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(photo: Greta Hoffman)

Fertilizing a vegetable garden is more of an art than a science. 

The amount of fertilizer your plants need depends on the nutrients in your soil, the time of the year, and the stage of growth the plants are in. That being said, with a bit of trial and error (and a lot of patience), you’ll soon develop a feel for when and how much to fertilize — especially if you start with a strong understanding of the basics. 

Strike the Right Balance
Step into the fertilizer aisle at any garden center, and you’ll see a spread of products, all claiming to be the best for various vegetables. Don’t buy into the hype — you don’t need to use one fertilizer for tomatoes and another for peppers. All your plants will benefit from a balanced, “all-purpose” fertilizer that will give them a boost at regular intervals throughout the growing season.

Usually, an all-purpose fertilizer will say so on the label, but those that don’t will give themselves away in a few clues. To start, all fertilizers are labeled with the letters N-P-K and a set of numbers below them, such as 2-2-1. 

The letters refer to nitrogen, phosphorus, and potassium, respectively, and they’re the fundamental macronutrients that all vegetables need to thrive. 

The numbers, meanwhile, refer to the quantities of the nutrients in the fertilizer. If the numbers are equal or near equal, you have an all-purpose balanced fertilizer that will work well for your garden. 

There’s Nothing Like the Real Deal
Another consideration is whether to use an organic or synthetic mixture. I prefer organic for a few reasons. Because organic fertilizers are derived from once-living materials like fish bones and food scraps, they’re bringing many more nutrients to the table besides just the core macros. Organic fertilizers don’t just nourish your plants, either — their variety of nutrients feeds the living organisms in your soil, promoting a healthier ecosystem.

Synthetic fertilizers, on the other hand, are formulated to include only the specific compounds listed on the bottle (such as N-P-K) and won’t promote the long-term health of your garden. To tell the difference between the two, consult the package again — organic fertilizers are labeled “OMRI Certified.”

Know When Enough Is Enough
Now for the hard part: Knowing exactly how much fertilizer you’ll need and when you’ll need it depends on the nutrient content of your soil. So, while I can’t tell you exactly what will work for your garden, I can tell you what works for me to send you off on a journey of trial and error. 

Let’s start with fertilizing vegetables in pots. I apply a dry all-purpose fertilizer at planting time and every three months onward while following the instructions on the package for the specific amount, which varies by plant type, time of year, and brand. 

I then give my plants a shot of liquid fertilizer almost every time I water (although I’ll admit I skip an application here and there). 

For my plants growing in the ground, my method for dry fertilizer is the same. Still, I apply the liquid fertilizer every other watering instead since my veggies are getting additional nutrients from compost I added to my soil at planting time. 

I recommend starting with this method and closely monitoring how your plants react throughout the season. If you’re feeling particularly scientific, you can even apply fertilizer to some plants and not others to compare the difference directly. As always, you can eliminate the guesswork by testing your soil at planting time. spt

Nadia Nizetich