Most people have some indoor plants. They help clean the air and brighten up a room. You may be wondering which of the hundreds of fertilizers on the market are right for your plants. The right fertilizer depends on the plant. Here is a general guide to picking the best fertilizer for each plant you grow indoors.
Do Indoor Plants Need Fertilizer?
Yes, indoor plants need fertilizer. Because houseplants are in containers, they have a small amount of soil from which to draw nutrients. This soil gets depleted quickly. Without fertilizer, the plants will not have enough nutrients to continue to grow.
Signs My Indoor Plants Need Fertilizer
If your plants are stunted, are not growing well, do not bloom (if this plant blooms inside), and have few blooms, they probably need fertilizer. If the leaves turn yellow, they may have a nutrient deficiency called iron chlorosis. Purple tints in plants that do not usually have that are an indication they need fertilizing, too.
Types Of Indoor Fertilizers
Fertilizer comes in several forms. Here are the different types of fertilizer and their pros and cons.
Liquid
Liquids are often used with indoor plants. They start to work immediately but need to be applied every seven to fourteen days. Some liquids are ready to use, and some are concentrates. I like to buy concentrates because while they are more expensive initially, they are cheaper per application. I simply mix them with water and pour them on the soil around the plant. Most liquids are applied as a drench on the soil. This means you soak the soil with the fertilizer.
Water Soluble
Water soluble fertilizers dissolve completely in water to form a solution similar to liquid fertilizers. I use them like liquid fertilizers.
Granular
Granular fertilizer resembles little rocks. It is spread on the surface of the soil around the plant and then mixed in the top few inches of the soil before being watered in. Some granular fertilizer has slow-release components, so it does not have to be applied for up to three months. While more convenient, granular fertilizers can form a salt crust on the top of the soil if enough water is not applied when they are used. This crust repels water and also can cause salt toxicity, so it is important to use plenty of water with granular fertilizers. About every three months, I put my houseplants in the sink and flush the soil to wash any salt residue out of the soil and keep my plants healthy.
Spikes
Spikes are just granular fertilizers that are compressed into the shape of a spike. The spike is hammered into the soil so it is an inch or two below the surface. It then dissolves slowly, so you do not have to fertilize again for anywhere from a month to three months. I find spikes have the same advantages and disadvantages as granular fertilizers. I also have had problems with them arriving broken in the package or breaking while I am hammering them into the soil, so buy more than you think you will need to compensate for broken ones.
Slow-Release Fertilizer
Some granular fertilizer is coated with a substance that slowly breaks down over time. As it breaks down, nutrients are released. The advantage of slow-release fertilizer is that you do not have to apply it as often as liquid or granular fertilizer that is not coated. I try to use a granular fertilizer that is at least half slow-release. The slow-release part of the fertilizer starts working in a week to ten days.
What Should I Consider When Choosing Fertilizer?
Fertilizers can be confusing. Here are some things I consider when I choose a fertilizer.
Types of Indoor Plants
The first thing I look at is what type of plant I am going to be fertilizing. Indoor plants vary from cacti and succulents to hydroponic plants. Flowering plants, vegetables, herbs, cacti, and succulents have very different nutritional needs and water needs. There is no one best fertilizer ratio for houseplants. Using the same fertilizer for all of them will help some plants but will kill others.
In general, plants grown for their foliage will appreciate fertilizers that are higher in nitrogen, while those grown for flowers or fruit will appreciate more phosphorous. I pick a fertilizer that mentions the type of plant I want to fertilize on the label. This is especially important when I fertilize plants that are edible. In fact, it is against the law to use a fertilizer on edible plants that do not mention those plants on the label. It has to at least say “vegetables” to use it on vegetables and so forth.
Organic vs. Synthetic
Organic fertilizers feed the microbes in the soil, which break the nutrients down into forms the plant can use. Synthetic fertilizers feed the plants directly. I prefer organic fertilizers, but many good houseplant fertilizers are synthetic. Organic fertilizers can only use things available in nature and on a list of allowed substances. Further, they must be submitted to a certifying agency (USDA or Oregan Tilth are the usual ones in the United States) and certified organic. Some fertilizers are made of all-natural ingredients, but the companies have not gone to the expense of getting them certified organic. They cannot be used in organic gardening just like synthetic fertilizers.
Frequency of Use
I also look at the frequency of use. Granular and spike fertilizers do not usually have to be used as often as liquid or water-soluble fertilizers. However, granule and spike fertilizers are more likely to cause salt crusts on the top of the soil. I prefer liquid and water-soluble fertilizers for my houseplants for this reason, even though I have to use them more frequently.
