Everything You Need To Know To Find The Best Fertilizer Enhancer

You might be new to gardening, learning the mysteries of plants, soil, seasonal changes, watering routines, etc. All of us (even us professionals) are engaged in constant learning about plant preferences, watering, sun or shade, etc.

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What about fertilizer (aka “plant food”)?

Perusing the fertilizer shelves at Swansons (or any garden store) can feel overwhelming at first. So many choices! So many specialties! Do I really need fertilizer? Will my plant survive if I don’t find the perfect fertilizer match?

And what do all those numbers mean???

THE NEED for Fertilizer

First, be assured that your plant is unlikely to die from lack of or the wrong type of fertilizer. Chronic nutrient deficiency left untreated for a while (maybe weeks in a vegetable or annual, months or years in a larger plant) might contribute to a plant’s decline, but serious stress is more commonly a sign of watering, disease, or pest issues.

Over-fertilizing is a bigger risk — stressful for plants and organisms, and potentially harmful to soil and groundwater, especially if inorganic fertilizer is overused.

Your plants need the right nutrients to survive, but in a natural environment, they receive a lot through healthy soil, water, and sunlight. Adding fertilizer is a way to supplement these natural sources, especially for younger and heavy-feeding plants, or if your soil isn’t very fertile to begin with.

Or, if you’re wanting that Show Garden, the right fertilizer can make your plants really pop! The Butchart Gardens in Victoria, B.C. pictured above, uses a carefully-planned fertilizer program (not to mention their staff of fifty full-time gardeners!) to keep their displays looking spectacular year-round.

FEED THE SOIL

We primarily feed the plants by feeding the soil. The goal is not to feed the soil just until the plants use up the nutrients and we have to feed it again; instead, the goal is to build the soil to make it more nutrient-rich and as self-sustaining as possible. So we first need to make sure our soil has the drainage and organic matter it needs. Then fertilizers are applied to the soil, by mixing in during planting, or sprinkling on soil surfaces over the root zones.

Garden soil, especially in urban areas, often suffers from compaction and low fertility. The most effective way to amend that is to add organic matter, commonly in the form of compost. This improves drainage, holds moisture, increases air circulation, and fosters beneficial microbial communities. Our previous posts on how to mulch, the importance of compost, and building healthy soil go into more detail.

Fertilizers, then, can boost soil fertility for the plants we want to grow.

Foliar feeding (spraying liquid fertilizer solutions on the leaves) is sometimes used as an alternative to fertilizing soil. Leaf tissue can absorb certain compounds more efficiently than roots. Most research indicates that foliar feeding may be effective for treating certain nutrient deficiencies or boosting plant growth in times of stress. But for more cost-effective and long-term benefits for plants, feeding the soil is best.

THE NUMBERS: N-P-K

The three numbers you see on most fertilizers are the analysis of essential elements, or “macronutrients” in the fertilizer and include:

• N - Nitrogen: The most basic element essential to plant life, evident in the growth of foliage.

• P - Phosphorus: Fosters flower and fruit production.

• K - Potassium: (Latin term: Kalium) Supports root development, overall vigor, and disease resistance.

The numbers are the percentage of these macronutrients within the total mix, so 6-3-4 indicates 6%-3%-4% respectively, of N-P-K. Most fertilizers include a balance of these three, but some are skewed toward one for a specific purpose. Examples are E.B. Stone® Organics Lawn Food, (10-1-4), or Espoma® Flower Tone Bloom Booster, (3-4-5).

For most (and especially newer) gardeners, we encourage using balanced fertilizers with all three macronutrients included. But there are some preferences among different plant types:

• Green, leafy plants such as lawns and salad greens are generally heavy feeders of nitrogen.

• Fruiting plants such as tomatoes, cucumbers, and melons like a balance of nutrients but need fairly frequent feeding.

• Perennials, trees and shrubs (incluing fruiting types) also prefer a balance of nutrients but at lower or less-frequent levels.

Higher numbers indicate higher concentrations of these elements. Is that better for your plants? Not necessarily. They are often found in synthetic fertilizers, such as lawn food with high nitrogen. High concentrations can bring quick, dramatic results, such as quick greening of your heavy-feeding lawn for that summer wedding. But the effect can be temporary and not so good for long-term health. If applied too heavily or not sufficiently watered in, high-number fertilizers can "burn" plants similar to salt toxicity. In most cases, it’s best to add nutrients slowly for the long term. For a healthy lawn, supplement it in fall and spring with a slower release lawn food.

So look for the proportion of the numbers, rather than their volume.

