Recycling Plastic Bottles for Starting Seeds
Seeds need constant moisture to germinate properly. Using the same method as above, you can recycle plastic bottles to keep the soil moist while seeds germinate.
Again, be careful that your bottle doesn't fog up. It's best to remove the bottle for a short time every day, so mold doesn't grow on the soil.
Once the seedling has emerged, it's even more important that you do not let the bottle stay fogged up, as this can cause "damping off", which simply means that the atmosphere around the seedling is too humid, causing fungus to destroy the seedling
Once the seedling has one set of true leaves, you should remove the plastic bottle and allow it to grow on its own.
Warning: You should never place plants under plastic bottle greenhouses in full sun, as the heat buildup inside the bottle will cook the plants. If you don't have a shady place for your mini greenhouse, take the top off of the bottle to allow heat to escape.