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Scarification   Horticulture ]

Dictionary of botanic terminology - index of names

  Any process of penetrating the protective seed coat of dormant seeds accomplished by chemical, mechanical, heat, or moisture treatment allowing water and oxygen into the seed, thereby helping to improve germination in some species.  
The testa or seed coat of some seeds is hard and quite  impermeable to water and gases (e.g. the seeds of Sclerocactus, Pediocactus and Toumeya ); This seeds will not germinate unless their seed coats has been altered physically. The seed coat is not really required for germination. In fact, many seeds do have a hard seed coat which is a physical barrier (external dormancy) that prevents germination. Any process of breaking, softening, drilling, scratching, or mechanically altering the seed coat to make it permeable to water and gases is known as scarification. Through this alteration of the testa the seed can imbibe water.
In nature, this occurs as the seed exposed to freezing temperatures or microbial activities that modify the seed coat during the winter. Scarification can also occur as seeds pass through the digestive tract of various birds and animals.
Methods of scarification commonly used are mechanical, hot water, and acid.

  Involves breaking or weakening the seed coat and can be carried out using sandpaper or a file to abrade the seed coat, or using a knife to nick the coat, or using an hammer to crack the the coat for allowing water to enter. Make attention to not crush the seed as to damage the embryo. Once scarified, seeds will not store well and should be planted as soon as possible after treatment or placed under cold/moist stratification if required. This treatment works well for larger seeds. Smaller seeds may be rubbed between sheets of fine grit sandpaper. If the seeds are too small to see the progress, a different method such as soaking should be used.
  Some seed coat can be softened in warm or hot water ( 75-95 C NOT BOILING! ) the seeds are left to soak in the water as it cools for 12 to 24 hours before planting. Use 10-20 times the volume of hot water versus seed. Seeds with a waxy coating should be washed several times in very hot water to remove the wax before the final soaking.
  The seeds are put in a glass container (Do not use any other type) and covered with concentrated sulphuric acid at about twice the volume of seed. The seeds are gently stirred and allowed to soak from 10 minutes to several hours depending on the hardness of the seed coat. When the seed coat becomes thin, the seeds can be removed, washed and planted. This method involves the use of concentrated Sulphuric acid that is a very hazardous chemicals that can, be very dangerous for an inexperienced individual and requires to observe meticulous SAFETY measures that should not be overlooked! It is very important to remember to NEVER pour water into acid! ALWAYS pour the acid into the water!!!  

Various reference books provide appropriate concentrations and durations of treatment.





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