F1 hybrid - this designates the first generation of a cross between closely related species or strains of a plant. Usually, this generation displays what is called hybrid vigor and has characteristics that are deemed highly desirable to the plant breeder. Seed collected from plants in this group will usually not produce plants with the same characteristics.
fall - 1) most commonly used to describe the part of the outer whorl of the perianth of the flower that is broader than the others and droops or is reflexed.

2) common term for autumn when frosts routinely occur in temperate zones of the world.

fallow - normally cultivated land kept free from a crop or weeds during the normal growing season. Sometimes when invasive, perennial weeds spread through a flower bed or border, one control measure is to remove all desirable plants, kill the weeds and let the area lay fallow for a year or two to assure that the weeds are gone.
family (plant) - in the hierarchy of the binomial nomenclature system, plants are grouped because they share certain characteristics. The most closely related plants are in the species, a little broader grouping is the genus and the next wider group is the family.

Knowing the family that a plant belongs to can be helpful in determining several things. For example, plants in the Ericaceae Family thrive in soils with a low pH i.e. acid soils. Those in the large Rosaceae Family share susceptibility to certain diseases such as fireblight.

fan - a unit of division for some perennials such as daylily and iris that consists of at least one pair of leaves attached to a piece of the crown.
fasciation - this refers to common malformations that occur on certain plant parts. It usually involves a swelling, enlargement, flattening or curving of a plant organ such as a cane, shoot or flower.

This is common in hybrid lilies, Lilium genus where the area at the end of the stem is thickened or flattened and gives rise to many more flower buds than normal.

fastigiate - a term for plants that have an upright, columnar form due to the branches growing more vertical and close together than usual. An example is the Lombardy poplar. Cultivars of this type are often named ‘Fastigiata’.
female flowers - having flowers with pistil, ovary, style, stigma, ovules but no stamens.
fertile or fertility - 1) plants or flowers able to produce viable seeds.

2) soils containing abundant plant nutrients for plant growth.

fertilization - 1)  the union of the male reproductive unit (pollen from the stamen) with the female reproductive unit (egg in the pistil) resulting in seed formation.

2) the application of nutrients (fertilizers) for plant growth.

fertilizer - a mixture of chemicals (natural and/or man-made) that provides nutrients for plant growth. By law, all fertilizer containers must show the percentage of N (elemental nitrogen), P (phosphorus in the form of phosphate) and K (potassium in the form of potash).

A 100 pound bag of 27-10-15 fertilizer would contain 27 pounds of nitrogen, 10 pounds of phosphate and 15 pounds of potassium.

Some fertilizers contain just one or two of the three elements. Urea has an analysis of 46-0-0 while muriate of potash is 0-0-60.

fertilizer burn - fertilizers generally contain elements in the form of chemical salts. Water moves from low concentrations of salts toward high concentrations. Therefore, when a clump of fertilizer is in close proximity to plant tissue, it pulls all the water out causing the tissue to "burn" or turn brown.

A similar reaction occurs when fresh (uncomposted) manure come into contact with plant roots. When composted over time, the salts in the manure are leached out by rain water.

Dog urine has the same effect on turfgrass.

fiber - elongated, narrow, thick-wailed cell in xylem or phloem
fibrous root - these are the thin, fiber-like roots that originate tiny root hairs which do most absorption of water and nutrients. Plants whose root system consists primarily of fibrous roots may be more difficult to transplant since so many of the roots are lost during the moving process when they are exposed to drying air.
field capacity - this it the ideal level of water in the soil for plant growth. In this situation, the soil still has plenty of air spaces but about 25% of the volume contains water available to the plants. 
filament - in flowers, this is the stem that supports the anther which produces the pollen.

The male part of a flower is called the stamen consists of a filament and an anther. Hybridizers move the pollen from the male parent to the pistil of the female parent when cross-breeding Hosta, Hemerocallis (daylilies) and other plants.

filler - usually nondescript plants (at least when massed or during most of the year) used in a garden area to back up, surround, or “fill” around a specimen plant.
fine-leafed fescue - a species (Festuca) of turfgrass with narrow leaf blades that is widely used for shaded and utility lawns.

Fescue is commonly combined with Kentucky bluegrass and perennial ryegrass in cool-season grass seed mixtures for the home landscape in temperate regions.

flag - a symptom where the tip of a stem or branch curls downward as a result of diseases such as fireblight or insect damage as by the bronze birch borer.
floret - the individual small flower, especially when part of a dense inflorescence.
floricane - in raspberries, these canes are the ones that produce fruit. May be first or second-year canes, depending on the type of plant and how the canes are pruned.
floriculture - in horticulture, this term applies to the science of cultivating flowering plants in controlled environments such as the greenhouse.
flower - the reproductive structure of seed producing plants (angiosperms).

