Hortsense Glossary of Terms

Select a letter from A through Z to see that section of the glossary.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Term	Definition
adelgids	a family of aphid-like insects that feed exclusively on conifers and typically are covered with white waxy material.
aesthetic	has to do with appearance; beauty.
alkaline	having a basic reaction, that is containing the OH- radical and turning red litmus blue when in solution.
allelopathy	the excretion by some plants of compounds from their leaves and/or roots that inhibit the growth of other plants.
alternate	an arrangement of leaves or other parts not opposite or whorled; parts situated one at a node, as leaves on a stem; like parts succeeding each other singly with a common structure.
alternate host	one of two kinds of plants on which a parasitic insect or fungus (e.g., rust) must develop to complete its life cycle.
annual	maturing and living one season only.
anthers	pollen-bearing part of a stamen, borne at the top of a filament, or sessile.
anthracnose	a leaf-, stem-, or fruit-spot type of disease caused by fungi that produce their asexual spores in an acervulus.
appendages	subordinate or derivative body parts.
APHIS	Animal and Plant Health Inspection Service
armyworms	caterpillar species closely related to cutworms. They often move in mass through crop stands while stripping plants of their foliage.
auricles	an ear-shaped lobe, generally used to describe the base of leaves or petals.
axils	the main stem or central support of a plant.

B

Term	Definition
bacteria	plural of bacterium, a unicellular microscopic organism that lacks chlorophyll and multiples by fission.
bacterial	adj. anything related to or caused by bacteria.
bacterium	a unicellular microscopic organism that lacks chlorophyll and multiples by fission.
basal	pertaining to the extremity of an organ by which it is attached to its support; said of leaves when at base of plant only. See rosette.
biennial	of two season's duration, normally flowering, fruiting and dying the second growing season from time of seed germination.
bipinnate	doubly compound leaves where primary leaflets are pinnately divided into secondary leaflets. Bipinnate leaves have a fine, feathery texture presenting a delicate, fern-like appearance.
blight	a disease characterized by general and rapid killing of leaves, flowers, and stems.
bracts	a much-reduced leaf, often scale-like and usually associated with a flower or inflorescence.

C

Term	Definition
callus	a mass of thin-walled cells, usually developed as the result of wounding or infection.
caltrops	an herb with spiny pods; I.e., puncturevine
calyx	the outer set of perianth segments or floral envelope of a flower, usually green in color and smaller than the inner set.
cambium	A one- or two-celled layer between the phloem and xylem that produces both these tissues and results in diameter growth.
canes	a long woody pliable stem rising from the ground.
canker	a necrotic, often sunken lesion on a stem, branch, or twig of a plant.
cast skins	the outer layer of an exoskeleton shed by an insect or mite and seen on leaves or twigs.
castings	fecal material; caterpillar pellets.
caterpillar	in general, the larvae of Lepidoptera; in Hymenoptera, the larva of the saw-flies.
chlorosis	of plants, fading of the color of the chlorophyll of plant leaves, caused by environmental stress, chemical deficiency, disease, insects, or mites.
chlorotic	of plants, fading of the color of the chlorophyll of plant leaves, caused by environmental stress, chemical deficiency, disease, insects, or mites.
cocoon	a covering, composed partly or wholly of silk or other viscid fiber, spun or constructed by many larvae as a protection to the pupa.
Colony Collapse Disorder (CCD)	A phenomenon where most worker bees in a honey bee colony disappear, leaving behind the queen, food stores, and a few nurse bees. The exact cause is unknown, but factors like pesticides, parasites, disease, and environmental stress are suspected
conk	the visible fruiting body of a bracket fungus.
crawlers	the first stage (nymph) out of the egg of certain plant lice (scales, adelgids, etc.). This stage is quite mobile, while subsequent nymphal stages are stationary.
cultivars	an organism of a kind (as a variety, strain, or race) that has originated and persisted under cultivation.
cultivated	maintained by humans.
cutworms	caterpillar stage of the night flying "millers" or noctuid moths.

