Farm Your Yard: Fertilizing 101

Aug 17, 2017

Carrie Hargrove shares why, how and when to fertilize your garden in this month's Farm Your Yard.
Credit Columbia Center for Urban Agriculture

I like to preserve what I can of my harvest, which is why I over plant some things, with the idea to enjoy them over the winter months. Tomatoes are pretty high up there on my “I want to eat some now, but I mostly want to eat them later” list. 


That is why I planted 25 tomato plants for me and my husband this year. 25 plants will produce way more tomatoes than we could eat this summer, but I am thinking about the long game, and homemade chili sauce, pizza sauce, and roasted tomatoes in the depths of winter.

In the past month, I have preserved 67 pints of tomatoes- all from tomatoes that came off of those 25 plants. Tomatoes come in waves, and I am in between the first and the second wave, so I am able to do some weeding and fall planting while I wait for the next flush to come. My goal is 100 pints, we will see if that happens. All of the plants in my garden are working double time for me right now, and so I want to help them along by sticking- or trying to anyway- to a regular fertilizer schedule, so that I can get those 100 pints of tomatoes tucked away in my pantry.

It took me a couple of years as a gardener to fully embrace the fact that you really do need to fertilize your garden. I just had this notion that forests aren’t fertilized and they grow huge plants, so why should my little garden need fertilizer? Well, the difference between a forest and a vegetable garden is that very little is taken out of a forest: the leaves drop on the ground and decompose. A tree falls and slowly breaks down. That process keeps feeding the soil, which will feed the trees. An annual vegetable garden is very different. Produce is plucked off the plant and taken away, so less of the plant matter is being dropped on the ground to decompose as compared to a forest.

I am a nature lover that is also a gardener. I am aware that a garden, while being a way to reconnect a person with the outdoors and nature, is not untrammeled nature in and of itself. My early assumption that my garden was like a forest is not accurate. The plants that we grow in our annual vegetable gardens are the products of plant breeders and seed companies- this is true even if you grow all heirloom plants. The sweet corn that is sold in the farmer’s market is way bigger than the teocinte that early native Americans grew. The tomato plants in my garden produce more tomatoes than the wild tomato plants of Peru do.

Take, for example the sunflowers in my garden. Imagine a sunflower seed. It’s like a half an inch long, if that. Then imagine what that seed turns into. In my case, the sunflowers that are in my garden are probably 15 feet tall, with stalks that look like baseball bats. All of that plant material from one tiny seed. To get that big, the plant is taking sunlight and turning it into metabolic energy that makes it shoot up towards the sky. It is also taking lots of water and nutrients to get that big. Because we are growing plants that have been bred to be more productive than their natural state, more is being asked from the soil and from the plants. That is why, in order to keep a healthy garden now and into the future, we need to amend the soil for next year’s garden and fertilize for this year’s crops.

If you continually plant your garden without amending the soil and fertilizing your plants, eventually you wear out the soil health and fertility, which are imperative to a plant’s growth. So, my advice to all gardeners is to feed your soil every year, and also feed your plants when they need it.

Now that you are on the soil amending and plant fertilizing bandwagon: let’s talk about how to put those convictions into action. Firstly, let me stress: amending the soil and fertilizing your plants are different activities, but should go hand in hand in your garden management plan. Let’s talk about soil amending first.

Amending your soil means that you are adding organic matter, minerals, or rock dusts to your soil. Usually this is done in the late fall, so that the amendments have time to settle into your soil. I call it the Crock-pot method: the more time you give the amendments to be taken up by the living things in your soil, the better. Meaning, you will have better results if you amend your soil in fall vs amending your soil in the spring. Amendments are added to the soil to feed the microbes that live down there. In the most simplified terms, the microbes eat the manure and other amendments that you spread in November, and the by-products of that process are what your plant utilizes to grow big and healthy. This is why you want to add soil amendments in the fall: the process takes some time. Amending your soil essentially means that you are feeding all of the millions and billions of little living creatures that are found in healthy soil, so that they can create healthy environment for a tomato plants’ roots the following year.

You don’t need to spread the amendments on thick, usually a dusting of any one in particular is sufficient. The application rates of each soil amendment is different, but usually application rates are easy to find on the package or from somewhere on the internet. The amendments I plan on applying to my garden this fall are greensand for trace mineral and potassium, rock phosphate for phosphorous, goat manure and compost for organic matter. In the fall after I pull out all of my dead plants, I will sprinkle this mixture over my soil, rake it in, and cover it with lots of straw. Then in the spring, I will be ready to plant.

Fast forward to next spring and I’ve got some broccoli that I am super pumped about. Broccoli is considered a heavy feeder, meaning it has an insatiable appetite, and needs a lot of nutrients to make a big head of broccoli. Well, the soil amendments are feeding the microbes which in turn are feeding the plant, but my broccoli could always take more, so I am going to fertilize it a couple of times, just for that extra push. Most organic fertilizers are some sort of liquidified fish, which is what I use in my garden.

Liquid fish is a good fertilizer because it has more phosphorous than nitrogen. While nitrogen is very important to plant health, if you give your vegetables too much, they will be all foliage with no fruit. Might make for a lovely garden, but one that doesn’t produce a lot of food. Phosphorous helps plants produce flowers, which are the beginnings of fruits, which is why I have been spraying my tomatoes with liquid fish: I want those flowers, because someday they will turn into tomatoes, which I will turn into gazpacho. My garden is small enough that I just follow the mixing directions on the bottle of fertilizer in a watering can and pour that over my plants.

I really try to fertilize most of my plants twice a month, so that they have a continuous supply of nutrients throughout their growth. I normally stop fertilizing a plant when I know that it’s life span is winding down. Like, I am kind of worn out by September, so I just let my tomatoes, peppers and tomatillos go without fertilizer until the frost. You can only do so much, you know? There are lots of fertilizers out there, and my main recommendation is pick one that works for you, and then follow the direction of the bottle to a “t”. Over fertilizing will negatively affect your plants, and can become environmental pollutants if you are careless, so make sure you do the right application rate.

To me, soil amending and plant fertilizing go hand in hand: one technique- fertilizing- is for the short term, and is feeding the plants that are growing in your garden right now, the other- amending- has an eye towards the long term, and keeping your soil healthy and productive for seasons to come. I highly recommend that all gardeners apply both techniques, but if you insist on only doing one, amending the soil provides better, longer term nutrition to your plants than a watering can with liquid fish does. As the organic farmers say: feed the soil, not the plant. But I say: if you are really into your garden why not feed the soil and feed the plants? Because that is how I will get my 100 pints of tomatoes for the winter, and have a happy and healthy soil for my garden next year.

For more gardening info, visit CCUA’s website or our Facebook page. And as always, happy gardening, and since it is the peak of the season, happy eating!