This article is part of our Mulch Madness series. Mulch Madness is The Spruce's gardening "full court press"—a curation of our very best tips and product recommendations to help you create a truly trophy-worthy lawn and garden.
Four types of fertilizers — compost, mulch, commercial synthetic products and organic products — come in several forms and are applied using different methods. All fertilizers provide nutrients to feed the plants in your landscape, but each offers benefits that more accurately and efficiently target specific projects like a vegetable garden or lawn.
Lawn and garden maintenance can be enjoyable but almost always require a commitment of time and physical labor. The good news is there are plenty of products out there to help you add beauty and value to your property and an important one to consider is fertilizer. We looked into the four different types of fertilizer and their uses to help you choose the best one for your green thumb project.
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- Best for: Rapid results, lawns
Synthetic fertilizers are manufactured chemicals in liquid or granular form and also available as a slow-release product. Full strength fertilizers are ready to use, or you can purchase concentrates to mix at home. They quickly provide nutrients to your lawn, flower beds, and vegetable gardens.
Synthetic fertilizers are fairly easy to apply and can be added to soil both before and after planting. Liquid forms are often diluted with water or added when soil is wet after watering or rainfall. Some liquid fertilizers can also be applied directly onto leaves for nutrient uptake. Granular fertilizers work best when watered in or worked into the soil. Other fertilizers, specifically for trees and houseplants are spikes that are pushed into the ground (trees) or pot (houseplants.) These are a slow-release type designed to break down over time for a longer, continuous feeding.
You can purchase an all-purpose product to use with a number of different plants or opt for one of a wide range of synthetics available that target specific plants. There are fertilizers to feed your tomatoes, roses, flower bulbs, trees and shrubs, houseplants and more. Other products may promote blooming or support root growth in seedlings. Most are readily available at garden stores with a greater range of specialty products at greenhouses and plant nurseries.
Synthetics are the most practical option for keeping the lawn lush, green and weed free because they are easily applied to existing turf where other fertilizers like compost or mulch would smother and kill existing grass.
You may see results almost immediately using synthetic fertilizer, but repeated applications are often necessary to keep your greenery looking its best. This type of fertilizer can also be costly.
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Best for: Improving soil, vegetable gardens
Compost is a mix of organic materials like grass clippings, dry leaves and other decaying plant material, kitchen scraps and manure. The mix is most often applied by tilling or digging it in to existing soil. You can make your own compost pile or purchase it by the scoop or bag. It is easiest to add before planting but can also be added at the time of planting or afterward as a side dressing. Compost has to break down in the soil before the nutrients are available to plants, which makes this a slow acting fertilizer with long-term results.
Compost provides nitrogen, improves the texture of your soil, and attracts beneficial organisms and microorganisms. It is an excellent annual addition to vegetable gardens, flower beds and shrubs, but not practical as an addition to existing lawns. Compost is eco-friendly and inexpensive but requires some physical effort to apply.
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Commercial Organic Fertilizer
Best for: Small applications, discouraging rodents
Some of the more common commercially packaged organic fertilizers include bloodmeal, bonemeal, bat guano, fish emulsion, and kelp meal. Some products boost the acidity or alkalinity of soil while others add a specific element. Only a few of these are easy to find at garden stores, although you may see a greater selection at plant nurseries. Cost is a factor when choosing these organics. Applying them to large garden areas can be cost-prohibitive.
They do work very well for small, specific applications like fertilizing certain vegetables and flowers. Cole crops, which are heavy feeders, benefit from bloodmeal which adds nitrogen to the soil and has the added benefit of deterring rabbits and other small rodents that are repelled by the odor. Fish emulsion makes an excellent foliar spray for feeding seedlings and bonemeal is high in phosphorous which promotes root growth to support healthier plants.
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Best for: Protection, appearance
Mulch as a viable fertilizer is made up of materials like tree bark, straw, decaying leaves and other natural materials. Common tree bark mulches are cedar, pine and hardwood and usually come in three sizes, shavings chips or nuggets. Straw is sold by the bale in most places and pine straw, another popular natural mulch, is sold by weight when you can find it. Grass clippings and leaves are usually gathered from your own yard. These types of mulch slowly break down over time to add nutrients and improve the texture of the soil.
Mulch serves several other purposes in the garden. It helps hold in moisture and keeps the soil surface cool. It suppresses weeds and works as winter protection for many plants including shrubs and ornamental trees. Finally, mulch adds a lovely finished look to your flower beds, and other plantings.
There are many materials called mulch that don't contain any nutrients for your plants and, in fact, may not be ideal for your gardens at all. Mulch can be made of rubber, stone, plastic, newspaper and other inorganic materials. Newsprint and even some decorative colored tree bark mulches contain dyes that you may not want to add to your soil. Stone or pebbles contain minerals that can leach into the soil with watering, however, stone takes a very long time to break down.
Choosing a Fertilizer
How to choose the best fertilizer for your yard and garden projects can be a simple process and you don't always have to limit yourself to just one type. You can choose to add a nitrogen rich synthetic fertilizer to start your vegetable garden and then side dress your crops with compost, manure or commercial organics mid-season. Although bark mulches don't work well in the vegetable garden they are effective in combination with synthetic fertilizers for flowerbeds and trees.
When you need a product that can be easily applied to an existing planting, such as a lawn, established flowerbed or trees and shrubs, synthetic fertilizers work to boost growth and don't require disturbing the soil. A large vegetable garden will benefit from an early application of slow-release granular fertilizer high in nitrogen before you transplant or sow seed. Synthetic fertilizers and commercial organics are good choices for your orchid collection, houseplants, roses and any other specific type of plant or small crop planting.
Compost is easiest to add before planting, is organic, and works best for long-term soil improvement. Most vegetable gardens are planted in the same place every year which depletes nitrogen. The nutrients need to be constantly replenished which makes an annual addition of organic compost the ideal fertilizer for edible crops. Compost can be worked into soil for new flowerbeds, added at the time of planting, or applied as a side dressing to both flowers and food crops during the growing season.
Natural mulch serves as a finishing touch to flowerbeds and landscape plants. It is applied in the spring or fall and, when added annually, will slowly break down as a slow release fertilizer for your garden projects. A few natural mulches, straw or decaying leaves, can work in a vegetable garden but because they break down more slowly than compost, won't supply the annual nitrogen requirement for most crops.
Reading NPK Ratios
The primary minerals plants need to grow are nitrogen, phosphorous and potassium. Synthetic fertilizer labels carry an NPK ratio that tells you what percentage of each of these minerals makes up the product. An NPK ratio of 15-10-10 means that the product contents include 15 percent nitrogen, 10 percent phosphorous, and 10 percent potassium. Labels may also list secondary minerals, resins and fillers to help you determine if the product has everything you need.
Fertilizer | University of Maryland Extension.
Soils and Fertility, Craig Cogger, University of Washington and Brad Lee, University of Kentucky. AGR 204