Stratification: that’s what we do to break dormancy in many seeds, particularly deciduous tree species from the northern hemisphere. It involves the storage of seed in semi moist conditions at temperatures near freezing for periods of from 1-3 months.
Seed should be from fully ripe fruit and is initially stored in cool conditions where it won’t dry out. This simulates the falling of bird pecked fruit with its subsequent drying and covering with leaf litter. The sticky outer coating of fruit initially prevents drying out of the seed and eventually breaks down exposing the seed to the conditions we refer to as stratification.
Seed from fruit consumed by humans shouldn’t have any sticky covering left. It can be briefly dried, dipped in a fungicidal solution and stored in a cool place where it won’t dry out. I store my seeds initially in plastic bags inside a styrofoam esky. This can then go straight into the fridge for the stratification stage.
A moist free draining mix of washed sand, sphagnum moss, perlite or the like is used for stratification. The medium should be damp but not wet. Traditionally seed is stratified in beds of sand outside. The southern side of a building increases the chill factor. A 3-4 cm bottom layer of sand is followed with a layer of seeds then covered with a layer of sand and so on. The top layer of sand is mounded up in the centre to allow for run off of rainwater. Protection from rats and mice is required. Similar conditions can be achieved by stratifying seed in a damp medium sealed in a plastic bag in the fridge. In spring after 1-3 months stratification stonefruit shells may have opened up. If not tap them gently with a hammer to open them and remove the seed. This can be planted in open ground or in pots. Well grown spring seedlings may be mature enough to be budded in late summer or grafted in winter.
If you’re in Adelaide, the Club meets on the 3rd Tuesday of odd months 7:45pm at the Burnside Community Centre, 401 Greenhill Road, Tusmore, corner of Portrush Road, behind Burnside Town Hall. Visitors Welcome. http://www.rarefruit-sa.org.au/
Harry Harrison – President – South Australian Rare Fruit Society
Sub-Tropical Fruit Club of Qld. Inc Newsletter February – March 2007