Plants provide nourishment for our bodies and souls. With the help of protists and fungi, plants provide the oxygen we breathe and the food which sustains us -- either directly or indirectly, by feeding other animals. At the same time, they provide shade over our heads and cool carpets under our feet while surrounding us with beautiful colors and marking the change of seasons.

Plants often serve as markers for entire habitats. Descriptions such as, "Redwood-Tanoak Forest" or "Oak Grassland" set up an expectation for which plants, animals, fungi, weather, etc. occupy that area.

Classification of the plant kingdom can be especially confusing to the amateur naturalist: despite a tremendous diversity, plant species are all strikingly similar in their essential structure -- much more so than members of other Kingdoms. As a result, classification systems tend to focus on more minute details; worse yet, the scientific methods often ignore the more conspicuous differences among plants.

For example, according to modern botany:

• A palm tree has more in common with a blade of grass than it has in common with other trees.
• A strawberry plant is more closely related to an apple or apricot tree than to a clover or geranium.
• A Ginko (Maidenhair) tree is so different from other plants that it is has a Phylum all of its own. But if you had to group it with other plants, it belongs with conifers such as Pine trees.

At least four classification systems are in common use. Plants are classified into 10 phyla or divisions based largely on reproductive characterstics; by tissue structure into non-vascular (mosses) and vascular plants (all others); by "seed" structure into those which reproduce through naked seeds, covered seeds, or spores; or by stature divided into mosses, ferns, shrubs & vines, trees, and herbs.

All of these higher-level groupings are decidedly lopsided: the vast majority of the 270,000 plant species are flowering herbs. The categories listed below are the result of an attempt to provide better balance: the largest Phylum has been split while the other Phyla are grouped according to one or more of the methods described above.

Mosses and Allies (Bryophyta)

Mosses are non-vascular plants -- they cannot transport fluids through their bodies. Instead, they must rely on surrounding moisture to do this job for them.

Though small in stature, mosses are very important members of our ecosystem. They lay the foundations for other plant growth, prevent erosion, and contribute to the lush green appearance of so many forested areas.

The 24,000 bryophyte species can be found growing on the ground, rocks, and on other plants.

Ferns and Allies (Filicinophyta and allies)

Ferns and allies are vascular plants which reproduce from spores rather than seeds. The main phylum, the Ferns (Filicinophyta = Pteridophyta) includes around 12,000 species.

Three other phyla are included as fern allies: the Horsetails (Sphenophyta = Equisetophyta, 40 species), Club mosses (Lycopodophyta, 1,000 species) and Whisk ferns (Psilophyta, 3 species)

(Angiospermophyta is also called Anthophyta or Magnoliophyta)

Conifers and Allies (Gymnosperms = Coniferophyta and allies)

The gymnosperms all produce "naked" seeds which are not covered by an ovary (fruit). Usually, the seed is produced inside a cone-like structure, although some members of the group, such as the Yew and Ginko, produce them inside a berry-like structure.

The conifers are, perhaps, the easiest plants to identify: they are usually trees or shrubs; have needle-like, scale-like or awl-like leaves; and typically produce their seeds in cones (aka pine cones).

Approximately 600 species are counted as conifers including the pines, firs, spruces, cedars, junipers, yew, etc.

Conifer allies include three phyla with a diversity of appearances: trees such as the Ginko (or Maidenhair Tree, Ginko biloba); palm-like Cycads; and herb-like cone-bearing plants such as Ephedra. Fewer than 200 species are identified as conifer allies.

Flowering Dicot Plants (Angiospermophyta, Class Dicotyledoneae)

The vast majority of plants fit into this "highest" evolutionary category of plants. Almost every plant that comes to mind, whether a tree, shrub, vine, or flower, belongs to this group of around 200,000 species.

Dicots start with two seed-leaves (cotyledon). In addition, mature leaves or leaflets usually have a single, branching, main vein originating at the base of the leaf blade, or three or more main veins that diverge from the base.

(Angiospermophyta is also called Anthophyta or Magnoliophyta)

Flowering Monocot Plants (Angiospermophyta, Class Monocotyledoneae)

Monocots start with one seed-leaf. Main veins of the leaf are usually nearly parallel. Around 30,000 plants including lilies, irises, orchids, palms, grasses and their relatives are classified as monocots.