The 10 Best Fertilizers For Indoor Plants
The best house plant fertilizer is harder to choose than the best fertilizer for berries or some other category of plants because the plants can be so different. Here are my choices for the best fertilizers in various categories.
1. Neptune’s Harvest Fish & Seaweed Fertilizer – Best Liquid Fertilizer For Indoor Plants
Neptune’s Harvest Fish-Seaweed Blend Fertilizer is my pick for the best liquid fertilizer for indoor plants. The NPK ratio is 2-3-1. In addition, it has over sixty major and minor nutrients and amino acids to promote lush plant growth. These growth-promoting substances enhance plant development, color, and vigor. Seaweed has been found to enhance a plant’s ability to resist heat and drought, as well as early frost. Neptune’s Harvest Fish-Seaweed Blend Fertilizer is certified organic. Keep the concentrate away from pets and children.
Anthony Parco, Sr., started Neptune’s Harvest in 1986 in an effort to use the seventy percent of an ocean fish that is left after the fillets are removed. Neptune’s Harvest cold presses the fish to avoid damaging the vitamins, minerals, and amino acids in the fish and seaweed used in the fertilizer.
Before use, shake the container well. Mix only enough for that day because it doesn’t store well. When using, do not let the fertilizer sit in the saucer below the pot or it can burn your plants.
For houseplants, mix one tablespoon of fertilizer with one gallon of water. Soak the soil around the plant. Use weekly. I use this half-strength for my seedlings and sensitive plants to avoid burning them. You can burn your plants if you mix the concentrate too strong.
I use Neptune’s Harvest Fish-Seaweed Blend Fertilizer for both adult houseplants and seedlings I am starting inside. It is available in a quart bottle, 1 gallon, 5 gallons, and a 55-gallon drum. A quart is reasonably priced and lasts me a long time.
When you take the cap off of the bottle, the fish smell is overpowering. However, when the fertilizer is mixed with water and applied, you can smell a slight fish odor for a few hours, but it is not noticeable after that. My dog has been very interested in my houseplants for several days after I use this fertilizer; however, so if you have pets that bother your houseplants, this might not be the fertilizer for you.
One problem is the lack of a measuring method in the package. One cap is about one tablespoon, but if you use the cap you have to wash it well afterward, or you get smelly stuff all over the outside of your fertilizer bottle. Otherwise, you have to dedicate a tablespoon measure to this fertilizer.
Pros:
- Organic
- Encourages vigorous growth
- Over 60 major and minor nutrients and amino acids
Cons:
- Smells strong
- Attracts pets
- No measuring spoon or method included in the packaging
2. Espoma Organic Indoor Plant Food – Best Organic Fertilizer For Indoor Plants
Espoma Organic Indoor Plant Food is my pick for the best organic fertilizer for indoor plants. The NPK ratio is 2-2-2, but it includes other ingredients intended to condition the soil and help your plants grow better. These include beneficial soil microbes, humic acid from Leonardite, and dextrose, sucrose, and maltodextrin to feed the soil microbes. The soil microbes break down the nutrients in the fertilizer, so they are readily available to your houseplants. They also help maintain soil structure so your plant’s roots can grow easily. The humic acid is a soil conditioner. Espoma Organic Indoor Plant Food is certified organic and is safe for use around pets and children when mixed as directed.
Espoma was founded by Herbert G. Sanders in 1929. In the 1940s, his friends Clarence Wolf and Daniel Fenton, founders of the Holly Society of America, asked him to develop a fertilizer for hollies. Realizing other groups of plants with special needs also needed fertilizers developed for them, Sanders developed a whole line of organic specialty fertilizers. The Sanders family still owns Espoma.
Espoma recommends wearing gloves while using fertilizer. Shake the bottle well before use and only mix what you will use that day. Mix one half cap full (two teaspoons) of fertilizer with a quart of water. Add the fertilizer first, then pour in the water so it mixes well. Soak the soil around the houseplant. Repeat every two to four weeks.
I like Espoma products and use them frequently. My plants grow well and grow bigger with Espoma fertilizers than with other similar products. However, most potting mediums are sterilized to eliminate microbes, and I wonder how effective adding beneficial microbes is in helping my plants grow larger and more vigorously. If adding them has not been shown to help, then this is a bit of greenwashing. I like organic products and am happy this one is safe for my dog. I do notice a buildup of concentrate when using the cap to measure the fertilizer, so I wash it out periodically. Espoma Organic Indoor Plant Food comes in an eight-ounce container and is moderately expensive considering the size of the container. However, you only have to use it every two to four weeks instead of once a week, so the bottle lasts a while. I like a smaller bottle because the product does not go bad before I can use it all. The fertilizer has a best-used-by date on the bottom, and the microbes will start to die off after that date.
