How to grow Holly
Holly is one of the slowest species on this site to raise from seed, a long warm spell followed by an equally long cold one, sometimes taking the best part of two years to germinate. It’s not difficult, just a genuine test of patience.
At a glance
- Scientific name
- Ilex aquifolium
- Family
- Holly (Aquifoliaceae)
- Can seed be stored
- Yes, dries and stores
- Type of dormancy
- Deep dormancy
- Pretreatment
- Warm ~40 weeks + cold ~24 weeks (over a year in total)
Quick links
Seasonal calendar
Year 1
Year 2
Year 3
- a Collect: Late autumn; possibly to April following year
- b Store: A week or two, ideally treated immediately
- c Treat: 18-month treatment begins
- d Treat: Full second year; needs full summer
- e Treat: Second winter completes
- f Sow: Worked example: collect Dec 2017 - spring 2019
- g Grow: Grown on until November, traditionally the start of the lifting and planting season, though this window has been shifting and shortening with a changing climate.
| Stage | Year | Month range | Note |
|---|---|---|---|
| Collect | Year 1 | November to December | Late autumn; possibly to April following year |
| Store | Year 1 | December to December | A week or two, ideally treated immediately |
| Treat | Year 1 | December to December | 18-month treatment begins |
| Treat | Year 2 | January to December | Full second year; needs full summer |
| Treat | Year 3 | January to February | Second winter completes |
| Sow | Year 3 | February to March | Worked example: collect Dec 2017 - spring 2019 |
| Grow | Year 3 | March to November | Grown on until November, traditionally the start of the lifting and planting season, though this window has been shifting and shortening with a changing climate. |
Picking
Holly berries ripen in the late autumn, usually in November or December. 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.
Extraction and storage
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. Click here to see the simplest way to extract the seed from the fleshy fruit. Ideally the extracted seed should be pre-treated immediately.
Pretreatment
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.
Sowing
After the seeds have spent a whole summer and the following winter outside, they are ready to be sown (eg. collect December 2017 and sow spring 2019).
Holly doesn’t like its root to be disturbed once it is growing. For this reason it is best grown in a pot – about 8cm in diameter. Sow each seed as it begins to germinate (when you can see a small root emerging). Sow one per pot. Cover the seed with a little compost and firm gently.
Growing
During the first year in pots, your holly seedlings will grow up to 20cm in height. In the autumn of this first year (about September/October) transplant the young trees into 1- or 2-litre pots, taking care not to disturb the roots too much.
If kept well fed, they will reach a size large enough for planting out during the second year.
Because holly is grown in pots, it will be more susceptible to drying out. Ensure that the pots are kept well watered and fed.
Planting your new tree(s)
When your Holly is tall enough, it can be planted into its new home. Prepare the site well by clearing away any weeds or grass and make a hole big enough to accommodate the root ball. Plant carefully in the hole, to the same depth as it was in the pot or ground, and firm back the soil. More tree planting details here.
