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Horticultural Terms for Vegetable Growers

By Louise Placek

The following are more general terms relating to plants and growing. Some are actual botanical terms and some are simply descriptive words you will likely hear in the plant trade.

Horticulture: In the strictest sense horticulture might be defined as the activity of growing flowers, fruits, vegetables, tropical, native and other ornamental plants, or the science or art of cultivating a garden. This covers a wide range of involve­ment with plants whether leisure or professional. For the pur­pose of this book, horticulture will be referring to the busi­nesses involved in the propagation, growing and selling of plant material in containers. (Note: Although licensing relating to commercial horticulture is under the department of agricul­ture, there is a distinct difference between the two. Agriculture is the process of cultivating field crops and/or production of livestock.)

Organic: Broad term referring to anything on earth (or beyond) containing carbon (and hydrogen), the inference being “living organisms.” All living beings from humans to plants to protozoans are carbon based. When the term organic is used to describe a method of growing, it is referring to the avoidance of laboratory-produced chemical fertilizers and pes­ticides and emphasis on earth-generated (“organic”) fertilizers and plant-based pesticides. The method also emphasizes the importance of encouraging a natural, environmental balance through the use of beneficial insects, trap crops, companion planting, sanitation, beneficial soil microorganisms and a healthy dose of patience and common sense.

A horticulture greenhouse.
A horticulture greenhouse.

Organic Horticulture: The business of commercially grow­ing plants in containers without the use of synthetic fertilizers, pesticides, fungicides or herbicides.

Xeriscape: A form of landscaping using xeric plants (those needing little water to survive) to conserve dwindling ground water and aquifers in regions where this is a concern. In these areas of water shortage and drought the use of non-native plants can substantially reduce the overall availability of water because of their greater need, and consequently their higher uptake from the soil. This means less water for humans and other animals as well as native flora. Native plants are adapt­able to water shortages and will survive by going into dor­mancy to conserve available resources.

Hardiness Zone: These are the geographical (zonal) guidelines set up by the U.S. Department of Agriculture that indicate average winter and, in some cases, summer tempera­tures. These extreme temperatures are important in deciding what kinds of plants will grow in your area. The problem with these “official” zones is that there are in reality many grada­tions of these temperatures to the point of being zones within zones. And when you factor in average rainfall and soil varia­tions, there may be significant differences in growing condi­tions within 50 miles of your local region. The USDA maps are great as general guidelines, but you need to dig a bit deeper when you are growing plants for an area, to make sure you understand what unique conditions your customers are living under.

Descriptive Terms

Allelopathy: This is where a plant inhibits growth and/or germination of other plants by releasing chemicals from twigs, leaves and sometimes roots into the surrounding soil. The word allelopathy means “mutual suffering.”

Annual: A plant whose entire life cycle (germination, growth, fruiting, death) is completed in the time-span of one growing season. These cycles vary in length with the species of plant, from only a few weeks to nearly a year.

Biennial: Plants that complete their life cycle in the span of two growing seasons. The first season is usually spent on foliar growth and the second season it blooms, fruits and dies. Some biennials may live longer in frost-free climates, but will lose vigor with time.

Bolting: Unusually rapid growth of an annual plant result­ing in premature flowering, often due to unusually warm weather, especially with plants that need cooler temperatures for growth and development.

Cold Hardening: In preparation of freezing winter tem­peratures, the cells of deciduous plants change structure and function slightly to prevent the fatal formation of ice crystals.

Deciduous: Refers to perennial plants that lose their leaves due to a quickened, hormonally induced aging process in the leaves, triggered by lower temperatures and shorter days. The process includes dormancy in which the roots and/or stems slow metabolism and store food. New growth will be stimulat­ed by warming and longer days and will be sustained by the stored nutrients until the foliage actively begins photosynthe­sis.

Determinate Growth: Generally refers to fruiting annuals that produce only one or two (often large) flushes of fruit and/or that have a predetermined growth pattern. Most determi­nate plants are hybrid vegetables or flowers that are bred for very specific (desirable) characteristics.

Dormancy: The state of a plant when growing (cellular activity) has diminished due to heat and/or drought or cold temperatures. Any of these situations bring on leaf drop and temporary interruption in active growth. The plant survives on stored nutrients until it produces enough foliage to begin pro­ducing food again via photosynthesis.

Drip Zone (Drip Line): This is the area of soil directly under the outer tips of the branches of trees and shrubs (perimeter) that often has root tips waiting for water to drip off the leaves. When fertilizing or watering, it is important to attend to the entire area under the foliage, including the drip zone. But be aware (especially with trees) that often the roots extend out beyond the drip line.

