A full-grown redwood tree will produce six to eight million seeds each year, but the seeds are so tiny that a million seeds weigh only eight pounds. The seeds fall within a few hundred feet of the parent tree; many stay in the litter found in the tree canopies.
If conditions are good, it takes about a month for the seeds to begin to grow. However, 95% of the seeds are not viable. Only a very few of the ones that do germinate will actually turn into seedlings.
Mature redwood cones slowly turn from green to brown as they begin to dry out in the fall. Once they are dry enough, the cone scales separate and release the seeds. Most seeds are shed between November and February as the winter storms blow through. To guarantee that you'll get the seeds before they drop out of the cone, pick one before it opens (around December or January) then allow it to dry for a few weeks or more until the scales separate enough for you to shake the seeds free. If you want to plant the tree outside, be sure to use seeds from local stock and grow redwoods that are adapted to the region.
WARNING! Even though a redwood is an awesome tree, Sequoia sempervirens is NOT a good choice for a suburban lot if you wish to remain a good neighbor. Even in average soil it will quickly overwhelm the surrounding area. After growing an extensive root system, a juvenile tree will generally add five or six feet to its height each year. It is easily capable of reaching a height of 120 to 150 feet during a person's lifetime. That's fifteen stories high.
The year-round heavy shade will not allow grass to grow and landscaping will be limited to shade-loving plants such as ferns. Winters underneath a redwood tree are cold and wet. Redwoods control the growth of other plants around them by 'bombing' them -- dropping chunks of wood and branches on competing plants (and your house.) The area around a mature redwood resembles a war zone. It is not possible to leave the paths in the redwood parks without having to clamber over the mess on the ground. The redwood is also by nature a messy tree, dropping a third of its branchlets each year as it renews them, clogging gutters and drains.
Its roots are very efficient at removing nutrients from your and your neighbor's soil. They are shallow and extend many feet from the tree, damaging foundations, driveways and cracking water and drain pipes. Many years after a tree's removal, the existing roots will continue to send up sprouts in the surrounding landscaping.
NEVER, NEVER, NEVER top a redwood. The top of the trunk will then send up multiple sprouts. Each sprout will become a trunk and will grow its own branch system. These will accumulate a tremendous amount of weight. The sprout trees are attached only on one side and to the outside of the trunk, not the heartwood, and a strong wind will peel them right off the tree with devastating consequences.
The tree maintenance companies love redwood trees because of the job security. Its fast growth and large mass makes it very expensive to prune or to remove. If you absolutely have to have a redwood tree, consider the costs of maintaining it, and be sure your homeowner's liability insurance will pay for the damage it will do. There's a reason they're in the parks.
Sowing Directions (these apply also to Dawn Redwood and Giant Sequoia):
Another method is to place the seeds between layers of damp tissue paper instead of in a pot. However, you will have to transplant them to a pot as soon as they develop a root sprout. This is a riskier method. Continued.
NEXT: Cloning a Redwood