Pros:
- Organic
- Beneficial microbes to help keep the soil healthy
- Safe for pets and children
Cons:
- Expensive
3. Jack’s Classic All Purpose 20-20-20 Plant Food – Best All-Purpose Fertilizer For Indoor Plants
JR Peters Jack’s Classic 20-20-20 Plant Food is my pick for the best all-purpose fertilizer for indoor plants. The NPK ratio is 20-20-20. It also has copper, boron, iron, manganese, molybdenum, and zinc. JR Peters Jack’s Classic 20-20-20 Plant Food feeds both through the roots and the leaves. It provides a fast green-up and rapid leaf expansion. This food is especially helpful to foliage plants and keeps them green and healthy. It can be used with Jack’s Classic Blossom Booster to bring more blooms and brighter colors to your flowering houseplants. The package contains a measuring spoon and a detailed instruction pamphlet. This plant food is not organic and should be kept away from pets and children.
Bob Peters started J.R. Peters, Inc. in 1947. He introduced Peters Professional Plant Food shortly after that. This was the world’s first blue water-soluble fertilizer. The company introduced the Jack’s Classic line in 1997. The company followed this with a reformulation of the original Peters Professional Plant Food under the Jack’s Professional fertilizer name in 2002. The company is still owned by the Peters family.
For indoor houseplants, mix ½ teaspoon of fertilizer into a gallon of water. Use it as a drench every two weeks. Alternatively, mix ¼ teaspoon of fertilizer into a gallon of water and use it as a drench every time you water.
My Dad used to keep a tub of Peters Professional Plant Food around to fertilize our houseplants when I was a kid. JR Peters Jack’s Classic 20-20-20 Plant Food is an improvement on that plant food. It is stronger than most organic fertilizers and has to be mixed according to the label, or it will burn your plants. However, JR Peters Jack’s Classic 20-20-20 Plant Food is easy to use and easy to mix. The 1.5-pound tub is moderately expensive to buy but mixes up into a lot of fertilizer for the money. A tub lasts a long time even if you have lots of plants. I use this plant food primarily for my plants I grow for foliage. The Espoma Organic Indoor Plant Food would be a better choice for flowering plants because you do not have to buy two products. I have also increasingly moved to organic products and as good as this product is, it is synthetic. I think synthetic fertilizers are harder on the environment to manufacture. However, JR Peters Jack’s Classic 20-20-20 Plant Food is a classic for a reason, and I would be remiss if I didn’t include it here.
Pros:
- Well-known brand
- Lasts a long time
Cons:
- Not organic
- A bit pricey upfront
4. Osmocote Outdoor & Indoor Smart-Release Plant Food – Best Slow-Release Fertilizer For Houseplants
Osmocote Outdoor & Indoor Smart-Release Plant Food is my pick for the best slow-release fertilizer for houseplants. The NPK ratio is 15-9-12. It contains eleven essential nutrients coated with a film that gradually releases the nutrients over as many as six months. These nutrients include boron, magnesium, sulfur, copper, iron, manganese, molybdenum, and zinc. This plant food has been tested on a wide variety of species and under a wide variety of growing conditions. The coating on the fertilizer is broken down faster in hot weather when the plant is growing more and slower in cold weather when the plant is dormant or growing slowly. The fertilizer looks like tan BBs and is about the same size pellets as a BB. Osmocote Outdoor & Indoor Smart-Release Plant Food is guaranteed not to burn your plants if used as directed. It is not organic.
Osmocote was the first slow-release fertilizer and was released in 1967. Osmocote is owned by Scotts and was developed by their research and development department. Scotts was founded in 1868 by Orlando McLean Scott in Marysville, Ohio. In 1995, Scotts merged with Miracle-Gro to become Scotts Miracle-Gro. Scotts Miracle-Gro has hundreds of products that are distributed throughout the United States and Canada.
To use Osmocote Outdoor & Indoor Smart-Release Plant Food spread half a cap full of fertilizer per two-gallon pot. Mix it in the top inch of the soil. Water regularly and reapply in six months.
Osmocote is the original slow-release fertilizer. I like using Osmocote Outdoor & Indoor Smart-Release Plant Food because I only have to use it twice a year. It has been tested for years, and the fertilizer allows just the right nutrients out for my plants. Scotts Miracle-Gro is a reputable company and has good products. The fertilizer is easy to use, too. I just use the cap as a measuring cup and sprinkle the fertilizer around my plants. I don’t have to worry about watering the fertilizer in, either.
