Blackberries are one of the wonder foods, full of flavor, fiber, vitamins--and are just beautiful. They can grow as weeds, as they are easily spread by seeds as well as by arching canes that sprout new plants. One of the issues with growing blackberries from seed is that the resulting fruit will not be the same as the original host of the seed. However, if you want to hand-pollinate some blossoms and combine the characteristics of two good plants to produce specific seeds, the results could be better than the original plants. To plant the seeds of a fresh berry you just tasted, follow these few steps.
Take the seeds from a soft, ripe blackberry by smearing the berry across a paper towel. Pick out the seeds from the fruit, and set them on a dry ceramic or glass shallow dish.
Blackberry seeds need to be scarified. This means that the outer woody coating needs to be scarred such as in nature when an animal eats the berry and it passes through the acid environment of the digestive tract. Pour about a tbsp. of sulfuric acid--the amount found in professional-strength drain cleaner--over the seeds. Let it sit in a safe place for about an hour.
Rinse the acid from the seeds using a wire strainer. Be very careful as the sulfuric acid can react to water as you rinse the seeds with warm water. Prepare a rinsing solution of about a tsp. of baking soda and a cup of water. Pour the solution over the seeds to neutralize the acid.
Place the rinsed seeds on a paper towel and fold it in half three or four times. Moisten it just enough to make it damp. You need to duplicate the moisture levels found in the natural setting of layers of leaves and debris, where the blackberry grows wild.
Refrigerate the seeds by placing the folded paper towel into a plastic bag. Store the bag in the back of your refrigerator for at least three months. This cold period will break the dormancy of the seed.
Check the seeds after three to four months to see if they have started sprouting. Remove them from the refrigerator. Prepare the plant pots by filling them with moist humus-rich potting soil and poking shallow holes about 1/4-inch deep and 3 inches apart with the back of a pencil or your finger. Gently place the sprouted seeds into the holes.
Cover the seeds lightly with 1/8-inch of soil. Water gently. Place the plant pots in a sunny window and keep them indoors until the weather is warmer. Water regularly so that the soil does not dry out.