The package ingredients might also list several “micronutrients” such as calcium and magnesium. A deficiency of one or a combination of these can cause problems. When diagnosed, they can often be corrected by adding single ingredient fertilizers or supplements. If not in combination fertilizers, you can find them in specialized products such as magnesium sulfate or dolomite lime (calcium carbonate).

SPECIALTY FERTILIZERS

Some fertilizers are specially formulated for a specific plant’s needs. Which one should you choose for your tomato plant, or azalea or rose bush? It helps that many fertilizers are conveniently labeled “Tomato…”, “Azalea…” and “Rose…” Before we get into details, remember that using the “wrong” type of fertilizer isn’t likely to cause great harm. But the designated fertilizers are more effective for their target plant types.

• Roses: Rose fertilizer is a balanced food that helps slightly raise soil pH to a less-acidic level preferred by roses.

• Acid-loving plants (rhododendrons, camellias, blueberries, most evergreen plants, etc.): fertilizer for acid-lovers feeds while maintaining the lower pH in the soil that these plants need.

• Flowers (especially annuals): bloom-boosting fertilizer has a higher percentage of phosphorus to boost flower development.

• Bulbs: bulb fertilizer also has higher phosphorus plus bone meal to enhance both flower and bulb (root) development.

• Lawn: a higher nitrogen percentage keeps lawns green, as mentioned earlier.

What is slow-release fertilizer? This type of fertilizer is good for many types of applications and is often used to supplement other fertilizers in container plantings. Many organic fertilizers are naturally slow-release. Others (such as Osmocote®) are pelletized for this function.

What We Like

• Contains organic matter to enrich the soil and increase root mass

• Verified by the Organic Materials Review Institute

• Resealable bag for easy storage

What We Don't Like

• Pungent scent may attract dogs

Jobe's Organics All-Purpose Fertilizer can be used to treat a wide variety of plants, making it the most versatile option on this list. With a nitrogen-phosphorus-potassium (NPK) ratio of 4-4-4, it can be used for vegetable gardens, flowers, trees and shrubs, and houseplants.

The addition of the beneficial microorganisms contained in this organic fertilizer can improve soil quality, increase root mass, and encourage plant growth. Applying it to garden beds in the spring provides plenty of nutrients for the flowers or veggies you're about to plant (or an application in late fall can help prepare the soil for the perennials that will emerge in the spring).

This fertilizer is entirely organic, and its ingredients have been verified by the Organic Materials Review Institute (OMRI) as approved for the growing and creation of certified organic products. While it is safe to use around children and pets, the pungent scent of this formula may attract dogs, so you may want to monitor your pets to prevent them from digging around in it. 

Jobe's Organics All-Purpose Fertilizer comes in a resealable bag for easy storage, and it’s available in several sizes, including 4- and 16-pound bags. This granular formula should be mixed with soil before planting. Note that this product also needs to be applied every four to eight weeks throughout the growing season.

NPK Ratio: 4-4-4 | Feed Duration: Apply every four to eight weeks during growing season | Application Type: Granular

What We Like

• Easy to mix and use, especially with a watering can

• Feeds up to 2,200 square feet

• Won’t burn plant roots

What We Don't Like

• Formula must be kept dry or clumping can occur

• Must be reapplied frequently

If you want to grow bigger, healthier plants, Miracle Gro’s All-Purpose Plant Food is an excellent choice. It comes in a resealable, waterproof bag and includes a measuring scoop for precise application. The water-soluble solution can go directly into your watering can, making it easy to feed container plants. It's especially good for giving your indoor plants a nutritional boost in the fall to prepare them for dormancy in the winter.

If you’re treating a larger outdoor garden, it’s probably best to apply the fertilizer with a garden feeder. This versatile formula can be used on all types of flowers as well as vegetables, houseplants, trees, and shrubs. A 5.5-pound bag will feed up to 2,200 square feet, and this solution is very cost-effective because you can mix the exact amount you need.

Keep in mind that the fertilizer needs to be applied pretty frequently—once every two weeks for best results. According to the manufacturer, this mineral-based formula won’t burn the roots of your plants though, if it's used as directed. Be sure to keep the powdered formula dry during storage, otherwise, clumping may occur.

NPK Ratio: 24-8-16 | Feed Duration: Apply every two weeks | Application Type: Water-soluble granular

What We Like

• Includes three liquid fertilizers for different stages of growth cycle

• Delivers incredibly fast results

What We Don't Like

• Must be applied in stages

This comprehensive trio from Fox Farm fertilizes plants throughout all stages of the growth cycle. As the name suggests, the Grow Big formula promotes a more abundant bounty in the early growth stages. You will want to apply the Tiger Bloom when you first notice buds or flowering. Tiger Bloom is an extremely potent, high-phosphorus fertilizer that will speed up the growth process even more.

