How to Harvest Coriander:
Harvesting coriander is simple and effortless. Your cilantro plant will eventually produce tiny white flowers with lavender accents (See Figure B below).
Once these flowers are pollinated, they will produce seeds (i.e., coriander) in its place (See Figure C below). Small flowers normally do not need help pollinating. However, if you are growing cilantro indoors, you will want to gently shake the cilantro plant or place it in a windy area to assist pollination. This will help the plant produce higher yields of coriander.
It took two to three weeks for my cilantro seeds to fully mature. You will want to pick the cilantro seeds when they are ripe. Cilantro seeds are ripe when the seeds are just starting to turn brown (See Figure C). Snip off the stems of plant, and place it in a paper bag. Allow the seeds to dry in a cool, dark place. After the seeds have dried out, collect the seeds and store them in a glass jar or other airtight container until you are ready to use them.
Young Cilantro Plant
Blooming Cilantro Flowers
The round balls are cilantro seeds a.k.a. coriander