In this week’s post we are going to cover everything you need to know to start fertilizing your plants.
Fertilizing can be an overwhelming topic in the beginning because there are so many different varieties and strengths. It is hard to know what is safe to use.
The goal of this post is to provide basic information that will allow you to confidently choose a quality fertilizer for all of the plants in your home.
Fertilizing Quick Start Guide:
- Fertilizing plants supports healthy growth and development
- Fertilizers list 3 numbers on the package, which represent the amount of Nitrogen, Phosphorous, and Potassium, in that order
- To start fertilizing, choose a balanced fertilizer where the 3 major nutrients (called macronutrients) are equal in strength (2-2-2, 10-10-10, etc)
- Provide your plant with fertilizer when it is growing. Withhold fertilizer when it stops growing or when light levels are too low for a plant to maintain healthy growth.
- Follow the directions on the package to determine how much and how often.
- If using synthetic fertilizers, the safest bet is to only use half or a quarter of the amount prescribed on the package to ensure plants do not experience fertilizer burn
To learn more about how to fertilize your houseplants and how to choose the right one for you, keep reading!
Table of Contents
- Why fertilize houseplants?
- How do you know what kind of fertilizer to use for a houseplant?
- What is the difference between organic and synthetic fertilizers?
- What’s the difference between liquid, granular, slow-release form fertilizers?
- How often and how much should you fertilize your houseplants?
- Related Posts
Why fertilize houseplants?
When a houseplant is first potted up, the potting mix it resides in will have a certain amount of nutrients in it. Those nutrients are absorbed by the plant each time it is watered and eventually they will be depleted.
Once the nutrients are gone, the plant won’t have what it needs to grow to its full potential.
If nutrient deficient for too long, the plant will begin to show it is nutrient deficient in a number of ways:
- Growing smaller leaves
- Deformed new growth
- Yellowing leaves or leaf veins
- Not growing at all
- Leaf color loss
Repotting will help to replenish those nutrients again for a time, but most plants do not need to be repotted when they run out of nutrients. That’s why we fertilize instead.
How do plants nutrients in the wild?
Plants gain the nutrients they need when growing in nature through multiple sources: animal droppings, plant waste decomposing, etcetera.
How do you know what kind of fertilizer to use for a houseplant?
Fertilizers are typically labelled using three numbers separated by dashes. For example, a fertilizer might be labelled 10-10-10.
The three numbers on a fertilizer’s package tells you the strength of the 3 major nutrients: Nitrogen (N), Phosphorous (P), and Potassium (K).
They are always listed in this order: N-P-K.
Each of these macronutrients, or major nutrients, play a key role in the growth and development of the plant.
Nitrogen helps to promote big, healthy, lush foliage.
Phosphorous supports flowering and fruiting as well as healthy root growth.
Potassium fosters overall health and vigor.
My recommendation for beginners is to choose a balanced fertilizer where the N-P-K ratio is the same for each nutrient. Choosing a balanced fertilizer ensures that the plant has each macronutrient available.
Ensure that the fertilizer you choose is labelled as indoor plant fertilizer/food.
There may come a day when you want to match your fertilizer more closely with the needs of a plant.
For example, if you are growing lettuce, you want the plant to focus on leaf growth and development so you may choose a fertilizer with a higher nitrogen amount.
Or perhaps if you want your mature plant to bloom and fruit this year, so you give that particular plant a fertilizer with a higher amount of phosphorous to support flower and fruit development.
Or you might be tailoring your fertilizer choice to suit cacti, which almost never have foliage, so you choose a fertilizer that is lower in nitrogen.
What is the difference between organic and synthetic fertilizers?
Organic fertilizers are derived from natural sources and are typically at much weaker strengths.
Organic fertilizers also provide a lot of additional nutrients, because the natural sources used to make them contain the micronutrients as well (such as Iron, Calcium, and more)
Synthetic fertilizers are chemically manufactured fertilizers available at much higher strengths.
Synthetic fertilizers only contain nitrogen, phosphorous, and potassium generally. Any additional nutrients have to be added.
In my opinion, the most significant difference between organic and synthetic fertilizers is the potential for fertilizer burn.
Synthetic fertilizers are much more likely to cause fertilizer burn because the concentration is much higher.
What is fertilizer burn?
Fertilizer burn is where the salts contained in the fertilizer build up to a toxic level within the soil. The salt buildup burns the roots of the plant, preventing the plant from being able to uptake water and nutrients.
It can significantly damage, and even kill, a plant.
To help prevent your plant from developing fertilizer burn, flush the soil of your plant periodically.
How do you flush a plant’s soil? By running water through the pot a few times to loosen and flush out excess salts.
What’s the difference between liquid, granular, slow-release form fertilizers?
Liquid fertilizers are added to the water used for hydrating your plants. These can be organic or synthetic.
Applying an organic liquid fertilizer when watering plants is my preferred method. I use:
Espoma Indoor Liquid Plant Food, Natural & Organic (linked to Amazon)
Liquid fertilizers are also available in Spray Form, which is sprayed on the foliage of plants. The plants absorb the nutrients through their stomata, which are tiny pores in their leaves that they can open and close to absorb or release gases.
I am not familiar with many people using foliar sprays on the majority of houseplants, but sprays are regularly used with some epiphytic plants, like orchids, hoyas, and air plants.
I use one spray currently, Cute Farms Orchid Plant Food Fertilizer Mist, for orchids, hoyas, and dischidias (linked to Amazon).
Granular fertilizers are mixed in to the top layer of potting mix and become available to the plant when it is watered. These can be organic or synthetic.
I do not use any granular fertilizers, so I don’t have a good recommendation here.
Slow-release fertilizers are similar to granular, in that they are added into the potting mix.
The big difference between granular and slow-release is that granular fertilizes at full strength immediately upon watering, where as the slow release fertilizer provides smaller amounts of nutrients over time as the product breaks down.
Slow-release fertilizers are only available in synthetic form.
I’ve heard lots of people having great success with one particular slow release fertilizer. I will link it below. I haven’t personally used it, but if I wanted a slow release product, this is the one I would choose.
Osmocote Smart-Release Plant Food (linked to Amazon)
You can also use Worm Castings, which are the waste produced by worms, as a fertilizer for your plant. It is an organic and natural way to fertilize that is mixed into the potting mix, similar to a granular form.
Dr. Verm’s Premium Worm Castings – Organic Soil Builder and Fertilizer (linked to Amazon)
So which one should you use?
You can choose the type of fertilizer that works best for you and your schedule.
Slow-release fertilizers are applied infrequently and liquid fertilizers are applied most frequently.
For me, liquid fertilizer works because I prefer organic, weaker strength fertilizers and I’m too lazy to mix granular or slow-release fertilizers into every pot in my home. It is easier for me to just add it to the water I use for my plants. 🙂
How often and how much should you fertilize your houseplants?
Any fertilizer you choose will have directions on the package for how much and how often to fertilize.
You can follow these directions exactly or you can provide less than the recommended amount to ensure your plants do not suffer from fertilizer burn.
I personally use Espoma Indoor Plant Food, which is an organic fertilizer, at half strength every other watering during the growing season.
Espoma Indoor Liquid Plant Food, Natural & Organic (linked to Amazon)
For my plants receiving natural light, that is typically between mid-March to mid-October.
For my plants under grow lights, they are pretty much always growing so I typically fertilize year-round.
I hope this post has helped you feel more confident to get started with fertilizing your indoor plants. If you have any questions, comment below and I will do my best help.