D

Term	Definition
deciduous	refers to trees or shrubs that shed leaves completely at the end of the annual growth period.
defoliation	the loss of needles or leaves due to pest activity, disease, or negative environmental response.
delayed dormant	time of year when dormancy is about to end; characterized by the beginning of bud swell.
desiccation	the drying or loss of moisture from a leaf or plant part.
dieback	progressive death of shoots, branches, and roots generally starting at the tip.
dioecious	having unisexual flowers, each sex confined to a separate plant, said of species.
distorted	taking on a shape that is unnatural.
distortion	taking on a shape that is unnatural.
drought	periods or conditions that demonstrate the lack of moisture or rain.

E

Term	Definition
ecdysone	A steroidal prohormone that plays a crucial role in insect molting and metamorphosis. It is secreted by the prothoracic glands and converted into 20-hydroxyecdysone, the active form that triggers molting. The key functions are: 1.) Molting Hormone: Regulates the shedding of the exoskeleton in arthropods. 2.) Gene Activation: Stimulates the expression of genes necessary for development. 3.) Neural Development: Recent studies suggest it influences neural stem cell transitions in fruit flies. 4.) Plant Defense: Some plants produce phytoecdysteroids as a defense mechanism against herbivorous insects.
ectoparasites	Parasites that live on the exterior of their host, such as fleas, ticks, and lice
ELISA	a test in which an antibody carries an enzyme that releases a colored compound, signifying the presence of the pathogen.
elytra	The hardened forewings of beetles and some other insects, serving as protective wing covers for the delicate hindwings used in flight. These coverings are often marked with grooved lines or with rows of punctate dots.
endophyte	an organism that grows within a plant.
eradicate	to do away with completely.
eriophyid	a family of tiny plant feeding mites that possess only 4 legs; they are highly host specific (feeding on only one species) and their damage is predictable and often dramatic.
evergreen	having green foliage throughout the year.
excrement	the waste products eliminated by an insect, principally from digestion; feces.
excreta	the waste products eliminated by an insect, principally from digestion; feces.

F

Term	Definition
fasciation	a symptom characterized by fusing (and flattening) of such plant organs as stems.
fertile (stems)	capable of producing fruit and seed.
flag	the loss of rigidity and drooping of leaves and tender shoots preceding the wilting of a plant.
flagging	the loss of rigidity and drooping of leaves and tender shoots preceding the wilting of a plant.
flocked	covered with white cottony material so as appear like snow.
frass	solid larval insect excrement.
fruiting bodies	complex fungal structures containing spores.
fungal	referring to a group of saprophytic and/or parasitic organisms that lack chlorophyll and conductive tissues, and often produce spores. Includes molds, rusts, mushrooms, smuts, mildews, and yeasts.
fungi	saprophytic and/or parasitic organisms that lack chlorophyll and conductive tissues, and often produce spores. Includes molds, rusts, mushrooms, smuts, mildews, and yeasts.
fungus	a saprophytic and/or parasitic organism that lacks chlorophyll and conductive tissues, and often produces spores. Includes molds, rusts, mushrooms, smuts, mildews, and yeasts.

G

Term	Definition
galls	an overgrowth of plant tissue.
girdled	showing mechanical damage (often from pests) to tree or shrub trunks or limbs that results in inability of cambial tissue to transport nutrients to roots.
girdling	mechanical damage (often from pests) to tree or shrub trunks or limbs that results in inability of cambial tissue to transport nutrients to roots.
gland	a general term applied to oil-secreting organs, or sometimes an obtuse projection or a ring a base of a structure.
gnarled	knotty and twisted.
growth regulator	a natural substance that regulates or interferes with growth functions in plants and insects.
grubs	an insect larva; a term loosely applied, but more specifically to larvae of Coleoptera (beetles) and Hymenoptera (wasps, etc.).

H

Term	Definition
herbaceous	having no persistent woody stem above ground.
honeydew	a sweetish excretion produced by certain insects notably aphids and scales; also an exudate from the surface of some galls.
hornworm	the immature stage or caterpillar of the hummingbird or sphinx moth family; characterized by having a rhino-like horn on the tail end.

