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Acidic Soil

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Soil pH is a means that measures alkalinity or acidity of the soil, which influences the nutrient availablity and uptake for plant growth. The pH scale is measured 1 through 14, with 7.0 being neutral. Acid soil is considered any measured unit below 7.0 and alkaline soil is anything measure above 7.0


What is an "aggressive" plant? One that has the potential to spread quickly in a location in which it is not wanted.

Alkaline Soil

What is alkaline soil? Soil with pH measurement above 7.0.


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The arrangement of leaves (or buds) where they are attached singly to the stem in a staggered pattern.


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


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


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


A plant that grows from seed to form a small plant the first year, and flowers and sets seed the following year

Bipinnately Compound Leaf

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A leaf that is divided, with each division (leaflet) further subdivided into smaller leaflets.


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An appendage (a modified leaf) often associated with arrangement of flowers.


Branch Collar

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

Bud Swell

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


Applies to Chicago area native plants; C-values are from Swink & Wilheim's Plant of the Chicago Region (used for natural areas). They represent whether a plant is likely to occur in a remnant natural plant community. A value of 0 indicates little confidence that it came from a remnant natural plant community. A value of 10 indicates high probability that it did come from one.


The layer of cells responsible for development of new tissue (xylem, which conducts water and phloem, which conducts food) and that leads to an increase in girth for a woody plant.


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


The crown or top portion of a tree; or, in forested areas, the top layer of growth provided by a group of trees


A group of flowers (inflorescence), often pendulous and usually one gender.

Chicagoland Grows®

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


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 maganese deficiency.

Circling Roots

Roots of a plant that tend to circle around the base of the tree or other roots, eventually restricting the growth of the trunk or roots


One of the mineral components of soil

Compound Leaf

A leaf divided into two or more leaflets. Can be palmate, pinnate, or bipinnate.


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A cone-bearing tree or shrub


Plants that are grown or sold in plastic containers; they maintain a complete root system because they are not dug out of the ground. They are easier to transport.


A horticultural variety of a plant that is man made (by breeding or propagation of cuttings) rather than occurring naturally in the wild


Pinching or removing faded flowers to tidy a plant, stop seed production and promote future flowering.


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


Falling off of leaves


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The splitting open, along seams, of a fruit to release the seeds


A progressive death of plant tissues


Having female (pistillate) and male (staminate) flowers on separate plants, such as holly (Ilex)

Disease Resistant

A plant that is able to resist a disease that interferes with the function and normal growth of a plant.


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

Drip Line

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


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


Plants smaller or shorter than the species


The edge (margin) of the leaf is unbroken, untoothed.


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A plant trained on a trellis; branches generally extend horizontally in a fan shape or single plane. The process of training a woody plant against a flat surface such as a wall or trellis.


A plant that retains it green growth (leaves) year round

Exfoliating Bark

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


In botanical classification, a group of several genera related to one another; sharing some, but not all characteristics


A narrow tree or shrub where the branches grow vertically (ascending) and close together

Feeder Roots

A system of smaller roots growing out of the main roots; these function in uptake of water and nutrients from the soil.




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


In botanical classification, a group or related plants with many different species. Plants within a genus share some basic characteristics, but are separated into species by varying smaller characteristics. Genera is the plural form.


When a seed begins to grow and put out shoots


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


Hairless leaves


A general term to refer to a plant organ or tissue that secretes some substance (oil, nectar, etc.)


A process used to propogate new plants; a shoot, twig, or bud of one plant is inserted into a slit of a stem/trunk of another plant and allowed to grow.


Usually a low-growing plant that spreads to fill in an area


The natural shape of a tree/plant, such as oval, round, columnar

Hardiness Zone

The US Department of Agriculture has divided the country into regions based on the average low winter temperatures. Plants are then assigned to a hardiness zone 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


The inner wood in a tree which supports the plant


The outer covering of a seed or fruit


A plant produced by cross pollinating two related plants.

Included Bark

A point of poor attachment that occurs where two branches or a branch and main trunk compress against each other causing bark to roll inward; and produce weak wood.


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A grouping of flowers arranged in a specific pattern (i.e. umbel or panicle)


The part of the stem between nodes (the points where leaves are produced)


An invasive plant is usually a non-native species, which competes with native species for water, nutrients and space, destroying the natural habitat and ecosystem of native species. (Different from aggressive; see definition for aggressive.)


A leaf shape where the leaf blade is much longer than it is wide; widest part below the middle and tapering inward.


One section of a compound leaf


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



A protruding/projecting part of a leaf margin.


The edge of the leaf


Staminate (male) and pistillate (female) flowers are on the same plant, but in separate structures.


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, will break down to improve soil structure and fertility.


A point on a stem where leaf buds originate


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


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


Two leaves or buds grow on opposite sides of a twig at the same node (growing point)


Materials derived from living matter such as plants or animals


Lives through the winter, often in a dormant state

Palmately Compound

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


A compound, branched inflorescence (flower cluster).


An organism capable of causing disease


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


The stalk on a leaf (synonymous with leafstalk)

Pinch Back

Taking out growing tips to get the plant to branch and be fuller; often achieved by physically pinching between two fingers

Pinnately Compound

Leaf blades arranged on opposite sides of a leaf midrib; feather-like


The process of transfering pollen from the male stamen (anther) to the female pistil (stigma) in a flower or from one flower to another


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


A leaf with hairs


A flower cluster (inflorescence) with a central stalk from which flowers arise; each flower has its own stalk (as opposed to a spike where each flower is connected directly to the central stalk)


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


An underground stem, typically horizontal


A dry fruit with a wing; a winged seed


The fluid that moves through the vascular system of the plant; it carries water and nutrients as well as sugars produced by the plant.


The wood located just under bark; made up of xylem (tissue that transports water up into the plant)


1. The protective covering on a plant's bud.

2. A type of sucking insect that attacks numerous trees and shrubs. It has a protective outer "shell".


The outer layer of floral parts; often (but not always) green and leaf-like in appearance, and serving to cover and protect the unopened flower bud


A leaf with a saw-toothed edge (margin); teeth point forward


A multistemmed woody plant that is shorter than a tree


A leaf with an undivided blade; not compound


A segment or space between two leaf lobes, as in oaks

Soil pH

A means that measures alkalinity or acidity of the soil, which influences the nutrient availablity and uptake for plant growth

Soil Structure

The arrangement of individual soil particles and pore space into units (aggregates); soil structure affects the amount of air and water held in a soil.


In botanical classification, the level below genus; a group of naturally occurring plants that share the same physical characteristics and are capable of producing offspring with those same characterisitics


A reproductive structure of nonflowering plants, fungi and algae


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

Structural Roots

The support roots of a plant


A plant/shrub that has slightly woody bark but often dies back to ground in winter and is treated more as a perennial


A shoot that arises from the roots; can increase the size of the plant by forming a colony


Not the accepted scientific name of a plant; may be an old name not currently used or an alternate


A central, vertical root that penetrates deeply into the soil


A dense growth of shrubs


The process in which water vapor is released through the leaves


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


A cluster of flowers (inflorescence) where all the flower stalks originate from one point, like spokes on an umbrella


Immature trees growing under a mature tree canopy


A plant that occurs naturally in the wild but has a variation from the original species.


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