A horizon--Topsoil, usually the top layer of a well-developed mineral soil.
abscissic acid--Plant hormone responsible for the ability of flowers and leaves to separate from the plant. It is released in the abscission zone, or abscission layer, at the point of attachment.
acclimate--A process whereby tender, indoor-grown plants are gradually exposed to outdoor conditions. During the process, new plant growth develops with thicker epidermis and cuticle that are adapted to the harsher outdoor conditions.
active transport--The technique of moving molecules into plant cells across cellular membranes and against the concentration gradient.
adenosine triphosphate (ATP)--Energy molecule that stores biochemical energy in its phosphate bonds. This energy is used in cellular processes such as protein manufacture and cell division.
adsorption--The binding of molecules or ions to a surface, such as the binding of positively charged minerals to negatively charged soil particle surfaces by chemical bonding.
adventitious (root, shoot)--A root or shoot that develops from plant tissue where it does not normally develop. Some examples are roots forming at the cut end of a stem cutting or roots that develop from a stem of branch.
aggregates--Soil particles held together by the weathering process and humic acid formed during the decomposition of organic matter.
allelochemicals--Chemicals emitted by plants that repel pests or prevent weed growth.
allomones--Chemicals emitted by plants or animals that allow communication between individuals of differing species and are usually of benefit to the individual sending the signal.
anion--Negatively charged molecule (ion).
annual--Herbaceous plant that completes its life cycle in one growing season. Seeds germinate, and seedlings grow, bloom, are pollinated, and set seed, usually in a period of weeks to a few months.
anther--Portion of the male organ, the stamen, that contains and releases pollen.
apical dominance--Tendency of the apical meristem to repress growth in axillary meristems. This tends to result in tall plants with short axillary stems or branches, rather than short, bushy plants.
arboretum--Place where trees and shrubs are grown for display and study.
arboriculture--Cultivation of trees.
arborist--Person who manages and cares for trees.
authority, author citation--Reference to the author(s) who described a species and gave it a name. The author citation follows the species epithet (not italicized) in binomial nomenclature.
auxin--Plant hormone found in varying parts of plants. It plays an important role in apical dominance and root growth, as well as in tuber formation and seed dormancy.
B horizon--Layer of soil that is composed chiefly of clay. It is usually found beneath the topsoil, or A horizon, but in recent construction the topsoil may have been removed and not replaced.
bacteria--Single-celled organism that lacks chlorophyll. They reproduce by cellular division and may cause disease in plant species by parasitism.
bactericide--Pesticide designed specifically to kill bacteria.
basal plate--Located on the bottom, or base, of a bulb or corm.
bedding plants--Plants grown for use in flower beds and vegetable gardens. Traditionally annuals, these increasingly include perennials as well.
bench grafting--Grafting practices that occur at a bench as opposed to those that are applied directly to plants growing in a field or greenhouse. Bench-grafted plants are placed into a specific cool, humid environment to allow healing together to occur before plants are rooted.
biennial--Plant that requires two growing seasons to complete its growth; the first year seeds germinate and the plant grows vegetatively, often a basal rosette of leaves. Above-ground vegetation dies back in winter, but roots persist, from which new growth emerges the following growing season, finally blooming in the second season.
binomial nomenclature--System of naming organisms developed by Carl Linne (Carolus Linneaus) using two names: genus and species, in that order. The genus is a more general term, whereas the species epithet is more specific.
bolt--Process of flowering in plants with a basal rosette whereby the flowering stem arises from the center of the basal rosette. In vegetables such as spinach and lettuce, leaves become bitter at the onset of bolting. borders--Flower beds that tend to be
elongated and are viewed primarily from one side. They may be backed by a wall or fence. In borders, tall plants are placed in the back, with progressively shorter plants placed in the front.
bridge grafting--This type of grafting is used when there is girdling damage that results from rodent feeding or other causes. It connects the area of a trunk below girdling damage to the area above it.
broadcast--Method of fertilizing that disperses granular fertilizer in a spreader to cover a large area over the surface of ground. It may be worked into the soil after application.
bulb--Plant organ composed of any or all of the following: scaly leaves, immature floral bud, and basal plate from which roots emerge. Tunicate bulbs have a papery covering called a tunic. Bulbs are one type of storage organs produced by plants.
