The 10 Best Fertilizers for Your Houseplants and Garden

Sure, plants make their own food through the process of photosynthesis. But it doesn't hurt to give them a little extra love occasionally, with the help of some fertilizer. But what exactly is fertilizer? Let's break it down. If you (vaguely) remember the periodic table in chemistry, you know that N stands for Nitrogen, P for Phosphorus, and K for potassium. These nutrients refer to the three numbers on a fertilizer bag listed in order (N-P-K). So, a fertilizer that contains 5-10-10 means it has 5% nitrogen, 10% phosphorus (phosphate), and 10% potassium (potash). A “complete” fertilizer contains all three.

Each nutrient has a different role. Nitrogen contributes to leafy growth, while phosphorus helps strong roots form, and potassium promotes vigorous growth and hardiness. A plant that's deficient in any of these will display slow or spindly growth, yellowing or purplish leaves, and no flowers or fruit. A weak plant is also more susceptible to diseases and pests. But don't think more fertilizer equals healthier plant; over-fertilizing is just as detrimental, so follow the package instructions for feeding amounts and timing.

You might be surprised to know that the term "organic" is not regulated for fertilizers, so essentially anyone can put it on the label. But you can look for products with the seal of the Organic Materials Review Institute (OMRI), a nonprofit organization that certifies which products are compliant with USDA organic farming standards. And pet owners, beware: Organic fertilizers can be deliciously enticing to cats and dogs, so keep your fur babies away from any fertilizer and always call your vet immediately if you suspect your pet has ingested any, no matter how little.

Below, discover 10 of the best fertilizers for all your houseplant and garden needs: