- Falcate or Seculate. Sickle-shaped
- False Veins. Small vein-like areas of thick-walled cells in the leaves of some lower vascular plants
- Farinaceous. Mealy
- Fasciated. Unnaturally and often monstrously connate or adnate, the coalesced parts often unnaturally proliferated in size and/ or number; e.g., inflorescence of Celosia
- Fascicle. Cluster of needles borne on a minute determinate short shoot in the axil of a primary leaf (bract); e.g. Pinus. Fascicle Sheath - Closely imbricated bud scales at the base of the fascicle of needles; e.g., Pinus
- Fascicled. Fleshy or tuberous roots in a cluster
- Fasciculate. Leaves or other structures in a cluster from a common point
- Fastigiate. Strictly erect and parallel
- Faucal Area. The throat area
- Female, Carpellate, or Pistillate. Plant with pistillate flowers only
- Fetid. Having an unpleasant, rotten odor
- Fenestrate. With windowlike holes through the leaves or other structures
- Fibonacci Phyllotaxis. A fundamental type of leaf arrangement expressed as a fraction in which each succeeding fraction is the sum of the two previous numerators and the sum of the two previous denominators, i.e., 1/2, 1/3, 2/5, 3/8, 5/13, 8/ 21, etc. The numerator represents the number of turns or spirals around a stem before one leaf is directly above another and the denominator represents the number of leaves in the turns or spirals before one is directly above the other. 2/5 phyllotaxy would mean two twists and five leaves before one leaf is directly above the other or an angle of divergence of 144 between succeeding leaves in the stem (2/5 of 360 ).According to Leppik anthotaxis and semataxis do not necessarily follow the same pattern, with anthotaxis in Michelia cited as being in 2/7, 3/7, 3/8, and 4/10 systems of arrangement.
- Fibrous. With fine, threadlike or slender roots or fibers
- Filament. Stamen stalk
- or Filiferous. Filamentose or Filiferous With coarse marginal fibers or threads
- Filantherous or Typical. Stamen with distinct anther and filament with or without thecal appendages, as in Rhexia or Vaccinium
- Filiform. Threadlike, usually flexuous
- Fimbriate. Margins fringed
- Fimbriolate. Minutely fimbriate
- Fistulose. Hollow, as without pith
- Flabellate. Fan-shaped branching
- Flabelliform. Fan-shaped
- Flaccid. Lax and weak
- Flagellate. Bearing flagella, whip-like strands or organs
- Fleshy. Succulent roots
- Flexuous. With a series of long or open vertical curves at right angles to the central axis
- Floating. Upon the surface of the water
- Floccose. Covered with dense, appressed trichomes in patches or tufts
- Flotophyllous. With floating leaves
- Flower. Reproductive structure of flowering plants with or without protective envelopes, the calyx and/or corolla; short shoot with sporophylls and with or without sterile protective leaves, the calyx and corolla
- Flushing Shoots. Shoots that develop from mature terminal buds several times during a season. Terminal bud will develop shoot with new terminal bud which will develop more shoots and a terminal bud which will develop etc. --several times in a season with several flushes of growth.