C horizon--Layer of mineral soil that consists of partially decomposed parent material.
cambium--Layer of tissue in plant stems that can give rise to xylem and phloem. Cell division occurs here, and new layers of xylem and phloem occur each year, contributing to the increasing girth of woody plants, most notably, trees.
caryopsis--Type of indehiscent dry fruit in which pericarp is fused with the seed coat.
cation--Molecule (ion) having a positive charge.
cation exchange capacity (CEC)--This is a chemical property of soil that measures the ability of soil particles to hold and store mineral nutrients. CEC is measured in units of milli-equivalents per 100 g of soil. Positively charged mineral nutrients (cations) are stored on negatively charged soil particles, such as clay or organic matter.
chelate--A special compound of a metal ion, such as iron, that allows the ion to remain soluble in the soil solution and to be taken up by plants. Iron is available as chelates in special fertilizers due to their propensity to become bound in the soil into insoluble compounds and thus become unavailable for plant uptake.
chilling--Exposure to temperature between 32 and 45[degrees]F that has a physiological effect within a plant. A common effect requiring chilling is floral development in fruit trees. Chilling units or chilling hours are the number of hours the plant is exposed to temperatures within that range. The chilling requirement is the specific number of chilling hours a particular cultivar requires for normal floral development prior to exposure to warmer temperatures.
chlorophyll--Plant molecule that reacts with light energy.
chloroplast--Chlorophyll-containing organelle in plants in which photosynthesis takes place.
chlorosis--Yellowing of leaves that is due to the breakdown of chlorophyll in leaf tissue. This is a symptom of many disorders, including nutrient deficiency and improper pH.
cleft grafting--Type of grafting in which the rootstock, which is growing in the ground, is cut off and split. One or more scions are placed in the cleft (split) matching the cambial layers.
clone--A plant that is identical to the parent plant, having been propagated from a vegetative organ, tissue, or cell(s).
collar--Swollen tissue at the base of a limb on a tree. It aids in the healing process after pruning the limb.
companion planting--The practice of planting species together because of the ability of one of them to repel pests off another one.
complete--A flower that has the four floral organs: sepals, petals, stamen, and pistil.
composite sample--A soil sample that is taken from scattered locations in the yard or area being tested. The samples are mixed together to provide a representative sample of the entire area.
compost--Decomposed organic material.
constant feed--The practice, usually in production of greenhouse crops, of fertilizing lightly each time plants are irrigated. This practice is sometimes referred to as fertigation.
contact herbicide--Chemical for weed control that kills on contact.
contact pesticide--Chemical for pest control that kills on contact.
cool-season crop--Crop that thrives under cooler temperatures. Seeds usually germinate better in cool soils, and plants may bolt (go to seed) when temperatures become hot.
core aeration--Practice on turfgrass that involves the removal of cores of soil that results in reduced compaction and better aeration.
corm--A compressed, fleshy stem.
cotyledon--Seed leaf that forms inside the seed and emerges upon germination before true leaves.
cuticle--A waxy coating on the leaf surface
cytokinin--A plant hormone that is involved in cell division; higher concentrations contribute to loss of apical dominance. In tissue culture, this stimulates shoot growth.
damping off--A disease of newly germinated seedlings that is caused by a fungal pathogen and results in the death of the plant, commonly within a few days.
deadheading--Removal of spent flowers that allows for further production of more flowers and prevents seed production.
deadman--In a timber wall, the timber that projects into the hillside behind the wall. This timber ties the wall into the hillside, providing strength and stability.
degree days--A tool for measuring degrees above a baseline temperature on a daily basis. Degree days are accumulated over time, and the resultant number can predict emergence of insect pests. For example, assume an insect requires 150 degree days for emergence. First, the average daily temperature is calculated by adding the high and low temperatures for the day. Then subtract 50 (the baseline temperature) from that value. The resulting number is the degree day for that day. This is done consecutively until 150 is reached or exceeded. On the day that happens, the insect in question is expected to emerge. Degree days have been calculated for many of the important crop pests.
