Glossary - P
Paper mulches – Mulches made from newspaper or paper fibers.
Peat moss – The partially decayed remains of sphagnum moss.
Perennials – Plants that live two or more years.
Perlite – Lightweight volcanic material often used in soil less media.
Permanent wilting point – The point where a plant can no longer remove the small amount of water remaining in the soil and the plant wilts.
Pest – Plants, fungi, bacteria, nematodes, insects and animals that occur in a place they are not wanted.
Pesticides – A chemical that kills undesirable plants, plant diseases, insects or other pests.
pH – Is – Log [H+] and a scale from 1 to 14.
Phosphates – The form of phosphorus used by plants.
Photodegradable mulch – Mulch that contains chemicals that cause the plastic to degrade when exposed to ultraviolet radiation.
Photosynthetically active radiation – Wavelengths of radiation (mostly reds and some blues and yellows) used by plants for photosynthesis (production of sugars).
Pickling cucumbers – Cucumbers that are one to six inches long with a warty skin that is used for pickling and sometimes for salads
Plant cages – Structures made from cloth or plastic that keeps out migrating insects while allowing sunlight, rain and wind to enter. They generally do not protect against cool temperatures.
Popcorn – A variety of corn that has small ears, kernels that are pointed at the base and apex and very hard starch in the kernels which explodes when heated.
Potash – A form of potassium contained in the soil and fertilizers and utilized by plants.
Preventative weed control – Practices whose aims are to prevent weeds from occurring in the garden.
Prevention – Preventing problems before they occur.
Pumpkin – The edible fruit of any Cucurbita species that is harvested mature and is not used as a baked vegetable.
Purity – The seed is true to type and does not contain undesirable contaminants.