Plant Propagation from Seed
Seed Quality
Because nearly all bedding plants are produced from seed, the use of high-quality seed is extremely important. The grower who tries to save on production costs by purchasing cheap, low quality seed may end up losing everything. Low quality seed often germinates poorly and slowly and produces weak seedlings. The result is a delayed, smaller-than-planned crop of low quality.
Seed Germination
Good quality seed has a high germination percentage (well over 90%). This germination percentage should be printed on the seed packet. Only seed that is packaged for the current production year should be purchased.
Graded, Primed, and Pelleted Seed
Producing plug-grown bedding plants has resulted in a demand for high-quality seeds with high germination rates that germinate uniformly. The combination of mechanical seeders and market demand has placed pressure on seed companies to consider seed quality as part of the overall effort to breed new cultivars. Several seed treatments are used in an effort to improve seedling stands in plug flats. There are three types of seed to look for: (1) graded seed, which is sorted by physical characteristics; (2) primed seed, which is partially germinated; and (3) pelleted seed, which is coated.
Graded Seed
These are cleaned seeds that have been physically separated by size, shape, weight, or density. Grading seed for size uniformity improves seeder performance while also producing more consistent rates of emergence.
Primed Seed
Seed priming is done to increase the speed, uniformity and overall percentage of seed germination. Seed priming involves soaking the seed prior to planting. Soaking starts the germination process, but the seed is planted before germination is completed. Seeds that have been primed may be then dried down and stored for a period of time, or they may be planted soon after priming.
Pelleted Seed
The practice of coating seed, called seed pelleting, was developed to improve the ease of handling and planting of small, irregularly shaped seed. In many cases, pelletized seed is used for ease in mechanical seeding (See Figures 24.1). Pelletizing increases speed of seeding and allows singulation (one seed per cell) within the tray. In the process of seed pelleting, the surface of the seed is covered with an inert material, such as clay, diatomaceous earth, polymers, sand, or some other material.
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