Why Collect Tree Seeds at All?

There is a quiet thrill in growing a tree from a seed you gathered yourself. It costs next to nothing, connects you to the rhythm of the year, and gives you a plant that is perfectly suited to your local soil and climate. Native trees — oak, hazel, hawthorn, rowan, birch, alder — support far more wildlife than most garden centre ornamentals, and raising them from seed is a gentle act of woodland gardening. You are also helping to preserve local genetic diversity, because each seed carries a slightly different story. Whether you have a few pots on a balcony or a corner of a field, collecting your own seed is rewarding and surprisingly straightforward.

Knowing When to Gather

Timing is everything. Most native tree seeds ripen in late summer and autumn, but each species has its own moment. Watch for the change from green to brown, dry, or fleshy. A simple test: if the seed comes away easily, it is probably ready. Never collect green, unripe seeds — they will not germinate. Also be aware of mast years, when trees such as oak and ash produce a bumper crop; these are your best opportunities.

• Oak: Acorns ripen from late September to October. Collect when they fall naturally and the cap detaches easily.
• Hazel: Nuts are ready in August and September, before the squirrels take them all. Look for brown shells and loose husks.
• Hawthorn: Bright red haws from September to October. Pick when they are soft and deep in colour.
• Rowan: Berries turn scarlet in August and September. Collect before the birds strip the tree.
• Birch: Catkins shatter in August and September. Shake the branches over a sheet to catch the tiny winged seeds.
• Alder: Cones turn brown and woody in October. Pick them before they open and release the seed.

How to Collect Without Harming the Tree

Always ask permission if you are gathering from land that is not yours, and never strip a tree bare. Take a handful from several different trees rather than everything from one. This ensures genetic variety and leaves plenty for wildlife. Wear gloves for thorny species like hawthorn and blackthorn, and use secateurs for tough stalks. A sturdy bag or a clean bucket is all you need. For low-hanging seeds, pick by hand; for higher branches, a long-handled pruner is safer than climbing. Avoid trees that look diseased or stressed — you want strong, healthy parents. And do not forget to label your collections straight away, as it is easy to forget which is which.

Cleaning and Preparing Seeds

Once home, clean your seeds promptly to prevent mould. The method depends on the type of fruit. Fleshy berries like rowan and hawthorn need to be mashed and soaked in water for a few days, then rinsed and rubbed to remove the pulp. Good seeds will sink; discard any that float. Nuts such as acorns and hazelnuts should have their husks or caps removed, then float-tested in water — viable acorns sink. Winged seeds from birch, alder, and ash can be rubbed gently to remove the papery wings, though it is not essential. Spread everything out on newspaper in a dry, airy room for a few days, but never use an oven or radiator, which can kill the embryo. Some seeds, like acorns, are recalcitrant — they must not dry out at all — so keep them moist from the start.

Storing Seeds for Winter and Beyond

Most native tree seeds need a period of cold, moist conditions — known as stratification — to break dormancy. The easiest way is to store them in the fridge. For dry seeds like birch and alder, place them in a paper envelope or a labelled airtight jar with a little silica gel, and keep them cool and dark. For fleshy and nut seeds, mix them with slightly damp vermiculite or sharp sand in a sealed freezer bag, then store in the salad drawer at around 4°C for 8 to 16 weeks. Check regularly for mould; if you see any, rinse the seeds and replace the medium. Acorns are best stored in a bag of damp leaf mould or compost in a cool shed, as they will not tolerate drying. Always label with the species and date. Come spring, sow the seeds in pots of peat-free compost and keep them watered. Some, like oak, may germinate while still in the fridge — pot them up as soon as you see a root.

A Few Species Notes to Get You Started

Oak: Acorns are easy — collect in autumn, float test, and either sow immediately in deep pots outdoors or store moist in the fridge. They have a long taproot, so use tall pots.

Hawthorn: The seeds inside the haws are very hard. After cleaning, stratify for at least 12 weeks, then sow. Germination can be slow and erratic, so be patient.

Rowan: Clean the berries, stratify for 8 to 12 weeks, then sow on the surface of moist compost and cover lightly. They need light to germinate.

Birch: Sow the tiny seeds on the surface of damp compost in early spring — do not bury them. They need light and warmth.

With a little care, your gathered seeds will become sturdy young trees, ready to plant out in a few years. Each one is a small piece of British woodland in the making.