Evergreen: Perennial plants that do not lose their leaves as a result of seasonal changes although growth often slows in times of drought, or extreme heat or cold. Leaves only drop as a result of normal aging or extreme stress and/or disease.

Hardening Off: The process of gradually exposing young plants to outdoor conditions so that they are well adapted by the time they are finally planted in the ground.

Hardy Plants: These are native or non-native plants that survive the challenging environmental stresses of your region. The stresses can be anything from extreme cold and/or heat to drought, humidity, rainfall and specific soil conditions.

Herbicide: Chemicals that have selective or broad-spec­trum plant killing properties.

Host: Plants used by parasites (see parasite) as a source of nourishment. Depending on the parasite, the host plant may suffer from as little as minor metabolic disruption to (ultimate­ly) death.

Indeterminate Growth: These are annual plants that fruit continuously and whose growth patterns and production are primarily influenced by soil, water and nutritional factors. Most heirloom vegetables are indeterminate. (In essence all non-hybrid plants are indeterminate, but the terms determinate and indeterminate are used to help gardeners understand what to expect of the seeds or plants they are purchasing for their home gardens.)

Native Plants: Generally speaking, these are plants that are indigenous to a specific region. That is, they have genetic traits similar, if not identical, to plants that grew in the region before the settlement (and ecological disturbance) of humans.

Naturalized Plants: These are non-native plants that have been introduced to a region by wind, animals, or humans and are uniquely suited to the area to the point of growing as well or better than the native plants. This can cause major problems for the survival of the native ecosystem if certain naturalized plants begin to dominate.

Necrosis: Death of a stem, roots and/or leaves often caused by calcium deficiency because of its importance in the synthe­sis of pectin, which is what holds cell walls together.

Parasite: From the Greek parasitos, meaning one who eats at another’s table. In botanical terms these are specific fungi, bacteria, viruses and some plants that are unable to manufac­ture their own food and so must attach themselves to a host plant and invade the root or arial (above-ground) tissue in order to procure enough nourishment to live out its life cycle, which includes reproduction. It often leads to death of the host, but might only drain specific resources like water or min­erals, which weakens the plant, making it more vulnerable to other disease or pest problems.

Perennial: Plants that have an indefinite lifespan. Some are short-lived (5-10 years) and some last for centuries. Some have continuous, above-ground growth and others have top growth that disappears (dies back) each year to return the following season. Some are deciduous (losing foliage in winter) and some are evergreen (maintaining foliage year-round). All have dor­mant periods where growth is slowed or temporarily suspend­ed due to extreme heat, cold or simply genetically predeter­mined growth cycles.

Phytotoxcity: Refers to the damaging effect of chemicals applied to plants, resulting in stress or even death of the plant. Environmental toxins, herbicides and some pesticides may cause this effect.

Shade Tolerant: Plants that photosynthesize better in low light. Many of these plants will actually die if exposed to bright sunlight for too long.

Stunting: Plants with abnormally short stems, small, often deformed leaves, and overall poor color and performance. Caused by environmental stress such as water or nutrient deprivation, disease, pest insect infestation, or consistently harsh climatic conditions such as extreme cold, heat or wind.

Symbiosis: When plants have a mutually beneficial rela­tionship with another species, such as insects that feed on the nectar and spread pollen, and birds that eat the fruit and drop the indigestible seed.

Xeric (pronounced zee’rik): Of or characterized by condi­tions requiring very little water to survive. The most obvious example would be the desert and its plants. Xeric plants are those that have adapted to very dry conditions, allowing them to survive extreme drought through a unique system of water and nutrient storage and the ability to become completely dor­mant during times of severe stress, conserving their resources and thereby allowing them to survive.


Genes: The molecular-sized hereditary units attached to chromosomes in the nucleus of all cells that dictate the inher­itable characteristics of an organism. Some genes are dominant and physically apparent, and some are present but tucked away in the chromosomes and passed on to later generations. When growing out non-hybrid seeds, it’s always interesting to see recessive characteristics popping out occasionally in a few of the plants. This of course is where much of the commercial horticultural selection process begins.

Genotype: The gene composition of a plant.

Heirloom: Plant whose characteristics are the result of natural selection rather than hybrid gene mixing. Many heir­looms are essentially, genetically identical to the parent plant with only subtle, (evolutionary) genetic differences occurring over time. These plant varieties are often very old; the seeds or cuttings having been carefully (and lovingly) handed down through the generations to protect the genetic heritage.

