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Why Not to Fertilize your Square Foot Garden

If you practiced conventional row gardening before you launched your Square Foot Gardening adventure, you may have a little voice in the back of your head that whispers, “Go ahead, add the fertilizer. You know you want to.” Resist the voice. We repeat — resist the voice; there is no need for any added fertilizers in a Square Foot Garden! Here’s why (and we’re using lots of food references because we all love food, right?).

Mel’s Mix™ has everything your SFG needs.

Mel’s Mix™ is a perfectly balanced mix of equal parts blended compost, coarse vermiculite, and peat moss. The blended compost component has everything (literally everything) your plants need nutritionally in order to grow and thrive, so no added fertilizers are needed. Think of a favorite dish you’re preparing for dinner — if you taste test it and it’s delicious, the best dish you’ve ever tasted, would you then add more salt “just because?” No, you wouldn’t. It would not only be unnecessary, it would ruin the balance of the spices and seasonings you’ve already added. Don’t mess with perfect.

Family making Mel's Mix on a tarp

Note on bagged compost: Many commercially bagged compost products contain a lot of wood material — good compost should look like soil, with no individually definable organic material. Those wood pieces will eventually break down in the soil, but they will use available nitrogen to do so, taking it away from your plants. If you spot wood pieces or any other definable material in your bagged compost, screen it to remove them before adding to your SFG. If you’ve already added compost with wood pieces into your Mel’s Mix™, it’s not going to be possible or practical to screen it at that point. In that case, go ahead and add some nitrogen-only fertilizer like blood meal in the amount recommended on the label — and use the screening method moving forward.

Hands holding compost

Read this blog post about Mel’s Mix™ for a refresher or an overview.

Added fertilizers upset the pH in Mel’s Mix™.

Added fertilizers upset the pH balance in the Mel’s Mix™. Soil pH that is too low or high can stunt plant growth, inhibit nutrient uptake, cause yellow spots or browning on leaves, and even lead to leaf death.

Once you’ve added fertilizers into your Square Foot Garden and those unintended side effects start showing up, now you’ve placed yourself on a hamster wheel of having to treat those plant issues, which then costs you more time and more money. Keep reminding yourself that your plants have everything they need from the very beginning when you simply add Mel’s Mix™ in as directed.

Listen to Laura and Steve Bartholomew from The Square Foot Gardening Foundation talk about added fertilizers in this YouTube video.

Added fertilizers are like candy bars.

Think about your daily nutrition. There are certain things you need everyday — sufficient calories, fiber, protein, healthy carbs, and healthy fats. If you’re only focused on getting sufficient calories, then eating a bunch of candy bars would do the trick, right? But since your goal is overall health through balanced nutrients, you will likely resist those candy bars and reach for something that is nutritionally sound and will feed your body properly. Mel’s Mix™ is the equivalent to eating a perfectly balanced diet, and added fertilizers are the candy bars. Back away from the candy bars, friends.

Fertilizers waste money and time.

Now, since we can see that added fertilizers are unnecessary, add nothing beneficial to your Mel’s Mix™, upset the balance of Mel’s Mix™, and create harmful side effects for your plants, it becomes obvious that they not only waste money, they waste time. Square Foot Gardening is all about saving precious resources and making gardening more productive and fun, and added fertilizers are simply counterproductive to what we’re trying to achieve.

Hear Rick Bickling talk about Mel’s Mix™ in this YouTube video he created for the SFG Foundation.

Are there any exceptions to the “no fertilizer” rule?

The only real exception to the “no fertilizer” rule in your SFG is if you use your beds primarily to grow ornamental flowers. These types of flowers are very heavy feeders and could benefit from a very diluted organic fertilizer — go easy on it and you’ll be good to go!

Learn more about the Square Foot Gardening Method by taking the introductory course


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