All the information shared here is in accordance to the climate of Bengaluru.
The oldest known technique of propagating a plant is by seed.A seed is a capsule containing the plant embryo.Some seeds are coated while some are not.In proper growing conditions the seeds becomes a new plant.
The seeds are part of the plant reproduction.Some seeds in nature are edible like nuts,cereals etc which contain essential nutrients.While some seeds are used to extract oil example Groundnut,Sunflower etc.
Common trees that are grown in this method are Gulmohar,Tamarind,Cassia,Albizia saman , Acacia, Syzygium cumini, Terminalia arjuna etc.
The seeds can be collected from the nature or it can be purchased online.How ever it is hard to find tree seeds in a retail store these days.Do not store the collected seeds for a long time use them at the earliest.Soak the collected seed in warm water over night.Soaking will help in softening the seed coat.If the seed size is small like a mustard do not soak them.
Take a germination tray 3 to 4 inch deep.Cover the holes of the tray with a mosquito net or a steel net.For potting medium use a mixture of cocopeat,perlite or sand.Cocopeat is available as block or powdered form.If it is in block form soak the block.Loosen the soaked block to extract the powdered cocopeat.If perlite is not available use sand.Put the potting medium in the tray and moisten it.Now sow the soaked seeds about 2cm deep.Do not sow it too deep.
Water the tray before they dry using a spray can.Keep the tray away from the pets and protect them from heavy rain.Some seeds germinate fast while some may take months to germinate.Allow the plants to grow properly at least for a season before transplanting them.Make sure they have healthy leaves and roots.Once the roots starts coming out of the tray holes,remove the plant and place them in a grow bag.
The soil in the growing bag can be a mixture of red soil,sand and manure.Allow the plant to grow healthy and prune them if required.Grow at least for a couple of years in the bag with proper fertilizing. If the trunk has to bent to achieve complex shape bend it went is flexible itself using wires.But do not wire all the branches .Allow the plant to grow and then shape them.Once your satisfied with the result shift the tree in to the bonsai tray or pot.Remember it may take several years to achieve a proper bonsai.So always have time for it.
The advantages of growing from this method
a) the durability of the tree is high
b) Shaping is easy
c) One can learn from the scratch the entire bonsai making process and growth of the plant.
d)The emotional bonding between human and the tree increases if he sees them grow from day one.