- Fly Trap. Hinged, insectivorous leaf, as in Dionaea
- Folded. Foliate embryo with cotyledons usually thin and extensively expanded and folded in various ways
- Follicetum. An aggregation of follicles, as in Caltha
- Follicle. A dry, dehiscent fruit derived from one carpel that splits along one suture
- Fovea. Pit or depression containing the sporangium in the leaf base of Isoetes
- Foveolate. Pitted
- Free. Unlike parts or organs unjoined and separate from one another
- Free-adnate. Hypanthium fused with ovary and having a free limb around or above ovary
- Free-central. With the placenta along the central axis in a compound ovary without septa
- Fringe. The modified margin of a petal, sepal, tepal or lip
- Frond. The leaf of a fern
- Fruit. Matured ovary of flowering plants, with or without accessory parts
- Fruticose. Shrubby
- Fugacious. Ephemeral, usually applied to plant parts
- Funicular. With a persistent elongate funiculus attached to seed coat, as in Magnolia
- Funiculus. Stalk by which ovule is attached to placenta
- Fusiform. Spindle-shaped; broadest in middle and tapering to each end
- Galeate. Helmet-shaped, as one sepal in Aconitum
- Geitonogamy. Fertilization of one flower by another on the same plant
- Gelatinous. Jellylike; soft and quivery
- Geminate or Binate. Paired; in pairs
- Gemma. A vegetative reproductive bud borne on the stem, as in Lycopodium; a multicellular reproductive propagule on gametophytes, as in ferns
- Geniculate. Abruptly bent at a node, zigzag
- Geoflorous. With subterranean flower
- Geocarpous. Fruits below ground, as in Amphicarpum
- Gibbous. Inflated on one side near the base
- Gigantic. Very large
- Glabrate. Without trichomes
- Glabrescent. Becoming glabrous
- Glabrous. Smooth; devoid of trichomes
- Gland. A secreting part or appendage
- Glandular. Covered with minute, blackish to translucent glands
- Glans (Involucre). Nut subtended by a cupulate, dry involucre, as in Quercus
- Glaucescent. Sparingly or slightly glaucous
- Glaucous. Covered with a bloom or smooth, waxy coating
- Globose. Round
- Glochidiate. With barbed trichomes, glochids, usually in tufts
- Glomerule. An indeterminate dense cluster of sessile or subsessile flowers
- Glume. Bract, usually occurring in pairs, at the base of the grass spikelet
- Glutinous. Having a shiny, sticky surface
- Granular. Finely mealy, covered with small granules
- Greasy or Unctuous. Slick, oily, slippery to touch
- Gynagamous. Inflorescence with pistillate flowers inside or above and neuter flowers outside or below (gynagamocephalous)
- Gynandrial or Gynostemial. With fused stamens and carpels (stigma and style) as in the Orchidaceae
- Gynecandrous. Inflorescence with pistillate flowers inside or above and staminate outside or below, as in spikes of some species of Carex
- Gynehermaphroditic. Inflorescence with pistillate flowers inside or above and hermaphroditic outside or below (gynehermaphrodicephalous)
- Gynobasic. Attached at base of ovary in central depression
- Gynodioecious. Some plants with perfect flowers and some with pistillate
- Gynoecium or Pistil. The whorl or group of carpels in the center or at the top of the flower; all carpels in a flower
- Gynomonoecious. Plant with pistillate and perfect flowers
- Gynophore. The stipe of a pistil or carpel
- Half-inferior. Other floral organs attached around ovary with hypanthium adnate to lower half of ovary
- Half-terete. Flat on one side, terete on other; semicircular in cross section
- Haplomorphic. Flowers with parts spirally arranged at a simple level in a semispheric or hemispheric form; petals or tepals colored; parts numerous; e.g., Nymphaea, Magnolia
- Hastate. Lobe pointed and oriented outward or divergent in relation to petiole or midrib; sinus depth variable; margins variable
- Hastiform. Triangular with two flaring basal lobes
- Haustorial. Absorbing roots, within host of some parasitic species
- Helicoid Cyme or Bostryx. A determinate inflorescence in which the branches develop on one side only, appearing simple
- Hemianatropous or Hemitropous. With body half-inverted so that funiculus is attached near middle with micropyle terminal and at right angles
- Herb. A usually low, soft, or coarse plant with annual aboveground stems
- Herbaceous. Soft and succulent
- Hermaphrodagamous. Inflorescence with hermaphroditic flowers inside or above and neuter outside or below (hermaphrodagamocephalous)
- Hermaphrodandrous. Inflorescence with hermaphroditic flowers inside or above and staminate outside or below (hermaphrodandrocephalous)
- Hermaphroditic or Monoclinous. Plant with all flowers perfect
- Hesperidium. A thick-skinned septate berry with the bulk of the fruit derived from glandular hairs, as in Citrus
- Heterandrous. With stamens of different sizes and/or shapes
- Heteranthous. Having different states in two different sets of flowers, only one state present in each set
- Heteroblasty. With juvenile foliage distinctly different from adult foliage in size or shape
- Heterocarpous. With carpels of different sizes and/or shapes
- Heterocephalous, Heterocymous, Heterospicous. Heads, cymes, spikes with flowers of different sexual conditions. Note: other inflorescence word stems could be used for appropriate inflorescence type.