I prefer to use Neptune’s Harvest for sensitive plants like seedlings because the seedlings need fast-acting nutrients. They will be in the ground in six months. I would choose another fertilizer for sensitive plants such as African violets, as this one may be a little strong for them. The tan pellets can be unsightly scattered on the surface of the soil in my pots if I don’t mix them into the soil well. I find them ugly, but you may not mind them.
Pros:
- Use only every six months
- Not expensive
Cons:
- Not organic
5. General Hydroponics Flora Series – Best Hydroponic Houseplant Fertilizer
General Hydroponics Flora Series: FloraMicro, FloraBloom, FloraGro – 3-Part Hydroponic Nutrient System is my pick for the best hydroponic houseplant fertilizer. There are three bottles in this system, each containing a different mix of nutrients. FloraMicro has nitrogen, calcium, and minerals for growth. Its NPK ratio is 5-0-1. FloraBloom has phosphorus, potassium, magnesium, and sulfur. The NPK for this component of the system is 0-5-4. FloraBloom helps with blooming and setting fruit. FloraGro has more nitrogen, phosphorus, and potassium, with an NPK ratio of 2-1-6. It is used to provide additional structural and foliar growth.
Having these components separate gives you the ability to mix a custom fertilizer depending on the stage of growth and what you are growing. The provided chart tells you exactly how much of which product to add to your water. Follow it for superior growth and better harvests. These products are not organic.
Lawrence Brook founded General Hydroponics in 1976 in a Berkeley, California, garage. William Texier and Noucetta Kehdi opened GH Europe in 1994. Before that, they grew vegetables and sold them to Michelin-starred chiefs from their famed White Owl WaterFarm in the San Francisco area. A Scotts subsidiary bought the company in 2015.
The chart that accompanies the General Hydroponics Flora Series: FloraMicro, FloraBloom, FloraGro – 3-Part Hydroponic Nutrient System bottles provides mixing instructions for several growth stages of vegetable plants.
For seedlings, mix ¼ teaspoon of each product per gallon of water.
For general-purpose plants with mild vegetative growth, mix one teaspoon of each product per gallon of water.
For aggressive vegetative growth, mix three teaspoons of FloraMicro, two teaspoons of FloraBloom, and one teaspoon of FloraGro per gallon of water.
To transition to the bloom stage, mix two teaspoons of each product per gallon of water.
For blooming and ripening, mix one teaspoon of FloraMicro, two teaspoons of FloraBloom, and three teaspoons of FloraGro per gallon of water.
I have not done much with hydroponic systems, but I think General Hydroponics Flora Series: FloraMicro, FloraBloom, FloraGro – 3-Part Hydroponic Nutrient System makes sense. Customizing the nutrients you feed your plants is crucial to successfully growing any plant, and this system lets you do that. If I were going to set up a hydroponic system, these are the nutrients I would use. This fertilizer is a lot pricier than most of the houseplant fertilizers I recommend. However, hydroponic systems are usually used to grow high-value vegetables and cut flowers that have a higher sales price, so I think it balances out.
Pros:
- Can customize nutrients to growth stage and crop
Cons:
- Pricey
- Not organic
6. Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer – Best Fertilizer For Indoor Vegetables And Herbs
Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly Bag is my pick for the best fertilizer for indoor vegetables and herbs. The NPK ratio is 4-6-3, and the nutrients calcium, sulfur, magnesium, iron, and manganese are included. To help your vegetables grow better and keep your soil in good shape, Dr. Earth includes seven strains of soil microbes and eight select strains of ecto and Endo Mycorrhizae. According to Dr. Earth, these organisms make vegetables more nutritious and make plants more drought and heat tolerant. In addition, the fertilizer contains six percent humic acid, derived from Leonardite, to condition the soil.
Dr. Earth is a mixture of nutrients that are immediately available and nutrients that are released slowly. This means the fertilizer can last for up to three months, although it doesn’t last that long in container-grown vegetables. This fertilizer is 100 percent natural and is certified organic. The label proclaims it has no GMOs, chicken manure, or sewage sludge.
Milo Lou Shamma founded Dr. Earth in 1991. According to the company, it produced the first probiotic soils and fertilizers in the United States. Dr. Earth only uses food-grade scraps to make their compost for their fertilizers. The products are safe for children and pets. All the products they sell are certified organic.
The use directions for Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly Bag depend on the vegetables you are growing.
Tomatoes, Peppers, and Herbs
New plantings: Use ½ cup per ½ cubic foot (about five gallons). Mix in the soil and water well.
