Holly tree seeds exhibit a deep dormancy that requires patience to overcome. Begin by preparing a well-draining substrate, such as a 50/50 mix of compost and sharp sand or perlite/vermiculite. Ensure the substrate is moist but not overly wet. Mix the seeds into the substrate, maintaining enough volume to keep them separated. Place the seed mixture in a clear plastic bag, leaving a small gap for air exchange, and note the start date of the pre-treatment. Initially, expose the seeds to a warm pre-treatment at around 20 degrees Celsius for approximately 40 weeks. Prevent the pre-treatment medium from drying out during this period.

Following the warm pre-treatment, initiate a cold period by placing the bag in the fridge at 4 degrees Celsius for at least 24 weeks, allowing for longer durations if needed for germination signs to appear. If germination occurs in the bag, carefully remove the sprouted seeds and plant them. Once the pre-treatment period concludes, small quantities of seeds can be sown in pots or trays with good compost, covered with a thin layer (no more than 1 cm) of compost.

For larger quantities, sow seeds in a well-prepared outdoor seedbed after completing the warm and cold pre-treatments, awaiting the emergence of seedlings. Natural temperature fluctuations during pre-treatment can mimic the natural cycle and enhance germination results. Ungerminated seeds can undergo the entire warm and cold process again to stimulate further germination. Fresh seedlings may continue to germinate for up to 5 years after the initial sowing. Avoid exposing newly sown seeds to high temperatures (above 25 Celsius), keep seedlings well-watered and weed-free, and allow 2-3 years of growth before planting them in a permanent position.