Answer: The three numbers on the package indicate the percentage of nitrogen, phosphorous and potassium. In general terms, nitrogen makes leaves green, phosphorous encourages strong stems and flower bud, and potassium strengthens roots. For a green lawn, choose a fertilizer higher in nitrogen. For instance, a 21-7-14 formula will green up your lawn and encourage strong root growth, but will not promote flowering. If you have a flowering plant such as a lilac, you'll want a fertilizer higher in phosphorous than nitrogen or potassium. In this case, you could use a 10-20-10 formula.
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