About Plant Families Explorer

Learn about our mission to make plant family identification accessible and engaging for everyone, from students to professional botanists.

Our Mission

Plant Families Explorer was created to help people understand and appreciate the diversity of plant families and their evolutionary relationships. By presenting plant families in phylogenetic order with intuitive identification guides, we aim to make botanical knowledge more accessible to students, educators, researchers, and nature enthusiasts.

Our goals include:

  • Providing accurate, up-to-date information on plant family classification based on modern phylogenetic research
  • Creating intuitive, visual tools for exploring plant evolutionary relationships
  • Offering practical guides for identifying plant families in the field
  • Making botanical knowledge accessible to people of all backgrounds and experience levels

The APG IV Classification System

This website uses the Angiosperm Phylogeny Group IV (APG IV) classification system, which is the most current and widely accepted system for organizing flowering plants based on their evolutionary relationships.

What is APG IV?

The Angiosperm Phylogeny Group (APG) is an international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) based on phylogenetic data. The APG IV system, published in 2016, is the fourth iteration of their classification system.

Unlike traditional classification systems that relied heavily on morphological similarities, the APG system is based primarily on genetic evidence, particularly DNA sequences. This approach provides a more accurate representation of evolutionary relationships between plant groups.

Key Features of APG IV

The APG IV system organizes flowering plants into the following major groups:

  • Angiosperms (flowering plants) - The largest group of land plants
  • Amborellales - The most basal lineage of extant angiosperms
  • Nymphaeales - Water lilies and related plants
  • Austrobaileyales - A small group of woody plants
  • Magnoliids: - An ancient lineage including magnolias, laurels, and black pepper
  • Monocots - Plants with a single seed leaf, including grasses, orchids, and palms
  • Eudicots - Plants with two seed leaves, including most familiar flowering plants

Within these major groups, plants are further organized into orders and families based on their evolutionary relationships.

Changes in APG IV

The APG IV system introduced several changes from previous classifications, including:

  • Recognition of additional orders and families
  • Merging of some previously separate families
  • Refinement of relationships between major plant groups

These changes reflect ongoing research in plant systematics and our evolving understanding of plant evolution.

References and Resources

This website draws on numerous scientific resources to provide accurate information about plant families and their characteristics. Key references include:

Primary References

  • The Angiosperm Phylogeny Group. (2016). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society, 181(1), 1-20.
  • Judd, W. S., Campbell, C. S., Kellogg, E. A., Stevens, P. F., & Donoghue, M. J. (2016). Plant Systematics: A Phylogenetic Approach (4th ed.). Sinauer Associates.
  • Simpson, M. G. (2019). Plant Systematics (3rd ed.). Academic Press.
  • Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 14, July 2017 [and more or less continuously updated since]. http://www.mobot.org/MOBOT/research/APweb/

Additional Resources

  • Christenhusz, M. J. M., Fay, M. F., & Chase, M. W. (2017). Plants of the World: An Illustrated Encyclopedia of Vascular Plants. Kew Publishing.
  • Heywood, V. H., Brummitt, R. K., Culham, A., & Seberg, O. (2007). Flowering Plant Families of the World. Royal Botanic Gardens, Kew.
  • Mabberley, D. J. (2017). Mabberley's Plant-Book: A Portable Dictionary of Plants, their Classification and Uses (4th ed.). Cambridge University Press.

Botanical Glossary

Understanding botanical terminology is essential for plant identification. Here are some key terms used throughout this website:

Angiosperm

A flowering plant that produces seeds enclosed within a fruit (ovary).

Compound Leaf

A leaf whose blade is divided to the midrib or base, with each division forming a distinct leaflet.

Eudicot

A major clade (monophyletic group) of flowering plants characterized by having two seed leaves (cotyledons), flower parts typically in multiples of four or five, and net-like leaf venation.

Family

A taxonomic rank in biological classification between order and genus. Family names typically end in "-aceae".

Gymnosperm

A group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes. Their seeds are "naked" – not enclosed within an ovary or fruit.

