- Best Fertilizer: The Effects of Fertilizer on Plant Growth
- What is fertilizer and why do plants need it?
- What are fertilisers?
- Essential elements that plants need
- Fertilisers replace essential elements
- The early fertiliser industry
- Adding nitrogen
- Fertilisers now
- Effects on the environment
- Nature of science
- Plant Care: Fertilizer
- You know your new plant needs the right light and just enough water, but what about fertilizer? While it can be great for plants in the long-term, it is by no means a daily requirement or a cure-all vitamin. Let’s take a closer look at fertilizer, different types and when you should and should not use it.
- Fertilizer is Not Food
- What is it Good For?
- How to Choose?
- Solid, Liquid, Organic
- Six Quick Tips for Fertilizing
- Houseplant fertilizer basics: How and when to feed houseplants
- When to feed houseplants
- The best houseplant fertilizer schedule
- Spring houseplant fertilizer schedule:
- Summer houseplant fertilization schedule:
- Fall houseplant fertilization schedule:
- Winter houseplant fertilization schedule:
- What’s in houseplant fertilizer?
- Ingredients in houseplant fertilizers
- Types of houseplant fertilizer
- Liquid houseplant fertilizer
- Granular houseplant fertilizer
- Slow-release houseplant fertilizers
- Houseplant fertilizer in a nutshell
Best Fertilizer: The Effects of Fertilizer on Plant Growth
- 12 bean seeds
- 4 small pots
- Potting soil
- 3 organic fertilizer sticks
- Face mask
- Old pan
- Old tea towel
- 1 tablespoon water
- Permanent marker
- Spray mister
- First, place potting soil in four small pots. Make sure that you have the same amount of soil in each pot.
- Place three bean seeds into each pot. Make sure that the soil in each pot is damp.
- Label the first pot “control”. This pot does not get any fertilizer.
- To create the fertilizer for the other three pots, put on your face mask and place a small stick of indoor plant fertilizer in an old pan.
- Place an old tea towel on top.
- Pound the stick with your hammer until it is a powder. Put the powder aside.
- Do the same thing with another stick of fertilizer. Put the powder into a small cup and mix this fertilizer with a tablespoon of water.
- Label the other three pots “liquid,” “solid,” and “powdered”. Place the liquid fertilizer in the first pot, place a solid stick of fertilizer into the second pot, and place the powdered fertilizer on top of the soil in the third pot.
- Now, watch your beans grow! After 4 days, carefully remove the seeds from the pots without losing track of which seeds came from which pots.
- Use a ruler to measure the length of each seed’s sprout. What pot produced the seeds with the longest sprouts?
- If you wish, replace the seeds and continue your observation for several more days.
Liquid fertilizer is the best fertilizer: the plants that receive the liquid fertilizer grow the best.
Just like people, plants need nutrients to grow. In a typical fertilizer, you’ll find lots of nitrogen, phosphorus, and potassium. These primary nutrients help plants grow new cells, and many enable different growth and food production processes to happen. If you choose a good quality fertilizer, it will also contain many other nutrients, including secondary nutrients like calcium, magnesium, and sulfur. Calcium helps plants grow roots and stand up straight. Magnesium helps plants make chlorophyll, which helps plants make food through photosynthesis. Sulfur is an important part of different proteins and plants enzymes. Plants also need very tiny amounts of trace elements like boron, copper, iron, chloride, manganese, molybdenum, and zinc as well.
The liquid fertilizer has tiny pieces of fertilizer held in suspension in the water. Placing the fertilizer into a liquid base helps that fertilizer move through the soil to the bean seed. It also helps the plant move nutrients around.
Think about it this way: the water in our bodies helps us move nutrients around, and same goes for plants. Plants need water to move nutrients from the soil into the plant. Osmosis is a process in which nutrients move from areas of low concentration to areas of high concentration. This process allows nutrients to move from the soil into the center of a plant’s roots where there are more nutrients.
Once the water and nutrients are inside the xylem tissue of the plant, the xylem acts as a tube that sends the water and nutrients up into the stem. The water molecules connect to each other through a process called adhesion, and as molecules cling together, they move up through the plant. The water becomes a long, cohesive column, and as water moves out of the plant’s leaves when the plant transpires, a new batch of nutrient-carrying water moves upwards.
