Book: Tree Planting & Aftercare Chapter: 5 Propagation Section: Seed cleaning and storage Metadata: Details Buy this book

Remove damaged or shrivelled seed as you clean, as these are not worth storing or sowing.

Seed cleaning

Seed cleaning is necessary for most seeds to:

• Extract seed from fruits for storage and sowing.
• Prevent seed going mouldy.
• Help reduce 'damping-off' or fungal contamination after germination.
• Allow the regulation of seed moisture content during storage and pretreatment.

Methods vary according to the type of fruit or seed.

Cones

Includes conifers, as well as alder and birch. Dry the cones indoors until they begin to open, and then place them in paper bags and shake to release the seeds.

Nuts

Species include oak, sweet chestnut and beech. Remove acorns from their cups, and remove chestnuts from their husks. Acorns collected from the ground should be checked carefully as they are often partially chewed. Discard any that are damaged.

Winged seeds

Species include ash and field maple. Remove from twigs and stalks, but leave wings intact.

Fleshy fruits

These include hips, haws and berries from species including crab apple, hawthorn, rowan and holly. These require cleaning in order to remove the flesh from the seed, as the flesh contains inhibitors to germination. In the wild, the flesh is removed as the seed is passed through the gut of birds and animals which eat the fruit. A cleaning process is required to imitate this, as follows:

1. Soaking or maceration will help soften the flesh, particularly of fruits which were not quite ripe at collection. Soak the fruit in buckets or other suitable containers, leaving them until they are soft, but not so long that they start to ferment, indicated by bubbles and smell.
2. With some fruit, the flesh and non-viable seeds will rise to the surface where they can be skimmed off, leaving the viable seeds at the bottom. Mashing with a stout pole, potato masher or similar will help to separate the flesh from the seed. Seeds can also be pressed through a sieve. Hawthorn and holly, which have very hard seeds, can be depulped in a food processor without risk of damaging the seed.
3. After depulping, thorough washing of the seed is needed to clean away all traces of the pulp. Washing under a fast jet of water is the best method.

Storage

Some species are best sown immediately in trays or pots. Other seeds should be stored until the correct time to start warm/cold treatment, in order to time germination for early spring.

Long-term storage may be needed where you have excess seed which you want to keep for future years, normally of species which only produce seed intermittently. The seed of most species, called orthodox seed, can be safely dried for storage. Orthodox seeds should be gently dried by spreading out on trays lined with kitchen paper or newspaper in a warm room. Put the clean, dry seed into poly bags, expel the air, label and seal securely. The bags can then be stored in a fridge at 2-5°C, for several years as required, and the seed will remain viable. When the seed is required, follow the recommended times for stratification or temperature treatment (see species details), before sowing.

Recalcitrant seed, produced by oak, beech and the non-native chestnut, will be killed if dried. They should be stratified or sown within a few days of collection, to prevent moisture loss.

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