Earth & Water (for Indoor Gardening)

”Earth and water” was the tribute demanded by Xerxes’ emissary played by Peter Mensah in the film 300. You may recall that this demand got him famously kicked into an enormous bottomless pit, which is a very normal thing to have in your town, and without so much as a guardrail.

Much like Xerxes, “earth and water” are the tributes demanded by our plants, and my job is to [Hank Hill voice] kick you down the Pit of Responsibility.

This! Is! Spartina*!

*a genus of coastal grass

🌿 Choosing the Right Soil

What kind of soil your plant needs is going to be determined by where it naturally occurs and the soil conditions there.

Is this something you have to know?

Not Necessarily: If your goal is to grow some vegetables or herbs, you can buy premade soil mix and trust that it’s going to be sufficient for one or more cycles of growth (your plant will eventually deplete what it needs from the soil which will have to be replaced. This is where fertilizer comes in.)

But You Should: If you want to actually get good with your plants, especially if you have any designs on providing for yourself or a network that may depend on your contributions, you need to learn as much s you can about soil, its composition, how and why it works, and your specific plant’s relationship with it

.This knowledge certainly won’t hurt you, isn’t overwhelming one plant at a time (and you’ll start to see patterns emerge), and it will help you be more intuitive with diagnosing problems before they get started, managing pests, disease, and deficiencies. Understanding soil will help you learn how to fertilize and with what, without having to be told every single time.

Discovering Your Plant’s Needs

There isn’t enough space here to give a comprehensive list of every type of soil needed for every type of plant, but you should be able to find out fairly easily. Don’t just trust the first AI-powered result you get, go search for your plant on r/gardening, do an internet search for “[your plant] optimal soil”. If you’re really stuck, ask on our Discord server!

Learning About Soil

But where can you go to learn about soil in general?

1. USDA Natural Resources Conservation Service: Soil Education

• Offers lesson plans, educator guides, and soil health posters to deepen your understanding of soil properties and health.
  Natural Resources Conservation Service
  
  

2. Soil Science Society of America: Soils 4 Teachers

• Provides a comprehensive collection of lessons, hands-on activities, and readings about various soil topics, suitable for all educational levels.
  Soils 4 Teachers

Soil Recommendations

I’ll be honest; I haven’t paid a lot of attention to the kind of soil I use in years, but that’s because I mainly make sure that I’m starting with a substrate that has sufficient drainage, and then I’m going to use compost and other amendments to make it whatever my plant needs. This is a good place to be, because it means you can work with and revive even dead, depleted soil.

In terms of premade mixes, my main criteria are that everything included be biodegradable and that no fungicides, pesticides or herbicides are mixed in. This can be hard to control completely with pre-bought soil mixes, because all kinds of things can end up in there, but I definitely wouldn’t use anything included on purpose. I want my soil in a healthy, living balance, and that includes some “pests” and definitely fungi.

A brand I particularly like and have had good results with is Fox Farm mixes. They can be ordered online from retailers and can be bought at many garden centers.

The Bottom Line

You can get started without in-depth knowledge, but you can’t continue indefinitely without it, and if your goal is longterm sustainability, then you’re going to need to learn not only about your plants, but about their soil environments.

🌾Fertilizing Basics

Soil is full of nutrients that become the building blocks of your plants. In nature, a plant grows, lives its life cycle, and dies on the spot and the nutrients it contains are delivered back into the soil to be used again in a perpetual cycle.

In gardening and farming, we tend to take the plant material (and those nutrients) away, and they aren’t replenished directly back into the soil. Over time, your soil will become depleted of the specific minerals used by that plant, and the plant will struggle to grow.

There are two things we can do about this:

Rotation

We can rotate plants with different nutrient needs through the same soil. But if we aren’t allowing vegetation to live and die there, eventually this soil can become super depleted and dead. This happens a lot with industrial farming - if farmers didn’t constantly spray fertilizer on those crops, the soil wouldn’t support them at all.

