A member of the cole or cabbage family, broccoli is a cousin to cabbage, cauliflower and Brussels sprouts. Grown for its vitamin-rich, immature flower crowns, broccoli emerges from tiny seeds. These seeds prefer cool temperatures for germination and growth, but are low-maintenance and easy to grow even for beginners. Proper care of broccoli seeds will ensure a better overall product and satisfaction with your crop.
Broccoli seeds are a few millimeters in diameter. Seeds are dark brown, hard, and completely round. Broccoli heads form florets of tightly closed green buds that are typically harvested and eaten. If left to seed, these buds will open and form bright yellow flowers. It is from these flowers that the seeds will form.
Prepare the ground by mixing in up to 3 inches of organic matter to a depth of 6 inches. A soil test may be performed to check for pH, the optimum level for broccoli seed cultivation being between 6.0 and 7.0. Amend soil according to soil test kit recommendations if necessary. Start seeds indoors or sow directly in the ground after hard frost. Some broccoli seeds will survive light frost conditions. Plant the smallest broccoli seed varieties at a depth of 1/8 inch under the soil, and larger seeds at 1/4 to 1/2 inch following seed packet instructions. Keep soil evenly moist during germination. Thin seedlings or space transplants to 2 feet, allowing 3 feet between rows.
Allow selected broccoli crowns to reach maturity on the stalk by allowing flowers to form seedpods. Once heads have dried as much as possible on the stalks, cut them, place in a paper bag, and store them in a cool, dry place. As the flowers dry out completely, seeds will fall into the bag for easier collecting.
Store fully dried seeds in tightly sealed containers. Label the seed container with the name of the species and date. Place containers in a cool, dry place such as a refrigerator.
Peronospora parasitica is the fungus that causes downy mildew, a disease that will affect the seedlings sprouting from your broccoli seeds. If too much moisture collects on immature leafs, a gray-colored mold will collect on the underside while the top wilts and yellows. Space plants properly and avoid overhead watering of seedlings to combat this problem. A second offender of the broccoli seed is damping off, caused by Pythium fungus present in the soil. Broccoli seeds that have sprouted into tender seedlings may be damaged and die due to exposure to this fungus. Plant seeds in clean soil that is previously disease-free for best results.