It is important to remember that during stratification seeds DO NOT need light. This process is to help break the dormancy of the seed and get it to germinate. Once they have germinated stratification is at and end and seeds can be treated normally.
Some seeds require a period of cold before they will germinate. For these simply placing the seeds in the refrigerator for at least 60 days is usually sufficient. Some however need as long as 120 days of cold before they will germinate. Some plants need really cold periods these need to be placed in the freezer compartment for at least 60 days before they will germinate.
Many seeds need a period of moist cold before they will germinate. There are several different methods that can be used to break the dormancy of these seeds. In all cases seeds should be kept in the refrigerator until you are ready to begin.
Seeds can be sown during the later autumn when the soil is still workable. Sow as you would normally sow in spring and leave over the winter to stratify naturally. This can be useful in many large species and to see that are to be planted in rows or if enough seed is available to broadcast seed a natural area. The disadvantage is there is not control over the seeds and they will germinate and if they may be eaten by wildlife during the winter months.
POTS OR TRAYS IN A COLD SPACE (recommended method).
Seeds can be sown in seed trays or individual pots and placed outside for the winter months. They can be placed on a deck, patio or anywhere where you can keep an eye on them to ensure that they do not dry out. Ice and snow are not a problem but cold sunny winters can easy dry out the pots. Watch them carefully and add water all winter as necessary.
Seed trays can also be placed in an unheated garage or shed to help protect them. It is important to keep moist at all times.
Trays can be placed into large plastic bags and sealed to keep moisture in. If this approach is taken be sure to place in dark or very shaded location where you can check on them regularly. If the bag is broken moisture will be lost, if there is sunlight (and so warmth even in winter) the bag will heat up and raise the temperature destroying the cold environment. Remove the bag when seedlings begin to appear and treat as normal seed tray, do not allow it to dry out, keep out of sunlight until seeds are large enough to handle brighter light and the heat it generates.
Cold frames can be used but do not shut them as the sun will heat up the interior in the winter to a higher temperature than the seeds require and may inhibit germination.
REFRIGERATOR STRATIFICATION METHOD.
Take some sand or sandy soil. Make sure it is clean sand, not builders sand which can contain impurities that can inhibit growth and not seashore sand as salt will also inhibit seeds. Lake or stream shore sand is good but may need washing first. Children's play sand is also suitable.
Place sand in a clear plastic freezer bag, quart size is ideal. Mix in the seeds that you wish to germinate, one type of seed to a bag, not mix different species of seeds in one bag or it will become too difficult to determine which is which later on. Do not add too much sand or seeds to each bag or weight may crush seeds when they begin to germinate.
Add just enough water to make the sand damp but not wet. Shake bag to mix water seeds and sand together. Label it well with marker with plant name and the date you added the mix.
Place in the refrigerator in an area where it will not be constantly moved or disturbed. Bags can be laid out flat and stacked on top of another for about 3 bags provided there is not too much contents in each bag.
Leave bags for at least 30 days. Try not to disturb them too much. After
which the bags should be checked at intervals, gently move the sand around
to see if the seeds are beginning to break free and show small roots.
When this happens remove them from the refrigerator and place in a cold area. Do not take seeds directly from the cold refrigerator to a warm place to germinate this can stunt or even abort the seedling development. Put them in a cold garage or protected space and gradually move them to a warmer temperature over a day or two before opening the bag and working with germinated seeds. Try to do this in a cool environment do not move to a warm kitchen or greenhouse.
Remove the germinated seeds gently from the bag and pot up normally in a mixture of good starting mix and a little sand. Use tweezers to remove seeds taking care not to damage the delicate roots that are beginning to sprout. Keep in a cool environment and only gradually change the temperature so as not to shock the plants. Keep in low to moderate light to begin with. Keep moist at all time.
Return ungerminated seeds and bag to the refrigerator. Not all seeds may germinate at the same time.
ADVANTAGES AND DISADVANTAGES OF STRATIFICATION METHODS.
By far the easiest method it is simple easy and ensures that the seeds are not agitated during germination. The main disadvantage no matter where you place the pots is keeping them moist. If outside it only takes one day of sunshine to dry pots out entirely. Vigilance is most necessary.
Pots Trays in cold building
This is by far the best method to control the temperature and humidity of the plants. Seeds can be sown normally in trays or pots moistened then left alone. As long as they are not disturbed the pots should stay moist and nothing can contaminate the soil. The only disadvantage is if you location does not offer a long enough cold period for the plants to break dormancy, or if the pots are moved around, temperatures changed of the plastic bags are torn so the pots dry out. It is important not to forget about them, check weekly when spring begins so you can spot when plants germinate and time when the plastic bags can be removed and plants given more light.
Bags in refrigerator.
Easy to keep the seeds moist and cold. The main problem is keeping the delicate seeds intact. Once the seeds begin to germinate the roots are very fragile. Moving the bags around in the refrigerator can damage or destroy the roots killing the plant. Also transplanting the little seeds into pots is a delicate process that takes a lot of care and patience.
The ideal refrigerator method.
The easiest way is to sow seeds in a tray or pot, place in a large plastic bag, seal it tightly and place in the refrigerator. However most people do not have enough space to allow for this luxury.
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