​Malabar spinach is a great heat-loving vining spinach that does really well in a container as you see in the photo here of my friend Grace's plant. Towards the end of the summer, you’ll see pretty pink round flowers that turn into dark blue/black berries. These berries are mostly tasteless but have historically been used as a bright pink/red dye for products like fabric and paper. The berries can also be used as an edible food dye. 
 
To save seed, wait until the berries are nearly dry (but before they drop all over your garden) and pull the berries off. Let them fully dry on a screen or a shallow bowl. When the berries fully dry, seeds will be easy to remove or sift and save.  Malabar spinach plants do produce a lot of seeds and some people have complained of rampant re-seeding.  My father allows his Malabar spinach to ramble in rows in the garden, but removes the plants shortly after they produce berries and before seeds dry and fall. He has never had a problem with unwanted reseeding.