Wild black raspberry patches are a source of food for both wildlife and humans. Cultivating the same varieties from seed gathered in the countryside allows you to bring the wild berries a little closer to home. Although these plants propagate fastest from root divisions and vegetative cuttings, they also reproduce readily and easily from seeds.
Gather mature raspberry seeds from healthy plants growing in the wild. Select berries past their prime that look slightly dry and wrinkled. These often fall to the ground below the plants as they lose their moisture. Place the gathered fruits in a dry paper bag for transportation from the wild berry patch to your kitchen.
Spread the wild black raspberries over a piece of newspaper. Pick out any debris, bugs or rotting berries. Place clean newspaper on a cookie sheet and spread the fruits evenly over the surface to continue drying. Place the cookie sheet in a dry, protected location for about five to nine days.
Remove the raspberry seeds from the dried fruit debris by gently crumbling them between your fingertips. Separate the seeds and place them in a jar. Tighten the lid to seal out moisture and place the jar in your refrigerator for about 45 days. This process, known as stratification, provides the necessary cold temperatures required for germination.
Fill a seed tray with rich, loamy potting mix. Sprinkle the raspberry seeds evenly over the surface of the soil in the tray, placing about three seeds per square inch of soil. Sprinkle a fine layer of potting soil over the seeds, barely covering them with less than 1/8 inch of mix. Press the palm of your hand over the surface to create a firm contact between the seeds and the soil.
Place the seed tray in a drip tray. Slowly apply water to the drip tray, allowing the soil to draw the water into the seed tray. This bottom-watering method reduces seed disturbance and provides even moisture throughout the seed tray. Offer more water whenever the surface of the soil begins to feel slightly dry to the touch. Set the tray in a sunny location that receives between 10 and 12 hours of daylight each day.
Pinch out crowded seedlings after they form their second set of leaves. Allow just one seedling to remain for each 2-inch section of soil. Transplant the young seedlings into the permanent berry patch when they reach about 4 inches tall. Grow wild black raspberry plants in a sunny location within your garden that contains rich, loamy soil.