HOW TO GROW HOLLY FROM SEED
Holly berries ripen in the late autumn, usually in November or December, which is why they make such great Christmas decoration. They sometimes remain on the tree throughout the winter, so could possibly be collected as late as April the following year. Berries are stripped from the trees by hand.
The collected berries should be separated from any twigs and ‘de-bunched’. They can be left in buckets or baskets for a week or two, provided they are stored in a cool, dry place.
You have a choice now. Do you want nature take its course or do you want to pre-treat the seed - stratification - to speed up germination?
Mix the seeds with equal parts horticultural sand or a sand/compost mixture. Use 50% leafmould or peat-free compost and 50% horticultural sand. For each handful of seeds add two or three handfuls of mixture. Select a pot that has enough room for this seed/sand mixture (and a bit more) and put a layer of stones in the bottom. Cover the stones with sand. Place the seed/sand mixture on top of this and cover this with 2-3cm sand. Label the pot and stand in a shady spot outdoors.
The pot needs to remain outside for eighteen months. This is where patience is required! Water the pots if they show signs of drying out and protect from birds and mice if they discover your seeds. We will be sowing the seeds the second spring following collection. Holly seed has a very hard outer seedcoat that needs a full summer (warm temperatures) to break down, allowing oxygen and water to reach the embryo tree inside.
You will need to stratify holly seeds in order to break the dormancy period. To achieve this, place a 1-inch layer of damp moss peat over the bottom of a zip top plastic bag. Place the holly seeds onto the moss peat and cover them with secondary 1-inch layer of damp moss peat.
Seal the zip top bag and store it at about 3 - 4 degrees Celsius for four to five months. The salad drawer in the bottom of your refrigerator will work well for this.
Remove the seeds from their chilled area in the spring or early summer as they will now be ready for sowing.
How to sow Holly Seeds
Plant the holly seeds out in a nursery bed in the garden. An area that has deep, loamy soil and full to part shade is ideal. Avoid areas that are prone to periods of standing water during the year.
Plant holly seeds ¾ to 1 inch deep and cover with soil. Keep the area damp with frequent, light water applications.
Place a tomato cage or other wire structure over the seedlings when they emerge to protect the young holly plants from being trampled.
Spread a 2- to 4-inch layer of compost over the seedbed to add nutrients to the soil and encourage strong seedling development. Keep the compost back 2 inches from the young holly plants to avoid smothering them.
Transplant the holly seedlings into their permanent position when they are 12 inches tall. Dig down 12 to 18 inches when transplanting to avoid damaging the taproot. Dig out the root ball 24 inches in diameter.