dehiscent--Dry fruit that splits open when it is ripe.
dew point--The temperature at which moisture vapor in the air condenses to form dew.
dicot (dicotyledon)--One of two classes of plants distinguished from the other class, monocotyledons, by several features. Dicots have two seed leaves (cotyledons) when the seeds germinate; they also have reticulate, palmate, or pinnate venation, and in stems vascular bundles are arranged in a ring pattern. Woody plants having secondary growth are all dicots.
dioecious--A species plant having male (staminate) and female (pistillate) flowers on separate plants.
direct-seeding--Planting seeds directly into the ground as opposed to planting transplants.
DNA fingerprinting--Method of separating out fragments of DNA that can be useful in uniquely identifying cultivars or genetically unique plants.
dripline--A circular line around a tree that extends to the outer line of its branches. This is where rainfall would drip off the outermost leaves.
drupe--A simple, fleshy fruit that has a stony endocarp (pit, or stone). Examples are peaches, cherries, apricots, and plums.
E horizon--Soil horizon caused by deposit of soil due to eluviation, or erosion due to water movement.
electromagnetic spectrum--The energy present in space in the form of waves that range in size and include microwaves, cosmic rays, gamma rays and X-rays, visible light, ultraviolet, and infrared radiation.
elevation view--In landscape drawing, the view that illustrates two dimensions, horizontal and vertical.
eluviation--Significant loss of minerals through movement of colloids in solution, such as occurs with rainwater. Eluvial soils are soil horizons that have lost material through this process.
emergence--When a seed germinates and the cotyledons push out of the soil, the seed is said to have emerged.
endocarp--Inner layer of carpel (ovary) tissue. In drupes (stonefruits), it is the hard stony layer surrounding the seed.
ethylene--A plant hormone that is present in the form of a gas. It is involved in ripening of seed and fruit ripening and petal fall.
etiolation--Stretching of plant stems that results from inadequate light, which in turn causes weakened plant growth and reduced chlorophyll production. If low-light conditions continue, it may lead to death of the plant.
exocarp--Outer layer of carpel tissue on fruit.
[F.sub.1] hybrid--Hybrid that results from cross-pollination of two inbred parents, resulting in genetically identical offspring. [F.sub.1] hybrid seeds are produced in order to provide improved cultivars of many species, including corn and tomatoes.
family and recreation area--Usually found in backyards, but sometimes incorporate side yards as well. The area used for entertaining, children's play, or other outdoor activities.
family inventory--Checklist of information regarding the family for whom a landscape design is being developed.
fertigation--See constant feed.
filament--The stalk of a stamen, to which an anther is attached.
final plan--A professional drawing that contains details such as shading and coloring of symbols. It incorporates client feedback and may be done on vellum for durability.
florets--Individual flowers that comprise an inflorescence.
floriculture--The science and practice of cultivating flowers. Floricultural crops are those that are grown for ornamental purposes such as those provided by the flowers, including cut flowers and greens, potted flowering plants, and bedding plants.
focal point--In landscape design, anything that calls attention to itself or catches the eye.
forcing--Providing cool temperatures under artificial conditions in order for flower development to take place at different times than it would occur in nature. This practice is commonly used on flowering bulb plants such as tulips, hyacinths, lilies, and daffodils.
foundation plant--A plant that is used to hide an unsightly foundation or is used near the house to soften the edges of the structure and provide a visual transition between the yard and the house.
frost-free period--The number of days that fall between the last frost of spring and the first frost of fall. This determines the growing season of warm-season crops.
frost-sensitive--Plants that will not tolerate frost. Their seeds do not germinate in cool soil.
frost-tender--Plants that will be killed by a frost.
frost-tolerant--Plants that tolerate light frosts and continue to grow during the day while freezing temperatures occur at night.
fumigation--Soil treatment that involves injecting pesticide into the soil before planting. It is usually used on perennial crops that will be in the ground for a period of years or other systems in which pest buildup in the soil is of concern.
functional drawing--The first step in the drawing process. It consists of rough sketches and shows practical details, such as routes of pedestrian traffic, wind direction, areas needing shade or screening, and so on. They are usually done on tracing paper and there are often more than one set of ideas put on paper.
