P: Symbol for phosphorus, an essential element.
Pallisade Cells: Leaf cells which form the upper layer of the mesophyll. The pallisade cell layer lies between the upper epidermis and spongy cell layer. It is in these and the spongy cells that photosynthesis occurs.
Palma: Holtkamp variety (Europe). Small, standard African Violet (4-inch pot size) with single, blue flowers and medium green, girl-type leaves. Available in the U.S. as Aquarius.
Pamela: Rhapsodie variety. Large, standard African Violet (4-inch pot size) with single, burgundy flowers and medium green leaves. Introduced 1988. Improved 1999. (AVSA Reg. No. 6988) More information.
Parent Plant: The variety or varieties from which a new African Violet is reproduced. An African Violet may only have one parent, as in the case of leaf propagation or tissue culture, or it may have two parents, as in cases of cross-pollination. A parent plant may also be the African Violet from which a sucker originates. (See Division and Separation.) Also see Pollen Plant.
Paris: Optimara variety belonging to the World Traveler series. Extra large, standard African Violet (6-inch pot size) with double, bi-color flowers. Flowers are purple with a white edge. Leaves are medium green (red reverse). Introduced 1994. (AVSA Reg. No. 8333) More information.
Pasteurization: Process of sterilizing a substance using heat. With regard to African Violets, pasteurization is often used to sterilize potting soil.
Patent: See Plant Patent.
Pathogen: A disease-causing organism, such a bacterium, a fungus or a virus.
Patricia: Rhapsodie variety. Medium, standard African Violet (4-inch pot size) with frilled, reddish-pink flowers and dark green leaves. Introduced 1993. (AVSA Reg. No. 8350) More information.
Patsy: Rhapsodie variety. Medium, standard African Violet (4-inch pot size) with frilled, bi-color flowers. Flowers are white with a purple center. Leaves are medium green. Introduced 1997. More information.
Paula: Rhapsodie variety. Medium, standard African Violet (4-inch pot size) with single, pink flowers. More information.
Pawnee: Optimara miniature variety. See Little Pawnee Girl.
Pearl: Optimara super miniature variety. See Little Pearl.
Peat: Partially decaying organic matter that accumulates in wetlands called bogs or fens. Favorable conditions for the growth of peat is achieved when the rate of decomposition is less than the rate of accumulation for dead vegetation. This happens in bogs, because the soggy conditions of these wetlands does not retain enough oxygen to support the micro-organisms which cause decomposition. Peat forms from various sources, such as marsh plants and mosses. Peat formed from Sphagnum Moss is called sphagnum peat moss. This is generally what is meant by peat moss.
Peat Moss: May refer to any peat formed from moss, but most generally refers to sphagnum peat moss, a peat formed from a type of moss called sphagnum. Of available potting soils for African Violets, those consisting of almost all peat moss are the most highly recommended. In fact, the best potting soils for African Violets will be mixed entirely from peat moss with only a little lime to increase the pH (5.8 to 6.2 for African Violets) and either perlite or expanded polystyrene to enhance porosity and improve aeration. When properly blended, peat moss makes an excellent medium for growing African Violets. While it allows water to drain and nutrients to move around, peat moss has a consistent absorbency that holds just the right amount of water for African Violets. In addition, the light, porous quality of peat moss prevents the delicate roots of African Violets from suffocating as they would in "backyard" soil mixes.
Pedicel: On an African Violet, a stem which grows from a peduncle and supports a single bloom.
Peduncle: On an African Violet, a stem which grows from the crown and supports the pedicels and their blooms.
Peduncle Cutting: A bloom stalk used to reproduce African Violets. This form of propagation involves removing a bloom stalk with about 1/2 to 1 inch of the peduncle from a parent plant. This cutting is placed into potting soil or some other rooting medium, stem first, up to the point where pedicels connect to the peduncle. For most growers, this is the only reliable method for reproducing chimeras. African Violets may also be propagated by seed, division (or separation), leaf cutting or by rooting a sucker.
Pelletized Fertilizer: See Granulated Fertilizer.
