Glossary

Bipinnate: Having pinnules that are further subdivided in a pinnate arrangement.

Blade: Anything that’s above the crown is blade.

Clay: Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clay minerals are typically formed over long periods of time by the gradual chemical weathering of rocks, usually silicate-bearing, by low concentrations of carbonic acid and other diluted solvents.

Cultivars: A plant variety that has been produced in cultivation by selective breeding.

Dormancy: Dormancy is a period in a perennial fern’s life cycle when growth and development are temporarily stopped.  Fern dormancy tends to be closely associated with environmental conditions, such as photoperiod, water availability and decreasing temperature.

Fern: A fern is a flowerless plant that reproduces by spores released from the underside of the fronds. Fern have stems, leaves, and roots like other vascular plants. There are about 12,000 species of ferns, which unlike mosses, have xylem and phloem (making them vascular plants).

Fiddleheads: While the new fronds are uncurling, they are called fiddleheads.  Another word for the spiral pattern is circinate.

Foot candle: A measurement unit used in the greenhouse to describe the intensity of light falling on a surface. One foot candle equals ten lumen.

Fronds: The leaves of ferns are called fronds.

Heuchera: The genus Heuchera includes at least 50 species of herbaceous perennial plants in the family Saxifragaceae, all native to North America. Common names include alumroot and coral bells. They have palmately lobed leaves on long petioles, and a thick, woody rootstock. The genus was named after Johann Heinrich von Heuchera (1677–1746), a 18th century German physician.

Hybrids: Hybrids are sexual crosses between two closely related species.  They are usually sterile.

Loam: Loam is soil composed of sand, silt, and clay in relatively even concentration (about 40-40-20% concentration respectively). Loam soils generally contain more nutrients and humus than sandy soils, have better drainage and infiltration of water and air than silty soils, and are easier to till than clay soils.

Peat moss: Widely used in horticulture for growing plants. It is a large absorbent moss that grows in dense masses on boggy ground, where the lower parts decay slowly to form peat deposits.  Peat moss holds water and aerates heavy, clay soil.

Photoperiod: Photoperiod is the developmental responses of plants to the relative lengths of day light and dark periods.  Here it should be emphasized that photoperiodic effects relate directly to the timing of both the light and dark periods.  Photoperiod is the day night mix.  It is not a physiologic response.

Pinnae: The divisions of a compound frond.

Pinnate: The term describes an arrangement of the pinnae arising at multiple points along the rachis.

Pinnules: A secondary division of a pinnate leaf of a fern.

Ploidy: The number of copies of a chromosome contained in a cell.  Pollen, eggs and spore have half the copies of chromosomes (n) than the parent (2n).

Poly: Short for polyethylene.  A plastic film that is used for commercial greenhouse coverings.  It is much stronger and less expensive than glass but must be replaced every few years.

PPM: Short for parts per million. It is a way of describing very dilute concentrations of something in water or soil. One ppm N is equivalent to 1 milligram of Nitrogen per liter of water (mg/l).

Prothallus/Prothalli: Prothallus is the gametophyte stage of ferns.  It is a small, flat, heart-shaped plant produced by a germinated spore.  It produces eggs and/or sperm which unite to form a sporophyte – the fern plant you recognize.

Rachis: The main stalk of the blade.

Sand: Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent is silica (silicon dioxide, or SiO2), usually in the form of quartz. Sand particles range in diameter from 0.0625 mm (or ⅟16 mm) to 2 mm.

Silt: Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil, as suspended sediment in water, or as soil deposited at the bottom of a water body.

Soil type: In terms of soil texture, soil type usually refers to the different sizes of mineral particles in a particular sample. Soil is made up in part of finely ground rock particles, grouped according to size as sand and silt in addition to clay and humus, organic material such as decomposed plant matter.

Sorus/Sori: Clusters of sporangia form a sorus.

Sporangia: Sporangia is the little pouch containing spores.  It is found on the underside of the fern frond.

Spore: Spores are fern’s reproductive unit. They are dustlike and gathered in sori.  They have half the ploidy of the parent plant.  They germinate and form a prothallus.

Stipe: A stipe is a stalk that supports the blade.

Tissue culture: The use of an artificial medium to grow plant tissues.

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