We are going to dig into what fertilizer is made of, why it's important, and some different brands to check out. Fertilizer can be underrated and, if used properly, could really help your plants grow to their fullest potential.
The main ingredients: NPK
The three sequence of numbers on your fertilizer can give you insight to what its focus is. These are usually known as the main ingredients of the macro-ingredients in fertilizer. The main ingredients are the chemicals Nitrogen, Phosphorus, & Potassium usually referred to as their chemical symbols, NPK.
Other macro ingredients include sulphur (S), magnesium (Mg), & calcium (Ca).
Nitrogen (N): This would be the first number in the sequence which encourage foliage and stem growth.
Phosphorus (P): This is the second number in the sequence which promoted bloom and bud growth.
Potassium (K): This is the third and last number in the sequence which is essential for root function, stem strength and overall stress tolerance. It also supports the plants ability to take up moisture and nutrients.
If you want to choose a fertilizer that has a specific focus, you would find one where the main ingredient has the highest number in the sequence. For example, if you chose a fertilizer with a sequence of 10-5-5, you would be choosing a fertilizer that encourages foliage and stem growth (high nitrogen).
The sequence of numbers represent the ratio of nutrients in the fertilizer. For example, if you has 1LB bag of granular fertilizer with a sequence of 10-5-5, then you would have 0.10 LBS of Nitrogen, 0.05 LBS of Phosphorus, & 0.05 LBS of Potassium with your LBS bag of fertilizer (note- it can also be seen as a percentage). The rest of the bag of fertilizer would contain micro nutrients and usually filler material.
Micro nutrients can be iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chloride (Cl), nickel (Ni).
Why is fertilizer important for houseplants?
Plants derive most of their initial nutrients from the soil they are planted in. Outdoor plants are constantly getting a replenishment of nutrients from the environment around them. Since houseplants aren't getting the natural nutrient replacement, fertilizer helps add back the nutrients as they are depleted from their soil.
Beyond using your liquid or granular fertilizer, you can top dress you soil with brand new soil to help add those nutrients back as well.
Overfertilizing
I usually practice putting about 3/4 the recommended amount of my liquid fertilizer when I am watering already but keeping it to about 1/2 - 3/4 the recommended amount should help prevent overfertilization.
If you are overfertilizing, you may experience browning leaf tips, browning roots, wilting, or even deformed leaves. Annoyingly, these are all symptoms of other potential houseplant issues so it can be hard to tell.
Does foliar feeding work?
Yes it actually does! Gynelle Leon said it is "instant way of providing plants with essential nutrients as the leaves absorb moisture more readily." Essentially there are openings on your plants leaves called "stomata" that have a main function of accepting carbon, hydrogen and oxygen through the foliage. The stomata can also bring in nutrients in the form of fertilizer.
This SHOULD NOT replace your normal fertilizing regimen. The best way to do this is find a brand you like that sells a specific foliar fertilizer or you can heavily dilute the liquid fertilizer you already use.
Fertilizer Brands & Companies
There is a wide range of fertilizer companies from large, well known companies to small businesses! There is NOTHING wrong with using any of those brands! I start getting suspicious when fertilizer companies starting trying to sell you a specific plant fertilizer like "Fiddle Leaf Fig fertilizer."
FoxFarm Soil & Fertilizer Company: I personally love this brand and have continued to use their soil and fertilizers for years. They do not sell to big box stores so you can find them through their Amazon shop, local plant shops, or garden centers.
Espoma: This is a larger organic fertilizer company that can be found almost anywhere. For houseplants, their liquid fertilizer works great and is reasonably priced.
Miracle Gro: This is one of the largest retail fertilizer companies but for a reason! They sell a product that works at an affordable price. You can find these products literally everywhere. Osmocote is brand under Miracle Gro that sells a great slow release fertilizer.
Dr. Earth: This is another larger organic fertilizer brand that sells a wide range of fertilizers that aren't all specific to houseplants (similar to FoxFarm).