Water and nutrients go hand in hand. Allowing nutrients to move through the soil in suspension helps those nutrients move more easily, and it also helps the plant use those nutrients to grow.
What is fertilizer and why do plants need it?
In order for a plant to grow and thrive, it needs a number of different chemical elements. The most important are:
- Carbon, hydrogen and oxygen – Available from air and water and therefore in plentiful supply
- Nitrogen, phosphorus, potassium (a.k.a. potash) – The three macronutrients and the three elements you find in most packaged fertilizers
- Sulfur, calcium, and magnesium – Secondary nutrients
- Boron, cobalt, copper, iron, manganese, molybdenum and zinc – Micronutrients
The most important of these (the ones that are needed in the largest quantity by a plant) are nitrogen, phosphorus and potassium. If you have read the articles How Cells Work and How Food Works, you have heard about things like amino acids, cell membranes and ATP. Nitrogen, phosphorus and potassium are important because they are necessary for these basic building blocks. For example:
- Every amino acid contains nitrogen.
- Every molecule making up every cell’s membrane contains phosphorous (the membrane molecules are called phospholipids), and so does every molecule of ATP (the main energy source of all cells).
- Potassium makes up 1 percent to 2 percent of the weight of any plant and, as an ion in cells, is essential to metabolism.
Without nitrogen, phosphorus and potassium, the plant simply cannot grow because it cannot make the pieces it needs. It’s like a car factory running out of steel or a road crew running out of asphalt.
If any of the macronutrients are missing or hard to obtain from the soil, this will limit the growth rate for the plant. In nature, the nitrogen, phosphorous and potassium often come from the decay of plants that have died. In the case of nitrogen, the recycling of nitrogen from dead to living plants is often the only source of nitrogen in the soil.
To make plants grow faster, what you need to do is supply the elements that the plants need in readily available forms. That is the goal of fertilizer. Most fertilizers supply just nitrogen, phosphorus and potassium because the other chemicals are needed in much lower quantities and are generally available in most soils. Nitrogen, phosphorus and potassium availability is the big limit to growth.
The numbers on a bag of fertilizer tell you the percentages of available nitrogen, phosphorus and potassium found in the bag. So 12-8-10 fertilizer has 12-percent nitrogen, 8-percent phosphorous and 10-percent potassium. In a 100-pound bag, therefore, 12 pounds is nitrogen, 8 pounds is phosphorous and 10 pounds is potassium. The other 70 pounds is known as ballast and has no value to the plants.
So why don’t people need fertilizer to grow? Because we get everything we need from the plants we eat or from the meat of animals that ate plants. Plants are factories that do all of the work to process the basic elements of life and make them available to us.
To get more information on fertilizer and other related topics, check out the links below.
Just as we have essential needs for our growth, plants also have essential needs for their survival. These include:
- appropriate temperature.
As long as plants have water, carbon dioxide and sunlight, they are able to photosynthesise. This means that a chemical reaction takes place within plant leaves to produce glucose (food) and oxygen. The glucose is broken down by enzymes in the plant to provide the energy that causes it to grow. But plants also need nutrients (chemical elements) from the soil to help them grow. These nutrients are often added to the soil in the form of fertilisers.
What are fertilisers?
Fertilisers are chemicals that are added to soil to supply nutrients to make it more fertile. The chemicals in fertilisers contain essential elements required for plant growth.
Essential elements that plants need
Plants need many different elements for their growth. Carbon, hydrogen and oxygen are available from air and water. Nitrogen, phosphorous, potassium, sulfur, calcium, magnesium and sodium are also needed for plant growth. In addition, plants need very small amounts (trace elements) of boron, copperiron, cobalt, manganese, molybdenum, chlorine, iodine, selenium and zinc for healthy growth. Some elements may not be needed for plant growth but may be important for the nutrition of grazing animals.
Nitrogen, phosphorus and potassium are the most important elements because they are:
- building blocks for cells in the plants
- needed in the greatest quantities
- often depleted in New Zealand soils.