The Big Bloom concentrate contains earthworm castings, which provide instant nutrition and improve soil conditions. You might even see growth results within days. Please note that you can also use the Big Bloom formula at any stage of the growing cycle though, to repair root systems and improve nutrient absorption.

We like that this system is tailored to the specific needs of plants and vegetables. However, the application process is a bit more complicated because the products must be used in sequence. In the fall, you can apply them to enrich the soil of your garden beds in preparation for the spring. Big Bloom is also great for boosting houseplants through the winter months.

These formulas are also concentrated, so you’ll have to dilute them based on the manufacturer’s instructions. You’ll also have to closely monitor your plant growth to determine the appropriate time to apply each product. If you’re willing to put in the time and effort, however, you can even expect your plants to produce vegetables year-round.

Not surprisingly, this three-pack is pricier than most standalone fertilizers, but it is a more thorough approach to fertilizing.

NPK Ratio: 6-4-4 (Grow Big), 2-8-4 (Tiger Bloom), 0.01-0.3-0.7 (Big Bloom) | Feed Duration: Not listed | Application Type: Concentrated liquid

What We Like

• Can be used on citrus, mango, and avocado trees

• Easy to distribute

What We Don't Like

• Needs to be worked into the soil before watering

Miracle-Gro Shake 'N Feed Citrus, Avocado, and Mango Plant Food contains many essential nutrients for ample fruit production, including potassium, magnesium, iron, and sulfur. This granular fertilizer can be used on new or existing in-ground citrus, mango, and avocado trees. While this fertilizer can be applied to other citrus trees, it may not be the best for other fruits like berries.

Applying this fertilizer formula is very simple. All you have to do is sprinkle 1.75 tablespoons of fertilizer per 4 square feet under the tree, making sure it doesn't come into contact with the trunk or foliage. Next, use a rake or shovel to work the fertilizer into the surface of the soil before watering. This formula comes in a 4.5-pound container with a spout at the top for easy dispensing.

If you want to learn more, please visit our website Fertilizer Enhancer.

Note that this product must be applied every three months during the growing season. It's useful in the fall to help enrich the soil and prepare for spring, and you can also use a light application to feed any winter-hardy citrus trees you have that continue growing through the cooler months.

The fertilizer contains chemical ingredients that produce fast results, but also risk burning the lawn or harming the environment. According to the manufacturer, however, this pick is guaranteed not to burn when applied as directed.

NPK Ratio: 8-2-10 | Feed Duration: Apply every three months | Application Type: Granular

What We Like

• Concentrated formula

• Can kill 40+ insects, and prevent new infestations for up to a year

What We Don't Like

• Should not be used on edible plants

This pick is specially formulated to treat trees and shrubs, providing a mix of inorganic nitrogen, phosphorus, and potassium for vital nutrition. The slow-release formula promotes healthy soil and moves systemically from roots to branch tips.

It’s also a highly effective pesticide that can kill over 40 types of insects, including aphids, leafminers, and borers, which can be deadly to trees and other vegetation. Just one application will prevent new infestations for up to a year, including through the fall and winter months.

It comes in a concentrated formula, which needs to be mixed with water before application. While it could be applied with a sprayer, it’s recommended that you mix it in a large bucket or watering can to apply directly on tree and shrub roots. Since this formula contains insecticides, it is not recommended for use on edible plants.

This product is a lot more expensive than other options, but it does double duty as a fertilizer and pesticide, which could save you money on professional tree care.

NPK Ratio: 2-1-1 | Feed Duration: Apply once every 12 months | Application Type: Concentrated liquid

What We Like

• Safe for all grass types

• Crowds out weeds by creating thicker grass

• Great value; 20-pound bag covers up to 4,000 square feet

What We Don't Like

• Must be watered in after spreading

• Does not contain weed killer

If you want to keep your lawn green and healthy, Scotts Turf Builder UltraFeed is the way to go. This fertilizer has a high nitrogen content with a ratio of 40-0-5, and it can be used on all types of grass, from centipede to Bermuda to St. Augustine.

Since this formula works to thicken grass, it helps to crowd out weeds as well. However, it's important to note that it doesn’t contain any weed killers or insecticides; you’ll have to treat those problems separately. For best results, this granular fertilizer should be applied with a fertilizer spreader and lightly watered afterward.

