Feed Me: The Key to Understanding Why & When to Fertilize Plants
Posted on August 22 2021
Fertilizer: You probably have an idea of what it is, right? Plant food! Well, that’s the wrong answer, actually. So, what is it? Why should you fertilize your plants? And how can you do it (without sending your leafy friend to the graveyard)?
What is it & Why Should You Fertilize Your Plants?
In a word: nutrients. Isn’t that the same as food? Not really. Your plant feeds itself through photosynthesis (leaves turn chlorophyll and oxygen into sugar) and respiration (roots turn sugar, oxygen, water, and carbon dioxide into usable energy).
So, why does your plant need more nutrients? Think of fertilizing your plant like you’re giving it a vitamin to boost its performance. For example, Nitrogen is a crucial ingredient of chlorophyll. Phosphorus is involved in sugar formation. Both are important in photosynthesis, and they are two of the predominant macronutrients of fertilizer. If you’re running low on nutrients, your plant will struggle to make the food it needs.
In a nutshell: Your plant needs the food it naturally produces and the nutrients from fertilizer to maintain continuous, healthy growth.
What are the components of fertilizer?
There are three macronutrients contained in fertilizer: nitrogen, phosphorus, and potassium. When you’re reading a fertilizer’s label, you’ll likely come across a number like this: 9-3-6. What does it mean?
That is the percentage of Nitrogen - Phosphorus - Potassium (aka by their elemental abbreviations n-p-k) contained in the fertilizer. Do you have a plant that requires a “balanced fertilizer?” That means all the numbers should be the same (such as 10-10-10).
Fertilizers that have large percentages (numbers) are more concentrated. The advantage? You often get more bang for your buck! The disadvantage? You have to be careful to dilute them properly.
Both organic and inorganic fertilizers also contain micronutrients, which benefit your plant! These should include calcium, magnesium, and sulfur.
What do Nitrogen, Phosphorus, and Potassium do?
Nitrogen amps up foliage production, phosphorus is for flowers, and potassium contributes to a healthy root system (and helps the plant handle stress-related issues, like pests and disease).
Do you want to encourage your flowering houseplant to bust out the blooms? Select a fertilizer with higher levels of phosphorus. The good news? Many flowering plants (like African Violets) have pre-made fertilizers to boost buds. Pick a fertilizer with a lower phosphorus content if you’re growing a flowering plant for its showy foliage instead of its blossoms.
Which Type of Fertilizer Should You Choose?
There are three different types of fertilizer to choose from:
- Liquid fertilizer is an additive to water. It can either start out as a liquid or a dissolvable powder. The downside? You will have to apply liquid fertilizer frequently (usually with each watering or every other, depending on the product instructions). The upside? This allows you to have more precision: when you decide it’s time to stop fertilizing, you stop fertilizing. These products are also usually in low concentrations, so the threat of over-fertilizing is less.
- Granular fertilizer comes in different forms, including little “pebbles” and compressed stakes. While you can find these products labeled for houseplants, they are generally used for outdoor gardens. Why? They are highly concentrated, the nutrients don’t evenly distribute in the soil, and the initial release of nutrients can shock your plant.
- Slow-Release fertilizer looks similar to “pebbly” granular products, so make sure the packaging specifies that it’s slow release. The perks? You only have to apply this fertilizer every 3-4 months (depending on the product instructions). Also, the coating thickness differs on each little “pebble,” which releases various nutrients at different times (mimicking mother nature). The downside? These products are synthetic, so it’s not for you if you’re looking for an organic option.
Our advice: If you’re a fertilizing newbie, your best bet is to purchase a liquid plant fertilizer.
What’s the Difference Between Organic and “Regular” Fertilizer?
It all goes back to origins. Organic fertilizer is derived from natural products from plants or animals (so, if you’re vegan, read the packaging carefully). “Regular” (aka inorganic) fertilizer is composed of minerals and synthetic chemicals. For instance, the nitrogen in many of these products is derived from petroleum.
Really, which you choose depends on your preference, lifestyle choices, and (sometimes) your plant. When applied correctly, both types of fertilizer are designed to benefit your plant. However, some specialty, exotic houseplants are extra sensitive, making an organic fertilizer the preferred choice.
Can Fertilizer Burn Your Plant?
Yes, it can. Both inorganic and organic products can hurt your plant by causing: burnt leaves, yellowing leaves, or brown spots. Salts contained in inorganic fertilizers pose a higher threat, especially when misapplied.
That’s why it’s essential to (1) research your plant species, (2) carefully read your fertilizer’s instructions, and (3) correctly measure the amount of product you use.
The #1 fertilizing rule: It’s safer to under-fertilize plants than it is to over-fertilize them. (Remember, your plant is still feeding itself!)
When to Fertilize Your Plant
While you shouldn’t water your plant on a set schedule, you should fertilize your plant on a set schedule. Here are a few fertilizing basics:
- Only fertilize during your plant’s growing season. In most areas, this is between March-August. Why does it matter, you ask? Even if your indoor plant isn’t experiencing low temperatures, it is experiencing less sunlight due to shorter days. Your plant naturally starts slowing down into dormancy, resting until next Spring! Fertilizing during dormancy will contribute to over-fertilization symptoms (burn, yellowing, brown spots).
- Start the first three Springtime treatments with a ½ strength dosage. Why? No one wakes up ready to eat dinner. Ease your plant into growth.
- Finish in the Fall with the last three treatments at ½ strength. Why? This will wean your plant off of the added nutrients and lull it into dormancy.
- Read up on your plant species. Many non-fussy foliage houseplants can be watered every other time with diluted liquid fertilizer prepared to package instructions. For exotic species, check out our product descriptions for specific instructions! Remember, even common Cacti and Succulents should be given fertilizer diluted to ½ strength (never more).