During warm weather or indoors, the zip-lock bag method of germination has many advantages over the traditional nursery flat method. Consistent moisture is assured, insect larva and slugs are kept away from germinating seeds and it is possible to inspect daily to control any mold or fungus that may attack the seeds. Some species will germinate up to twice as fast using this method.
Larger hard shell seeds should be nicked, filed, sanded or scratched then soaked for 1 to 4 days depending on hardness of seed. The use of potassium nitrate "saltpeter" at the ratio of 1 teaspoon per quart of water can speed up the process of softening up these kinds of seeds. Mix this solution in hot water to get the seeds started. After each 12 hour period of soaking it is best to change the water to keep it fresh and clean. It is not necessary to use the potassium nitrate again at each 12 hour water change. The solution can be kept for use again and again as each new batch of seeds are to be soaked.
Use sphagnum moss or coarse peat moss. Get it wet and squeeze out most of the water. Put a couple of handsfull of this damp peat moss into a clear plastic zip-lock bag and add 10 to 20 seeds. Blot the seeds to eliminate excess water before dropping them into the bag. If the seeds are small enough, the little seed bags with labels can be used. In these smaller bags, only about 1 Tablespoon of the damp peat or sphagnum moss is needed. Hang these clear bags up in a window preferably where there is morning light and inspect daily to be certain that no mold is growing. If germinating outdoors, do not allow bags to remain in direct sunlight where heat inside the bags can reach more than 85 or 90 degrees F. Filtered light or partial shade is best. If mold is detected, get the seeds out and wipe them clean. If the sphagnum or peat moss is badly contaminated with mold or fungus, it is best to start over with fresh damp moss. The seeds can be dusted lightly with a powdered fungicide if the problem persists. This problem can be an indication that the sphagnum moss is too wet. It should be squeezed until hardly any water drips from it.
Label the specie and include the date that the seeds were put into the bag. Drop this note inside the bag or tape it to the outside in order to keep track of the kinds of seeds inside each bag.
When the seeds begin to sprout, they are ready to be put into regular nursery flats or pots. At this early stage it is advised to keep some kind of plastic cover over the germinating container to keep out pests and to keep humidity in. When the second set of leaves appear it is no longer necessary to keep the containers covered. Feeding at this time is recommended in order to grow the plants out of this vulnerable period as quickly as possible. The all-purpose plant foods available at nurseries and garden centers will work fine. Follow the label and do not be tempted to change the formula to make it stronger. "More" is not better for these young seedlings. A slightly weeker solution (more water) would be recommended over one that is stronger. Some species of these seedlings can take direct sun right away but most cannot. It is best to keep them in filtered light or partial shade and only gradually expose them to direct sunlight as they grow and become stronger. Many seedlings have withered and died because of exposure to direct sunlight too soon.
Once plants are well established they can be fed once a month. 6 inch pots are usually the best size for starters then change them to larger pots as they grow. Water as needed, usually when the top surface is dry 1/2 inch deep. Consult your local nursery or garden center for using pesticides in the event that insects of any kind attack the young plants. A wide variety of solutions are available including natural pesticedes and detergents.