Borer

An insect larva that tunnels into stems and trunks of shrubs, trees, etc.

Bract

1. A more or less modified leaf subtending a flower or belonging to an inflorescence, or sometimes cauline.

2. The similar structure in cryptogams surrounding reproductive organs.

Brochidodromous

Describes leaves with pinnate venation in which the secondary veins do not terminate at the margins but rather are joined in a series of prominent arches. See also: acrodromous, eucamptodromous, semicraspedodromous.

Bundle scars

iny, somewhat circular dots within the leaf scar, caused by the breaking of the fibrovascular bundles which run through the petioles into the blades of the leaves.

Bush

A shrub, especially one that is low and thick with many stems rather than a single trunk.

Capillary water

The part of soil water which is held cohesively as a continuous layer around particles and in spaces, most of it being available to plant roots.

Caterpillars

The larvae of butterflies and moths, which often feed on leaves.

Chafers

Beetles that attack plant roots as larvae and leaves as adults.

Chlorosis

(adj. chlorotic)

A yellowing of the leaves, reflecting a deficiency of chlorophyll and caused by waterlogged soil or a lack of nutrients, often iron.

Cirrate

(syn. cirrhate)

Applied to leaves which curl up in drying. Cirrate leaves are more regularly curled than crispate leaves.

Coalescence

The union of parts or organs of the same kind.

Coma

Comal tuft, a tuft of leaves at the tip of a stem or branch.

Conceptacle

A flask-like structure containing reproductive organs.

Cotyledon

(syn. seed leaf)

One of the first leaves to appear after germination (there may be one, two, or more); the foliar portion of the embryo as found in the seed. See also: true leaf.

Crown

In roses, the region of the bud union; the point near soil level where the top variety and the understock are joined

Cutworms

Soil-living brownish caterpillars that feed at night, often severing stems of herbaceous plants.

Cytokinin

Any of various plant growth hormones, such as kinetin, that grow and promote cell division and delay the senescence of leaves.

Deep Watering

Inundating an area with water for a long period of time, perhaps 24 hours or more, to permeate the deepest layers of subsoil, thereby pulling roots down where they will not easily perish from drought.

Defoliant

A chemical substance which causes a plant to drop its leaves.

Defoliate

(n. defoliation)

1. To cause the leaves of a plant to drop.

2. To remove the leaves of a plant.

Double-worked

Twice grafted. The plant consists of the rootstock, an intermediate scion, and the upper scion

Downy Mildew

Downy mildew refers to any of several types of oomycete microbes that are obligate parasiteof plants. Downy mildews exclusively belong to Peronosporaceae.

Downy Mildew is not as widespread and much more dependent on ideal temperatures and moisture conditions to cause devastating results on roses.

Drip Line

The line that could be drawn on the ground under a tree beneath the outermost tips of the branches. Rain flows off the tree at this point, so it is the area where roots congregate and the best point to place fertilizer, water, etc.

Drip Point

(alt. drip-point, alt. drip-tip)

1. A leaf tip with an extension–acuminate, caudate, aristate–from which water drips during wet conditions.

2. A long drooping tip on leaves, particularly those of rain forest trees.

Epicotyl

The stem of a seedling between the cotyledons and the first true leaves.

Epiphyll

An organism that grows on leaves. See also: epiphyte.

Facultative Apomict

A plant that can reproduce either sexually or asexually (apomixis.)

Fasciation

An abnormal flattening or coalescence of stems or leaf stalks.

Feedback

Any partial reversion of the effects of a given process to its source, such as leaves falling to the ground and furnishing calcium for uptake by the roots of the plant.

Flower

The reproductive structure of a flowering plant consisting of a pistil and/or stamen, and usually including petals and sepals.

Foliage

The leaves of a plant taken collectively.

Foliar Diagnosis

Evaluation of the nutrients in a plant, or the plant nutrient requirements of a soil, by analyzing the leaves.

Foliar Feeding

(alt. foliar fertilizing)

The process whereby plants are fertilized by application of liquid onto the leaves rather than through the soil.

Folic Acid

(syn. pteroylglutamic acid)

A member of the B vitamin complex, found mostly in the leaves of plants.

Fructification

The act or organs of fruiting.

Guttation

1. The formation of drops of water on plants from moisture in the air.

2. The exudation of liquid water from the uninjured surface of a plant leaf.

3. The process of water being exuded from hydathodes at the enlarged terminations of veins around the margins of the leaves

Hardening

1. The process of gradually taking plants into a harsher environment, e.g., from the hothouse to the garden.

2. The term can also mean sustaining a plant from summer to winter, which may include a three-staged process:

1) phytochrome clocks signal the shortening days with a color change.

2) Growth ceases, carbohydrates are transported to the roots, and abscisic acid forms at the union of leaf and stem, dropping the leaf and healing the wound. The dropped leaves serve as mulch and protect the roots from excess cold in the winter, while cell walls toughen.

3) A smooth ice forms around the cells without rupturing them, a process called vitrification.

Hip

The closed and ripened receptacle of a rose which contains the seed.

Homologous

Refers to organs or parts that are similar in form or function.

Imperfect

Describes a flower which contains only one set of sexual organs, either stamens or pistils.

Interpetiolar

Describes a stipule located between the petioles of two opposite leaves.

Juxtaposed

Refers to the relative placing of organs.

Leaf (pl. leaves)

A usually flat, green structure of a plant where photosynthesis and transpiration take place and attached to a stem or branch.

Leaf Blight

Any of various diseases which lead to the browning and dropping of a plant’s leaves

Leaf Bud

A bud which contains undeveloped leaves.

Leaf Curl

A disease that causes leaves to roll up.