Inflorescence

The complete flower head of a plant including stems, stalks, bracts, and flowers; the arrangement of flowers on a floral axis.

Monocot

A major clade (monophyletic group) of flowering plants characterized by having a single seed leaf (cotyledon), flower parts typically in multiples of three, and parallel leaf venation.

Phylogeny

The evolutionary history and relationships among individuals or groups of organisms (e.g., species, families).

Simple Leaf

A leaf with a single, undivided blade (though the blade may be lobed or cleft).

Stipule

A small, often leaf-like appendage typically found in pairs at the base of the petiole (leaf stalk).

Alternate Leaves

Leaves arranged singly at different heights along the stem, not opposite or whorled.

Axil

The upper angle between a leaf stalk or branch and the stem from which it grows.

Basal Leaves

Leaves arising from the base of the stem, often forming a rosette.

Bract

A modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale.

Calyx

The collective term for the sepals of a flower; the outermost whorl of floral leaves.

Corolla

The collective term for the petals of a flower; the whorl of floral leaves typically inside the calyx.

Cotyledon

An embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.

Deciduous

Falling off at maturity or tending to fall off; typically used to describe trees or shrubs that seasonally shed leaves.

Dioecious

Having male and female reproductive organs in separate individuals (separate male and female plants).

Drupe

A fleshy fruit with thin skin and a central stone containing the seed, e.g., a plum, cherry, almond, or olive.

Entire Margin

Referring to a leaf margin (edge) that is smooth, without teeth or lobes.

Epiphyte

A plant that grows on another plant but is not parasitic, such as the numerous ferns, bromeliads, air plants, and orchids growing on tree trunks in tropical rainforests.

Evergreen

A plant that has leaves throughout the year, always green.

Genus

A taxonomic rank above species and below family. A group of closely related species.

Herbaceous

Having non-woody stems that die back to the ground each year.

Inferior Ovary

An ovary situated below the point of attachment of the calyx and corolla.

Leaflet

One of the separate blade-like divisions of a compound leaf.

Lobe

A partial division of a leaf, petal, or other organ, usually rounded.

Margin

The edge of a leaf blade.

Monoecious

Having both male and female reproductive organs on the same individual plant.

Node

The point on a stem where a leaf, bud, or branch arises.

Opposite Leaves

Leaves arranged in pairs at the same height on opposite sides of the stem.

Ovary

The enlarged basal portion of the pistil (female organ) where ovules are produced. Develops into the fruit after fertilization.

Palmate

Lobed, veined, or divided from a common point, like the fingers of a hand (e.g., palmate leaf venation or a palmately compound leaf).

Pedicel

The stalk supporting a single flower in an inflorescence.

Perennial

A plant that lives for more than two years.

Petal

A modified leaf that surrounds the reproductive parts of flowers. Often brightly colored to attract pollinators.

Petiole

The stalk that attaches the leaf blade to the stem.

Pinnate

Resembling a feather, as in a compound leaf with leaflets arranged on opposite sides of an elongated axis.

Pistil

The female reproductive part of a flower, typically consisting of stigma, style, and ovary.

Rhizome

A modified subterranean plant stem that sends out roots and shoots from its nodes.

Sepal

A leaf-like structure that forms part of the outer whorl (calyx) of a flower, typically enclosing the petals in bud.

Serrate Margin

Referring to a leaf margin that is toothed, like the edge of a saw.

Sessile

Attached directly by the base without a stalk or petiole (e.g., a sessile leaf).

Shrub

A woody plant smaller than a tree, usually with several permanent stems branching from or near the ground.

Species

The basic unit of classification, ranking below genus. A group of organisms capable of interbreeding.

Stamen

The male fertilizing organ of a flower, typically consisting of a pollen-containing anther and a filament.

Stigma

The receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower, where pollen germinates.

Style

A stalk-like structure connecting the stigma to the ovary in the pistil of a flower.

Superior Ovary

An ovary attached to the receptacle above the attachment of other floral parts (sepals, petals, stamens).

Taxonomy

The science of classification of organisms into an ordered system that indicates natural relationships.