fungal pathogen--Multicelled organism that reproduces sexually by spores and asexually by long, threadlike mycelium. These organisms lack chlorophyll and a vascular system and may cause disease in plants by parasitism. Mushrooms are fungi that are grown as food.
fungicide--Formulations that are used to treat fungal pathogens.
gamete--The reproductive cells of plants, eggs, and sperm.
gene--A segment of DNA responsible for a particular trait that is passed to offspring. Each gene codes for a protein or enzyme.
genetically modified organism--Organism that contains a foreign gene using gene transfer techniques. The foreign gene may be from another organism or artificially produced. This is also known as a genetically engineered or transgenic organism.
genus--The general classification of an organism into which closely related species are grouped.
geotropism--Movement of plant in response to gravity. Positive geotropism results in plant roots growing toward the earth (down), whereas negative geotropism results in plant shoots growing away from the earth.
gibberellin--Plant hormone responsible for cellular elongation, stimulation of flowering, and seed germination, among other things.
gradual--Type of insect metamorphosis having three stages: egg, nymph, and adult. Nymphs resemble adults, except they are smaller and do not have wings.
grafting--A technique of vegetative propagation whereby cambial tissue from two different plants are joined together and held into place. Various types of grafting include whip, whip and tongue, splice-approach, banana, cleft and others.
growing degree days--Plant growth is a response to the temperatures as long as no other limiting factors, such as light or carbon dioxide availability, exist. The term growing degree days (GDD) refers to the amount of heat required for different amounts of growth in a plant.
guard cells--Two cells located on either side of the opening, or pore, that forms the stomate.
harden-off--The practice of preparing seedlings for planting outdoors. It consists of placing the seedlings outside for increasing time periods each day, beginning with 1 or 2 hours. If the weather is favorable, they may be left for a longer period. Also if they are in a sheltered location so that they do not receive much sun or wind exposure, they may be left longer. Finally, before actual planting outside, the seedlings may be left overnight a few times to acclimate them to the fluctuating temperatures experienced there compared with their former indoor or greenhouse location.
hardpan--Compacted layer of soil under the topsoil.
hardscape--The segment of landscaping that involves nonplant materials, including fences, walls, pavements, and others.
hardwood cuttings--Cuttings taken from woody plants in winter. heading back--A pruning technique of removing a lateral shoot back to a major bud or lateral.
heat-hardy--Warm-loving plants that thrive and grow in hot temperatures.
herbaceous stem cuttings--Herbaceous cuttings are taken from plants that never get woody. Herbaceous stem cuttings are made from a portion of the stem that is removed from a plant and placed into soil or water and allowed to develop roots.
herbicide--Pesticide that kills plants.
hermaphroditic--Having flowers with both male and female reproductive organs.
homozygote--Inbred plant having matching pairs of genes.
honeydew--Sugary excretion of sap-sucking insects such as aphids. Honeydew attracts ants and allows growth of sooty mold.
horizon (soil horizon)--Layer in a soil profile that usually consists of topsoil, subsoil, or partially decomposed parent material.
horticulture--The cultivation of flowers, fruit, vegetables, or ornamental plants.
host plant--Plant that serves as a host for a pathogen, parasite, or insect pest that infects it or feeds off it.
hybrid--The progeny that results from a cross between two inbreds.
imbibe--To uptake water, as when seeds germinate.
imbibition--Water uptake by a seed.
imperfect (flower)--A flower lacking either male or female reproductive organs. They are then either pistillate or staminate.
in vitro--Latin term meaning in glass. This term refers to operations conducted in laboratories in test tubes, Petri dishes, and others.
inbred--Plant that results from several generations of continuous self-pollination.
incomplete (flower)--A flower lacking one of the four floral organs: sepals, petals, stamens, and pistils.
indehiscent--Not splitting open when ripe, as with dry fruit types.
inflorescence--A compound flower composed of florets arranged on a central peduncle. Florets may be attached by small stems called pedicels.
instar--Stage of insect life cycle between two molts.
interiorscaping--The profession of decorating and designing with indoor plants.
