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Sprout Home Q&A Of The Week: Fertilizer, To Feed Or Not To Feed

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Q: My houseplant seems to be unhappy as of late and I have gone through every step to make sure that I am following all of its light and water requirements. It is as if it needs a protein shake -- is giving it some fertilizer my answer? Do plants really need to be fed?

A: Plants do need certain things to grow and stay strong. Plants naturally get carbon, hydrogen and oxygen but you might need to feed them a fertilizer cocktail on occasion when they are not getting everything they require. The most important part of that 'shake' cocktail is the macronutrient super combo: nitrogen, phosphorus and potassium. This triple threat is what is readily sold as fertilizer. Secondary nutrients are sulfur and magnesium. Micronutrients are comprised of boron, cobalt, copper, iron, manganese, molybdenum and zinc.

Q: I see plants growing outside without much help, why can't my potted plants act the same way and be a little more self sufficient?

A: You still might need to fertilize your outdoor landscape plants but they naturally obtain those macronutrients from dying things around them. If it is not naturally available to a plant, like your indoor potted plants, you need to supply those key nutrients to them in the form of fertilizer.

Q: I have looked at fertilizer bottles before but it is a little intimidating and confusing. Is fertilizer the combination of those main cocktail ingredients?

A: They are the main elements of fertilizer, and without the macronutrients the plant does not have its building blocks. The three numbers on the label of your fertilizer is the conctentration of those three super powers. The first number is Nitrogen which helps the foliage grow strong. The second number is Phosphorus which aids in root and flower development. The third is Potassium which helps with overall plant health. The numbers vary by type of fertilizer and can be selected by specific needs of the plant.

Photo by Tara Heibel

Q: How do I know when to use it and how much? I guess if I give it too much food it can only be good, right?

A: Follow the instructions on the fertilizer that you selected. In many cases you can actually reduce the instructed amount of fertilizer you are using with plants that are not heavy feeders such as houseplants that do not provide large blooms or fruit. Only feed your plant when it is actively growing, spring being an opportune time to start the cycle again as your plant is coming out of dormancy. There is no use in giving your plant more fertilizer than what it needs, the plant will not be able to use it and in fact you might be hurting your plant by doing so. Do not go overboard.

Q: I just purchased my plant. How do I know if it was recently fed?

A: I would suggest waiting a month or two before feeding your plant if it was recently purchased and especially if it was also repotted. Most potting mixes will have some type of fertilizer in them and the plant can feed off of that for a while before you need to concern yourself with supplementing it. Give your plant a chance to acclimate to its new home and go through any shock before you start fertilizing - the food cocktail is not necessarily a quick fix or answer for a stressed out plant.