Tendril

A slender, thread-like appendage of a climbing plant, often growing in a spiral form, that stretches out and twines around any suitable support.

Tepal

A segment of the outer whorl (perianth) of a flower that cannot be easily differentiated into sepals or petals.

Tree

A woody perennial plant, typically having a single stem or trunk growing to a considerable height and bearing lateral branches at some distance from the ground.

Venation

The arrangement or pattern of veins in a leaf blade.

Whorled Leaves

Leaves arranged in a circle of three or more around the stem at the same node.

Woody

Containing wood or xylem; having hard, lignified stems.

Achene

A small, dry, one-seeded fruit that does not open to release the seed.

Adventitious Root

A root that arises from an organ other than the primary root, typically a stem or leaf.

Androecium

The collective term for the stamens (male reproductive organs) of a flower.

Annual

A plant that completes its life cycle (germination to seed production) within a single year or growing season.

Anther

The part of a stamen that contains the pollen.

Apical Meristem

A region of actively dividing cells at the tip of a root or shoot, responsible for primary growth (increase in length).

Berry

A simple fleshy fruit that usually has many seeds, like a tomato or grape.

Biennial

A plant that takes two years to complete its life cycle, typically growing vegetatively the first year and flowering/fruiting the second.

Blade

The broad, flat part of a leaf.

Bulb

A modified underground bud consisting of a short stem base with fleshy leaves or leaf bases that store food.

Capsule

A dry fruit that develops from multiple carpels and typically opens (dehisces) in various ways to release seeds.

Carpel

The female reproductive organ of a flower, consisting of the stigma, style, and ovary. One or more carpels form the pistil/gynoecium.

Clade

A group of organisms believed to have evolved from a common ancestor, according to the principles of cladistics.

Corm

A rounded underground storage organ present in some plants, consisting of a swollen stem base covered with scale leaves.

Crenate Margin

Referring to a leaf margin with rounded teeth.

Cuticle

A waxy layer covering the epidermis of leaves and stems, helping to prevent water loss.

Cyme

A type of inflorescence where the central or terminal flower opens first, halting the main axis growth, with subsequent flowers developing on lateral branches.

Dehiscent

Splitting open at maturity along a built-in line of weakness to release contents (e.g., fruits releasing seeds, anthers releasing pollen).

Dentate Margin

Referring to a leaf margin with teeth pointing outwards, perpendicular to the edge.

Endosperm

Nutritive tissue surrounding the embryo within seeds of flowering plants.

Epidermis

The outermost layer of cells of a plant.

Filament

The stalk-like part of a stamen that supports the anther.

Follicle

A dry, dehiscent fruit derived from a single carpel that splits open along one seam.

Fruit

The mature ovary of a flowering plant, enclosing the seed or seeds.

Gynoecium

The collective term for the carpels or pistils (female reproductive organs) of a flower.

Habit

The characteristic form or mode of growth of a plant (e.g., tree, shrub, herb, vine).

Head (Capitulum)

A dense inflorescence of small, often sessile flowers, typical of the Asteraceae family (e.g., sunflower).

Indehiscent

Not splitting open at maturity to release seeds (e.g., achenes, nuts).

Internode

The section of a plant stem between two nodes.

Latex

A milky fluid found in many plants, such as poppies and spurges, that exudes when the plant is cut.

Legume

A type of simple, dry fruit that develops from a simple carpel and usually dehisces (opens along a seam) on two sides. Also refers to a member of the Fabaceae family.

Lenticel

A pore in the bark of woody stems, allowing gas exchange between the internal tissues and the atmosphere.

Midrib

The central, main vein of a leaf.

Nectar

A sugary fluid secreted by plants, especially within flowers, to encourage pollination by animals.

Nut

A dry, indehiscent fruit with a hard shell, usually containing a single seed (e.g., acorn, hazelnut).

Order

A taxonomic rank used in the classification of organisms, between class and family.

Ovate

Egg-shaped, especially referring to a leaf shape, with the broader end at the base.

