Growing indoors

Do you want to get started in indoor gardening or do you need a refresher on the fundamentals? In this series, we cover the basics of indoor growing. The goal is to take each of a plant’s needs and outline why it needs them, how to provide that indoors, and recommend products so you have an idea of anything you might need.

Plants 101: What plants need to grow

Let’s go over what plants need to live:

Light
A place to grow in and something to grow in
Air
Nutrients

All of this can vary wildly over different plant types and what your grow expectations are, but let’s concentrate on plants you would commonly grow at home.

Light

Light – Plants need light to grow. The amount of light is very dependent on the plant you are trying to grow with herbs and small leafy plants requiring the least, and large flowering plants requiring more (as a general rule).

As you might have discerned, since chlorophyll is green, plants can’t use green light to synthesize anything. That means that they are far more sensitive to blue and red light, and why you see a lot of purple grow lights on the market.

Blue drives cell signalling and macro process that determine plant size and leaf direction (More blue = plants thinking it has more light = plant decides to grow more compactly = small yield). Red drives sugar production (more red = bigger yields = plants that spread out).

At a basic level, you need an efficient light that provides enough to keep your plant happy. We only recommend using LED lights at this time due to the efficiency and longevity, and get about 30W per square foot (actual draw, not “equivilent”) to light an area for maximum growth. 15W will be fine for smaller plants or where you can put the light very close. Learn more in our Indoor Garden Basics: Light article to get very detailed into how it works.

Grow space

Providing your plants with all they need to grow is made easier when you create the space correctly. Outside, they can potentially get all the air, light, and water they need. When you bring the plants inside, having a windy, wet, and directly sunny area in your house are design fails most of the time.

Your space has to optimize for:

Light containment – Lighting and electricity are the majority cost of running and indoor grow and maximizing that light saves you money
Ventilation – Plants that are not getting enough CO2 don’t grow as uickly as they can
Isolation – If you’re growing bigger plants, or medicinal/food plants, keeping bugs and mold off is key to getting a usable harvest.
Temperature and humidity – Sometimes plants can’t handle heat or humidity, and most plants grow far better when you have these dialed in.
Containment – Spilling things, dropping fruits, getting dirt everywhere is not cool. Design your space to keep potential messes contained.

This could just be a spot by a window with a fan, or turning your attic into a Carolina Reaper farm. In all cases, you’ll get the best results by actively thinking about what that area needs to grow.

Check out our Indoor Grow Area article to get more in-depth into how to lay out your space.

Grow media (dirt, sand, artificial media, etc)

Plants we want to cultivate need to grow in something. Generally it’s dirt, but increasingly, we can use other substances if they offer sufficient benefit.

What you normally need from your grow media is

Nutrients
Oxygen for the roots
Support for the plant

This pepper plant has expanded clay balls in the basket to support the plant, and water as the growing media

Very roughly this breaks down into:

Soil is a fine particulate mixture of minerals and organic compounds that is loosely packed and can transport water and air through it. Bacteria, fungus, worms, bugs, etc. grow in soil and are essential in nature to keep the soil happy
Soil-like medias like potting mix, or coco-coir look and physically behave like soil. However, manufacturers make them to fit a specific role like seed starting or bing a hydroponics base. These may or may not include organic/inorganic nutrients, so be very aware of this to see how it fits in your grow.
Rock-like medias (expanded clay balls, perlite, grow stones, etc.) provide a great base for flood-drain hydroponic systems.
Many hydroponics system use aerated water as the base grow media, while using one of the other ones to support a portion of the plant roots.
You can use a more exotic or specialized medias like agar gel, or dung for specific purposes, but they lack practicality indoors or aren’t suitable for anything but an experiment.

Air and ventilation in your grow space

Plants use CO2 in the air to make the sugars they store for food. In order to supply them with fresh CO2, grow areas should have a steady supply. Plants don’t need more than the environment can supply, but if the air is very still they might use up all CO2 near them too quickly. This is why most indoor grows will benefit from a fan to move fresh air and distribute the expelled oxygen.

Additionally, sometimes plants have a smell you want to contain, or use more CO2 than a fan will provide. That’s when you need a ventilation system to reach your goals.

Learn more in our Indoor Garden Ventilation article

Water and Nutrients

Plants need water for just about every biological process. The vast majority of a plant’s weight is made up by water. Your water needs to be:

Mostly free of contamination – Plants don’t like more than about .8% of anything but the water in there.
Appropriate pH – If the water is too acidic or alkaline, the plant can no longer extract certain nutrients from it, and if taken to an extreme, the acidity or alkalinity will “eat” the plant!

With that in mind, plants need a variety of nutrients available in that water. We won’t list them all here, as this info is all available in our in-depth article. In order to get them into the plant, they have to be dissolved in a usable form, and generally available in the roots (some nutrients can be sprayed on the leaves if needed). Most organic forms of nutrients are not immediately available (how does a plant use eggshells, for example). Microbes and other fauna in the soil must digest the organic compounds and release easily absorbed nutrient salts.

Because of all this, you need to provide plants with available nutrients. You can do this by:

Using partially decomposed organic matter to fertilize… you know… compost. It’s a mix of everything plants need and will continue to break down, providing more nutrients over time.
Use non-decomposed organic matter to supplement a living soil. These amendments will eventually add whatever it is they say on the box, but might need 3-6 months to fully release. Good examples include bone meal, fish meal, bat guano, sea bird droppings, etc.
Use chemical fertilizers to make all the nutrients immediately available. These work great and are what you should use when your plant has a pressing nutrient need.