Fertilisers replace essential elements
Fertilisers supply plants with the elements that may be missing or in short supply in a form that can be used by the plants for faster growth. Most fertilisers supply nitrogen, phosphorus and potassium. The other elements needed by plants are required in much lower quantities (trace elements) and are generally available in most soils. In nature, nitrogen, phosphorus and potassium often come from the decay of plants that have died.
The early fertiliser industry
Forests were burnt to clear the land. The ash provided a source of nutrients, but once these were depleted, pastures and crops began to fail. Early farmers added chemical elements to the soil by adding compost, animal manure, dried and ground animal blood and bone or ground nutrient-rich rocks mixed with chemicals that allowed the plants to absorb the nutrients.
Superphosphate is an artificial fertiliser and is the most important fertiliser used in New Zealand. Farmers often shorten its name to ‘super’.
Superphosphate was developed to address the shortage of phosphorus in soil. It is made by reacting finely ground phosphate rock with sulfuric acid. In this form, phosphate is rapidly released into the soil, where it can be used by plants. Superphosphate manufacture began in New Zealand in 1882, and over 3 million tonnes are produced annually. The main nutrients in superphosphate fertiliser are calcium, sulfur and phosphorus.
Potash (potassium chloride) is often combined with superphosphate to provide potassium. The nutrients in superphosphate promote the growth of clover. The clover then converts nitrogen gas in the atmosphere to the essential plant-available nitrogen.
Farming has become increasingly more intensive (more is produced from the same size piece of land) due to the cost and availability of land and demand for produce. Compared to clover, manufactured nitrogen fertiliser was found to be more productive (because it could be applied at just the right time to increase production). Urea CO(NH22) became the main nitrogen fertiliser, particularly on dairy farms. Diammonium phosphate (NH42HPO4), more commonly known as DAP (invented in the 1960s), contains both nitrogen and phosphorus and is now in common use.
Fertiliser companies now often blend superphosphate with potash and add forms of nitrogen such as ammonium sulfate (if needed). Other elements may be added in. Different nutrient combinations are made depending on the needs of the soil and plants.
Effects on the environment
Water quality is a concern and focus of research. Run-off from farms can carry nutrients from fertilisers (and animal effluent) into waterways. The nutrients stimulate plant growth in streams, rivers and lakes, which can upset the balance of natural flora and fauna and affect water quality.
Farmers try to balance their fertiliser use to manage production while minimising nutrient loss through leaching to surface and groundwater.
Nature of science
The application of science has certain impacts on the environment and on society. Sometimes, there are impacts that were not intended and could be harmful. The understanding of nutrients and the introduction of fertilisers significantly helped farmers increase their production. Fertilisers solved a problem but created another one – pollution in the wider environment.
Plant Care: Fertilizer
Fertilizer is Not Food
Plants make their own food using light in a process called photosynthesis. Fertilizer is more like a vitamin you would take every so often to boost your health (it’s essentially a mixture of minerals). Minerals from soil are released every time you water so your plant can absorb all that goodness. Excess minerals from fertilizer will not be used by your plant and can even damage it.
What is it Good For?
Fertilizer replaces essential nutrients your soil will eventually lose over time. You’ll want to add nutrients back into the soil via fertilizer to keep those levels up and your plant healthy. If you have a plant like an orchid that uses peat moss or bark chips instead of soil, you’ll want to add nutrients less often because orchids are epiphytes — a plant that grows on another plant and depends on it for support but not food. Recently potted plants and low-light plants will not require fertilizer. And of course, neither will dead ones. No worries on that front; it’s just time for a new plant.
How to Choose?
When looking for a fertilizer, the brand name is not important. What is important is the N-P-K ratio. N for nitrogen, P for phosphorus and K for potassium are the key macronutrients your plant needs. N-P-K will look something like 15-30-15. Fertilizers with higher ratios are more concentrated than those with lower ratios. Your fertilizer may also have micronutrients, making it a complete fertilizer. These can include calcium, magnesium, boron, iron, zinc, sulfur, nickel, manganese, copper and molybdenum. Each micronutrient serves a role in plant enzymatic, cellular and developmental processes.