Scotts' long-lasting, low-maintenance formula sets it apart from the competition: each application feeds your lawn for up to six months, and it doesn’t need to be reapplied in most parts of the United States during growing season.

You can apply it in the fall to help recover from summer stress, but make sure to follow the instructions on the label for late-season feeding. A 20-pound bag covers up to 4,000 square feet of lawn, giving you plenty of bang for your buck.

NPK Ratio: 40-0-5 | Feed Duration: Apply every six months | Application Type: Granular

What We Like

• Best for January to April applications

• Contains calcium to protect lawn from disease

What We Don't Like

• Not ideal for St. Augustine or centipede grasses

• May take weeks to see results

This Espoma fertilizer is made with feather meal and pasteurized poultry manure, giving it a nitrogen-rich formula that results in greener grass. It has an NPK ratio of 8-0-0 that promotes early-season lawn growth, and it also contains 3-percent calcium to protect lawns from disease. The formula is available in a 30-pound bag and can feed up to 5,000 square feet of lawn. Plus, the granular application is a breeze. 

According to the manufacturer, it’s best to apply this fertilizer in February, March, or April for any cool-season grasses and in January or February for any warm-season grasses. If you live in a region that experiences mild winters, you may also want to consider applying it in the fall to give your grass a nice headstart going into the spring growing season.

Please note that this formula doesn’t contain potassium, so it may need to be supplemented with a potassium-rich formula late in the growing season if you have St. Augustine grass. We do not recommend this formula for centipede grass, as it prefers a fertilizer with a lower nitrogen percentage.

Since this is an organic formula, it may take a few weeks to see results. On the plus side, it's safe to use around children and pets.

NPK Ratio: 8-0-0 | Feed Duration: Apply every two months | Application Type: Granular

What We Like

• Includes a mix of beneficial microbes

• Fast-absorbing

• Suitable for all indoor plants

What We Don't Like

• Doesn't work with other fertilizers

• Not compatible with outdoor plants, too

Featuring organic ingredients and made by worms (yes, really!), We the Wild's Grow Concentrate is our favorite fertilizer for indoor plants. It works well all year long, but a diluted solution in the fall can be especially useful for helping maintain healthy plants through the cooler and darker winter months.

This potent little bottle of liquid contains 20 groups of microbes and over 4 million microorganisms per teaspoon to help plants thrive. We particularly like that this formula is suitable for use on all indoor plants, making it easy to treat every variety in your home with the same fertilizer.

We also love how easy it is to apply this liquid fertilizer to indoor plants of all kinds. With just a small amount (less than a teaspoon) per quart of water, you can apply all of the concentrate's beneficial microbes. Plus, we really like that the formula is designed to be fast-acting and low-odor.

Just be aware before applying this concentrate that it doesn't work in tandem with other types of fertilizers. You'll want to use it solo on your indoor plants. Additionally, while the product says this liquid formula can technically be used just fine on outdoor plants, its mix of microbes is really best for indoor varieties, and it doesn't contain all of the nutrients outdoor gardens might need.

NPK Ratio: Not listed | Feed Duration: Apply when soil feels dry | Application Type: Liquid

Final Verdict

Our favorite fertilizer is Jobe’s Organics All-Purpose Fertilizer. It promotes steady plant growth and improves soil conditions. It can be used for vegetable gardens, flowers, trees and shrubs, and houseplants. If a lush, green lawn is your goal, we recommend Scotts Turf Builder UltraFeed. This nitrogen-rich fertilizer provides fast results and feeds lawns for up to six months.

How We Picked Fertilizers

Since different types of plants each have their own nutrient requirements, we focused on the type of fertilizer and the nutrient ratios to make our selections. We identified options with the ideal nutrient mix for grass, flowers, vegetables, trees, and all sorts of indoor plants.

We also made sure to identify both organic and inorganic (or synthetic) fertilizers, since each serves different purposes—improving soil over time for organic, and providing a quick boost at just the right time for inorganic.

What to Look For in a Fertilizer

The Nutrients Your Plants Crave, and NPK Ratios

On fertilizer packaging, you'll see numbers like 5-5-5 or 10-10-10. These numbers are the percentage of nitrogen, phosphorous, and potassium (the NPK numbers). For example, if you see 5-10-5 on the product label, it stands for 5 percent nitrogen, 10 percent phosphorus, and 5 percent potassium

Every plant has specific nutrient requirements, so it's important to select a fertilizer that has the right nutrients for your flowers, vegetables, shrubs, trees, or lawn.

