HELLO HIVE
I walked past a large number of African spinach on a farm that are in seed producing period with the plant changing color and having an unhealthy look for a plant that ought to be green this goes down to the fact that the plant has gone way past its maturity and it can only produce seeds at this point after which both the plant and the seed dries up, its seeds are so small that it takes a lot of care to be able to harvest and dried it up for future planting.
We take our time and observe if the seed is changing from green to black then we will cut the part of the branch on which the seeds are we don't need all the plant in this case, we only need a small portion and we are good. The seeds have to be dried on a sack to prevent most of the seeds falling off because of how small they are, African spinach seeds are actually smaller than mustered seeds so it is impossible to pick it from the ground if it falls off that's we have to be extra careful with it.
Storage : after drying for some days the seeds have to be store in a good environment, not in polythene bags of any kind but you can use a container that allows some amount of air through it. Not properly storing the seeds will result in the seeds not germinating at all when we plant it.
We normally leave the seeds on the branches that we cut them with and when we want to plant it we just shake the seeds off the branches.