Fertilizing

This is the process of adding back in the nutrients that your plant needs. There are many mixes commercially available, but many nutrients can be replaced simply buy burying every day organic items near your plants - ashes, bananas, and egg shells all contain nutrients your plants love. Even fish!

Burying organic matter (and composting, which is more of the long form of doing this) is  good way to reintroduce nutrients without much risk of burning your roots by introducing way too much (a risk more common with concentrated mixes).

Fox Farm also makes highly specialized liquid and dry fertilizers.

Ideally, you will learn how to compost effectively, and thereby create your own fertilizers, but while you’re learning, store bought is fine.

What kind of fertilizer do I need and when?

There are a lot of variables here! Much like you looked up your plant’s specific soil needs, so too look up their fertilizer needs! Try to take advice from experienced gardeners, not people who sell fertilizer.

💧 Learning Your Plant’s Watering Needs

There are a lot of memes about houseplants being left to dry out, while others will die if you water them. After lighting, I would say that mastering watering is the second biggest hurdle to successful gardening, and the one that will help you feel like you’re really starting to get it once you learn what you need to know and get some practice.

Each plant has its own needs, and its needs change based on things like weather and relativey humidity, soil conditions, and the plant’s stage/cycle. A huge, productive tomato plant is going to need more water than a tiny sprout.

How can you possibly be expected to keep track of all of this?

You need to know two things about your individual plants:

1. How dry is the soil right now?
2. How dry does the soil need to be before I water it again?

High water needs: 🌿 Ferns, herbs, tropicals → Keep soil slightly moist.

For most herbs, you’re going to keep the soil slightly damp — that is, you want to be able to feel the moisture, but you don’t want water to squish out when you press it. Herbs are usually good, once they’ve grown a bit, at shielding their soil to help with retention. You’ll do more regular misting than deep watering with these guys, but you’re still going to monitor the top inch of the soil to make sure it isn’t drying out beneath.

Moderate water needs: 🥬 Vegetables, flowering plants → Water when top inch dries out.

For most veggies and flowers, you’re going to monitor the top inch of soil. Figure out where on your measuring finger is the 1” mark. You’re going to stick your finger in the soil up to there. If it’s dry, you water.

Low water needs: 🌵 Cacti, succulents → Only water when soil is bone dry.

If you’re growing succulents, you’re going to let them dry out almost completely. Succulents are not in my wheelhouse, so seek advice from someone who knows more about them than I do.

💦 Time to water if you see:
✅ Dry, crumbly soil
✅ Wilting or limp leaves
✅ Leaves looking dull or droopy

🚫 Avoid watering if you see:
❌ Soil is still damp or smells musty
❌ Yellowing, mushy leaves (signs of overwatering!)

🗓 Managing a Watering Schedule

One of the earliest lessons I learned about indoor gardening is that until I have a longterm schedule that I follow automatically, I absolutely have to have some kind of reminder to check my plants for watering. I highly recommend you do the same.

Whatever You Use To Remember Things, Use Here

Calendars, journals, apps. Whatever you use to keep track of tasks, integrate your plant care directly into those systems. Most plants don’t need to be checked every single day, but maybe do check every single day until you establish a pattern - “it takes my tomato plant six days to dry enough to need water”. Great. Set your reminder for five days to be safe. And remember, those patterns will change, so don’t take them for granted!

Here Is An App I Recommend:
Planta 🌱- iOS and Android

✅ Smart watering schedules based on plant type & environment
✅ Light meter to check if your plant has enough sunlight
✅ Care tips and plant health diagnosis

🚨 How to Fix Overwatering & Underwatering

💧 Fixing Overwatering:

• Stop watering immediately and let soil dry out.

• Check for root rot (black, mushy roots = bad news).

• Improve drainage by using well-draining soil and pots with drainage holes.
  
  

🔥 Fixing Underwatering:

• Slowly rehydrate by watering in small amounts over an hour.

• Soak dry, compacted soil from the bottom (place pot in a tray of water).

• Increase humidity if necessary.