Dyna-Gro: I've known several houseplant lovers to use this fertilizer as a great all purpose product and brand
Arbor: This is another organic company that has a nice range of essential fertilizers and nutrients beyond houseplant care. You can purchase it online, your local plant shop, garden centers or at some larger stores like Target or Walmart.
We the Wild Plant Care: This is a small business that sell only a few products that are the essentials to plant care. You can usually find this at your plant shops.
Happy Happy Houseplant: Another small business with one liquid concentrate fertilizer.
Flourish: Is another small business with one liquid concentrate fertilizer
Urban Gardener: This is another small business that sells all houseplant sprays. This is a great option for foliar feeding!
Maxsea: This is a great option for a seaweed based fertilizer.
Neptune: This is another great seaweed and fish fertilizer option.
A few more to mention are Jack's, Joyful Dirt, Schultz, Jobe's, Bonide, & Southside Plants.
Other Facts
I recommend fertilizing during the active growing season and significantly reducing it during the rest of the month. I fertilize about every 2 weeks (based on my package instructions), starting around the end of February through the beginning of October. I only fertilize once or twice in winter because the plant isn't as active.
It is best to feed plants while they are moist. Dry soil conditions could cause the plants to take up more fertilizer while watering first will allow the plant to replenish before using the fertilizer.
There can stress caused buying a new plant and moving into a new environments. Its encourage to hold off fertilizing a little bit.
After repotting a plant or replacing the soil, I was recommend waiting at least a month before fertilizing. This is because the brand new soil contains the nutrients your plant need to sustain it for a period of time and to help reduce stress.
Instagram Q&A
I always ask followers if they had any specific questions, opinions or hot-takes I can address in this podcast and blog. Here are the questions and answers for this topic:
"Water from the fish tank. All plants love it. Begonias bloom three days after every time"
This is also a great alternative! If you don't have a fish tank to pull from, using a fish emulsion fertilizer or seaweed fertilizer can be a good alternative. The University of Illinois says "A possible benefit of fish emulsion, and many of the organic-based fertilizers, is that they offer protein to feed our soil microorganisms, which may help to build a more robust soil food web resulting in improved plant health for the long term"
Keep in mind there is a fishy smell so use sparingly and monitor your pets who also may be interested in the smell.
"Fav fertilizer: Happy Happy Houseplant"
YES! Support small business! I linked their website above!
"I use miracle gro but its because I'm overwhelmed by the options for fertilizers?"
Absolutely nothing wrong with this! Just like I say for soil, there isn't one main option you need to use or one solution. As long as you are following the instructions or using slightly less than the recommended, you should be good!
"Fav fertilizer: Miracle Gro Indoor and Miracle Gro Orchid- the Miracle Gro pump right into soil, and orchid spray. Probably not the best, but easy and I haven't burned anything as far as I know!!"
Like I said above, this is still great! I am suspicious that it allows you to pump the fertilizer directly onto your soil but as long as you are watering that in, it's fine! The ratio is only 1-1-1 so its a great balanced fertilizer that shouldn't burn.
"How long after repotting should I wait to fertilize a plant?"
I would wait at least a month after repotting to fertilize your plants.
"I use a miracle grow 'basic plant' fertilizer because I bought a large box of it... back when I just had plants because that is what you do... now that I have developed more of a hobby, I know that there are better options and will be taking notes for when I finally finish off the never ending box! I have compost for my outdoor plants, which if it is a finicky plant, I will occasionally use too."
This is all great! Saving some money and buying in a larger quantity is also a great option! Especially if you have many plants in your home and outdoors! Compost is great as well, similar to replenishing the top of soil.
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Love, Holly (Owner & Creator of Houseplant Homebody LLC)
Here are some of the resources I used in this episode/blog:
International Fertilizer Association- specifically for macro & micro nutrient chemicals. This article has a TON more good information micronutrients as well.
Plant: Houseplants: Choosing, Styling, Caring by Gynelle Leon
University of Illinois- Scale up your garden’s health with fish emulsion fertilizer
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