intergeneric hybrid--Hybrid between plants of different genera.
interspecific hybrid--A hybrid between two different species.
interstock--Used in grafting or budding between the rootstock and scion, which usually imparts some special trait to the scion, such as resistance or tolerance, but may also be used for its straight stem, as with standard roses.
interveinal--Between the veins.
intraspecific hybrid--A hybrid within a species.
invasive--Weedy plants that spread profusely and are detrimental to the native ecosystem by out-competing native plant species.
island bed--Style of flower bed that can be viewed from all sides. This bed may be circular, but not necessarily.
kairomones--Pheromone that specifically appeals to and benefits other species.
lake effects--A weather phenomenon that occurs when air passes over a lake or other body of water and picks up moisture. It then releases the moisture when it passes over land, often producing snow in the winter.
leaf (leaflet)--Vegetative structure consisting of a blade that may be attached to a stem by a petiole. Compound leaves are composed of leaflets attached to a rachis.
leaf-bud cutting--Type of cutting consisting of a leaf and attached axillary bud with a short piece of stem.
leaf cutting--A type of vegetative propagation using just a leaf or a leaf and petiole. Adventitious roots form at the base of the leaf which has been inserted into soil or other rooting media.
lenticel--A pore located on plant stems that permits gas exchange. It may appear as a horizontal or small circular marking and can serve as an identifying feature.
macroclimates--Environmental conditions that are consistent on a relatively large scale.
macronutrients--Nutrients required by plants in relatively large amounts. They are usually expressed in percentage or parts per thousand.
meristems--Places in plants where cell division occurs.
mesocarp--In fruit, the middle layer of pericarp, the wall of a ripened ovary.
metamorphosis--Change in body form, as when insects undergo the transformation from larvae to pupa or pupa to adult.
microclimate--Localized area that has a modified climate from the surrounding area. This may include frost pockets, sheltered alcoves, wind tunnels, and so on.
micronutrients--Nutrients required by plants in relatively small amounts. They are usually expressed in parts per million.
micropropagules--Plants produced through micropropagation.
molt--In insects, the shedding of its exoskeleton, or outer shell.
monocarp--A plant that lives for a period of years, eventually flowering, and then dies.
monocot (monotyledon)--One of two classes of plants (the other is the dicotyledon), in which the seedling has one seed leaf. Other features that distinguish monocots from dicots are the parallel venation and arrangement of vascular bundles in stems in a scattered arrangement.
monoecious--Plant on which male (staminate) and female (pistillate) flowers are borne on the same plant. From the Greek mono- (one), and--oecious (house).
mycorrhizae--Fungus that forms a symbiotic relationship with plants. The hyphae grow within roots and may extend outside of the roots and obtain nutrients that benefit the plant, whereas the fungus obtains sugars from the plant.
necrotic--Dead, as in plant tissue.
needle-feeding--An injection method used in fertilizing trees by applying fertilizer directly to the root system.
nomenclature--The system of naming organisms.
nonselective herbicide--Chemical that kills both monocot and dicot weeds.
nonselective pesticide--Pesticide having a wider range than selective pesticides and capable of killing all insects or a large group of related species.
noxious weeds--Plants that can directly or indirectly injure or cause damage to crops, including nursery stock.
nut--A dry, indehiscent one-seeded fruit with a bony pericarp. Examples are acorn and chestnut.
O horizon--Top layer of soil, above the topsoil, consisting of organic matter, such as decaying leaves, twigs, and other plant residue. The O layer can add valuable nutrients to the root zone of growing plants.
olericulture--Cultivation of vegetables.
open-pollinated seeds--Seeds resulting from plants that are pollinated by numerous others of the same species.
open-pollination--Type of pollination that allows any pollen of a species to germinate and fertilize the eggs of a plant of the same species. The resultant seeds express genetic diversity.
organelle--Individual structure within a cell having a specialized function. Mitochondria and chloroplasts are examples of organelles in plant cells.
organic matter--Remains of a living organism that releases nutrients as it decomposes. In compost or soil amendments, organic plant matter is used exclusively. Some examples of organic matter include peat moss, leaves, and grass clippings.