Ovule

The structure within the ovary that contains the female gamete (egg cell) and develops into a seed after fertilization.

Panicle

A branched, indeterminate inflorescence with flowers on pedicels.

Pappus

Modified calyx consisting of scales, bristles, or feather-like hairs at the apex of the achene in Asteraceae family members (e.g., dandelion "parachute").

Parallel Venation

Veins running parallel to each other for the length of the leaf blade, typical of monocots.

Parasite

An organism that lives on or in a host organism and gets its food from or at the expense of its host.

Peduncle

The main stalk supporting an entire inflorescence or a solitary flower.

Perianth

The outer part of a flower, consisting of the calyx (sepals) and corolla (petals) collectively.

Phloem

The vascular tissue in plants that conducts sugars downward from the leaves.

Photosynthesis

The process used by plants and other organisms to convert light energy into chemical energy, through a process that converts water and carbon dioxide into sugars and oxygen.

Pollen

A fine powdery substance, typically yellow, consisting of microscopic grains discharged from the male part of a flower (anther), containing the male gametes.

Pollination

The transfer of pollen from the anther to the stigma of a plant.

Pubescent

Covered with short, soft hairs; downy.

Raceme

An unbranched, indeterminate inflorescence with flowers on short stalks (pedicels) along the axis.

Receptacle

The part of a flower stalk where the parts of the flower are attached.

Reticulate Venation

Veins arranged in a net-like pattern, typical of eudicots.

Root Cap

A section of tissue at the tip of a plant root that protects the apical meristem.

Rosette

A circular arrangement of leaves, typically basal and close to the ground.

Samara

A dry, indehiscent fruit in which the ovary wall develops into a wing-like structure to aid dispersal (e.g., maple fruit).

Seed

A flowering plant's unit of reproduction, capable of developing into another such plant. Contains the embryo and stored food, enclosed in a protective coat.

Spadix

A type of spike inflorescence having small flowers borne on a fleshy stem, typical of the Araceae family (e.g., Jack-in-the-pulpit).

Spathe

A large bract enclosing the spadix inflorescence.

Spike

An unbranched, indeterminate inflorescence bearing sessile flowers (attached directly without stalks).

Spine

A modified, sharp-pointed leaf or part of a leaf.

Stolon (Runner)

A creeping horizontal plant stem or runner that takes root at points along its length to form new plants.

Stoma (plural: Stomata)

A pore, surrounded by guard cells, in the epidermis of leaves and stems that controls the rate of gas exchange.

Taproot

A large, central, and dominant root from which other roots sprout laterally.

Thorn

A modified, sharp-pointed stem.

Tomentose

Covered with densely interwoven, matted, woolly hairs.

Transpiration

The process where moisture is carried through plants from roots to small pores (stomata) on the underside of leaves, where it changes to vapor and is released to the atmosphere.

Tuber

A much thickened underground part of a stem or rhizome, e.g., in the potato, serving as a food reserve and bearing buds from which new plants arise.

Umbel

An inflorescence in which a number of short flower stalks (pedicels) spread from a common point, somewhat like umbrella ribs.

Vascular Tissue

Plant tissue consisting of cells joined into tubes that transport water (xylem) and nutrients (phloem) throughout the plant body.

Vine

A climbing or trailing woody-stemmed plant.

Xerophyte

A plant adapted to survive in an environment with little liquid water, such as a desert.

Xylem

The vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to form the woody element of the stem.

Zygomorphic

Bilaterally symmetrical, referring to a flower that can be divided into two equal halves by only one plane (e.g., orchid, snapdragon).

Acuminate

Tapering gradually to a long, narrow point.

Falcate

Sickle-shaped; curved like the blade of a sickle.

Glabrous

Lacking hairs or pubescence; smooth.

Glaucous

Covered with a bluish-green or whitish waxy bloom that can be rubbed off.

Perfoliate

Having the base of the leaf surrounding the stem so that the stem appears to pass through the leaf.

Pinnatifid

Having lobed or cleft leaves with the divisions extending halfway or less toward the midrib.

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