of its imported water.

Berm – An elevated ridge of land. Typically several inches to several feet in height.

Capillary action – Attraction of water to surfaces. Allows for water to move opposite of gravity.

Catch can test – A method used to determine irrigation efficiency. Catch cans are water-holding containers, about one cup in size. When placed on the ground in a pattern, they catch water from an operating sprinkler zone for a specified time. Once the sprinklers are turned off, the water in each catch can is measured. The greater the difference in the volume of water in each catch can, the greater the irrigation inefficiency. 

Circuit – See “Zone.”

Clock – Another name for an irrigation timer or controller.

Compost – Made of organic matter that has decomposed. It can be incorporated in soil as an amendment or applied to the top of soil as a mulch. It looks nothing like the original materials that were used to make it. Compost is typically dark brown and has an earthy aroma.

Controller – Another name for an irrigation timer or clock.

Deadheading – The removal of dead flower or seed heads from a plant.

Deciduous – Seasonal shedding. An example is the loss of leaves from trees in the winter months.

Decomposition – The natural biological and chemical process by which organic matter (such as dead plants) is broken down into compost.

Desalting – A water treatment process of removing salt from water. Fresh water is produced from brackish or seawater.

Exudate (from plant roots) – Chemically diverse compounds from the circulatory system of the plant. It is excreted from the roots into the soil as a defense mechanism against pathogens.

Feel method – An unscientific way to determine the state of soil by feeling it. A desirable soil feels somewhat squishy, but not gooey; somewhat crumbly, but it will hold together when squeezed.

Garden Room – An outdoor area that is defined with elements similar to an indoor room to create a sense of space. Elements can include flooring such as stone or tile; an overhead cover such as a pergola; walls from hedges, pottery, or curtains; a fireplace; kitchen equipment or bar-b-q; seating, etc.

Genera – A class or group marked by common characteristics.  Plants are named botanically with a genus and species name.  The genera would be all plants with the same genus name.

Groundwater – Water that is found underground in the spaces of soil, sand, and fractured rock. It is considered a type of water storage.

Habitat – A natural environment for an organism such as a plant or animal.

Head – A shortened name for sprinkler head.

Heat island – An area that is significantly warmer compared to its surrounding area. 

Humus – An organic component of soil consisting of well-decayed plant and animal matter. Microorganisms can’t decompose it any further, so it is a very stable product can that last for years. It greatly increases the water-holding capacity of soil by aggregating soil particles. 

Hydrozone – An area of plants with the same or similar water needs.

Inorganic – Consisting of matter other than living or formally living substances. An example would be minerals or most types of rock.

Loam – A desired soil consisting of sand, silt, and clay.

Microbes – Microscopic critters that live in the soil such as bacteria, fungi, protozoa, and nematodes. They can be beneficial or pathogenic.

Microclimate – A local climate formed in a small site or habitat. Many things can form a microclimate such as shade, reflected heat, structures, topography, soil, etc.  

Mulch – A material spread on top of the soil to protect and possibly enrich the soil. It can be either organic, such as wood chips, or inorganic, such as rocks.

Mycorrhizae – a beneficial soil fungus that greatly enhances water and nutrient uptake by performing as an extension of plant roots. It actually helps plants communicate with each other. Approximately 90% of land plants have formed some type of mycorrhizal relationships with other plants.

Native plant – A plant that has evolved and adapted naturally in a local ecosystem or location without direct or indirect human intervention.

Non-potable water – Water that is not safe to drink.

Nozzle – a device used to control the output of water from a sprinkler head.

Organic – Derived from living organisms. Contains the element, carbon.

Ornamentals – Plants that are used for ornament rather than plants used for crops and food sources. 

Pathogen – An organism that causes disease.

Precipitation rate – A measure of the rate at which water is applied to a specific area in a specified time. Usually measured in inches per hour.

Point-source drip irrigation – A method of drip irrigation where drip emitters are placed only in the plants root zone.

pH – A measure of how acidic or alkaline water is. A scale of 1 to 14 is used with 7 being neutral, below 7 being acidic, and above 7 being alkaline.

Photosynthesis – A process in green plants that uses sunlight to create and transfer energy.

Potable water – Water that is safe to drink.

Prune – Selective removal of parts of a plant such as branches, twigs, or roots.

PSI – Pounds per square inch. It is a measure of force.

Rain garden – From the National Resource Conservation Service: Rain gardens are low or depressed areas landscaped with perennial flowers and native vegetation that soak up rainwater. They are strategically located to capture runoff from impervious surfaces, such as roofs and streets. Rain gardens fill with a few inches of water after a storm and then water filters into the ground, rather than running off to a storm drain. As urban areas grow, increased storm water runoff from impervious surfaces becomes a problem. As more impervious surfaces are added to our communities, it is more important than ever to help rainwater infiltrate. This protects water quality and reduces storm water runoff.

Recycled Water – Wastewater that has been adequately treated for use as irrigation water or recharge of groundwater basins.

Reservoir – A body of water used as a source of water supply such as a lake or pool.

Runoff – Water that drains off of a land surface. When speaking in terms of irrigation, runoff is water that flows off of the irrigated target area and is wasted.

Sacramento Bay Delta – See Bay Delta

Smart controller – An irrigation controller that uses weather data to automatically determine appropriate watering schedules.

Soil food web – A community in the soil consisting of a diversity of organisms from one-celled bacteria to small vertebrate animals and plants. The organisms interact and depend on each other to produce energy and provide nutrients to plants. 

Soil texture – The ratio of sand, silt, and clay particles in a soil.  For example, clay loam, or silty clay are soil texture names.

Solenoid – An electromagnetic device on an irrigation valve that allows a valve to open and close via an electrical current. The solenoid is connected to an irrigation controller with electrical wiring. 

Species – A group of living organisms, such as plants or animals, with similar characteristics in which two individuals can produce offspring.

Spray Sprinkler – A sprinkler type that has a nozzle with a fixed spray pattern, typically fan-shaped, with a radius of approximately four to 15 feet.

Sprinkler – A device that emits water with a controlled rate, pattern, and distance.

Stormwater – Surface water resulting from heavy rain or snow melt.

Sunset® climate zones – Refined climate zones for the western United States developed by Sunset, Time, Inc. 

Swale – A low place in the landscape where water collects.

Timer – Another name for an irrigation clock or controller.

Transpiration – A process where water enters plant roots, transports through the plant, and exits the leaves as water vapor.

Treated wastewater – Sewage and wastewater that has been treated chemically, physically, and biologically to remove contaminants so it can be safely returned to the environment or put to beneficial use such as groundwater replenishment or irrigation.

Turf or Turfgrass – Grass that is used as a lawn as opposed to wild grasses, prairie, or agronomic grasses.

Valve – An irrigation device that controls the flow of water through pipes and sprinklers.

Watershed – An area of land where all streams and rainfall drain to a common outlet. If you are standing on land, you are standing in a watershed. 

Weather-based controller – See “smart controller.”

Zone – An irrigated area controlled by one valve.