Established plantings: Use ¼ cup per five gallons. Mix in the soil and water well.
Repeat the applications every two months.
Eggplant, Cucumber, Corn, Beans, Lettuces, and Broccoli
New plantings: Use ½ cup per half cubic foot. Mix in the soil and water well.
Established plantings: Use the same quantities as new plantings.
Repeat applications every other month.
Carrots, Onions, Potatoes, Beets, and Other Root Vegetables
You can only grow root vegetables in containers that are at least two feet deep. There are no directions provided for containers. These directions are the ones provided for raised beds.
New plantings: Use two cups per twelve feet of row or 1 ½ cups per ten square feet. Mix in the soil and water well.
Established plantings: Use ¾ cups of fertilizer per ten square feet or one cup of fertilizer per twelve feet of row.
Apply every two months, except for carrots. Do not feed carrots mid-season.
I appreciate Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly Bag being made from food-grade scraps from supermarkets that would otherwise go to waste, along with the fish bone meal, fish meal, and kelp meal. I think claiming the finished product doesn’t contain GMOs is disingenuous. As far as I know, no fertilizer contains GMOs in the final product, with the possible exception of corn gluten. This is a case of greenwashing, claiming benefits that are not really benefits. However, the fertilizer works well and will help you grow good, healthy, flavorful vegetables and herbs. Be mindful that excess fertilization will reduce the amount of essential oils in herbs. They have to suffer a bit to be as flavorful as possible. This fertilizer is relatively expensive, but I think buying a premium fertilizer for my food is worth it.
Pros:
- Organic
- Produces healthy, flavorful vegetables and herbs
Cons:
- Greenwashing
- Pricey
7. J R Peters Jacks Classic 10-30-20 Blossom Booster – FertilizerBest Fertilizer For Indoor Flowering Plants
JR Peters Jack’s Classic 10-30-20 Blossom Booster is my pick for the best fertilizer for indoor flowering plants. The NPK ratio is 10-30-20, and it is a synthetic fertilizer. It also contains magnesium, boron, copper, iron, manganese, molybdenum, and zinc. It does not contain calcium, chlorine, or sulfur. The ratio of one part nitrogen, three parts phosphorus, and two parts potassium is proven to make flowering houseplants flower the best. This formula is the Original Blossom Booster with a new name. The package contains a measuring spoon and a pamphlet with detailed instructions on it. This fertilizer can be used during bud set to produce abundant buds and during blooming to increase the size and number of blooms.
You can read about JR Peters company above, so I will skip that here.
The company recommends you wear gloves when handling JR Peters Jack’s Classic 10-30-20 Blossom Booster. You can either mix ½ teaspoon in a gallon of water and use it as a drench every two weeks or mix ¼ teaspoon of fertilizer in a gallon of water and use it as a drench every time you water your plant.
JR Peters Jack’s Classic 10-30-20 Blossom Booster is a useful supplement to make houseplants bloom better. I would use it in conjunction with JR Peters Jack’s Classic 20-20-20 Plant Food as a complete fertilizer for my houseplants. Using JR Peters Jack’s Classic 20-20-20 Plant Food to feed my houseplants from when they break dormancy until they start to bloom, then switch to Blossom Booster while the plant is blooming, then go back to the classic plant food works best. Of course, this means you have to buy two products and know when to switch between them. That makes this system more complicated than others and more expensive. On the other hand, the results are spectacular if you are willing to go to the trouble. I would either have all my plants on JR Peters Jack’s Classic 20-20-20 Plant Food and supplement that with Blossom Booster for my flowering plants or use something like Espoma Organic Indoor Plant Food for everything.
Pros:
- Makes plants bloom well
Cons:
- Not organic
- Must be used with JR Peters Jack’s Classic 20-20-20 Plant Food
8. Grow More Cactus Juice – Best Fertilizer For Indoor Cacti And Succulents
Grow More Cactus Juice Cacti & Succulents Fertilizer is my pick for the best fertilizer for indoor cacti and succulents. The NPK ratio is 1-7-6, and it also includes calcium. This supports healthy growth and drought resistance. Plants need water to draw nutrients into their tissue. Since cacti and succulents do not need as much water as other plants, it is a good idea to use a liquid fertilizer to make the nutrients available to the plant. The low nitrogen and high phosphorus and potassium are exactly what cacti and succulents need to grow and stay healthy. This product is not organic.
Grow More was founded in 1918 by William H. Atwill as National Chemical NACCO. Initially, the company manufactured chemicals for photography and other industries. After World War II, the company expanded into more industries. In the 1970s, Grow More started producing agricultural chemicals and fertilizers. In the 1980s, the name of the company was changed to Grow More, and the emphasis of the business changed from heavy industries to agriculture.