For example, Scotts' Turf Builder UltraFeed (our best for lawns pick) has a lot of nitrogen, which is why it's good for grass. That much nitrogen can damage other plants though, so it isn't a good all-purpose option like Miracle-Gro All Purpose Plant Food (our best for plants pick).

The Type of Soil You Have

Knowing what type of soil you have has is important for finding the right fertilizer. To accurately determine the type of soil you have (and any nutrient deficiencies) you can collect a sample and have it tested at a local extension agency.

Soil types (and common fertilizers for them) include:

• Loamy soil is ideal for growing a wide variety of plants. It is high in nutrients and contains the perfect blend of clay, sand, and silt. Balanced fertilizers do well in loamy soil, and you typically won't need to apply it as often as you would with other soil types.
• Clay soil contains densely packed particles that are great for retaining nutrients and moisture, but they can restrict oxygen and impede drainage. To amend clay soil, it’s best to add organic matter during the springtime before planting. Our best overall fertilizer, Jobe’s Organics All Purpose Fertilizer is a good option.
• Sandy soil doesn't retain water very well, and it's usually very deficient in nutrients. Slow-release fertilizers with high phosphorous content can help sandy soil (along with materials like sphagnum moss and coconut coir to help retain moisture).
  

The Right Fertilizer Type for the Job: Granular or Liquid

Fertilizer is available in liquid and granular form, so one of the first decisions you need to make is whether liquid or granular is right for the plants and soil you need to fertilize.

“Liquid fertilizer is quicker for plants to absorb and provides nutrients right away, while granular fertilizers are more of a slow-release fertilizer,” says Will. “Liquid fertilizers are a great option if you want to perk up your plants right away or treat specific nutrient deficiencies.”

Liquid fertilizers, like We the Wild's Grow Concentrate (our best for indoor plants pick) begin supplying nutrition to plants immediately, so you’ll often see results within a few days. The downside is they need to be reapplied frequently.

Our best for vegetables pick, the Fox Farm Liquid Nutrient Trio Soil Formula, contains three liquid fertilizers, which can be used at various stages of the growing cycle. 

Granular fertilizers are better for feeding over a period of time, but there are also quick-release formulas that completely dissolve into the soil within a few weeks. Slow-release formulas often contain microbes that break down the fertilizer gradually, providing nutrients over an extended period of time, like Jobe’s Organics All Purpose Fertilizer (our overall best pick).

Choosing an Organic or Synthetic Formula

In addition to all the other factors, you will need to choose between an organic or synthetic fertilizer. Organic formulas are made from natural sources like plants, animals, and minerals (and act slowly) while synthetic formulas contain chemically processed compounds such as ammonium nitrate or urea (and provide nutrients fast)

Since organic fertilizers are slow-acting, it’s best to apply them in the fall so that nutrients are available in the spring planting season.

Our overall best recommendation, Jobe’s Organics All Purpose Fertilizer, is an organic option that also contains microorganisms to improve soil conditions and feed plants. Over time, the organic microorganisms will break down the soil, improving water use and airflow.

Synthetic formulas are both highly concentrated and water-soluble, so they work very quickly to help plants and lawns get a jumpstart on spring growth, with the precise nutrient mix you need.

Unlike organic fertilizer, synthetic products typically don't contribute to long-term soil health, and following application guidelines is essential to prevent burning plant roots and foliage.

Our best for plants pick, Miracle-Gro's All-Purpose Plant Food, is a synthetic formula that delivers incredibly fast results. Fertilizers like this are usually applied just before or during a plant’s active growing season.

One More Thing

What about weeds, you ask? “Fertilizers themselves do not control weeds, but an unhealthy lawn is far more susceptible to weed growth than a healthy lawn,” says Will. “By fertilizing your lawn on a regular basis, and addressing any nutrient deficiencies, you’ll be helping your lawn crowd out weed growth.”

Why Trust The Spruce?

This article was written by Sage McHugh, a writer for The Spruce who specializes in home and garden topics. When selecting the best fertilizers for this roundup, she considered dozens of products, carefully evaluating their NPK ratios, feed duration, application type, ease of use, and overall effectiveness. McHugh also looked at hundreds of customer reviews.

Our Experts:

Contact us to discuss your requirements of Fertilizer Enhancer Products. Our experienced sales team can help you identify the options that best suit your needs.

• Liz Will, a master gardener, garden coach, and author of the blog Learn To Grow Gardens
• Daniela Galvez, senior editor at The Spruce
• Jeremy Laukkonen, updates writer at The Spruce