Leaf Litter

The leaves that have fallen from a plant, either through normal seasonal changes or due to disease. Especially in the latter case, leaf litter can harbor pathogens and should be cleaned up promptly, particularly around plants such as roses. In a naturalized, woodland setting, leaf litter can be a normal part of the workings of the garden.

Leaf Miners

Tiny grubs that tunnel in leaves leaving whitish blotches or trails.

Leaf Mold

A form of humus composed of decayed leaves, often used to enrich soil.

Lignification (adj. lignified)

The process by which herbaceous stems become hard and woody.

Meristem (alt. apical meristem)

The undifferentiated tissue from which new cells are formed, e.g., the tips of roots or stems; the growing tip.

Mildew

A fungus that leaves a thin white coating on the surface where it grows.

Monopodium (pl. monopodia, adj. monopodial)

The main axis of a stem or rhizome maintaining a single direction of growth and giving off lateral branches or stems. See also: sympodium.

Multifoliate

With many leaves.

Multiplanar

Describes divided leaves, with the lobes held in several to many planes.

Natural Layering

The spontaneous rooting of stems when they make contact with the soil.

Node

The place upon a stem which normally bears a leaf or whorl of leaves.

Opposite

Describes leaves arranged along a twig or shoot in pairs, opposite each other at a single point along an axis.

Paraphyllia

Minute leaf-like or much-branched organs among the leaves.

Paraphysis (pl. paraphyses)

1. Jointed hyaline hairs growing among the reproductive organs. 2. The thread-like hyphae between the asci.

Paroicous

Having its male and female organs in the same cluster, but not mixed, the antheridia being in the axils of the perichaetial bracts below the archegonia.

Periderm

An outer, cortical protective layer of many roots and stems that typically consists of phellem, phellogen, and phelloderm

Persistent

Lasting beyond maturity without being shed, as some leaves remaining through winter, etc.

Petal

A division of the corolla; one of a circle of modified leaves immediately outside the reproductive organs, usually brightly colored.

Petal Cells

The tissues and cells that contribute to scent biosynthesis in scented and nonscented Rosa x hybrida cultivars as part of a detailed cytological analysis of the rose petal were localised. Adaxial petal epidermal cells have a typical conical, papillate shape whereas abaxial petal epidermal cells are flat. Using two different techniques, solid/liquid phase extraction and headspace collection of volatiles, is was shown that, in roses, both epidermal layers are capable of producing and emitting scent volatiles, despite the different morphologies of the cells of these two tissues. Moreover, OOMT, an enzyme involved in scent molecule biosynthesis, was localized in both epidermal layers. These results are discussed in view of results found in others species such as Antirrhinum majus, where it has been shown that the adaxial epidermis is the preferential site of scent production and emission

Phenology (adj. phenological)

The science of the relations between climate and periodic biological phenomena, e.g., the fruiting of plants or the color change of leaves.

Phenotypic

Refers to a plant’s adaption to surrounding conditions, which are neither stable nor capable of being inherited (genotypic). Such visible changes occur especially where plants are grown in a wide variety of conditions, but will not carry over to different conditions, e.g., red leaves may occur in hot dry areas, but turn green when grown in normal conditions.

Pheromones

Chemical substances produced by animals that attract and stimulate sexual partners of the same species.

Pinch Back (syn. pinch out)

To remove the growing tips on main stems, usually using the fingernails of thumb and forefinger, in order to induce branching and thereby thicken and strengthen the plant.

Pinnate

1. Consisting of several leaflets arranged on each side of a common petiole or rachis on a compound leaf or frond.

2. The feather vein pattern of simple leaves.

Pith

The spongy or hollow center of twig or some stems.

Plant

Any of the members of the kingdom Plantae typically lacking locomotive movement or obvious nervous or sensory organs and possessing cellulose cell walls and usually capable of photosynthesis.

Plant Breeders’ Rights

Plant breeders’ rights (PBR), also known as plant variety rights (PVR), are rights granted to the breeder of a new variety of plant that give him exclusive control over the propagating material (including seed, cuttings, divisions, tissue culture) and harvested material (cut flowers, fruit, foliage) of a new variety for a number of years.

Polarity

The tendency for plants to develop from its poles, roots growing down, stems growing upward, making it essential to plant bulbs, etc, in the correct position.

Powdery Mildew

A fungus forming a white powdery coating on leaves and stems.

Proliferous (syn. proliferating)

1. Freely producing offshoots, bulblets, or plantlets.

2. In mosses, bearing young shoots from the antheridial or archegonial cluster of leaves.

Propagule

Any structure having the capacity to give rise to a new plant, whether through sexual or asexual (vegetative) reproduction. This includes seeds, spores, and any part of the vegetative body capable of independent growth if detached from the parent.

Pseudostem

An erect aerial growth which appears to be a stem with leaves, but is actually packed or overlapping sheaths and stalks of essentially basal leaves

Rank

1. A vertical row, as of leaves. When you sight along the length of a branch from the tip end, if it appears there are two rows of leaves, either opposite or alternate, the branch is 2-ranked; if three rows, it is 3-ranked, etc.

2. In taxonomy, the position of a taxon in the hierarchy, e.g., species, genus, family, etc.

Receptacle

1. The more or less expanded or produced portion of an axis which bears the organs of a flower (the torus) or the collected flowers of a head, and in roses, enfolds the developing ovaries to form a hip.

2. Any similar structure in cryptogams

Rejuvenation pruning

The practice of cutting all the main stems of a shrub back to within half-inch of the ground during winter dormancy.

Retentive sepals

Sepals that remain attached to the apex of the receptacle after it has ripened into a hip.

Rootstock (syn. rhizome, syn. understock)

1. A rhizome.

2. The root system and lower portion of a woody plant to which a graft of a more desirable plant is attached.