Brassica flowers

Seeds used in: New Plants, Insects and Plants
Brassica – Brassica rapa

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Background. A seed is a magnificent work of nature. It is the living result of successful plant reproduction, efficiently packaged for storage, distribution, and survival. Every seed is a living organism prepared to produce a plant similar in every way to the parent plant that gave rise to it.

Microscopic inspection of a seed will reveal a tiny embryo (resulting from the fusion of the female egg inside the ovule and the male sperm inside the pollen grain), a relatively large starchy or fatty food supply, and a tough wrapper called a seed coat that surrounds the whole thing. A healthy seed can withstand adverse conditions for extended periods of time, waiting for the right combination of conditions for growth to begin. Some seeds, like those of grass, clover, and garden flowers, may remain viable for a few months to a few years, while others, like those of evergreen trees and some cacti, can stay alive for decades.

Seeds have different requirements to trigger the onset of germination. Some seeds are ready to germinate immediately. Citrus seeds and the huge seed found in an avocado can be planted as soon as they are separated from the fruit that surrounds them. Other seeds must dry out thoroughly before they can receive the message to start growing. Tomato, pumpkin, pea, and sunflower have seeds that must dry out. Others must be subjected to more exacting conditions before germination. Some, like spruce seeds, must be cold for a while, and some pines germinate only after the seeds have been scorched in a forest fire.

Brassica is a genus of plants that includes mustard, cabbage, collards, bok choy, kale, cauliflower, broccoli, and turnip. Some of them are fast growing and progress through their life cycle quickly. One variety, Brassica rapa, has been selectively cultivated to produce a plant that has an exceptionally short life cycle—one month! This plant, developed at the University of Wisconsin and known by the trade name of Wisconsin Fast Plants, is used extensively in plant pathology research and has excellent characteristics for education at all levels. Brassica rapa seeds (Wisconsin Fast Plants) are very special seeds available only from biological supply companies and through Delta Education.

Brassica is used as an example of a typical flowering plant. By providing ideal (albeit unnatural) conditions of perfect nutrition and continuous light, students can observe germination, leaf formation, budding, flowering, and seed development in a few weeks rather than a few months. Check on viability of seeds. About 200 tiny brassica seeds come in a small envelope—enough for two or possibly three classes. Check the date on the brassica package to make sure that the seeds are not too old. If you question the seeds’ viability, plant a few seeds 1 week before starting the investigation to make sure you have close to 100 percent germination.

How to care for your brassica plants. This brassica is completely dependent on continuous cool light, or it will fail to grow at all. Cool does not refer to the temperature, but rather to the color of the light. Brassica needs light that is strong in the blue (cold) wavelengths of light, rather than the red (warm) wavelengths. For this reason, if you need to replace a fluorescent lamp in the light source, specify a cool bulb.

Brassica grows best when it is kept moist and well fertilized. To do this we suggest putting water in the tray in which the planter cups stand. The water will soak up into the cups. Add water only after all of the water has been soaked up (or evaporated). At that time add four drops of liquid fertilizer to 1/2 liter of water and pour it into the tray.

The light that falls on the brassica plants should be as intense as possible. Therefore the distance from the bulbs to the plants should be between 3 and 7 cm (between 1"and 3")—never more than 8 cm (3-1/4"). As the plants grow, the lamp should be raised using the chain-and-hook system. Other than that, just keep the soil moist, and you can almost watch the plants grow. See the fast plants website for more information on tending the brassica plants.

Contact Wisconsin Fast Plants for more information. The Brassica rapa seeds were developed at the University of Wisconsin and are widely used in education at many levels. There is a phone hot line in Wisconsin for teachers who are using the seeds and have questions about their growth or need more information for extension activities. That hot line is 1-800-462-7417. The website is

What to do with them when the investigations are completed. The plants and seedpods can be dried and stored for later planting. See the fast plants website for details. Any seeds left from the original packet can be stored in its paper sleeve and in a zip bag. The seeds should be kept dry.