Artificial regeneration refers to the planting of seeds, seedlings, or cuttings. Artificial regeneration usually is more expensive than natural regeneration, but permits better control over species selection, genetic characteristics, and tree spacing.
Direct seeding is the process of sowing or planting seeds. It often is used to establish jack pine and black spruce, as well as some hardwoods, including black walnut. Direct seeding of black spruce is preferred to planting seedlings on sites with poor access, such as spruce bogs. The appropriate site preparation, moisture, and temperature requirements vary by species and are similar to those necessary for natural seeding. Often the seed is chemically treated to protect it from diseases, rodents, and birds.
Planting seedlings, either bare-root or container-grown stock, is the most reliable way to regenerate a stand, especially for conifers. Bare-root seedlings are dug from the nursery bed and shaken to remove most of the dirt around their roots. They frequently are designated as 1-0, 2-0 or 2-1 stock, with the first number referring to how many years they were grown in the original nursery seedbed and the second to how many years they were grown after being transplanted to another nursery bed. Transplants generally have a more fibrous root system and larger stem diameter than seedlings that are not transplanted. Transplants are recommended for regenerating slow-growing conifer species such as spruce and fir, and for harsh planting sites where survival is likely to be a problem.
Seedling costs vary depending on tree age, grade, species, and quantity ordered. Transplants survive very well, but are expensive and, therefore, are not widely used. One- or two-year-old seedlings are less expensive than transplants and are recommended for most hardwood and conifer plantings. Tree seedlings sometimes are graded and sold by height class, stem diameter, or root condition.
Container-grown seedlings usually are grown in a greenhouse in 1- to 2-inch diameter containers. Some biodegradable containers may be planted in the ground with the seedling in them. Other seedlings must be removed from the container before they are planted. Container-grown stock can be very useful for dry planting sites or for late season planting.