Garden plants need nutrients to grow and remain healthy. Adequate soil fertility is as important to plants as a healthy diet is to animals and people. The more you garden, the more important it is to understand soil nutrients and to use—at the right time and in the right proportion—the right fertilizer to supplement your soil.
Choosing a fertilizer can be downright overwhelming. Read on for tips and suggestions to help in your search, and don’t miss our roundup of top-favorite picks among the best garden fertilizer options available.
- BEST OVERALL: Jobe’s Organics All Purpose Granular Fertilizer
- BEST VEGETABLE FERTILIZER: Dr. Earth Home Grown Tomato, Vegetable & Herb
- BEST FLOWER FERTILIZER: Jobe’s Organics Annuals and Perennials
- BEST STARTER FERTILIZER: Espoma Organic Bio-Tone Starter
- BEST ACID FERTILIZER: Dr. Earth Organic Acid-Lovers Fertilizer
Types of Garden Fertilizers
Fertilizer comes in three basic forms: granules, liquid, and stakes. Each type of fertilizer can be classified as either organic or inorganic.
Gardeners apply fertilizer granules by either mixing them into the soil at planting time or by “top dressing.” Top dressing simply means sprinkling the granules on the soil surface over the plant’s root zone. You’ll find granular fertilizers in either slow-release or quick-release formulas.
- Slow-release fertilizer should provide a steady flow of nutrients for an extended time, up to a full growing season. These fertilizers comprise organic or inorganic ingredients. Soil microbes break down organic slow-release fertilizer and make it available for plants to use. Manufacturers coat inorganic slow-release fertilizer pellets to slowly dissolve as water moves through the soil.
- Quick-release fertilizer is inorganic. It should dissolve fully into the soil within just a few weeks, giving plants a quick burst of nutrients.
Liquid fertilizers include ready-to-mix dry granules and liquid concentrates. They can consist of either organic or inorganic ingredients. Liquid plant food can soak the roots, or in some instances, spray right onto plant foliage. These formulas are available to the plant immediately.
Fertilizer spikes also come in either organic or inorganic formulas. They act similarly to slow-release fertilizers. Calculate the number of spikes needed for a plant based on plant size and manufacturer directions. Space the spikes evenly around the edge of the plant’s root zone and push them into the soil.
Organic vs. Inorganic Fertilizers
There are two major differences between organic and inorganic fertilizers: ingredients and the way nutrients become available to the plant.
- Organic fertilizers add vital organic matter to the soil and work with the living microorganisms in the soil to feed plants. These fertilizers come from plant and animal sources: composted chicken manure, bone meal, blood meal, alfalfa meal, cottonseed meal, and kelp meal.
- Inorganic fertilizers are highly concentrated and feed plants directly. Manufacturers make inorganic, or synthetic, fertilizers from the synthesized chemicals of nitrogen, phosphorus, and potassium, sometimes as byproducts of other industrial processes.
It is usually best to begin with a soil test to determine the natural fertility of your garden soil before applying fertilizer. Contact your local Cooperative Extension Service to submit a soil sample for testing. The results will show which nutrients your soil might lack, so you can provide those nutrients in the form of fertilizer.
The major nutrients in fertilizer are nitrogen (N), phosphorus (P), and potassium (K). Fertilizer products list these elements on the bag as a ratio such as 10-10-10 or 4-3-4. The package listing always appears in the order N-P-K.
Determining the right ratio for your garden depends on what your plants need.
- Nitrogen supports foliage growth. High-nitrogen fertilizer is useful to help grass get growing in spring or to help collard greens produce a heavy yield.
- Phosphorus helps plants establish roots, produce flowers, and develop fruit. High-phosphorus fertilizer is useful as a starter fertilizer or to spruce up annual flower beds.
- Potassium is an important element for rigid stems and overall plant health. Potassium helps plants get through drought and other growing stresses.
