That's why many plantation owners have turned to vegetative propagation to increase their supply of genetically improved seeds (usually from controlled pollinated seed orchards). The most frequent of these methods is rooted cuttings, which is common in New Zealand, Australia and Chile for radiata pine. It's also being actively pursued in other species in the United States, Canada and Scandinavia.

This approach works but it also has drawbacks.

Growers must first make crosses between superior trees, then wait for the resulting seeds to produce "mother plants", or hedges. These donor plants usually require 2 or more growing seasons to reach the desired size. Once the size has been achieved, the tree is cut into smaller sections to produce rooted cuttings. The cuttings are then grown into mother plants, and the cycle repeats itself.

It's not a quick process.

It's also limited. The number of cuttings per mother plant is generally quite small, often less than 30-50 per year, and usually for no more than 3-4 years. Nor can the process be repeated indefinitely, because of physiological aging of the donor plant.

For the majority of Conifer 

A cone-bearing vascular plant belonging to the order “Coniferales” which is a sub-class of the botanical group “Gymnospermae”. Conifers used in forestry and reforestation include various species of pines, spruces, cedars, firs, hemlocks and cypress. Conifers produce commercial “softwood”.

species, vegetative propagation forestry is not possible using rooted cuttings because of the aging phenomenon.