I

Term	Definition
imidazolinones	a class of synthetic herbicides that act as inhibitors of the acetohydroxyacid synthase (AHAS) enzyme.
immatures	usually the larval or nymphal stages of various insect groups.
infection	the establishment of a parasite within a host.
instar	A developmental stage of insect larvae between molts. A species may have several instars. Newly hatched larvae before their first molt are first instars or first instar larvae.
Integrated Pest Management (IPM)	An environmentally sensitive approach to controlling pests that does not rely totally on pesticides. IPM depends on frequent monitoring of plants or structures and the accurate diagnosis of the pests so that control strategies are used only when and where needed. A variety of control methods–cultural, mechanical, biological, and chemical–may be employed. IPM takes a look at the entire system and thus monitors the entire system, not singling out only one pest problem.

J

Term	Definition
No entries

K

Term	Definition
No entries

L

Term	Definition
larva	a young insect which quits the egg in an early stage of morphological development and differs fundamentally in form from the adult; in a strict zoological sense, the immature form of animals which undergo complete metamorphosis.
larvae	plural - young insects which quit the egg in an early stage of morphological development and differs fundamentally in form from the adult; in a strict zoological sense, the immature form of animals which undergo complete metamorphosis.
larval	describing features, behaviors, or conditions of a larva.
leaflet	a foliar element of a compound leaf.
leafminer	refers to the feeding style of certain flies, caterpillars that feed between the upper and lower surfaces of leaves resulting in blotching or snake-like passages.
ligule	(1) a strap-shaped organ; (2) (in grasses) a minute projection from the top of the leaf sheath; (3) the strap-shaped corolla in the ray flowers of Composites.
lobes	a projecting part or segment of an organ as in a lobed ovary or stigma; usually a division of a lf., calyx, or petals cut to about the middle (I.e. midway between margin and midrib.
looper	a geometrid or other caterpillar in which some or all the middle abdominal legs are wanting and which moves by bringing tail to thorax and forming a loop of the intervening segments.

M

Term	Definition
maggot	the legless larva of Diptera.
membranous	parchment-like texture
metamorphosis	A biological process in which an organism undergoes a dramatic transformation in body structure, often accompanied by changes in behavior and habitat. This process is common in insects and is controlled by hormones such as ecdysone, which triggers molting, and juvenile hormone, which regulates the transition between life stages. There are three main types of metamorphosis: Ametaboly, Hemimetaboly, Holometaboly.
midge	name for certain fly families.
midrib/midvein	the primary-rib or mid-vein of a leaf or leaflet.
mildew	a fungal disease of plants in which the mycelium and spores of the fungus are seen as a powdery or downy growth on the host surface.
molt	The shedding of an insect’s outer covering during growth. The form assumed between molts is called an instar. Also known as ecdysis.
mutation	something qualitatively new appearing abruptly without transitional forms or slow development; a sport; a potential species.
mycelia	several hyphae, perhaps a considerable mass of hyphae, that make up the vegetative body of a fungus.
mycelium	a hypha or mass of hyphae that make up the vegetative body of a fungus.

N

Term	Definition
native	inherent and original to an area.
necrosis	in a dead and decayed condition; of or pertaining to necrosis.
necrotic	in a dead and decayed condition; of or pertaining to necrosis.
needle miner	see leafminer (needle miners are only seen on conifers).
nematodes	generally, microscopic, wormlike animals that live saprophytically in water or soil, or as parasites of plants and animals.
noctuid	a moth of a large family (Noctuidae) whose members typically have dull forewings and pale or colourful hindwings. Also called owlet.
nocturnal	of the night; applied to insects that fly or are active at night.
nodes	a joint on a stem, represented by point of origin of a leaf or bud; sometimes represented by a swollen or constructed ring, or by a distinct leaf scar.
nymph	young insects which quit the egg in a relatively advanced stage of morphological development, differing from the adult in having the wings and the genitalia present only in an incompletely developed condition; a young stage of insects with an incomplete metamorphosis, (e.g., stinkbugs, aphids, etc.).