To use Grow More Cactus Juice Cacti & Succulents Fertilizer, shake the container well. Mix one teaspoon of fertilizer with one gallon of water. Drench the soil around the cacti and succulents. Reapply every two weeks during the growing season or as needed.
Grow More Cactus Juice Cacti & Succulents Fertilizer is specially formulated for the unique nutritional requirements of cacti and succulents. They don’t need a lot of nitrogen but do need phosphorus and potassium. My mother has a lot of succulents, and they need special care. I only fertilize cacti and succulents in the growing season, from about March to September. This fertilizer works great for my plants. Because the requirements for succulents and cacti are so different from other plants, I just use this fertilizer on them. I do not use it on my other plants. The fertilizer is not expensive, but it is a pain to have to buy a special fertilizer just for cacti and succulents. Cacti and succulents grow slowly, so you may not see much reaction to being fertilized at first. Be patient, and the plants will deepen in color and start putting out buds. Be consistent with when you fertilize, and the cacti and succulents will grow better and be healthier than if you do not fertilize them properly.
Pros:
- Formulated especially for cacti and succulents
Cons:
- Not organic
- Can’t use on other plants
9. Jobe’s, 01612, Fertilizer Spikes – Best Fertilizer For Indoor Citrus Trees
Jobe’s, 01612, Fertilizer Spikes, Fruit and Citrus are my pick for the best fertilizer for indoor citrus and fruit trees. The NPK ratio is 9-12-12 with not more than 12 percent chlorine. Citrus and fruit trees are popular to grow inside especially since many people live in places that are too cold for these trees outside. Jobe’s fertilizer spikes are a convenient way to fertilize your citrus and fruit trees. Simply hammer in the spikes two inches below the surface of the soil. No need to worry about runoff, chemical smells, or burning your plant. You do need to have a big pot to use these spikes as they should be thirty inches away from the trunk. This is not an organic fertilizer.
Jobe’s was founded in 1969. It was purchased by Easy Gardener in 1997. In 2007, Easy Gardener launched Jobe’s Organics. Easy Gardener was bought by Centre Lane Partners in 2015. In 2016, they changed the name of the company to The Jobe’s Company. This company makes over 200 fertilizers and other gardening products from Waco, Texas, and Kentucky.
To use Jobe’s, 01612, Fertilizer Spikes, Fruit and Citrus, first water the tree. Then, use a hammer and the cap included to hammer the appropriate number of spikes along the dripline of the tree. Hammer the spike into the soil, remove the cap, and hammer the spike two inches below the soil level. For a tree one to two inches in diameter, hammer two spikes in opposite each other. Add one spike for each inch in diameter up to five.
Spikes are an easy way to fertilize a tree. However, you have to have a big container for them to work well. Placing the spikes too close to the tree will hurt it. By watering the tree before putting the spikes in, you soften the soil and make it easier to hammer the spikes in. I like the fact that you only have to use the spikes in the early spring and then in the late fall. This makes them much easier to use than liquids you have to use each week. I have found that the spikes will crumble or break in the package or when they are being hammered in the soil, so you have to be careful handling them. I wear gloves to hammer in the spikes.
Pros:
- Use twice a year and forget
Cons:
- Not organic
- Can break or crumble
- Need a big pot to use them in
10. Down to Earth All Natural Acid Mix Fertilizer – Best Fertilizer For Indoor Berry Bushes
Down to Earth All Natural Acid Mix Fertilizer 4-3-6 is my pick for the best fertilizer for indoor berries, including blueberries, raspberries, and strawberries. Blackberries need a different fertilizer but are not commonly grown indoors. The NPK ratio is 4-3-6, and it contains calcium, magnesium, and sulfur as well. This fertilizer also has humic acid from Leonardite to condition the soil. The package is biodegradable, but the fertilizer is not certified organic. Keep the fertilizer away from pets and children.
Down to Earth was founded in 1977 by Jack Bates to provide organic fertilizers to his customers. It now sells a wide variety of natural and organic fertilizers, composts, soil amendments, and potting media. Down to Earth uses premium ingredients that work with nature, not against it.
To use Down to Earth All Natural Acid Mix Fertilizer 4-3-6, thoroughly mix one to two tablespoons into each gallon of soil for new plantings. Every month of the growing season, mix one to two tablespoons per gallon of soil in the top few inches of soil in the pot. Water the plant after fertilizing it. For established plants, mix one to two tablespoons per gallon of soil in the top few inches of soil monthly. After fertilizing, water the plant well.
