Planting trees is fun, and you should protect them to become big trees someday -- so you can cut some of them and build your own wooden house from the trees you have planted a decade or 2 ago, some you can keep so you can tie long hammock to lie down and sleep, or play with your children or grand children someday.
Watching the big trees producing their own seeds is also fun. Some tidbits about the seeds of some trees.
1. Mahogany -- among the fastest-growing hard wood species.
The seeds are lumped on one bundle of brown, oblong-shape thick cover, lit ooks like chiko fruits, but much bigger. Inside this bundle is around 65 seeds on average. A seed has a wing on its tail. So when that bundle matures, it releases the seeds from the tree, and the seeds fall and fly like small rotor blades of helicopters, enabling the seeds to travel farther, thus ensuring that they can perpetuate their specie to a much wider area. One mature tree can produce thousands of seeds per year. Even assuming that only 5 to 10% of those seeds would grow to become young saplings, there are hundreds of new saplings (or seedlings?) of them that grow around or near the mother tree.
2. Narra -- the Philippines' "national tree".
This is slow-growing, but hard wood quality. The seeds are small, enrircled by tiny layer that acts like wings too. So when the seeds fall from the mother tree, they can fly away if there's a strong wind, ensuring the preservation of their specie to far away places. Narra can produce lots of branches, so if you want to produce long and huge trunks someday, you should plant them close to each other (2x2 meters distance initially, later make them 4x4 by removing the trees in the middle).
Note: birds don't eat the seeds of these 2 trees. The seeds are big for most birds, and they don't seem to taste yummy for the birds too.
3. Acacia auri, acacia mangium, eucalyptus, others -- are fast-growing.
But you can hardly see their seeds, very small. Some bird species eat their seeds, when the birds make po-po, they scatter the seeds to far away places. Of course there are forestry techniques how these very small seeds can be collected and planted to produce seedlings.
Other trees that have very tiny seeds are benguet pine (like the trees you see in Baguio), ordinary pine trees, some local dipterocarp species like molave.