Starting a tree from a seed is a slow process but rewarding way to grow a tree. Tree species may be grown from a seed since the seedling usually retain the characteristics of the parent plants. Raising a tree from hard coated seeds is a rather simple process even though it is a slow method of growing trees.
When planting tree seeds, certain treatments need to be given the seeds for them to germinate. This is due to the natural dormancy of tree seeds when they are first produced. Among the many causes of natural dormancy of seed, the seed coat and dormancy of the embryo are the two most frequent encountered.
The protective covering of some seeds should be removed first. The method for this varies, depending on the type of seed coat. A good example is the coating on a winged maple seed may be removed by rubbing it between the finger and thumb whereas the hard covering of an oak has to be nicked with a knife.
The three methods commonly used to treat a seed having an impermeable seed coat is to soaked it in sulfuric acid, soaked in hot water or using a mechanical scarification. All three methods have been found to be effective on “hard” coated seeds.
These processes are called stratification. Stratification is a process in which certain seeds are subjected to low temperatures for a period of time in order to germination to take place. Natural stratification occurs when the seeds are shed in autumn and become covered with soil, leaves or other materials during the winter. This process allow moisture to penetrated the seed coat for germination.
Mechanical scarification is the cheapest and most adapted for homeowner use. The whole idea of the treatment is to wear off or scratch the seed coat with some mechanical device to allow moisture to enter the seed. This can be done with sandpaper, a knife, needlepoint or other sharp tools.
Another cause of natural dormancy of a seed is the dormancy of the embryo. This dormancy is the most common cause of the delay of seed germination. Seeds with a dormant embryo must complete a process of “after-ripening” before they will germinate. After-ripening takes place only at the proper temperature and in the presence of adequate moisture and air. For most trees in Oklahoma, an average temperature of 40 degrees is favorable for after-ripening.
In handling of dormant seed, mix the seed with moist sand or peat moss. The latter is preferred because it has a very large water holding capacity and does not interfere with aeration of the seed.
After being thoroughly mixed with the medium, the seed is placed in a basket, crate, jar or any other container. This container should be stored in a place where a 32 to 40-degree temperature will be maintained within the range effective in after-ripening.
Standard bushel and half-bushel baskets, glass jars and tin cans work well as containers. To reduce chances of infection, it is a good practice to line the inside of the basket with clear paper before placing stratified seeds into it. The stratified seed should never be packed tightly together because this will interfere with aeration and cause an environment for disease growth.
After the mixture of seed and medium is in the container, it is advisable to put on the top an additional layer of peat moss or sand. Then, the container should be covered with paper to help keep the seed moist throughout the stratification period.
For some tree species, fall planting is a satisfactory substitute for stratification. For these species, fall planting is effective only if the seed remains moist and the temperature stays low for a sufficient length of time. In Oklahoma, however, low winter temperatures cannot be depended up-on, so mechanical stratification is a more certain method of after-ripening tree seeds.
The length of the stratification period varies with seeds of different species.
Jim Coe lives in Lawton.