I like Down to Earth All-Natural Acid Mix Fertilizer 4-3-6 because it acidifies the soil as it fertilizes. Blueberries, raspberries, and strawberries prefer an acid soil and will not grow well in soils with a higher pH. I can use this fertilizer on other acid-loving houseplants I grow. The fertilizer says, “All Natural,” but is not certified organic. I prefer fertilizers that are certified organic, but this is the best option for acid-loving plants. I use a dust mask when handling this fertilizer because the label suggests doing so. Inhaling fertilizer is not on my list of fun things to do. Do not use too much of this fertilizer because it can burn your plants if you do. It can also make the soil too acidic. Do not use this fertilizer on plants that grow in more alkaline soils, or it will damage or kill them. This is one of the more expensive fertilizers I recommend, but the five-pound package lasts a long time if you are just using it on houseplants.
Pros:
- Acidifies soil as it fertilizes
- Useful for all acid-loving plants
Cons:
- Not organic
When Do I Fertilize My Houseplants?
What you fertilize with is important, but so is when you fertilize. Here are some things to consider.
Time of Day
You should fertilize in the morning before ten o’clock for the best results. Doing so allows the plant to completely dry out before nightfall. While you should not get the leaves of a plant wet when fertilizing, sometimes drops do land on the plant. These wet spots can allow fungi on the plant to grow and infect the plant. Watering in the morning gives the best opportunity for these wet spots to dry before the fungus has time to colonize your plant. Since most granular fertilizers require water to activate them, this applies to all fertilizers, not just liquids.
Stages of Growth
Some plants, especially vegetables and berries, need different types of fertilizers during different growth stages. Seedlings often need milder fertilizer than full-grown plants, as well. I follow the directions on the label for mixing strength and application rates for the different plant growth stages. My fertilizer mixes for seedlings I am starting are much milder than for a full-grown tomato plant, for example.
Time of Year
The time of the year is not as important in houseplants as it is in plants outdoors, but it does matter. The different amounts of light available to plants cue them to go dormant or stay active, so fertilize less in the winter, if at all. If you keep your plants under a grow light all year, they will not go as dormant as plants in the window. Most plants need more fertilizer in the spring and summer than in the winter so they can grow their foliage. Pay attention to your plant’s life cycle and vary your fertilizer applications accordingly.
How Do I Fertilize Houseplants?
Most liquids and water-soluble fertilizers are used as a drench. This means they are poured on the soil until the liquid comes out of the drainage holes in the bottom. Some liquids are sprayed on the foliage. If you are using a foliar spray, spray the underside and top of the leaves until the spray drips off them.
Most granular fertilizer is spread on the soil around the outer rim of the pot, then watered in to activate it. Do not get fertilizer on the foliage or it can burn the plant. Spikes are hammered in around the outer rim of the pot, as well. For some spikes, the directions say to water the soil before hammering the spikes in, so pay attention to the directions.
Can I Over-Fertilize Houseplants?
You can definitely over-fertilize a houseplant. If you fertilize and the plant leaves start to brown within 48 hours, you have put too much fertilizer on your plant. More fertilizer is not better, so be sure to follow the label directions for how much fertilizer to use at a time and how often to repeat the application.
When Do I Stop Fertilizing Houseplants?
If your plant goes dormant in the winter, stop fertilizing in the fall. Start fertilizing in the spring when the plant starts to show some green growing on it. If your plant does not go dormant in the winter, keep fertilizing it all year.
How Do I Fix Over Fertilization?
If you fertilize and your plant shows signs of being burned such as brown tips on the leaves, put the plant in the sink and run water through the soil for about fifteen minutes. This should dilute the fertilizer in the pot and will help avoid further burning. Sometimes, the plant will be burned so badly that this will not save the plant, but it is the best way to treat over-fertilization. Reduce the strength of fertilizer you apply to this plant and the frequency of application in the future to avoid burning the plant again.
Homemade Fertilizer for Houseplants
Houseplants do not have much soil from which to draw nutrients. It is important that any fertilizer you use meets all the plant’s needs. It is possible to make homemade fertilizer for houseplants, but you need to make sure you include enough nitrogen, phosphorus, and potassium. You will also need to add trace minerals.
I often get asked about using eggshells, coffee grounds, and banana peels as fertilizer. Eggshells are a good source of calcium but must be ground into a fine powder to make that calcium available to your plants. Crushed eggshells have been shown not to release their calcium until they break down into a fine powder. This can take literally years, so grind them first.
