You've heard the expression "Timing is everything"? That applies to collecting seeds from clover. Once clover begins blooming it is vital that you check the blooms frequently and watch for the blooms to begin wilting and drying out. This is your cue to collect the seeds. One reason it is so important for you to watch for drying blooms is that not all of the blooms on a clover plant will dry at the same time. This means your seed collection can be spread out over several days.
Stop mowing and allow your clover to grow flowers. Flowers will usually appear toward the end of summer or the beginning of fall.
Inspect your clover flowers on a daily basis. Watch for the flowers to wilt and begin to dry.
Carefully pinch off the dry clover flowers with your thumb and fingers and place the dry flowers into a plastic baggie.
Spread out a sheet of newspaper and dump the contents of your baggie on it. Pick up each flower stem individually and slide your thumb and index finger along the stem from the bottom to the top. The clover seeds should pop right off and drop onto the newspaper. Discard the stems once the seeds have been removed. If you are removing the seeds from a large number of stems at once you may wish to wear a glove to protect your fingers.
Separate the seeds from the chaff by lightly blowing on them--the chaff will blow away, leaving the seeds. Put the dry seeds into a small glass container with a tight-fitting lid and store them in a cool, dry place until you are ready to plant.