Plant Food Basics – the Numbers

The dizzying array of plant food boxes, bags, bottles, and jars call out from the garden center or nursery shelves. How to choose? Catchy name? Brightly-colored package? Organic? Fast-acting? Mix-it-yourself? Ready-to-spray?

One way is simply by the nutrient content – those three numbers that are on each and every fertilizer package (usually on the front, but sometimes hiding elsewhere). And they are always in the same order – so there’s no trickery going on.

The first one is nitrogen. This is the element that plants use the most of. It’s the one that encourages leafy growth and green color. Of course it’s used to build the proteins in every cell in a plant, but lots of nitrogen means lots of green growth.

That’s why you see the big first numbers on lawn food – ‘cause you want lots of green growth on that grass.

But, beware – using lots of nitrogen on a tomato may get you lots of lush, green leaves at the expense of lots of yummy tomatoes. So, when choosing a tomato food, pick one where the first (nitrogen) number is smaller than the second number.

That second number is for phosphorus. Phosphorus is also in every cell in the plant. It stores the sun’s energy for use by all the plant systems. Building a root system and producing flowers, fruits and vegetables takes a tremendous amount of energy. So, we often say that phosphorus helps plants get started (make roots) and encourages flowers (fruits or vegetables).

The third number is potassium (potash). Potassium is used in many systems in the plant that have to do with drought resistance, fighting off disease, and winter hardiness.

There are many ways to decide what plant food product to choose from – the three numbers can be a place to start.