Answer: If a plant flowers then it comes from seeds. The reason I say this is that plants flower as part of their seed making process. This is true whether you are talking about an oak tree or a little marigold.
Some types of perennial flowers may be easier to start from divisions or cuttings than from seed, but that is a matter of convenience rather than necessity. Annual flowers, meaning those that live only a season, are nearly always seed grown. Plants in this group are generally easier to start from seed and quickly grow to mature blooming size. Many of our favorite summer flowers such as marigolds and zinnias are annuals.
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