Every plant requires 4 things to grow successfully: light, air, water, and fertilizer.
How plants get each of these can change dramatically depending on where they live in the wild and how we choose to grow them in our homes.
But all plants need all 4 of these to thrive and survive.
When caring for your houseplant, your job is to provide the light, air, water, and fertilizer your plant needs.
The purpose of this blog post is to discuss WHY your plant needs each of these and some quick suggestions for how to ensure your plant is receiving each of them.
Then, in the next few weeks, I’ll share a more in-depth description of how to successfully provide your houseplant with enough light, air, water, and fertilizer.
Table of Contents
- #1 Why do plants need Light?
- #2 Why do plants need Air?
- #3 Why do plants need Water?
- #4 Why do plants need Fertilizer?
- Related Posts
#1 Why do plants need Light?
Light is the single most important resource you can provide your plant with and find success.
It is the most important of the 4 non-negotiables because light single-handedly fuels the process a plant uses to create food from water and carbon dioxide.
Without light, a plant doesn’t have the energy it needs to use the water, air, or nutrients you provide.
And as a result, the plant will decline, sometimes rapidly, depending on how light-starved it is.
Quick notes on how to give your plant enough light:
- If your plant wants bright, indirect light, place it near a window that receives a few hours of direct sunlight each day with lots of bright indirect light the rest of the day. This is generally an East- or West-facing window.
- If your plant wants full sun or high light, place your plant in a window that receives AT LEAST a few hours of direct sun. The more sun the better. The best window for high light plants is South-facing windows.
- Most plants do not want low light conditions. The plants that are generally labeled as “low light tolerant” do not actually prefer low light. They can just tolerate it, which means they may not grow much or look their best.
- North-facing windows and locations in your house that are farther than a couple of feet from a window are considered low light. Some of these locations may even be NO light, so be careful when choosing a low light position! In most cases, the closer the plant is to a window, the better off it will be.
#2 Why do plants need Air?
Air comes in as the second most important resource for plants because, somewhat similar to humans, plants need oxygen to keep their cells alive and can suffocate or drown without enough of it.
The process through which plants “breathe” is called respiration.
All parts of a plant need oxygen.
Roots require and use oxygen just as the rest of the plant does.
Roots that are planted in soil absorb oxygen in the small gaps that naturally occur in the soil.
How do plants use oxygen? Plants use oxygen to convert food into energy, just like we do.
Essentially, plants use light to fuel the process that turns carbon dioxide and water into sugars (or food).
Then plants use oxygen to convert those sugars into energy that can be used to keep the plant alive and growing.
Ensuring the plant parts above soil receive enough oxygen is easy because its already exposed to the air.
Ensuring the plant’s roots receive oxygen is the tricky part.
We want to ensure that the soil a plant is growing in has enough porosity to allow the roots to breathe.
For this reason, most houseplant growers add things like perlite, pumice, bark, and others to ensure the soil remains light and airy.
Plants have adapted to varying amounts of porosity in soil.
For example, cacti are used to having lots of air around their roots and tiny amounts of water.
On the other hand, bog plants (like the Venus flytrap) require very little porosity in the soil to survive because they have adapted to wet, soggy conditions.
Quick notes on how to ensure your plant receives enough air:
Most houseplants do well in a mix of potting soil and airy substrate (pumice and perlite are the most common airy substrate).
The ratio of potting mix to airy substrate is highly variable depending on the grower and the environmental conditions of where the plant is growing. BUT, I do feel comfortable recommending a good starting place, which would be 2 parts potting mix to 1 part airy substrate.
The mix I use these days is probably closer to 50% potting mix and 50% airy substrate.
For most plants: You know you’ve added enough air when the plant looks healthy and happy, is using the water you provide within a week, and is growing.
You know you need to add MORE air when the plant is still wet a week after watering it, the soil smells mildewy or musty, or the leaves/stems are turning to mush and dying.
You know you’ve added TOO MUCH air when the plant dries out completely within a day or two when the plant is wilting often, the plant is turning brown and crispy, or when the plant isn’t growing.
It is possible for all symptoms listed here to be a result of other issues, but your plant’s substrate can be a good place to start when troubleshooting your houseplant.