- Heterocladous. With stems of different sizes and/or shapes
- Heteromerous or Anisomerous. With different number of members in different whorls
- Heteropetalous. With petals of different sizes and/or shapes
- Heterophyllous. With leaves of different sizes and/or shapes. Heterophyllous Shoots - Shoots that develop from winter buds which do not contain the primordia of all the leaves to develop during the year
- Heterophytous. Having different states in two different sets of plants, only one state present in each set
- Heterosepalous. With sepals of different sizes and/or shapes
- Heterosexual. Inflorescences or flowers within the plant with different sexual conditions
- Heterosporous. Having two kinds of spores, usually differing in size
- Heterostichus. With unequal rows
- Heterostylous. With styles of different sizes or lengths or shapes within a species
- Heterotropous. Ovule position not fixed in ovary
- Hibernal or Hiemal. Appearing in the winter
- Hilum. Funicular scar on seed coat
- Hip or Cynarrhodion (Receptacle and Hypanthium). An aggregation of achenes surrounded by an urceolate receptacle and hypanthium, as in Rosa
- Hippocrepiform. Horseshoe-shaped
- Hirsute. Covered with long, rather stiff trichomes
- Hirsutullous or Hirtellous. Minutely hirsute
- Hispid. Covered with very long, stiff trichomes
- Hispidulous. Approaching hispid, minutely hispid
- Homandrous. With stamens of same size and shape
- Homanthous. Having more than one state within each individual flower, all flowers the same
- Homocarpous. With carpels of same size and shape
- Homocephalous, Homocymous, Homospicous. Heads, cymes, spikes with flowers sexually uniform
- Homochlamydeous. With perianth composed of similar parts, each part a tepal
- Homogamous. With maturation of stamens or anther and carpels or stigma at same time
- Homophytous. Having more than one state within each individual plant, all plants the same
- Homosexual. Inflorescences or flowers sexually uniform
- Homosporous. Having spores of only one kind
- Homostylous. With styles of same sizes or lengths and shapes
- Hood. A cover-shaped perianth part, usually with a turned down margin
- Horn. A curved, pointed and hollow protuberance from the perianth
- Hyaline. Thin and translucent or transparent
- Hydrophily. Pollinated by water
- Hymenopterophily. Pollinated by bees
- Hypanepigyny. The condition in which the sepals, petals, stamens are attached to the elongate floral tube or hypanthium above the inferior ovary, as in Oenothera
- Hypanthium. The fused or coalesced basal portion of floral parts (sepals, petals, stamens) around the ovary
- Hypanthodium. An inflorescence with flowers on wall of a concave capitulum, as in Ficus
- Hyphodromous. With a single primary vein and all other venation absent, rudimentaryj or concealed within a coriaceous or fleshy blade
- Hypocotyl. Embryonic stem in seed, located below cotyledons
- Hypocotylespermous or Macropodial. With food reserve stored in hypocotyl, derived from zygote
- Hypogynium. Perianth-like structure of bony scales subtending the ovary, as in Scleria and other members of the Cyperaceae
- Hypogyny. The condition in which the sepals, petals, stamens are attached below the ovary
- Hypophyllous. With small leaves, as bracts, scales, cataphylls
- Hypotropous. Dorsal - Ovule erect, micropyle below, raphe dorsal (away from ventral bundle). Ventral - Ovule erect, micropyle below, raphe ventral (toward ventral bundle)
- Hysteranthous. With leaves appearing after flowers