Soil | Indoor Gardening Methods

Growing in soil

Soil grown plants in fabric potsHarking back to the days of when stuff started growing on land, soil is the oldest and perhaps the most studied of growing medium. Soil is alive. It is an ecosystem. It brings together a wide array of organisms that together bring about what is either the most harmonious of growing environments, or a month’s worth of head scratching.

Hey, guys, this post contains affiliate links for the products we recommend. These cost you nothing and keep the website running. If you’re going to buy them anyway, please consider helping us out and buying through our links. Thank you!

Why should you grow this way?

Soil is extremely forgiving and doesn’t require the rigid feed schedules that most pure-hydroponic methods require. Because it contains a varying density of nutrients and retains water well, you don’t have to be as strict with watering or getting your nutrient schedules right. Minor issues are buffered by the soil’s living nature to self correct. Which is great, but also causes issues when troubleshooting when something is going wrong.

Also, for many people, Soil just feels “right”. The taste of your end result is subtly different from other grow techniques and it’s how plants are meant to grow.

How it works

Soil is a mixture that roughly breaks down into:

  • Inorganic matter – Bits of rock, clay, and sand. These make up the structure of the soil and supply some minerals when placed in acidic or alkaline environments, but are mostly inert.
  • Organic matter – This portion, known as “hummus”, contains the majority of the nutrients within the soil. Many of the nutrients are not available to the plants directly until soil-dwelling organisms have had time to break down long and complex organic molecules into simpler nutrients that plants can readily absorb.
  • Soil microorganisms – The bacteria, fungi, and other single-celled organism that can subsist on the complex nutrients in the hummus and break them down into the simpler molecules that plants need for nutrient uptake.
  • Soil creatures – Bugs, worms, etc. These feed from the minerals and nutrients and convert even more nutrients into plant-ready waste. Additionally, worms especially, provide valuable soil aeration, which greatly helps plants grow.

As you can see, soil is a complex environment, and the people who truly love tending to it talk endearingly of “no-till” soil; the holy grail of soil that has the right ecosystem, requiring no additional effort to make it better for the plants. This is difficult for the new-comer to achieve, and also not 100% consistent for masters, but you can always supplement with ready-to-use nutrient supplements (organic or not) and get similar results while still taking advantage of soil’s ability to be resilient and forgiving.

What you need to get started


Soil really only needs a few things. We like to use fabric pots as our grow containers. They are cheap, durable, and have great drainage characteristics. Because roots can grow through them, it’s almost impossible to get root-binding of a plant; they simply hit air and stop growing, rather than choking out the grow medium for space.

Air pots/Power pots or any other name for the plastic pots that have guides to point roots out to air prune are also excellent and provide the same air-pruning. they are more efficient at it, pack away flat, and are excellent overall. However, prices are high.

The soil you use is also important. For organic farming, you ideally want to use you own no-till soil, but even the masters occasionally have issues making that work. We like to use Pro-Mix All Purpose. It drains very well, and contains a reasonable amount of hummus  with some time-release nutrients. It will, however, require nutrient additions once your plants get large enough.If you want to be fully in control, Pro-Mix HP drains very well, and has no nutrients.

Organic gardeners will usually go with Fox Farms Ocean Forrest. It’s packed with nutrients and ready to go immediately.

If you want to make your own mix, you will need compost and dirt at a minimum. Typically, if you are getting this from your yard, it’s not going to be conducive to a fast growing. You need it to retain water at a certain rate, drain well, and provide root-zone aeration. We typically use a mix of coco coir or peat(5%-50%), perilite(10%-30%), compost(10%-20%), and dirt (30%-50%) to get the right consistency. The formula depends on what your dirt and compost are composed of. Test it to make sure that water you put on top doesn’t pool up too much and can drain to the bottom within a minute or so.


  1. Fill your container about 3/4 of the way with soil.
  2. Make a hole the depth of your seedling container.
  3. Bury the plant in the hole.
  4. Add a little more soil on top and an optional mulch.
  5. Mix up a starting feed of water, and any inoculant you want to use. Water the soil until some runs out the bottom.
  6. Water again when the top gets dry and is dry about 1 inch down. You are looking to let it dry out a bit to pull some air into the root zone.
  7. Once the plant is large enough to begin flower or is producing the leaves you want, fertilize lightly once a week when it’s time to water. As the plant grows, you can increase the concentration


Plants’ root nutrient uptake depend heavily on soil pH. Soil is very good about keeping a steady pH, but it can get out of the acceptable range f 6-8 (most plants you’ll grow for food or herbs like it in the low 6s). If your plants start to look sick, the first thing most people will ask you to do is to test pH. There are several ways to go this. First you make a mixture of 1 part soil and 2 parts distilled water. Then you let it sit, and test the liquid on top. GH’s test solution is easy and simple and wildly difficult to read. Test strips are better, but still lack some precision. We use digital meters, but they are finicky and do need to be maintained by properly storing them.

If you need to modify the pH you can make slight adjustments by using hydroponic pH adjusters in the water. This works quickly, but might be over kill in the short term and not last very long. Usually, we mix 1ml/gal of GH’s pH Up or Down and give a light watering for a few days. Longer term care can be done with adding lime to raise the soil pH. Lowering the soil pH is a bit easier, since you can add more nutrients (which tend to be acidic) especially ones with ammonium nitrate and urea. If you want a slow acting acidifier, adding sulfur is a good way to go.


Soil doesn’t need too much attention, but it does need to be watered regularly. There are a bunch of ways to do this.

My preferred system for watering multiple plants is the Blumat watering system. It senses soil moisture level using a ceramic spike, and keeps watering until the spike is moist enough. It’s fiddly, but ultimately super-convenient.

Smaller plants can use conventional water spikes. They also have porous bottoms and they pull liquid from the inside when they start to get dry as a result of capillary action. Again, simple and easy. These don’t really support large plants, but they are great for window boxes.

Unless you have a soil moisture sensor, regular watering through a timer is not recommended in containers. While it does work, the lack of feedback means that over- and under-watering is a likely issue.

6 years ago