A complete or perfect flower contains both male and female parts while incomplete or imperfect blooms have one or the other but not both.

flower parts - in the center of a typical flower are the carpals which are modified leaves that enclose the ovules. These are often fused to form a single pistil in the center of the flower.

Surrounding the carpals are several narrow stalks topped by pollen sacs which are called stamens. Around these reproductive organs is the perianth, usually consisting of an outer whorl of sepals and an inner whorl of petals. In monocotyledons and "primitive" dicotyledons, the sepals and petals may be indistinguishable, as in the lily the perianth parts are called tepals

flower stem - the stem that supports the flower is called the peduncle
folded - this is a leaf variation where the blade is bent upward parallel to midrib forming a keel-shape.
follicle - a dry seed vessel or pod, consisting of a single carpel that splits at maturity
foot-candle (ft-c) - the amount of light measured 1 foot away from a lit candle. It is a common unit for measuring the amount of light. For example, a normal reading lamp provides 40-75 ft-c.
forcing - controlling the environment to make plants bloom when they normally would not. The process of bringing plants, branches, and bulbs into flower ahead of their normal outdoor flowering period. It is commonly used to make Easter lilies and poinsettias bloom during the festive seasons.
formal garden - a landscape laid out mainly in straight lines, which may incorporate intricate bed designs, hedges, and/or specimen plants of extreme or contrived shapes.
formal landscape plant - a plant that is rigid, dense, or compact in form or can be pruned so that it fits into a formal garden design.
foundation plantings - either the basic structural and shelter plantings of a garden, or plantings of bulbs or other plants along the footings of a structure such as a house or wall.
fragrant flowers - flowers that emit certain chemicals which make them distinguishable to the sense of smell.

Some species and cultivars of hosta produce flowers that are of varying degrees of fragrance. Those on cultivars that originated from the species, Hosta plantaginea, tend to be very fragrant.

frass - excrement of an insect that looks similar to sawdust
friable - refers to soil that is easily crumbled into small aggregates. Often describes a soil that is good for plant growth because it has adequate air and water pore spaces.
frond - a fern leaf.  In the strictest sense, refers to the foliage of ferns, but the word is sometimes used to designate any foliage that looks fernlike, and also the featherlike leaves of many palms.
frost damage - subfreezing temperature that causes individual cells in a plant to freeze, expand and burst. Newly emerged leaves, flower buds and flowers tend to be the most susceptible to this damage.

Some hostas (such as those with H. montana parentage) emerge early in the spring and may be subject to injury by spring frosts. This damage usually shows up in two ways.

One is when the frost occurs during the "bullet" stage of the plant emergence. Cells on the outside of the bullet may be damaged and, when the leaf unfolds, rips and tears will appear in the leaf. It is easy to tell this damage since the two sides of the tear will fit back together like a jigsaw puzzle.

Two, if the leaf is already unfolded when the frost occurs, the damage will often result in a bleached out, water soaked area in the leaf blade.

fruit - mature ovary or cluster of mature ovaries
fruit set - stage of fruit development after pollination and fertilization occur.
fruiting body - structure of most fungi that bear the spores for reproduction. Mushrooms are a common fruiting body for certain species of fungus.
fumigant - a pesticide that is applied in a vapor active, gaseous form. Soil fumigants to sterilize plots of soil are often applied beneath a plastic covering to make them penetrate and to prevent them from disbursing into the air. Fumigants tend to be very toxic and dangerous to handle so they are usually only available through professional pest control companies.
fungi - multi-cell plants that lack chlorophyll and water conductive tissue (xylem and phloem) like higher plants. They absorb their nutrients from either living or dead organisms.

Many fungi are involved in decomposing organic matter. The mushrooms often found in lawns are fruiting bodies of fungi that are rotting dead roots or other organic matter below the surface.

The vast majority of plant diseases are caused by fungi.

fungicide - a chemical or physical agent that kills or inhibits the growth of fungi. For plant diseases, most fungicides are preventative and must be on the plant tissue before the spores land and germinate to be effective.
funnel form - a flower where the corolla tube gradually widens to the opening. An example is morning glory flowers.
furled - Hosta leaves with edges or sides curled or coiled in to the midrib are called furled. H. 'Stetson' has furled leaves.

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