Coffee grounds are a good source of nitrogen. However, they are acidic and can quickly make your soil too acidic for many houseplants. I use them very sparingly for that reason. They do work well for acid-loving plants.
Finally, burying a banana peel in your potting soil doesn’t work well for the same reason crushed eggshells do not work well. You can soak the banana peel for twenty-four hours and use the water to water your plants. This banana water does have some potassium and phosphorus in it, as well as some trace minerals.
Fish fertilizer is basically ground fish with some water added. Some fish emulsions also have seaweed in them. These fertilizers, like Neptune’s Harvest Fish-Seaweed Blend Fertilizer, which I recommend above, have all three major nutrients as well as many trace elements and amino acids. They make a good fertilizer if mixed properly. Follow the label directions for the fertilizer to mix it and use all the solutions you make that day. Mix the fertilizer half-strength for seedlings and sensitive plants. Use it once a week for seedlings and once every one to two weeks for other plants.
Indoor Plants Fertilizing Tips And Common Mistakes To Avoid
Here are some fertilizer tips and common mistakes to avoid.
- Some plants, such as African violets, are very sensitive to over-fertilization, so use a fertilizer specifically developed for those plants and follow the directions to avoid a problem.
- Wear waterproof gloves when handling fertilizers to avoid skin irritation. Wash your hands after fertilizing plants, even if you wore gloves.
- Use a dedicated water jug for each type of fertilizer you use, and mark the type of fertilizer on it with a waterproof marker so that you won’t confuse them.
- Get a dedicated set of measuring spoons and cups in a color that is different from your regular kitchen measuring spoons and cups so you can tell which has had fertilizer in it. Never mix fertilizer in measuring spoons and cups you later put food in.
- I fertilize on the same day of the week, so I don’t forget to do so. I also don’t fertilize too often that way.
- Store your fertilizer in a cool, dry place out of reach of pets and children. Do not store your fertilizer where the washer and dryer are, as it will get too hot and humid. Heat and humidity degrade fertilizers.
- If your pets bother your plants, you can place a tent of chicken wire or hardware cloth over the plants to protect them. Laying hardware cloth on the surface of the soil will discourage digging.
- Most potting soil has an initial charge of fertilizer. You will only need to start fertilizing after that is used up, usually after a month. The potting soil label will tell you how long to wait to start regular fertilization.
- Use filtered or distilled water to mix your fertilizer with and water your plants. This helps avoid a mineral crust on the top of the plant’s soil.
Final Verdict
Houseplants need different types of fertilizer depending on the plant. Here are my picks for the best fertilizers for houseplants.
Neptune’s Harvest Fish-Seaweed Blend Fertilizer is my pick for the best liquid fertilizer. It contains all the nutrients found in fish along with those found in seaweed, so it is a complete fertilizer.
My pick for the best organic fertilizer for houseplants is Espoma Organic Indoor Plant Food. Espoma is a good company, and their organic products are very good.
JR Peters Jack’s Classic 20-20-20 Plant Food is my pick for the best all-purpose houseplant fertilizer. My plants grow well with this fertilizer, and my Dad used the precursor to it.
I think Osmocote Outdoor & Indoor Smart-Release Plant Food is the best slow-release houseplant fertilizer. Scotts literally invented the slow-release fertilizer and has fine-tuned it over many years.
My pick for the best hydroponic fertilizer is General Hydroponics Flora Series: FloraMicro, FloraBloom, FloraGro – 3-Part Hydroponic Nutrient System. This system gives you a lot of control over what nutrients you give your plants.
Dr. Earth Organic 5 Tomato, Vegetable & Herb Fertilizer Poly Bag is my pick for the best fertilizer for vegetables and herbs. You can grow large, nutritious vegetables and herbs with this fertilizer.
My pick for the best fertilizer for flowering plants is JR Peters Jack’s Classic 10-30-20 Blossom Booster, used in conjunction with JR Peters Jack’s Classic 20-20-20 Plant Food. The extra phosphorus and potassium during bud set and blooming lead to lots of large, showy flowers.
Grow More Cactus Juice Cacti & Succulents Fertilizer is my pick for the best fertilizer for cacti and succulents. This fertilizer has the nutrients these plants need in exactly the right ratio they need them.
My pick for the best fertilizer for citrus and fruit trees is Jobe’s, 01612, Fertilizer Spikes, Fruit and Citrus, Includes 15 Spikes, 12 Ounces, Brown. Just hammer them in and forget about fertilizing for six months.
Finally, my pick for the best fertilizer for indoor berries is Down to Earth All Natural Acid Mix Fertilizer 4-3-6. This fertilizer acidifies the soil as it fertilizes your plants.
