After getting your grow bags and assorted pots, you need dirt. And you can’t just use any dirt. This may come as a surprise, but containers are not ideal growing situations for most plants. You have to help them regulate the water and nutrients they receive so they don’t drown, starve, or dry out. But don’t worry, it’s not as hard as it sounds. We will take it one step at a time. And on a fundamental level, this is what I’ve learned about soil. Soil is everything. If your soil is no good, your plants will struggle. I realized something about the Stay Home Garden Club being a container garden (for a lot of us) in the beginning. Think of all this potting soil you’ll invest in as the foundation of your growing garden. Almost more important than what crops you are growing this season, it’s this soil you’re growing. You won’t throw this soil away in the fall when you’ve eaten your last (fresh) tomato. You will re-use it, either by adding it to your garden in the no-till beds you’ve been laying the groundwork for all summer (more on this later). Or, you will refresh it with new amendments for a new season of winter container crops. But this is soil that will be the oldest soil you’ll touch in this new garden of yours. It’s the grandparent soil for all your future seasons. So invest in this soil, love it, nurture it. And I urge you to keep it organic. It’s just better for all of us, and for the world of creatures besides us humans. This soil will give you back what you give to it for years to come. 🖤

The Soil Mix

Maybe you just used straight up potting soil in your containers, if so, don’t worry. I would still recommend adding a few other amendments to your pots. It’s easier to do all this before you’ve planted your transplants and seeds, but once your plants are established, you can still add amendments by removing the two inches of mulch you’ve hopefully applied on top, and carefully trying to stir it in with your hand. The most important thing for container gardening is that you don’t use regular garden soil. Regular garden or topsoil won’t allow water to move through the container easily. It also doesn’t contain the nutrients plants need to thrive in their self-contained root systems. So make sure the soil you use is designed to be used in pots. Or make your own using the recipe I describe a little further down.

Soil Amendments

In whatever potting soil you buy, if it doesn’t include perlite you should add a generous amount. Perlite is the little white, Styrofoam-looking pieces you’ve surely before seen in soil mixes. It’s actually volcanic rock, and it’s so light that a huge 4 cubic yard bag of it can easily be lifted with one hand. What does it do? When mixed with soil, it helps get oxygen to your plant’s roots by creating little pockets of air in the soil. It prevents the soil from compacting, so roots can go wherever they need to. This is more important in pots rather than fabric grow bags where they have more oxygen and flexibility, so if you only have a little bit of perlite for now, save it for the plastic pots you are using. I also add this directly into my raised beds and in-ground beds to help break up the very compacted, clay soil. Perlite creates good drainage but also retains moisture and helps keep temperatures stable inside the pot. If your potting soil had a generous amount of perlite in the mix, you may be fine, but if your plants are not thriving in the pots, if they are turning yellow and you haven’t forgotten to water them, then they are most likely not getting good drainage. And it’s worth it to carefully re-pot them after adding perlite.

Soil Nutrition

Vegetables require more nutrients than most plants to grow big harvests. You have to give them something hearty and nutritious to help them grow. So another great thing to add to your soil is organic compost. My favorite (if you are local in Austin) is Whittlesey’s screened compost. This is really easy to add to soil if you didn’t pre-mix it by just topping the soil with it, being careful to keep the compost or mulch from touching any of your plants directly. I like doing this again when plants start getting a little sad in the hot summer. The water that filters through the compost feeds the roots below and everything just perks up afterward and seems so happy.

If I was making my own potting soil, I wouldn’t use “soil” at all. Instead, I would mix 1 part coconut coir (I love these blocks for seed starting too, cheap and easy to store), 2 parts compost, and 1 part perlite. So if you are using a pre-made potting soil, I would use 1 part that, 1 part perlite, and 1 part compost. If you are planting something that grows really tall, like sunflowers, double the compost. I also like to use manured compost for sunflowers. They are really hungry flowers.

Feeding + Fertilizer

Fertilizer has numbers on the bottle that tell you the breakdown of the following: nitrogen(N) - phosphorus(P) - potassium(K). An all-purpose food has low numbers in all three columns. You have to be a little careful with fertilizer as some plants, like beans and peas, don’t need much nitrogen. Some flowers want nothing at all. Feeding too much of the wrong thing, can cause your plants to produce tons of foliage but no fruit, or kill them altogether. So I like to use as fool-proof methods as possible when feeding my garden.

