Fertilizing
Should I?
In my opinion, there is a lot to consider when deciding on fertilizers.
Many folks never fertilize their houseplants and never have a problem. This is likely because the soil they are using contains fertilizer.
If this is your preference, I would suggest being sure to repot at least annually to refresh the soil. Just like water, plants utilize nutrients in the soil and will eventually need to be replenished.
My first experience with fertilizer was when i realized my Philodendron Brazil looked exactly the same for about four months. I couldn’t figure out why it wasn’t growing. I watered it, gave it bright indirect sun, and it still just sat there.
I did one of those things that I look back on embarrassingly now and googled what to do. Oh, hello world of five million fertilizer options.
My gut instinct was to go for an organic fertilizer but some of what I read suggested they were weaker. I wanted my Brazil to take off so I snagged Miracle-Gro Indoor Plant Food
I noticed new growth on my Brazil almost immediately! This was the first time the houseplant addiction dug in its claws. I had figured something out! I was caring for a plant properly!
I started reading more about fertilizers and when/why/how to use them. After a lot of trial and error, I found my system.
Weakly, Weekly
I fertilize weakly, weekly.
Because my collection of over 300 plants ranges widely in genus, I need a plan that keeps things simple and applies to almost all of my plants.
I used the Miracle Gro fertilizer at 1/4 strength directly into the watering can.
The weekly part is loose. I just used it each time I water, which happens to be every 7-10 days on average.
Going Organic
I’m only going to address commercial fertilizers in this post, so if you’re interested in coffee grounds, egg shells, bone meal, etc., sit tight for my “Budget Care” post.
When I ran out of my Miracle Gro fertilizer, I went for Espoma Organic Indoor Plant Food
There was.
I noticed that I had to use more of it. Organic fertilizers are weaker overall, so it is not necessary to dilute them as much, or at all if you’re feelin’ spicy. The upside to organic fertilizer is that you have more room for error. It is much more difficult to over-fertilize with an organic option.
I also noticed that the fertilizer burn on my prayer plants stopped appearing once I made the switch to organic.
Overfertilization
There are exceptions to every rule, even those loose rules I apply to most things.
Calathea are a big exception here. They require very little fertilizer and will develop fertilizer burn if exposed to too much. It looks very similar to damage from low humidity. The margins of the leaves will brown and crisp up a bit.
If you know your Calathea are receiving a good amount of humidity (>60%), I recommend cutting back on the fertilizer.
Even if you are fertilizing a plant that is considered hardy, more is not better. Overfertilizing can harm microorganisms in your soil, leaving your plant more susceptible to pests and disease.
Numbers Game
You’ll notice as you peruse a selection of fertilizers, that there is a series of numbers on the packaging. (Like “1-3-1” or “3-5-5”). This is the ratio of Nitrogen to Phosphorus to Potassium.
I teach with a lot of metaphors because I find it makes content more memorable, so I’m going to use the human body for a metaphor and explain how each of these elements affect your plant.
Nitrogen
All plants need nitrogen. It is arguable the most important nutrient as it is essential to their ability to produce chlorophyll (which plants need in order to convert light and water into food).
Houseplants that are kept because of their foliage benefit from a higher nitrogen concentration, or a “well-balanced” fertilizer. These include ratios like 1-1-1 or 5-3-3, where the ratio is equal or slightly higher in nitrogen.
You can think of nitrogen as the nutrient that would give you healthy, glowing skin.
Phosphorous
Phosphorous is the second number in the N-P-K ratio, and it is particularly necessary for flowering plants. I use a fertilizer higher in phosphorous (1-3-1) on the Hoya and Aeschynanthus in my collection.
Phosphorous should be present in all of your houseplant fertilizers, however, because it is also responsible for healthy growth overall.
You can think of Potassium as the reproductive system. It is vital for the growth of roots and reproductive structures.
Potassium
Potassium is the driving force for plants to open and close their stomata (essentially pores on plants that allow plant cells to breathe).
You can think of potassium as the skeletal and immune systems. Potassium keeps plants strong and healthy as sort of a behind the scenes player. It helps with disease and pest resistance as well as the strength of the overall plant tissue.
Fertilizer Types
Liquid
Liquid fertilizer is my preference because of the control you have. I mix my fertilizer with water and I like that I can see it in the water before I dose my plants.
Granular
Granular fertilizers are mixed into the soil or dressed atop the soil in the pot.
It can be hard to determine how much fertilizer your plant is receiving when using granular fertilizer. I typically only use granular outdoors.
Stick/Slow Release
These are a real bother to me. I don’t know exactly why I hate them so much to be honest.
I don’t like that they stick into one place in the pot and stay there. I prefer an even application of fertilizer, even though I’ve never read or heard of anything that would say even application is more beneficial.
They also last for six months, sometimes more, and I can barely remember when I last gave my dog her monthly flea treatment, I know I am not going to remember to change out those little sticks.
They also cost more upfront and I just find them creepy…
Purchasing Fertilizer
I have lots of favorites, but I found this list to be the most helpful because I personally love the brands they included and the descriptions under each one.