Answer: "Thinning" is removing all extra seedlings, so that the remaining plants are left at a desired spacing.
There is more than one plant which goes by the common name Bachelor Buttons. The most common use of the name refers to Centaurea cyanus, also known as "Cornflower". These upright plants will reach 2 to 3 feet in height and are usually thinned to about 8 to 10 inches apart.
Another plant often called by the name Bachelor Buttons (expecially in the south) is Gomphrena globosa, commonly called "Gomphrena". These plants have a more spreading habit and grow 18" to 24" inches tall. They may be thinned to about a foot apart.
Thanks for the question!
Q&A Library Searching Tips