Pendula: See Saintpaulia pendula.
Pennsylvania: Optimara variety. Medium, standard African Violet (4-inch pot size) with semi-double, red flowers and medium green leaves (red reverse). Introduced 1988. Improved 1998. (AVSA Reg. No. 6968) More information.
Penny: Rhapsodie variety. Medium, standard African Violet (4-inch pot size) with single, light pink flowers. More information.
Perfect: Describes flowers which have both the male (stamen) and female (pistil) parts. African Violets have perfect flowers. Also see Complete.
Perianth: On African Violets, the calyx and all the petals of a flower, collectively.
Pericarp: Also called seed pot or seed vessel. The lining of an ovary which contains fertilized seeds. On African Violets, the pericarp will hold these seeds until they have matured, usually 4 to 6 months after pollination.
Perlite: A volcanic mineral heated to make it expand. This reduces its density and helps increase porosity when added to potting soil.
Pesticide: Any substance, natural or synthetic, formulated to control pests which feed on plants. Types of pesticides used on African Violets include fungicides, insecticides, miticides and nematicides. Pesticides may work on contact, or they may have to be ingested. They may also be systemic. Depending on the source of the pesticide, they may be organic, elemental or synthetic, and they may be formulated as dust, emulsifiable concentrate, granules, soluble powder or wettable powder.
Petal: Also called lobe. On African Violets, the petals are the colored part of a bloom, usually white or some shade of red or blue. African Violets with single blooms have five petals. African Violets with double or semi-double blooms have additional petals on the interior. Also see Calyx, Corolla and Perianth.
Petiole: Also called leaf stem or leaf stalk. On African Violets, the stem which connects a leaf to the crown.
Petiole Rot: See Leaf Rot.
pH: Puissance de hydrogen. The measure of acidity or alkalinity of a substance. Specifically, a pH below 7.0 is acidic. A pH above 7.0 is alkaline. A pH of 7.0 is neutral. For African Violets, the pH should be between 5.8 and 6.2.
Phloem: In African Violets and other plants, the vascular tissue which transports nutrients and plant carbohydrates from the leaves to other parts of the plant. Also see Xylem.
Phoenix: Optimara variety. Medium, standard African Violet (4-inch pot size) with frilled, double, red flowers and dark green, girl-type leaves. More information.
Phosphate: See Phosphorus.
Phosphoric Acid: See Phosphorus.
Phosphorus: (P) Also called phosphate or phosphoric acid. Major element essential to the growth and vitality of African Violets. One of the three primary elements. Phosphorus aids in the production of healthy roots and plays a vital role in the production of flowers.
Phosphorus Deficiency: Condition which describes an African Violet that is not getting enough phosphorus. Among other symptoms, a phosphorus deficiency will cause African Violets not to flower. More information.
Photoperiodism: Describes the alternating periods of light and darkness which African Violets and other plants need for peak flowering. In addition to receiving plenty of indirect light, particularly in the red range of the spectrum, African Violets need at least six hours of darkness each day. Red light is absorbed by the phytochrome pigment in the leaves which activates the production of florigen, the hormone which regulates flowering. While the production of this hormone is stimulated by light, exposure to light actually destroys florigen. Thus, an African Violet must have sufficient light to produce florigen, while having enough darkness to use it in the production of flowers. Also see Florescence.
Photosynthesis: Process by which the leaves of plants absorb light to convert carbon, hydrogen and oxygen (in the form of carbon dioxide and water) into usable energy called plant carbohydrates. The process is catalyzed by the presence of light-sensitive molecules in the leaves. Together, these molecules are called chlorophyll.
Phototropism: A phenomenon describing the tendency of African Violets and other plants to bend toward the light. This tendency is activated by a light-sensitive hormone called auxin.
Phytochrome: A pigment in the leaves of African Violets and other plants which, when exposed to light, activates the production of florigen.
Phytophthora: The fungus which causes Crown Rot.
Phytotoxicity: Refers to the level of toxicity caused by a specific pesticide in African Violets and other plants. Also see Elemental Toxicity.
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