osmosis--Movement of a liquid through a semipermeable membrane from an area of low concentration of a solute to an area of high concentration of the solute.
ovary--Female organ on a flower. It comprises the base of the pistil and contains one or more ovules. Ovaries ripen onto fruits.
ovule--Contained within an ovary. A ripened ovule develops into a seed.
panicle--Compound inflorescence, such as a compound spike or raceme commonly of the type found on many grasses.
parent material--Bedrock or other mineral source material from which soil is formed.
parthenocarpy--Development of seeds in the absence of pollen fertilization.
pasteurization--Soil treatment to kill pathogens and weed seeds by heating the soil to 145 to 165[degrees]F for 30 minutes.
ped--Naturally formed shapes of aggregates that may be platy, blocky, subangular blocky, prismatic, columnar, granular, and crumb.
peduncle--The stem of an individual floret in an inflorescence.
perennial--A plant that grows from seed for 1 year; then the herbaceous top portion dies in winter but the root system remains alive. The following season the plant sends up new shoots and continues to grow. They may not bloom until their second year. Woody perennials do not die back and may be deciduous or evergreen.
perfect--Flower that contains both the male (stamen) and female (pistil) organs. Perfect flowers are sometimes referred to as hermaphroditic.
pericarp--The ripened ovary wall that becomes part of the fruit. It may develop distinct layers of endocarp, mesocarp, and exocarp.
perspective--A type of drawing that attempts to re-create the way we perceive depth. In this type of drawing, a focal point is used to draw the eye into the distance.
pesticides--Chemical controls used to eliminate or reduce plant disease. These may be naturally occurring or manufactured.
petal--Floral organ that is usually colored and serves to attract pollinators. Petals often fall off once pollination has occurred.
petiole--Leaf stem that attaches leaf blade to plant stem.
petiolule--Stem that attaches a leaflet to a compound leaf.
pheromone trap--Insect traps that use chemicals detected by insects to lure them into the trap.
pheromones--Chemicals that are detected by insects and are usually species specific.
phloem--Vascular tissue that carries sugars and other biochemicals from leaves to the rest of the plant.
photons--An elementary particle that is the basic unit of light energy.
phototropism--Growth of plants in response to light. Positive phototropism is growth of plants toward light. Negative phototropism is growth away from light.
phytochrome--Photoreceptor involved in phototropism, seed germination, and internode elongation.
pistil--Female floral organ.
pistillate--Flowers lack a stamen (male floral organs).
plan view--Type of drawing that provides a two-dimensional view. The two dimensions are horizontal and directional, e.g., north-south and east-west. Height is not depicted.
plant pathologist--One who studies and diagnoses plant disease problems.
plugging--A method of planting some species of turf that requires digging up established turf and dividing it into smaller plugs that can then be planted in individual holes.
polarity--In taking scion wood and rootstock cuttings, the end of the wood closest to the cut is the proximal end and the end of the wood farthest from the cut is the distal end. This spatial arrangement must be maintained for the pieces to heal together. Typically, proximal ends are joined together.
pollen sac--Contains pollen within the anther.
pollinizer--Plant that is grown specifically to provide pollen to ensure fruit set on compatible plants.
pomology--Study of fruit culture.
post-emergence herbicide--Herbicide that is applied after weeds have emerged.
post-plant fertilization--Fertilizer that is applied after planting.
pre-emergence herbicide--Weed control chemical that is applied before an area is planted. This type of herbicide destroys seeds as they germinate. It can be used where transplants are going to be grown or after a seed-planted crop has emerged.
preliminary drawing--A drawing that incorporates ideas and information from the functional drawing. It suggests possible plants for each area but does not select specific plants. It is used to obtain client feedback before the final drawing is made.
pre-plant fertilization--Fertilizer that is applied before planting.
private area--The area in the landscape that is used for personal, private activities. It is usually attached directly to a bedroom or other private area of the house.
prothallus--In ferns, this is the structure that develops after spores germinate. The prothallus bears the female (archegonia) and male (antheridia) organs.
public area--The most visible area, usually a front yard.
quantitative traits--Traits that are controlled by numerous genes.