Solid, Liquid, Organic
Fertilizers come in different forms: liquid or powder, time-release pellets or organic. Liquids and powders are the most common, most cost effective and easiest to use. You can also dilute them with a little or a lot of water, depending on your plants needs. Time release pellets last a long time — about 3 to 6 months — and release small doses of nutrients every time you water, but you can run the risk of over-fertilization here. Stay cautious of a quick fix.
Chemical fertilizers are made from ground up minerals and formulated with a near-perfect amount of each macro and micro nutrient. They are also more concentrated and usually more affordable than say, organic types.
Organic fertilizers contain all natural ingredients and are the most mild of all. Organic fertilizers obviously have some decaying organism so naturally, they stink. Make sure that organism is 1. worth the stench and 2. providing the right amount of nutrients for your plant. You can DIY it or, for the less adventurous, buy it readymade. Organic fertilizer can be a little more costly than other types, but it’s chemical-free alternative.
Organic and chemical fertilizers do the same thing in different ways: delivering nitrates, potassium ions, and phosphates to plants. One is not necessarily better than the other, but if you’re living that clean green life, go for organic. It’s a balance of personal preference — both yours and your plants’.
Six Quick Tips for Fertilizing
Tip 1: Spring is the best time to fertilize plants because that’s when they do the most growing. Plants that grow faster, like begonias, should be fertilized more often than plants that grow slowly, like a cactus, or are dormant, i.e., all plants in winter.
Tip 2: Dilute your fertilizer. It’s always best to under-fertilize than over-fertilize. If there is a nutrient deficiency in the soil and you have not fertilized in a year or so, you can increase the potency by adding less water when you’re diluting the fertilizer.
Tip 3: Plants that give us fruits or flowers will require more fertilizer in their lifetimes. When we pick off fruits or flowers, we are taking away those nutrients and should restore them.
Tip 4: Know your N-P-K values. That’s the ratio of macronutrients your plant needs and what should be in your fertilizer. It looks something like 10-15-10. If you don’t see this on the package, find another fertilizer stat.
Tip 5: Micronutrients are just as important as macronutrients, plants just need less of them. They are found in fertilizers and that’s great because each micronutrient plays a part in plant enzymatic, cellular and developmental functions.
Tip 6: Organic or chemical fertilizer? It’s your call. Make sure your organic fertilizer has organisms that provide the right amount of nutrients for your plant. Chemical fertilizers are formulated with the near-perfect amount of marco and micronutrients and may be your best bet especially if you are new to the whole fertilizing thing.
Keep growing your plant knowledge.
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Houseplant fertilizer basics: How and when to feed houseplants
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Being a houseplant parent can be confusing business! Unlike human babies, houseplants don’t cry when they’re hungry or uncomfortable. Instead, they respond to their environment in different, far more subtle, ways. Knowing when it’s time to feed houseplants is challenging stuff, even for long-time houseplant growers. Today, I’d like to review the basic ins and outs of houseplant fertilizer, and cue you in on how and when to feed your houseplants.
When to feed houseplants
Houseplants wilt when they need water. Their leaves grow pale and lanky when they aren’t getting enough sunlight. When the humidity is too low, they turn crispy; when it’s too high, they may develop rot. But, knowing when your houseplants need to be fertilized is far trickier. There’s no clear signal from your plant that shouts “Hey, it’s time to feed me!”, other than perhaps slowed or stagnant growth, which for many houseplant parents, is barely noticed. So, instead of waiting for a signal from the plant, you’ll have to take matters into your own hands and use houseplant fertilizer on a schedule that’s based on their growing cycle.
The timing of houseplant fertilizer applications should follow the seasons and their growth habits.
Each specific houseplant has slightly different needs when it comes to houseplant fertilizer amounts and frequency, but there’s no need to overly complicate the process. Yes, you could study up on each individual houseplant species you care for, determining its specific nutritional needs, but the truth is that the vast majority of common houseplants have fertilizer requirements that are similar enough that treating them in a singular way is more than enough to satisfy their nutritional needs. Some houseplants are heavier feeders than others, it’s true. But, a houseplant fertilizer schedule like the one found below, offers a good balance that both satisfies heavy feeders and keeps you from going overboard with those houseplants that require lower amounts of fertilizer.
Here’s the best fertilizer schedule for most common houseplants. It’s based on the cycle of the growing season, which, though they are inside where temperatures are more consistent, influences houseplants much the same way it influences outdoor plants.