Different kinds of plants, and plants at various stages of life, have different nutrient requirements. Are you planting a brand new flower, vegetable, or herb bed? Use a starter fertilizer to help the young plants become established in their new home. Do your azaleas, camellias, gardenias, or blueberries look weak and puny? Perk them up with a fertilizer specifically formulated for acid-loving plants. Flowering and fruiting plants need plant food with higher phosphorus content, while plants grown for foliage need more nitrogen.
Regular fertilizer applications keep plants vigorous and productive. But, how much should you buy? How often you apply fertilizer depends on your soil type and whether your plants are in raised beds or containers. Most plants growing in porous, well-drained soil or in containers need more frequent feeding, about every three to four weeks throughout the growing season. Plants growing in clay soils typically require less fertilizer. One application every four to six weeks after planting will suffice.
Typically, granular fertilizer will go further than a liquid fertilizer. To determine how much fertilizer you need, look at how much area one bag or bottle covers and divide that by the square footage of your garden beds. This will tell you how much fertilizer will get your plants through the growing season.
Our Top Picks
These organic garden fertilizer recommendations are unlikely to harm plants from accidental over-application, are generally people- and pet-safe, and pose a lower risk for water pollution when used according to the directions.
This all-purpose fertilizer includes a combination of healthy bacteria, mycorrhizal fungi (fungi that form a symbiotic association with plants), and Archaea (a microorganism that aggressively breaks down material). It checks the boxes for most plants and basic plant needs, plus it is Organic Materials Review Institute (OMRI) listed for organic gardening by the USDA, which means it’s 100 percent organic and made with all-natural ingredients. The blend of beneficial microorganisms in the fertilizer helps to improve soil quality, increases root mass, and promotes plant growth without adding harmful chemicals to the environment. The N-P-K ratio is 4-4-4, which makes it a suitable fertilizer for flowers, vegetables, shrubs, trees, and houseplants.
- Contains bacteria and fungi for soil health
- Certified organic
- Increases root mass and promotes plant growth
- Fast-acting, balanced, multipurpose formula
- Needs reapplying every 4 to 8 weeks
- Organic formulation can smell, attracting dogs
Made from human and feed-grade ingredients, Dr. Earth fertilizer is enriched with multi-minerals, proteins, carbohydrates, humic acids, and trace elements that promote the healthiest soils. It’s versatile too. Use Dr. Earth as a starter fertilizer during initial planting and transplanting, and regularly as a top dressing or in compost tea. Dr. Earth fertilizer contains no synthetic chemicals, chicken manure, or toxic ingredients, so it’s safe for pets and people. This fertilizer is sustainably made in the United States and carries the OMRI seal and verification by the Non-GMO Project, a nonprofit organization committed to preserving and building sources of non-GMO products.
- Includes feed-grade ingredients
- Includes nutrients and trace elements
- Safe and certified organic
- Use as starter, top dressing, or compost tea
- Designed primarily to promote vegetable growth
- Powder form must be worked into soil
Featuring Biozome with Archaea (Jobe’s proprietary microbe package), this fertilizer rapidly breaks down nutrients in the soil for faster results and improves soil condition over time by increasing microorganism activity for a healthier, living soil. Made from all-natural materials and certified for organic use, this fertilizer is pet- and people-friendly, will not cause fertilizer burn, and is safe for the environment.
The fertilizer analysis for this Jobe’s product is 3-5-4, which makes it a good source of nutrients for most annual and perennial plants. Use the granular formula on flowering plants such as impatiens, begonias, marigolds, zinnias, blue minks, lilies, daylilies, peonies, ferns, and more.
- Improves soil condition over time
- All natural, certified organic
- Balanced formula for flowering plants
- Small package (1.5 pounds)
- Strong smell attractive to pets
Specially enhanced with beneficial bacteria and starter cultures of seven different beneficial mycorrhizal fungi, Espoma Bio-Tone Starter promotes maximum root development directly after transplanting. Mycorrhizal fungi work symbiotically with the root system of the plants to greatly increase the amount of water and nutrients a plant can use.
