Growing bamboo from seed is the least common method of bamboo propagation. It can take a bamboo plant up to 120 years to flower and produce seed, and some species never flower. Bamboo grows very easily through rhizome propagation, cuttings and breaking up clumps, so starting it from seed is an uncommon practice. Additionally, plant mortality often is high when started from seed, and the resulting plants are rarely similar to the parent plants. This makes other propagation methods preferable.
Pre-treat the seeds by washing them in clean water. Dissolve one part salt in 10 parts cold water in a plastic container. Soak the seeds in the solution for five minutes. Fill another container with clean water and soak the seeds for another 15 minutes.
Fill a large shallow plastic box, such as an under-the-bed storage container, with a 50-50 mix of peat moss and perlite. There should be about 4 inches of the potting mix in the container. Water the potting mix so that it is thoroughly moistened.
Drill a few small holes in the lid. The bamboo seedlings need a very humid environment, so the box should be sealed but not enough to block out all oxygen.
Sprinkle the seeds over the surface of the mix and cover them with a thin layer of more potting mix. Cover the box and snap the lid down tightly.
Place the box outdoors in partial shade. Put the box in a greenhouse or in a window that has little sun exposure if it is very cold outside. Open the box twice a week to check the moisture of the potting mix. Mist the soil with a spray bottle If the soil feels dry.
Keep the box covered even after the seeds have germinated; they still need a lot of humidity. Remove the cover when the seedlings are tall enough to touch it.
Fertilize the seedlings when they are about a month old. Feed the leaves and roots a nitrogenous foliar spray such as diluted compost tea. Mist the seedlings and soil surface with a spray bottle.
Fill some pots with a loamy garden soil mixed with compost. Transplant the seedlings into the pots after they are about 6 weeks old. Dig them from the very bottom of the container because even young bamboo plants have extensive root systems. Plant all of the seedlings together and thin them out later if the roots have become tangled.
Place the pots in a place that is mostly shady. Thin the seedlings as the weaker ones die off. Transplant them to larger pots as they become established and start sending out new shoots. Move them to the garden when they are about 1 year old.