O

Term	Definition
oedema	a blister formation due to an increase in intercellular water in leaves.
opposite	two at a node, as leaves.
overwinters	survives the winter in a protected place in a state of physiological "shut-down".
oxalate/oxalic acid	a very strong acid. (COOH)2

P

Term	Definition
palmate	digitate, radiating, fan-like from a common point, as leaflets of a palmately compound lf. or veins or palmately-veined lf.
panicle	an indeterminate infl. whose primary axis bears branches of pedicelled fls. (at least basally so); a branching raceme.
parasites	any organisms that live in or on, or at the expense of another; organisms living in such a way as to derive all nourishment from the tissues of the host.
parasitic	referring to any organism that lives in or on, or at the expense of another; referring to an organism living in such a way as to derive all nourishment from the tissues of the host.
parasitoids	organisms, usually insects, whose larvae develop on or inside a host, ultimately killing it.
pathogen	a bacterium, virus, or other microorganism that can cause disease.
perennial	having a life cycle of three or more years.
pest	Any insect, animal, or organism that feeds on or damages plants, reducing crop yields, stunting growth, or causing plant death. Common garden pests include aphids, caterpillars, and rodents as well as invasive weeds that outcompete desirable plants for nutrients, water, and sunlight.
pesticide	A substance or mixture used to prevent, destroy, repel, or control pests, including insects, weeds, fungi, and rodents, to protect crops and environments.
petiole	a stem or stalk; the slender segment between the thorax and abdomen in certain Diptera and many Hymenoptera; in the latter, a pedicel formed of only one segment, or the first segment of a two-segmented pedicel in ants; in plants, the slender stalk of a leaf.
pheromone	chemical emitted to air currents by an insect to stimulate behavior of other members of species (e.g., mating pheromone).
phloem	cells that conduct food and the products of photosynthesis throughout a plant, including back to the roots.
photosensitive	responsive (sensitive) to light.
physiological	resulting from some unfavorable physical or environmental factor (e.g., light, temperature, water, soil nutrients, chemical, physical, or mechanical injury).
pinnate	having leaflets arranged on either side of the stem, typically in pairs opposite each other.
pollen	A fine powder containing male reproductive cells of flowering plants, essential for fertilization and seed production.
predaceous	any animal that eats others; living by preying upon other organisms, as certain insects.
predators	any animal that eats others; living by preying upon other organisms, as certain insects.
predatory	any animal that eats others; living by preying upon other organisms, as certain insects.
prostrate</span	lying flat on the ground; a general term.
pupa	the resting inactive instar in all holometabolous insects; the intermediate stage between the larva and the adult; applied to all insect orders with complete metamorphosis.
pupae	plural - the resting inactive instar in all holometabolous insects; the intermediate stage between the larva and the adult; applied to all insect orders with complete metamorphosis.
pupate	The process in which an insect larva transforms into a pupa, undergoing metamorphosis before emerging as an adult.

Q

Term	Definition
No entries

R

Term	Definition
raceme	a flower stalk on which the florets start blooming from the bottom of the stem and progress toward the top.
rachis	a stem of a plant, bearing flower stalks at short intervals. The midrib of a compound leaf or frond.
regenerate	to reform; to regrow.
rhizomes	an underground stem distinguishable from a root by presence of nodes, buds or scale-like leaves.
rhizomorphs	a compact bundle of hyphae that has an outer covering and serves as a survival structure.
rosette	a crown of leaves radiating from a stem and at or close to the surface of the ground.
rosetting	short, bunchy habit of plant growth.
rotavate	break up or till the soil.
row covers	fine netting placed over plants to prevent insects from getting at them (e.g. Agrinet, Remay, etc.).
russet	brownish roughened areas on skin of fruit as a result of cork formation.
russetting	brownish roughened areas on skin of fruit as a result of cork formation.
rust	a disease giving a "rusty" appearance to a plant and caused by one of the rust fungi.