Water-soluble liquid houseplant fertilizers are applied only during periods of active growth.
The best houseplant fertilizer schedule
In a bit, I’ll discuss different houseplant fertilizer products mentioned here and how to apply them, but here’s the low-down on when they should be used.
Spring houseplant fertilizer schedule:
- Start fertilizing houseplants about 8 weeks before the last expected spring frost. For example, here in Pennsylvania, where I live, the danger of spring frost typically passes around May 15th. This means I begin to fertilize my houseplants in mid-March. This is when the days begin to lengthen noticeably and houseplants shift from a semi-dormant state into a period of active growth.
- The first three fertilizer applications should be made at half the recommended strength. If it’s a granular product, use half the amount suggested on the label. If it’s a liquid houseplant fertilizer, mix it to half strength (more on these two types of fertilizers in a bit). This feeds houseplants at a time when they’re really just gearing up for active growth and they don’t yet require larger amounts of nutrients to fuel prolific growth.
Summer houseplant fertilization schedule:
- When summer arrives, it’s time to switch to a more regular houseplant fertilizer program.
- Base the frequency of summer fertilizer applications on the type of fertilizer you’re using.
- Liquid fertilizers are applied more frequently, bi-weekly or monthly, for example.
- Granular products are used less frequently, perhaps once every month or two.
- Slow-release houseplant fertilizers break down slowly and release their nutrients in small amounts, over a longer period of time. A single application of most of these products lasts for three to four months.
Liquid organic houseplant fertilizer is a great choice because it’s made from naturally derived ingredients.
- Follow this schedule regardless of whether you move your houseplants outdoors for the summer or not. Houseplants are in a state of active growth when summer light levels are high, regardless of whether they’re exposed to the consistent temperatures of a home environment or the ups and downs of sitting out on a patio or terrace.
Fall houseplant fertilization schedule:
- About 8 weeks before your first expected fall frost, taper off your houseplant fertilizer amounts and frequency. At my house, that means starting in mid-August, I reduce the amount of fertilizer by half and start extending the amount of time between fertilizing for about 3-4 applications, which typically takes me to about the time of winter’s arrival.
Winter houseplant fertilization schedule:
- None. Houseplants are not in a state of active growth during the winter and therefore should not be fertilized. Doing so can lead to fertilizer burn and brown leaf tips (more on why this happens here).
Don’t fertilize houseplants, such as this large spotted Dieffenbachia, during the winter when they’re not in a period of active growth.
Two exceptions to these rules:
- If you live in a climate that does not receive regular winter frosts, continue to fertilize houseplants all winter long, but do it at half the strength and frequency of your summer applications. Again, this is due to light levels more than temperatures.
- And, if you live in a tropical climate, where it’s warm all the time, keep your houseplants on a summer fertilization schedule year-round.
What’s in houseplant fertilizer?
Most houseplant fertilizers contain a mixture of both macro- and micronutrients. The three primary macronutrients, nitrogen, phosphorous, and potassium, found in a container of fertilizer are listed as a ratio on the front of the bottle or bag. Called the N-P-K ratio, these numbers tell you the percentage of each of those nutrients inside the container. The ratio of these macronutrients in a tomato fertilizer or a lawn fertilizer is different than the ratio found in a houseplant fertilizer as each of these groups of plants has different nutritional needs. This means using a fertilizer formulated specifically for houseplants is a must. That should be the first thing you look for when purchasing houseplant fertilizer. It should say “for houseplants” somewhere on the packaging.
The ratio of N-P-K is on the label of every houseplant fertilizer. This one is higher in P, making it good for blooming plants like African violets.
Phosphorous (the middle number on the container) is essential for flowering. Houseplant fertilizers for flowering plants should have a slightly higher amount of phosphorous in them (1-3-1, for example). Those used on green houseplants that don’t typically produce flowers, should be slightly higher in nitrogen. They may also contain a balanced ratio of nutrients (5-3-3 or 5-5-5, for example). I typically use one houseplant fertilizer for my flowering houseplants and a separate one for non-flowering types. This isn’t necessary unless you’re growing flowering houseplants like African violets, begonias, or gloxinia.
