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Glossary

Acidic Soil

Soil with a pH less than 7.0

Aggressive

Refers to plants that have the potential to spread quickly through areas in which they are not wanted; (Different from invasive; see definition for invasive)

Alkaline Soil

Soil with a pH greater than 7.0

Alternate

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An arrangement in which leaves or buds are attached singly to the branch in a staggered pattern; (can also apply to the arrangement of branches on a stem)

Annual

A plant that completes its life cycle in one year; it grows from seed, flowers, and produces new seeds before it dies.

Balled-and-burlapped

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Plants that are dug from a nursery with soil around their roots, then covered in burlap and twine to hold the root ball together until being planted

Bare-root

Refers to dormant plants that are sold without soil surrounding their roots; often used for shipping mail order plants and fruit trees

Biennial

A plant that completes its life cycle in two years; it grows from seed to form a small plant the first year, and then flowers and sets seed the following year.

Bipinnately Compound

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A leaf that is divided into multiple leaflets, with each leaflet further subdivided into smaller leaflets

Bract

1. A modified leaf often positioned at the base of a flower or group of flowers

2. One of multiple structures interspersed among the scales (seed-bearing portions) of certain conifers

 

Branch Collar

The swollen area located where the base of a branch attaches to the trunk of a tree; pruning cuts should be made on the outside of the branch collar so they heal properly.

Broadleaf

Refers to plants that have leaves with a flat, relatively broad surface, often marked with a network of prominent veins

Bud Swell

The time of year when plants are emerging from winter dormancy and buds are visibly swelling

C-value

Coefficient of Conservatism; C values range from 0 - 10, and represent the estimated probability that a native plant is likely to occur in a remnant natural plant community (applies to Chicago area native plants).

Cambium

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The layer of cells responsible for development of new xylem and phloem, leading to an increase in girth of a woody plant

Canker

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A wound in bark or wood that is infected with a fungal or bacterial organism

Canopy

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1. The crown or top portion of a tree

2. In forested areas, the top layer of growth provided by a group of trees

Catkin

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A type of inflorescence (group of flowers) that is often pendulous and usually of a single gender

Chicagoland Grows®

A collaborative plant introduction program consisting of partnerships between Chicago Botanic Garden, The Morton Arboretum, and the Ornamental Grower’s Association of Northern Illinois (OGA), designed to develop and promote the use of new plant cultivars that are well-adapted to the growing conditions of the Upper Midwest

Chlorosis

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The yellowing or loss of green pigment in a leaf; interveinal chlorosis refers to a yellow leaf with green veins often due to iron or manganese deficiency

Clay

One of the mineral components of soil

Compound Leaf

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A leaf that is divided into two or more leaflets; can be palmately compound, pinnately compound, or bipinnately compound

Conifer

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A cone-bearing tree or shrub

Container-grown

Plants that are grown in containers; they maintain a complete root system and are easier to transport because they are not dug out of the ground

Cordate

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Refers to a leaf that is heart-shaped

Cultivar

A horticultural variety of a plant that is produced by breeding or propagation of cuttings, rather than occurring naturally in the wild

Dead-head

To pinch or remove faded flowers in order to tidy a plant, stop seed production, and promote future flowering

Deciduous

Refers to plants that lose their leaves naturally at the end of the growing season

Defoliation

The loss or removal of leaves from a tree or shrub

Dehiscent

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Refers to a fruit that splits open along seams to release seeds

Dieback

A progressive death of plant tissues

Dioecious

Having female and male flowers on separate plants

Disease Resistant

A plant that is able to resist a disease that interferes with its normal growth and function

Dormant

A state in which a plant is not actively growing; a resting stage

Drip Line

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The area under the outer most edges of the branches on a tree

Drupe

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A fleshy fruit that contains a seed enclosed in a hard pit (i.e. cherry)

Dwarf

A plant variety that is abnormally small for a given species

Entire

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Describes a leaf margin (edge) that is unbroken (lacking teeth, lobes, or serrations)

Espalier

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1. A plant trained on a trellis, with branches generally extending horizontally in a fan shape or flat plane

2. The process of training a woody plant to grow in a flat plane, usually against a wall or trellis

Evergreen

A plant that retains its leaves year round

Exfoliating Bark

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Bark that peels off in layers or shreds to reveal the inner bark layer

Family

A level of botanical classification consisting of several related genera that share similar characteristics

Fastigiate

Refers to a narrow tree or shrub in which the branches grow vertically upward and close together

Feeder Roots

A system of smaller roots growing out of the main roots, functioning in uptake of water and nutrients from the soil

Foliage

Leaves

Follicle

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A dry fruit that opens along one edge to reveal seeds (i.e. milkweed)

Genus

A level of botanical classification consisting of related species that share some basic characteristics

Germinate

The process by which a seed begins to grow and send out roots and shoots

Girdle

Physical strangulation of a branch, or the removal of bark on a branch, leading to a disruption in the flow of water and nutrients, causing dieback

Girdling Roots

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Roots that encircle the base or roots of a tree, eventually restricting the growth of the trunk or roots

Glabrous

Hairless

Gland

A general term referring to a plant organ or tissue that secretes a substance such as oil or nectar

Graft

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A method of propagating plants in which a shoot or twig is attached to the stem of another plant and allowed to grow

Groundcover

Typically refers to low growing plants that spread to fill in an area

Habit

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The natural shape of a tree or plant

Hardiness Zone

The US Department of Agriculture has divided the country into regions based on average low winter temperatures. Plants are assigned to hardiness zones based on the lowest temperature the plant can tolerate before cellular damage occurs.