R horizon--The undecomposed parent material of a mineral soil.
rachis--Central stem of a compound leaf.
radicle--The seed root that is the first evidence of germination.
receptacle--Specialized structure on a flower that serves as a base for florets or floral organs such as pistils and stamen.
renewal prune--Pruning technique in which one third of the stems are removed each year, leaving newer, younger growth for a continued vitality of growth.
rhizome--Underground stem that may be fibrous or fleshy, usually growing horizontally.
root cap--On the tip of the growing root, an accumulation of dead cells preceding the meristem in the soil.
root cuttings--Vegetative propagation technique made on portions of root tissue.
root hair--An epidermal cell near the tip of a root that extends into the surrounding soil or medium to take up nutrients and water.
rootstock--Part of a graft or bud-union that provides the roots for the grafted plant. Rootstocks often are more disease tolerant and may be hardier and faster growing than the scion wood.
rotary mower--Type of mower with a blade that rotates parallel to the ground.
scarification--Technique of scratching, nicking, or otherwise breaking impermeable seed coat to permit imbibition and subsequent germination.
scion--Top part of a graft that has improved flowers, fruit, nuts, and others. Scion wood is collected from desirable cultivars for vegetative propagation.
selective herbicide--Weed killer that kills only monocots, only dicots, or some other small group of plants.
selective pesticide--Chemical that is very specific in which pests it controls.
self-incompatible--Floral reproductive system in which pollen is incapable of fertilizing ovules from the same plant. This is a response that is not due to any abnormality but to a molecular recognition system that is genetically determined.
self-sterile--Plants that will not set seed when they are self-pollinated.
semi-hardwood cuttings--Vegetative propatules taken from woody plants in summer, when woody tissue has begun to form.
sepal--Vegetative tissue forming the outer ring of floral organs.
service area--Utilitarian areas that are no larger than needed for the function they serve. Examples include enclosures for garbage cans, garden storage sheds, or dog runs.
sessile--Leaves lacking a petiole.
side-dressing--Method of applying fertilizer by placing it alongside plant in the field.
side grafting--Method of grafting where the trunk of a tree remains in place in the ground and scion wood is placed into V-shaped cuts around the outside, into the cambial layer. Multiple scions may be placed on a single trunk, depending on the diameter of the trunk.
sign--In disease, actual evidence of a pathogen, such as hyphae or spores.
site analysis--A review of the site to be landscaped. It includes an inventory of plants and flower beds, location of utility lines or other obstructions, layout of the property, and information from soil tests.
sleeper--In timber walls, a piece of timber that is attached to the deadman at a perpendicular angle, it ties the deadman into the hillside.
softwood cuttings--Vegetative propagules taken from woody plants in late spring, after the initial flush of growth.
soil profile--A vertical section through the soil.
soil structure--Character of soil dealing with the formation of aggregates. Spheroidal structures such as granules or crumbs are ideal for plant growth.
soil texture--Character of soil dealing with particle sizes and their effect on drainage and water retention.
solarization--Method of pasteurizing or sterilizing soil by covering with plastic to trap heat.
sorus (sori)--Region where sporangia are clustered on reproductive fern fronds.
source-to-sink movement--Movement of sugars in the organs where they are produced (source) to the location in the plant where they are most needed (sink).
spadix--A compound flower enclosed by a spathe, or bract, and having a thick or fleshy axis.
species--Members of a taxonomic group sharing specific characteristics that are capable of interbreeding. Plants within species groups are grouped within genera based on more general shared characteristics. Further divisions within a species include varieties, cultivars, or cultivated varieties and subspecies.
specimen plant--Landscape use of a plant in which it is planted alone to show off its ornamental qualities, such as showy flowers, fruit, and framework.
spiking--A method of aerating turf using solid tines to poke holes into the turf surface.
splice grafting--A simple method of grafting wherein the rootstock and scion both have an angled cut made into the adjoining ends, they are joined and wrapped with grafting tape so that they can grow together.
sprigging--Method of vegetatively establishing turf using sprigs or simply a shoot and root portion of turf grass.
spur--A short, usually pointed branchlet, found on some fruit trees. Flowering and fruiting occurs on these organs.