Important note: You do not necessarily need to use soil!
Plenty of people grow their houseplants in soilless media like LECA (lightweight expanded clay aggregates), perlite, LeChuza Pon, sphagnum moss, and others.
These substrates and growing methods allow for maximum air and hydration by wicking water as needed to the plant. The nutrients that are normally present in soil are added to the water to ensure the plant receives proper nutrition.
Below is a photo of a plant I was growing in LECA, which I eventually moved to a potting mix.
You can see how healthy the roots look and how it is solely planted in these little clay balls. The plant’s pot sits in a little bowl of water and the LECA pulls water up to the roots as needed to keep them consistently moist while still maintaining large air gaps between the balls.
#3 Why do plants need Water?
Plants use water to:
- hydrate their cells
- create the sugar/food they need to live and grow.
Photosynthesis uses light energy to turn water and carbon dioxide into sugar or food.
Just as roots need air, roots also need water.
Roots that have too little air: rot and turn to mush.
Roots that have too little water: dry up and die back.
So there is a balance between these elements.
Quick notes on how to provide your plant with enough water:
Most plants like to dry out a little before being watered again. To decide when you water, you can:
- Stick your finger deep into the soil and if it is dry to the touch, water the plant
- Use the weight of the pot to know whether it is time to water
- This method works well for plastic pots and terracotta pots. It is harder to tell with other pot types.
- If the pot is light, it is ready for water.
- If the pot is still heavy, the plant still has moisture
- Use a moisture meter to gauge how wet the potting mix is. If the meter reads a 2 or 3, it is time to water.
Desert plants, like cacti, want to dry out fully before they are watered. If in doubt, don’t water these plants. Wait another week and reassess.
#4 Why do plants need Fertilizer?
Fertilizer provides plants with nutrients and minerals.
These nutrients and minerals are vitamins for plants that ensure plants remain healthy, vibrant, able to grow, and able to reproduce.
Fertilizing houseplants is especially important because the plants can use up any nutrients in their soil relatively quickly and the soil can’t replenish these indoors without your help.
Outdoors, the soil has a fairly consistent nutrient source through decaying and decomposing organic matter. Even so, some locations may need outdoor fertilization as well.
Quick notes on how to provide your plant with enough fertilizer:
The easiest way to provide nutrients to your houseplant is to purchase an all-purpose indoor plant fertilizer. This type of fertilizer will offer all 3 macronutrients: Nitrogen (N), Phosphorous (P), and Potassium (K).
These 3 macronutrients are written in shorthand as N-P-K. The 3 numbers that appear on the labels of fertilizers represent the percent of N-P-K in that order.
For example, a fertilizer that is labeled as 10-5-7 is 10% Nitrogen, 5% Phosphorous, and 7% Potassium.
Chemically derived fertilizers usually only offer the 3 macronutrients listed above unless the manufacturer has intentionally added something else.
Organic fertilizers will offer the 3 major nutrients AND also offer trace elements and micronutrients. This is because organic fertilizers are made from natural sources, which already have many different vitamins and minerals.
Organic fertilizers, because they are less concentrated than chemical fertilizers, are much less likely to overfertilize and damage your plants.
How do you know whether the fertilizer is organic or chemical?
- Chemical fertilizers will be higher in macronutrient ratios on the label (10-10-10 or 20-20-20); organic fertilizers will have low ratios (2-2-2 or 6-4-5)
- Organic fertilizers will include a list of the micronutrients and trace elements with their percentages on the label. Chemical fertilizers will not because these aren’t included.
- Organic fertilizers typically say they are organic on the label.
Then, you just need to read the directions on the bottle for how much and how often to apply the fertilizer.
My recommendation is to always cut the recommended application amount in half so more sensitive plants aren’t overfertilized.
If your plant is growing, give it fertilizer.
If you are currently in the growing season for your region, give your plants fertilizer. The growing season for my region in the northern United States is from about March to the end of September.
Well, that’s it, folks! We’ve covered the 4 most important resources we can provide our plants with. Hope you found the post super helpful! Do you think I missed something or got something wrong? Let me know in the comments below!