Heading Back

A type of pruning in which a cut is made to reduce the length or height of a branch or stem

Heartwood

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The dense, inner part of a tree trunk, yielding the hardest timber and providing stability to the tree

Husk

The outer covering of a seed or fruit

Hybrid

The offspring that results from breeding plants of two different species or varieties

Imperfect Flower

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A flower that bears only one sexual reproductive structure, either male or female

Included Bark

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A point of poor bark attachment that occurs when two or more stems grow closely together, causing the bark to roll inward and produce weak, under supported branches

Inflorescence

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A grouping of flowers arranged in a specific pattern

Internode

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The region between two nodes on a stem

Invasive

Typically, a non-native plant that competes with native plants for water, nutrients and space, destroying the natural habitat and ecosystem of native species in the process; (Different from aggressive; see definition for aggressive).

Lanceolate

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A leaf shape in which the blade is much longer than it is wide, with the widest part below the middle and tapering inward

Leaflet

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One section of a compound leaf

Lenticel

A small corky area on a stem that allows for gas exchange

Lobe

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A protruding/projecting part of a leaf margin

Lobed

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A leaf margin (edge) that has projections separated by gaps that do not reach the middle vein

Margin

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The edge of a leaf

Monoecious

Having male and female reproductive structures on the same plant, which can be contained in either individual flowers or in separate flowers

Mulch

A layer of material, such as woodchips or compost, that is applied on the soil surface to retain soil moisture and moderate soil temperature extremes; if organic, it will break down to improve soil structure and fertility

Native

A plant that occurs naturally in a given area and has not been introduced

Naturalized

A plant that has adapted to and become established in a nonnative environment

Node

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A point on a stem where leaf buds originate

Nut

A dry fruit in which the seed is surrounded by a hard structure

Oblong

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A leaf shape that is longer than it is broad and has nearly parallel sides

Opposite

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An arrangement in which leaves or buds that are attached to opposite sides of a branch at the same node; (can also apply to the arrangement of branches)

Organic

Derived from plant or animal matter

Ovate

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Refers to a leaf that is egg-shaped, with the broad end toward the base

Overwinter

Living through the winter, often in a dormant state

Palmately Compound

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A compound leaf with leaflets originating from a center point and radiating out in a fan-like fashion

Panicle

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A compound, branched inflorescence

Pathogen

An organism capable of causing disease

Perennial

A herbaceous (non-woody) plant that lives for three or more years

Perfect Flower

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A flower that bears both male and female reproductive structures

Petiole

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The stalk on a leaf

Phloem

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The vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves

Photosynthesis

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The process by which green plants use sunlight to synthesize food from carbon dioxide and water, releasing oxygen in the process. 

Pinch Back

A type of pruning that encourages branching and fuller growth by removing growing tips; often achieved by physically pinching between two fingers

Pinnately Compound

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A compound leaf with leaflets arranged on opposite sides of the rachis or midrib; feather-like

Pollination

The process of transfering pollen from the male anther to the female stigma, either within a single flower or from one flower to another

Pome

A fleshy fruit with a papery core surrounding the seeds in the center, such as apple or pear

Pubescent

Having hairs

Raceme

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A type of inflorescence in which flowers arise from a central stalk, with each flower having its own stalk (as opposed to a spike, where each flower is connected directly to the central stalk)

Rachis

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An extension of the petiole on a compound leaf; leaflets are connected to the rachis

Rhizome

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An underground stem that typically grows horizontally

Samara

A winged seed or fruit

Sap

A fluid that carries water, nutrients, and sugars through the vascular system of a plant

Sapwood

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A region of the trunk located just beneath the bark, consisting of xylem tissue

Scale

1. The protective covering on a bud

2. A type of sucking insect that attacks numerous trees and shrubs

Sepals

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The outer layer of floral parts, often green and leaf-like in appearance, and serving to cover and protect the unopened flower bud

Serrate

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Refers to a leaf margin (edge) that is saw-toothed, with teeth pointing forward

Shrub

A multistemmed woody plant that is shorter than a tree

Simple Leaf

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A leaf with an undivided blade; not compound

Sinus

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The space between two lobes of a leaf

Soil pH

A measure of the acidity or alkalinity of soil; pH influences the availability and uptake of nutrients for plant growth, and is measured on a scale ranging from 1 - 14, with 7.0 being neutral.

Soil Structure

The arrangement of individual soil particles and pore space into larger units, or aggregates; soil structure affects the amount of air and water held in the soil.

Species

A level of botanical classification below genus that consists of naturally occurring plants that share similar characteristics, and are capable of producing offspring with those characteristics

Spore

A small, typically one-celled reproductive unit of nonflowering plants, fungi and algae

Stolon

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An above ground, horizontal stem, often rooting at the nodes

Structural Roots

The support roots of a plant

Subshrub

A shrub that has slightly woody bark but often dies back to ground in winter

Sucker

A shoot that arises from the roots, with the ability to increase the size of a plant by forming a colony

Synonym

An alternate or previously used name for a plant; not the current, accepted scientific name

Taproot

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A central, vertical root that penetrates deeply into the soil

Thicket

A dense growth of shrubs

Transpiration

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The process by which water vapor is released through the leaves of a tree or plant

Transplant

To move a plant from one place and replant it in another

Umbel

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A type of inflorescence in which all the flower stalks originate from one point, like spokes of an umbrella

Understory

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The layer of vegetation beneath the canopy of a forest

Variety

A group of plants of the same species having one or more distinguishing characteristics and occuring naturally in the wild

Vein

A vascular structure in a leaf that provides supports for the leaf and transports both water and food

Whorled

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An arrangement in which leaves or buds are attached in groups of three or more at a single node

Xylem

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A vascular tissue in plants through which water and nutrients are transported from the roots to the canopy