Many, but not all, fertilizers also contain secondary macronutrients, like calcium and magnesium, as well as micronutrients, such as iron, zinc, and boron. These nutrients are used in smaller amounts than the primary macronutrients of N, P, and K, but they are still essential to every plant’s metabolic pathway. You’ll want to be sure your houseplant fertilizer contains a small amount of these nutrients as well.
Houseplants won’t tell you when they need to be fertilized, so you’ll need to put them on a schedule.
Ingredients in houseplant fertilizers
The ideal houseplant fertilizer is made from naturally derived sources of these macro- and micronutrients, not made from chemicals synthesized in a laboratory. Though those blue, water-soluble fertilizers are commonly recommended, they aren’t the most eco-friendly source of nutrition for your plants, nor do they contain any micronutrients. Instead, turn to either a liquid or granular houseplant fertilizer made from natural ingredients to feed your houseplant babies.
Organic plant fertilizers are made from plant-, animal-, and mineral-based components.
Types of houseplant fertilizer
Now that you know when to fertilize houseplants and what nutrients houseplant fertilizers should contain, it’s time to look at the different types of houseplant fertilizer to determine which one is right for you.
Liquid houseplant fertilizer
They need to be used a bit more frequently than granular fertilizer, but organic liquid houseplant fertilizers are my personal favorites. Brands like Grow!, Espoma’s Indoor Houseplants, Liquid Love, and Jobes Water-soluable All-Purpose Fertilizer contain ingredients derived from plants and animals, as well as from mined minerals. Liquid fertilizers also come with a reduced risk of fertilizer burn. Another benefit of using liquid fertilizers made from naturally-occurring ingredients is that in addition to providing a houseplant with nutrients, they also act as growth enhancers. They are full of dozens of micronutrients, trace elements, vitamins, amino acids, and plant hormones, each of which plays a vital role in the health and vigor of your houseplants.
Organic liquid houseplant fertilizers are made from liquid kelp, fish emulsion, compost tea, worm tea, liquid bone meal, rock phosphate, plant extracts, and humic acids, to name just a few.
Liquid and water-soluble houseplant fertilizers are mixed with irrigation water and applied to plants.
Granular houseplant fertilizer
Granular fertilizers for houseplants are found in one of two formulations: as loose, granular pellets or as compressed fertilizer “spikes.” Pelletized granular fertilizers for houseplants, such as Organic Plant Magic and Be-1, are sprinkled on the surface of the soil. Compressed fertilizer “spikes,” such as Jobes Organic and EarthPods, are pushed down into the soil to come in close contact with plant roots.
The best pelletized and compressed granular houseplant fertilizers are made from naturally derived ingredients. These include dehydrated worm castings, bone meal, blood meal, sulfate of potash, limestone, rock phosphate, and other animal-, mineral-, and plant-based ingredients. Synthetic chemical-based granular fertilizers are available for houseplants, too, though I avoid them. A quick check of the ingredient list on the label tells you what the fertilizer is made from. If you don’t see any ingredient list at all, it’s a synthetic fertilizer.
Houseplant fertilizer spikes are easy to insert into the soil.
Slow-release houseplant fertilizers
Also called time-released fertilizers , slow-release houseplant fertilizers are made from a synthetic source of nutrients. The liquid nutrients are encapsulated in a coating. This coating breaks down slowly and releases the nutrients in low doses over a long period of time. Products like these mean you’ll be fertilizing less frequently. It’s very convenient, but do be aware that they aren’t made from eco-friendly ingredients.
The coating on slow-release fertilizers mean the nutrients are available to plants for a long period of time. However, they are chemically derived.
Houseplant fertilizer in a nutshell
As you can see, fertilizing houseplants doesn’t have to be an overly complex practice. Use the right products and apply them according to a seasonal schedule, and your houseplant family will be as happy and healthy as can be.
For more on houseplants, check out the following articles:
Apartment Plants: The best houseplants for apartment living
Air Plant Care: How to tend, water, and fertilize Tillandsia
Tips for repotting a Phalaenopsis orchid
Easy projects for mini holiday houseplants
How do you feed your houseplants? We’d love to hear about it in the comment section below.