Warm and Cold Pre-treatments

Warm and Cold stratification mixed with sand and compost

Recommended for the following:

Species Advised Treatment Duration
Field Maple (acer campestre) 10 weeks warm + 24 weeks cold
Paperbark Maple (acer griseum) 17 weeks warm + 17 weeks cold
Manchurian Maple (acer mandsuricum) 17 weeks warm + 17 weeks cold
Three-flowered Maple (acer triflorum) 17 weeks warm + 17 weeks cold
Snowy Mespilus (amelanchier canadensis) 4 weeks warm + 16 weeks cold
Hornbeam (carpinus betulus) 4 weeks warm + 35 weeks cold
Wedding Cake Tree (cornus controversa) 12 weeks warm + 31 weeks cold
Cornelian Cherry (cornus mas) 16 weeks warm + 23 weeks cold
Turkish Hazel (corylus colurna) 2 weeks warm + 14 weeks cold
Spreading Cotoneaster (cotoneaster divaricatus) 12 weeks warm + 27 weeks cold
Rockspray Cotoneaster (cotoneaster horizontalis) 12 weeks warm + 27 weeks cold
Many Flowered Cotoneaster (cotoneaster multiflorus) 12 weeks warm + 27 weeks cold
Hawthorn (crataegus monogyna) 8 weeks warm + 31 weeks cold
Handkerchief Tree (davidia involucrata) 21 weeks warm + 13 weeks cold
Spindle Tree (euonymus europaeus) 12 weeks warm + 27 weeks cold
Manna Ash (fraxinus ornus) 4 weeks warm + 30 weeks cold
Witch Hazel (hamamelis mollis) 8 weeks warm + 24 weeks cold
Holly (ilex aquifolium) 40 weeks warm + 24 weeks cold
Winterberry (ilex verticillata) 9 weeks warm + 9 weeks cold
Crab Apple (malus sylvestris) 2 weeks warm + 14 weeks cold
Japanese Hop Hornbeam (ostrya japonica) 8 weeks warm + 31 weeks cold
Korean Pine (pinus koraiensis) 8 weeks warm + 12 weeks cold
Siberian Apricot (prunus armeniaca) 2 weeks warm + 11-18 weeks cold
Wild Cherry (prunus avium) 2 weeks warm + 28 weeks cold
Cherry Plum (prunus cerasifera) 2 weeks warm + 30 weeks cold
Bird Cherry (prunus padus) 2 weeks warm + 22 weeks cold
Peach (prunus persica) 2 weeks warm + 27 weeks cold
Black Cherry (prunus serotina) 4 weeks warm + 27 weeks cold
Blackthorn (prunus spinosa) 2 weeks warm + 27 weeks cold
Wild Pear (pyrus communis) 2 weeks warm + 14 weeks cold
Caucasian Pear (pyrus communis ssp caucasica) 2 weeks warm + 14 weeks cold
Dogrose (rosa canina) 12 weeks warm + 12 weeks cold
Red Leaved Rose (rosa glauca) 12 weeks warm + 12 weeks cold
Burnet Rose (rosa pimpinellifolia) 12 weeks warm + 14 weeks cold
Blackberry (rubus fruticosus) 8 weeks warm + 12 weeks cold
Blue Elderberry (sambucus caerulea) 6 weeks warm + 12 weeks cold
Elderberry (sambucus nigra) 10 weeks warm + 14 weeks cold
Red Berried Elderberry (sambucus racemosa) 10 weeks warm + 14 weeks cold
Whitebeam (sorbus aria) 2 weeks warm + 14 weeks cold
Rowan/Mountain Ash (sorbus aucuparia) 2 weeks warm + 14 weeks cold
Swedish Whitebeam (sorbus intermedia) 2 weeks warm + 14 weeks cold
Wild Service Tree (sorbus torminalis) 2 weeks warm + 14 weeks cold
Bladdernut (staphylea pinnata) 12 weeks warm + 27 weeks cold
Snowberry (symphoricarpos albus) 14 weeks warm + 25 weeks cold
Small Leaved Lime (tilia cordata) 20 weeks warm + 19 weeks cold
Manchurian Lime (tilia mandshurica) 13 weeks warm + 13 weeks cold
Large Leaved Lime (tilia platyphyllos) 20 weeks warm + 32 weeks cold
European Silver Lime (tilia tomentosa) 20 weeks warm + 32 weeks cold
Wayfaring Tree (viburnum lantana) 10 weeks warm + 10 weeks cold
Guelder Rose (viburnum opulus) 10 weeks warm + 10 weeks cold

Germination Information for Deeply Dormant Species

All of the above species have deep dormancy that requires an often lengthy 2 stage pretreatment to enable them to germinate successfully.

Prepare a free draining substrate into which the seeds are to be mixed, this can be a 50/50 mixture of compost and sharp sand, or perlite, vermiculite. The chosen substrate needs to be moist (but not wet), if you can squeeze water out of it with your hand it is too wet and your seeds may drown and die. Mix the seeds into the substrate, making sure that there is enough volume of material to keep the seeds separated.

Place the seed mixture into a clear plastic bag (freezer bags, especially zip-lock bags are very useful for this -provided a little gap is left in the seal for air exchange) If it is not a zip-lock type bag it needs to be loosely tied. Then write the date on the bag so that you know when the pretreatment was started.

The seeds first require a period of warm pretreatment and need to be kept in temperatures of around 20 Celsius (68F) for the time period outlined above for each species.

During this time make sure that the pretreatment medium does not dry out at any stage or it will be ineffective!

Once the warm period of pre-treatment is over the seeds require a cold period to break the final part of the dormancy, this is achieved by placing the bag in the fridge at around (4 Celsius or 39F) for the correct number of cold weeks as described for each species above.

It is quite possible for the seeds to germinate in the bag at these temperatures when they are ready to do so, if they do, just remove them from the bag and carefully plant them up.

When the period of pre treatment has finished the seed should be ready to be planted. Small quantities can be sown in pots or seed trays filled with a good quality compost and cover them with a thin layer of compost no more than 1 cm deep. For larger quantities it is easiest to sow the seeds in a well prepared seedbed outdoors once the warm and cold pretreatments have finished and wait for the seedlings to appear.

Fluctuating pre-treatment temperatures can often give the best germination results and often excellent results can be had by keeping the mixed seeds in a cold shed through the winter for the cold stage of their pretreatment and allowing the temperature to fluctuate naturally.

Ungerminated seeds can have the whole warm and cold process repeated again to enable more seeds to germinate. Fresh seedlings can keep germinating for up to 5 years after the original sowing date.

Do not expose newly sown seeds to high temperatures (above 25 Celsius) as these high temperatures can induce a secondary dormancy which will require a repeat of the original pre-treatment to break.

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