The blackthorn shrub gets its name from the sharp, black thorns dotting its branches. Native to Europe and Asia, nearly all parts of the blackthorn are useful for food or medicinal preparations. People add pricked blackthorn berries to gin for an extra kick of flavour, and practitioners of natural medicine use the leaves, bark, fruit and flowers to treat a number of ailments, including fever and stomach problems. You can grow blackthorn shrubs from the seed in the centre of a blackthorn berry.
Collect berries from a fully-grown blackthorn shrub in late fall or early winter. Place the berries in a burlap sack and set them aside until October.
Step on the bag in very early October to crush the berries inside. Wait a week to allow the flesh of the berries to decompose and start to fall from the central seed.
Stretch 1/4-inch mesh over the top of a bowl or other container. Place the crushed berries on top of the mesh. Run a rolling pin gently over the berries to force the flesh down through the mesh and into the bowl, while leaving the seeds intact on the mesh. Wash the seeds thoroughly to finish removing any excess flesh.
Moisten the vermiculite and compost and mix them together. Add them to the seeds with a ratio of 3 parts seed to 1 part vermiculite and compost. For example, mix 1/4 cup of vermiculite and compost with 3/4 cup of seeds. Make as much of the mixture as desired, then place it in a freezer bag. Add just enough water to make the entire mixture damp, then seal the bag.
Store the freezer bag in a location with a temperature between 15.0 and 18.3 degrees Cor two to four weeks. Open the bag and shake the seeds once per week, adding water to the bag and removing mouldy seeds as necessary.
Place the bag in the refrigerator after two to four weeks. Keep the bag in the refrigerator until roots start to emerge from the seeds, which may take four to five months. Continue opening and shaking the bag weekly.
Fill a seed tray with compost until it reaches 1/2 inch from the top of the tray. Tap the tray gently on a table to settle the compost.
Identify which seeds have a 1/2-inch root. Sow those seeds in the compost. Cover the seeds with compost, followed by fine-grain sand.
Place the tray on an inside windowsill in the winter months. Rotate it regularly to avoid the stems leaning toward the sun. Set the tray outside from September until winter. Water the plants enough to keep the roots moist, which translates to every two to three days in the summer and slightly less frequently in cooler months.
Transplant the shrubs to a permanent location in March or April.