S

Term	Definition
sanitation	the removal and burning of infected plant parts, decontamination of tools, equipment, hands, etc.
saprophyte	a plant, fungus, or microorganism that lives on dead or decaying organic matter.
saturated	full to capacity; in soil - very wet.
sawfly	not a fly - a primitive wasp.
scab	a roughened, crustlike diseased area on the surface of a plant organ or the common name of a disease in which such areas form.
scopae	a group or arrangement of short stiff hairs on the body surface of an insect that usually functions like a brush in collecting something (as pollen)
scorch	burning" of leaf margins as a result of infection or unfavorable environmental conditions.
sepals	one of the units comprising the calyx; a usually green foliaceous element subtending the corolla.
serrations	tooth-like" edge at leaf margin.
sheaths	any elongated, more or less tubular structure enveloping an organ or part.
shepherds crook	appears like the handle or bent end of a walking cane.
shothole	a symptom in which small diseased fragments of leaves fall off and leave small holes in their place or small holes in wood resulting from beetle boring.
silica	silicon dioxide (SiO2)
skeletonize	feeding by certain insects which leads to the elimination of all or most of the leaf tissue - often leaving only the veins.
smut	a disease caused by the smut fungi, characterized by masses of dark, powdery spores.
sooty mold	a sooty coating on foliage and fruit formed by the dark hyphae of fungi that live in the honeydew secreted by insects such as aphids, mealybugs, scales, and whiteflies.
spikelets	(1) a secondary spike; (2) one part of a compound inflorescence which of itself is spicate; (3) the floral unit, or ultimate cluster, of a grass inflorescence comprised of flowers and their subtending bracts.
spikes	(1) a usually unbranched, elongated, simple, indeterminate inflorescence whose flowers are sessile; the flowers may be congregated or remote; (2) a seemingly simple inflorescence whose "flowers" may actually be composite heads (Liatris).
sporadic	irregular events such as insect population outbreaks that are largely unpredictable.
spores	comprised of a single gametophytic cell, it functions as the reproductive unit of fungi and some primitive plants.
stamens	the unit of the androecium and typically comprised of anther and filament, sometimes reduced to only an anther; the pollen-bearing organ of a seed plant.
sterile	barren, not able to produce seed.
stippling	the appearance of tiny white or yellow green spots on leaves resulting from mite, leafhopper, etc. feeding.
stipules	a basal appendage of a petiole, usually one at each side, often ear-like and sometimes caducous (falls of easily).
stolons	a horizontal stem that roots at its tip and there gives rise to a new plant.
succulent	bearing a thickened, juicy, soft, fleshy appearance (e.g., new leaves, or thick-leaved plants like cactus).
sulfonylureas	a class of broad-spectrum herbicides widely used for weed control in crops such as wheat, rice, maize, barley, potatoes, soybeans, and blueberries
symptoms	the external and internal reactions or alterations of a plant as a result of a disease, insect, or mite.
systemic	spreading internally throughout the plant.

T

Term	Definition
taproot	primary root that grows downward.
terminals	situated at the tip or extremity; opposed to basal.
toxic	poisonous to living organisms
toxicant	a poisonous substance, such as the active ingredient in a pesticide formulation
toxicity	the degree or extent that a chemical or substance is poisonous
toxin	a naturally-occurring poison produced by plants, animals, or microorganisms. examples are the venom produced by black widow spiders and rattlesnakes

U

Term	Definition
uracils	In horticulture, uracil refers to the naturally occurring pyrimidine nucleobase found in RNA, which plays a critical role in plant growth, development, and metabolism.
ureas	In horticulture and agriculture, “ureas” most often refers to urea fertilizer, a nitrogen-rich compound widely used to promote plant growth
USDA	United States Department of Agriculture

V

Term	Definition
viability	capability of living.
viable	alive; capable of living.
viral	referring to submicroscopic obligate parasites consisting of infectious nucleic acid usually surrounded by a protein coat.
virus	a submicroscopic obligate parasite consisting of infectious nucleic acid usually surrounded by a protein coat.
viruses	submicroscopic obligate parasites consisting of infectious nucleic acid usually surrounded by a protein coat.

W

Term	Definition
whorl	arrangement of three or more structures arising from a single node.
wilt	loss of rigidity and drooping of plant parts generally caused by insufficient water in the plant.
wings	(1) the lateral petal of a papilionaceous flower; (2) a dry, thin, membranous appendage.
witches' brooms	broom-like growth or massed proliferation caused by the dense clustering of branches of woody plants.
WSDA	Washington State Department of Agriculture

X

Term	Definition
xylem	water-conducting element of a plant.

Y

Term	Definition
No entries

Z

Term	Definition
No entries