Hybrid: Often designated in seed catalogs as F1 meaning the plant will be an offspring of two related species of plants, each of whom contribute specific, desirable characteristics to the genes of the hybrid plant. Successive seeds from these hybridized plants (after growing out and fruiting) will, if not sterile, eventually go back to the original parent plant charac­teristics.

Non-Hybrid: Although this category includes many heir­looms the term simply refers to plant species and varieties that have not endured genetic tampering. Many of these plants are tried and true, solid producers.

Open-Pollinated: Refers to non-hybrid plants that are wind-, insect- or self-pollinated and are capable of cross-polli­nating with other plants of similar species. These plants carry the foundational genetic makeup of the species and pass it on to the next generation.

Phenotype: This is the apparent or visible expression of a genetic characteristic such as leaf shape, height, width, color, etc.

Selected Variety: Variety of a species bred through natural genetic selection, from the process of growing the plant out over time, and selecting progeny with desirable characteristics rather than gene mixing via intentional cross-pollination (resulting in a hybrid from two specific members of a species).

Variegation: Even or uneven color patterns found in leaves or flowers of plants that is mostly an inherited genetic trait. Probably adaptive but may also be induced by viral genetic meddling.

Plant Classifications

Binomial Nomenclature: The two-part naming system (genus-species) developed by a Swedish naturalist Carolus Linnaeus in the 18th century.

Cultivar: A specific, named variety of a certain species of plant, carefully cultivated to retain its desirable characteristics. The cultivar name is listed after the genus and species in a scientific name and is either preceded by the abbreviation cv., or surrounded by single quotation marks. Most cultivars are plants that produce showy flowers or unusual variegation, shape or size outside the norm for that genus/species. An example would be Rosa multiflora cv. ‘Lilliputian’.

Taxonomist: These are the plant scientists that give plants their internationally recognized scientific names. They are also the ones that change the names about the time you have them memorized.

Family: This is a group of plants of various genera with broad similarities. According to the International Code of Botanical Nomenclature, all family names end in -aceae. For example, the rose family is Rosaceae.

Genus: A taxonomic subdivision of plant families which, in turn, contains a number of related species. The scientific name of all plants begins with the genus, which is usually Greek or Latin, and always capitalized. These names come from mytho­logical figures, common (Greek or Latin) names for the plants, or are named in honor of someone involved in plant history. The genus for the rose family is Rosa.

Species: A sub-group (often large) of a genus with primary genetic characteristics similar enough to be identifiable, and whose individual members are able to interbreed freely. The second word in a scientific name is the species and is not capitalized. These words generally describe identifying charac­teristic of the plant. Sometimes the second word is officinalis or officinale (meaning “of the workshop”) referring to its historical use as a traditional medicinal plant. A species for the rose fam­ily might be multiflora (many flowered).

Plant Nutrients

Chlorosis: A condition of a plant producing yellowing of the leaves, which decreases photosynthesis and therefore food production. Causes may be overwatering, environmental tox­ins, or deficiencies in magnesium, iron or nitrogen. The defi­ciencies may be caused from a lack of the nutrient in the soil, or from high or low pH causing the nutrients to be inaccessible to the plant.

Macronutrients: Mineral elements used in small amounts by plants for healthy growth and development. These are car­bon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), sulfur (S) and calcium (Ca).

Micronutrients: Mineral elements used in small to tiny amounts by plants for healthy growth and development. These are magnesium (Mg), iron (Fe), copper (Cu), zinc (Zn), manga­nese (Mn), molybdenum (Mo) and boron (B).

NPK: Nitrogen, phosphorus and potassium and their rela­tive amounts in a fertilizer or soil sample. All three are funda­mentally important to normal, healthy plant growth.

pH: A scale from 1 to 14 assigning numbers to soil indicat­ing relative acidity or alkalinity, 1 being extremely acidic, 14 extremely alkaline, and 7 being essentially neutral. Most plants will grow in a soil with a pH of 6.5 to 7, but some require a more acidic or alkaline soil for robust growth. A highly acidic or alkaline soil may also liberate excessive amounts of certain minerals that, although needed by plants in tiny proportions, would be toxic at higher levels. Even small increases or decreases in pH can profoundly affect nutrient uptake by the plant.

Trace Nutrients: Mineral elements used in tiny amounts by specific plants for healthy growth and development. These are chlorine (Cl), aluminum (Al), sodium (Na), silicon (Si) and cobalt (Co).

Source: Made from Scratch