stamen--The male floral organ that consists of a filament and anther. Pollen are contained in the anther.
staminate--A flower having a stamen and lacking pistils.
stigma--The often sticky surface of the pistil where pollen lands and begins the germination and fertilization process.
stipule--A modified leaf that subtends a leaf or shoot.
stolon--Horizontally growing aboveground stem, sometimes called a runner.
stomate (stomata)--Pores on the leaf surface that allow for gas exchange and permit loss of water in a process known as transpiration. Stomates are formed by two guard cells that open and close depending on the water status of the plant.
storage organs--Vegetative structures for storage of carbohydrates or other plant food.
stratification--Seed treatment that consists of moist, cold conditions that meets physiological dormancy requirements of some species.
structure--See soil structure.
style--The often-elongated portion of a pistil that is located between the stigmatic surface and the ovary base.
subtropical fruits--Fruits that are not hardy to extreme cold, yet tolerate some frost and may have a modest chilling requirement for complete flower development.
subtropical nuts--Tree nuts that are not hardy to extreme cold, yet tolerate some frost and may have a modest chilling requirement for complete flower development.
subordination pruning--Removal of specific branches to aid in growth of a strong central leader. If there are two leaders, one is headed back, or subordinated to the other one, that will become the main leader.
subsoil--The B layer of soil that is found beneath the A layer in the soil. In this layer, organic matter is nonexistent, and soil particles are mostly clay.
symptom--In disease, an indication on the plant that something is wrong, such as dead spots, chlorosis, and so on.
systemic herbicide--Chemical that translocates through a plant, usually taken up by the roots, but affecting pests that feed on the leaves, stems, or roots.
systemic pesticide--Chemical that translocates through a pest when they ingest it, causing it to die.
taxonomy--The science or technique of classification, naming, or identification of organisms based on appearance, genetics, physiology, or other identifiable features.
temperate fruits--Fruits that can grow in a climate where they will receive chilling in the winter.
temperate nuts--Tree nuts that can grow in a climate where they will receive chilling in the winter.
texture--See soil texture.
thatch--In turf, accumulated layer of dead stems and leaves above-ground and below the live stems and leaves.
thorn/spine--A sharp-pointed modified stem found on stems or shoots.
tilth--The physical characteristics and moisture condition of soil.
title block--Located on the final plan, often in a small blocked-out area, that provides information about the landscape plan: owner and location of the residence or business, designer name, company, address, and the date or year of the plan.
topsoil--In a soil horizon, the A, or upper layer of soil, although it may be covered by the O (organic matter) layer. Topsoil is the best horizon for optimal plant growth.
trichomes--Hairlike protuberances on leaves and stems that may have a variety of shapes and may exude a variety of substances that can be toxic to pests or sticky.
tropical fruits--Fruits that do not tolerate frost at all.
tropical nuts--Tree nuts that do not tolerate frost at all.
tube nucleus--One of two types of nuclei found inside pollen. The tube nucleus is also known as the generative nucleus.
tuber--A storage organ that is an underground stem.
tuberous root--Underground storage organ that is somewhat enlarged and tapers at either end.
tunic--Papery coating found on some bulbs.
understory--Trees, shrubs, and vines growing in a forest under the canopy.
vector--Insect who transmits diseases to plants, usually during feeding.
venation--Arrangement of veins in a leaf.
vernalization--Arrangement of leaves within the bud. In turfgrasses, this can be an identifying feature.
very hardy--Vegetables that are not damaged by a hard frost and can withstand freezing temperatures.
viability--Measurement of the ability of a seed to germinate.
virus--Pathogen that is made up of DNA enclosed by a protein coat. It replicates itself inside its host.
whip-and-tongue grafting--Type of graft in which matching slant cuts are made on both the scion and rootstock, followed by a vertical cut into each, creating tongues on each piece of wood. The pieces are then inserted into each other and wrapped with grafting tape to heal together.
xylem--A component of vascular tissue, along with phloem. Transports water and nutrients from the roots, upward through the plant to other plant tissues.
zone of cell elongation--Located just behind the meristem, this is the place in the growing root where cells elongate.
zygote--Cell that results from the union of egg and sperm.