Classification of plant

PLANT CLASSIFICATION I. GENERAL TERMINOLOGY
        1. By growth habit:

Succulent plants - herbaceous or herbs (succulent seed plants possessing self-supporting stems)
Vine - a climbing or trailing herbaceous plant (Liana - a climbing or trailing woody plant)
Trees - having a single central axis
Shrub - having several more or less upright stems

2. By leaf drops:

Deciduous - no living leaves during dormant (winter) season (apple)
Evergreen - retaining functional leaves throughout the year (spruce)

3. By life span:

Annuals - plants that normally complete their life cycle during a single growing season (lettuce, spinach, marigold)
Biennial - plant that normally completes its life cycle during a period of two growing seasons (celery, carrot, parsnip)

Vegetative (often rosettes) during the first growing season. The winter following the first growing season provides the low temperature necessary to stimulate to 'bolt' or to send up a seed stalk during the second growing season. Carrots, radish and beets are harvested as annuals at the end of the first growing season after they develop over-wintering storage organs.

Perennial - plants that grow year after year, often taking many years to mature.

Unlike annuals and biennials, the perennial does not necessarily die after flowering (fruit trees; asparagus, rhubarb whose above ground parts are killed each year (in temperate regions) but roots remain alive to send up shoots in the spring; subtropical perennials such as tomato and eggplant are considered annual in temperate regions; Rubus (raspberries) has perennial roots and biennial shoots)

4. By temperature tolerance:

Tender plant - damaged or killed by low temperature
Hardy plant - withstands winter low temperatures
Wood hardy - a whole plant is winter hardy
Flower-bud hardiness - ability of flower buds to survive low winter temperatures (peach, ginkgo tree)

5. By temperature requirements:

Cool-season crop - prefers cool temperatures (peas, lettuce, cole crops)
Warm-season crop - prefers warm temperatures (tomato, pepper)

6. By habitat or site preference:

Xerophyte - prefers dry sites
Shade plants - prefers low light intensity
Acid loving - prefers low pH soils
Halophyte - prefers salty soils (in constrat to glycophyte)

II. HORTICULTURAL PLANT CLASSIFICATION

1. Edibles

A. Vegetables

Plants grown for aerial portions

Cole Crops(broccoli, cabbage, cauliflower)
Legumes (bean, peas)
Solanaceous fruit crops (Capsicum pepper, eggplant, tomato)
Cucurbits or vine crops (cucumber, melon, squash, pumpkin)
Greens or pot herbs (chard, dandelion, spinach)
Mushrooms (Agaricus, Lentinus)
Other vegetables(asparagus, okra, sweet corn)

Plants grown for underground portions

Root crops

Temperate (beet, carrot, radish, turnip)
Tropical (cassava, sweet potato, taro, yam)

Tuber crops (Jerusalem artichoke, potato)
Bulb and corm crops (garlic, onion shallot)

B. Fruits

Temperate (Deciduous)

Small fruits

Berries (blueberry, cranberry, strawberry)
Brambles (blackberry, raspberry)
Vines (grape, kiwifruit)

Tree fruits

Pome fruits (apple, pear, quince)
Stone fruits (apricot, cherry, peach, plum)

Subtropical and tropical (Evergreen)

Herbaceous and vine fruits (banana, papaya, passion fruit, pineapple)
Tree fruits

Citrus (grapefruit, lemon, lime, mandarin, orange)
Non-citrus (avocado, date, fig, mango, mangosteen)

C. Nuts

Temperate (almond, chestnut, filbert, pecan, pistachio)
Tropical (Brazil nut, cashew, macadamia)

D. Beverage Crops

Seed (cacao, coffea)
Leaf (tea, mate)

E. Herbs and Spices

Culinary herbs (dill, rosemary, sage)
Flavorings (peppermint, spearmint)
Tropical spices(cinnamon, clove, nutmeg, pepper)

2. Ornamentals

A. Florist Crops

Cut flowers (rose, carnation, chrysanthemum, alstroemeria)
Flowering pot plants (geranium, poinsettia, Easter lily, gloxinia)
Foliage plants (philodendron, ficus, aglaonema)
Bedding plants (petunia, impatiens, marigold, zinnia)

B. Landscape Plants

Trees

Deciduous (maple, elm, aspen, oak, willow)
Evergreen (pine, juniper, spruce)

Shrubs

Deciduous (lilac, azalea, privet)
Evergreen (juniper)

 Vines (ivy, bougainvillea, pyracantha)Herbaceous perennials (penstemon, peony, columbine)
Ground covers (ivy, vinca, juniper)

C. Lawn and Turf Plants

Bermudagrass, bluegrass, fescue, perennial ryegrass, buffalograss

3. Industrial Crops

Drugs and Medicinals(digitalis, quinine, opium poppy)
Oil Seeds (oilpalm, jojoba, tung)
Extractives and Resins (Scotch pine, Para rubber tree)
Insecticides (pyrethrin, neam plant)

III. NOMENCLATURE (SCIENTIFIC PLANT CLASSIFICATION)

Early classification started by the Greek philosopher Theophrastus who classified all plants into annuals, biennials, and perennials according to life spans, and into herbs, shrubs, and trees according to their growth habits.The modern taxonomy for plant classification is based on Linnaeus (a 18th century Swedish physician, now considered "father of taxonomy") who revolutionized the fields of plant and animal classification.
1. The Plant Kingdom

Kingdom Plantae 
        Division Anthrophyta 
                Class Dicotyledonae 
                        Order Rosales 
                                Family Rosaceae 
                                        Genus Malus (or Malus) 
                                                Species pumila (or pumila) 
                                                        Variety 
                                                                Form 
                                                                    Individual

Horticulture deals with mostly family, genus, species, and cultivars.

- Botanical names are binomial.
- Underline or italicize genus and species:
        Genus species (or Genus species)
- Do not underline the family and cultivar names:

Rosaceae, Golden Delicious

- Variety names may be underlined. Examples:

Juniperus communis var. depressa (Prostrate Juniper)
Malus domestica cv. Red Delicious (Red Delicious Apple)
Malus domestica 'Red Delicious' (Red Delicious Apple)
Malus pumila cv. Red Delicious (Red Delicious Apple)

2. Some frequently used terms
 

Variety - a group of variants within a species which have similar characteristics.
Cultivar - cultivated variety
Ecospecies - a subdivision of species that are formed by ecological barrier. i.e., Cercis canadensis (Redbud)
Clone - a group of plants all of which arose from a single individual (the ortet) through asexual propagation.
Clonal cultivar - asexually propagated clones (potato, rose, etc.).
Pure line cultivar - homozygous inbred lines grown from seed.
Hybrid cultivar - a cultivar composed of hybrids between genetically diverse parental lines uniform phenotype, genetically heterozygous)