The easiest way to feed your container plants is with a slow release organic plant food added directly to the soil mix, or with plant spikes in the container. I like these, as they are easy and cheap, but I use about half the amount they advise since I like to feed the soil with other organic matter, like the compost I just described. If you are only growing a few plants, it is good to research their exact needs. I think it’s great info to share with the Garden Club. This is all a big experiment, and we are all researchers after all. Let’s pool our findings and help each other.

If you want to really geek out on organic soil amendments, you could forgo the plant food and work out the right combination of bone meal and blood meal for each kind of plant you’re growing. It’s exactly what it sounds like it is. Bone meal is powdered animal bones, which adds calcium and phosporus. Blood meal is powdered animal blood, which adds nitrogen. It’s non-vegan, but still the most organic, and it’s a slow-release type fertilizer so you can’t really kill your plants. You can still get the NPK balance wrong though, and not get the result you want. If that happens, don’t dispair, just make a note of it. Remember, you’re a scientist now. Also if you are growing tomatoes, they need some calcium in their soil or they will develop blossom end rot. A little bone meal is good for this. I pulverize eggshells in my blender and add them to the soil, which works too.

A treat you can give your plants when they are very good, and/or once a week, is a sea kelp liquid food. Cannabis growers swear by this stuff, and I soak my transplants in water with this before planting. It’s expensive, but it’s so concentrated, you mix a tsp with a gallon of water. This sized bottle should last you all summer. If a plant gets thrashed by a pet, attacked by insects, or endures some kind of trauma, seaweed is the chicken soup of a plant’s soul that will nurse it back to life. You can also mix some kelp food granules into the potting mix, for the same benefits. It has very low numbers on the N-P-K scale, so you don’t have to worry about over-feeding, with either form, in addition to whatever plant food or compost you’re adding.

Free Additives: Coffee / tea grounds & crushed eggshells are easily-collected organic matter that improve soil acidity and adds calcium, which can ward off blossom end rot in tomatoes. They both have the tiniest bit of snail repellent qualities.

Bonus Joy Max Pumpers

These are soil additives that I discovered way late in my gardening journey. If you truly want to give your plants and veggies their best life, I highly recommend them. But I also got through many, many harvests without them. I know a lot of us are struggling with uncertain financial prospects, so I’m putting these in a bonus nutrition category. If you have the means, these are the most-loved soil additives for both raised beds, in-ground beds, and containers:

Rock Dust: Potting soil, with exceptions of course, is lifeless. Plants need life in the soil to thrive, so adding compost and other organic matter is a way to introduce that life at a microscopic level. That’s when the magic happens. Volcanic rock dust contains a lot of the minerals the microbes are looking for, so add a tbsp for every gallon pot you’re using, and your soil will wake up with life. Only use it after seeds are germinated, when a transplant is young. Don’t use it later when the plants are flowering or producing fruit.

Greensand: Mined from the sea floor, greensand is a rich source of glauconite, which is high in iron, potassium and magnesium. It’s an easy, gentle, slow-release way to deliver those minerals important to plant growth. It’s also great to break up clay soils and improve moisture retention, soften hard water, and increase root growth. Mix in two tablespoons per gallon of potting mix. It’s especially good for tomatoes.

Earthworm Castings: Earthworm poo is garden gold. It’s full of beneficial microbes that help your plants in so many ways. You can even get a worm composter to make your own! Worms are the best companions your garden can have, and since your containers won’t have them, they can at least benefit from their castings. They aren’t gross, don’t worry. They look like dusty coffee grounds. Add 1/4 cup for every gallon in your container.

Note about Miracle-Gro and other synthetic fertilizers: I do not use these products and I strongly advocate for organic gardening methods. If your store-bought potting soil contains Miracle-Gro, then ignore all the amendments I listed above, as the chemicals will kill the microbes. Once you are on the Miracle-Gro train, you have to stay on it in those containers. It may work great, but I like to use potting soil from my retired container plants in other places in my garden beds. And I’m maintaining organic practices throughout to build a healthy eco-system for all the creatures that live there. Something to think about from the beginning, as these are early days for all of us.