Use of Bio-Tone Starter during planting will help seedlings develop a healthy colony of mycorrhizal fungi so the plants will settle into their new homes quicker and thrive in the long run. With an N-P-K ratio of 4-3-4, Bio-Tone Starter is a good all-purpose starter fertilizer that gardeners can use in garden beds for all types of plants.
- Starter fertilizer promotes root growth
- Contains beneficial fungi
- Balanced formula
- Good all-purpose starter fertilizer
- Works best when placed in hole at planting
Some plants need a little acidity to look their best. Acid fertilizers lower soil pH to free up and help plants access nutrients rendered unavailable in high-pH soils. Dr. Earth Organic Acid-Lovers Fertilizer is ideal for hollies, gardenias, hydrangeas, blueberries, evergreens, ferns, shade plants, azaleas, camellias, rhododendrons, and maples. It temporarily lowers pH values in the soil, allowing the plants to absorb the nutrients they need to promote healthier foliage and bigger blooms.
This fertilizer is specially designed to release a portion of nutrients quickly and provide continuous feeding for several months for long-lasting results. It’s also safe for people and pets when used as directed.
- Helps lower soil pH
- Assists plants with absorbing nutrients
- Designed for fast release and continuous feeding
- Safe for people and pets
- Smell can attract pets
- Specialty product for acid-loving plants
Organic fertilizers can improve plant health right away and soil health over time. Jobe’s Organics All Purpose Granular Fertilizer can be your go-to root booster for all the plants you grow, from vegetables to trees. To give vegetables or flowers a great start, apply Espoma Organic Bio-Tone Starter right to the planting hole.
How We Chose the Best Garden Fertilizers
Garden fertilizers can give new plants a boost and feed plants throughout their growing season. We looked at fertilizer type and common plant needs to come up with this carefully curated list of the best garden fertilizers. We analyzed the nutrient ratios, the purpose of various formulas, and the quantity of fertilizer in packages. The list includes multipurpose formulas and a few designed for specific garden uses.
Q. When should I fertilize my garden?
The best time to fertilize plants is when you place them in the ground, beginning with added compost or a starter fertilizer. After that, plants need nutrients during their peak growing season, typically spring through summer. If you select a long-acting or continuous feeder, you can apply it less often.
Q. What is the best fertilizer for vegetables?
Vegetables need a good start, since they typically have a short, one-time growing season. Start them out with a boost of nutrients and good soil, then apply a balanced fertilizer for vegetables and herbs like Dr. Earth Home Grown Organic Fertilizer.
Q. What is the best fertilizer for garden plants?
The best fertilizer depends on the plants. Many native plants need little to no fertilizer, assuming they are growing in decent soils. But flowering plants often need a boost so the plant can stay healthy plus send extra energy into producing lots of large, colorful flowers. Try Jobe’s Organics 9621 Fertilizer for beautiful blooms.
Q. When should I apply 10-10-10 fertilizer to my vegetable garden?
Apply most balanced (10-10-10) fertilizers monthly during the growing season to boost the health of perennial plants. But be sure to check the package directions, since some fertilizers have slow-release formulas that last longer.
Q. How do you naturally fertilize soil?
Nutrient-rich soil is the best type to grow in, and keeping soil balanced and with plenty of humus is preferred by many gardeners over adding fertilizer regularly. Get healthy soil with annual additions of organic compost such as manure, homemade compost from kitchen scraps, and even leaves or grass clippings. Mix up the ingredients for the best effect, and use organic fertilizer as needed.
Q. Are eggshells good for fertilizer?
Ground-up eggshells can add some calcium and other nutrients. They won’t necessarily provide all nutrients all plants need, and they break down slowly, so effects are not immediate. Still, adding them can be part of any effort to keep soil health up; they do not contain enough of any ingredient to harm plants.