Picking a fertilizer can be complicated. You have to consider what plants you are fertilizing, what growth stage the plants are in, and what kind of soil you have. While trying to pick one fertilizer from the hundreds in the store, you may wonder, “What is 13-13-13 fertilizer?”
Need a hand figuring out what fertilizer to use? This guide will tell you all about 13-13-13 fertilizer and when to use it.
What Is 13-13-13 Fertilizer?
Triple 13 fertilizer is composed of thirteen percent nitrogen, thirteen percent phosphorous, and thirteen percent potassium. The numbers on the front of the fertilizer bag are explained in more detail in this article.
Briefly, nitrogen is in every cell of the plant and all the compounds it makes. Without nitrogen, the plant can’t grow. Phosphorous helps with strong roots, and healthy growth, and to trigger blooms. Potassium also helps produce healthy plants that can resist diseases.
Triple 13 is considered a balanced fertilizer because all the numbers are the same. This fertilizer is best for new and established ornamental plants, such as flowers.
What Is 13-13-13 Fertilizer Used For?
Triple 13 fertilizer is usually used in the spring as the initial fertilizer of the year. The balanced formula is a good choice if you do not have a soil test. Triple 13 fertilizer can also be used to fertilize a new area before planting new ornamental plants. While you can use triple 13 fertilizer on any plant, including vegetables like tomatoes, it is most often used on ornamental flowers. You may also use triple 13 during the growing season to add nutrients your plants need to the landscaping bed or row.
When Do I Apply 13-13-13 Fertilizer?
Triple 13 fertilizer is best for the initial fertilizer of the year. The balance of nitrogen, phosphorus, and potassium gives most ornamental plants the nutrients they need to grow for six to eight weeks. Triple 13 can be reapplied to everything but lawns throughout the growing season. Triple 13 is not the best fertilizer for lawns.
How Do I Apply 13-13-13 Fertilizer?
The exact amount of triple 13 fertilizer you need depends on what plant you are fertilizing. The label instructions for each fertilizer will tell you how to apply that fertilizer. Here are some examples of what you can expect to use when fertilizing different types of plants.
For annual flowers, spread 2 1/2 cups per 100 square feet out after your bed is prepared for planting. Work the triple 13 fertilizer into the top two to three inches of soil. Plant your annual flowers as usual. Every six to eight weeks, spread another 1 1/4 cups per 100 square feet.
Existing Ornamental Plants
For existing ornamental plants, including shrubs, you typically spread 2 1/2 cups of granular triple 13 fertilizer per 100 square feet. Do not let the fertilizer touch the plants. Every six to eight weeks, spread 1/2 cup per 100 square feet. Stop fertilizing about one month before the first frost.
Bulbs and Tubers
For bulbs and tubers, spread three cups of triple 13 per 100 square feet before planting the bulbs. Work into the top two to three inches of soil. If you are planting your bulbs and tubers in a row, use 2 1/4 cups per 100 feet of row. Place triple 13 fertilizer in the trench the bulbs and tubers will go in, then cover with an inch of soil. Place the bulbs and tubers on the soil. The fertilizer should not touch the bulbs.
For vegetable gardens, use 2 1/2 cups per 100 square feet before turning the soil for the new season.
Alternatively, you can wait until the soil is turned and spread 2 1/2 cups per 100 square feet and work the fertilizer into the top three inches of soil.
If planting in rows, use 1 1/4 cups per 100 feet of row. Place the fertilizer two inches from the plant or seeds in a trench two inches deeper than the seed or plant. Cover the trench in soil.
For vegetables that grow a long time, like onions or corn, spread 1 1/4 cups of fertilizer per 100 feet of row six inches from the plants and parallel to the row every six to eight weeks until harvest.
For tomatoes, this fertilizer will work for the initial fertilizer at planting. After that, it has too much nitrogen to be used. You will get all foliage and few or no tomatoes if you apply it after the tomato plants are planted. For anything you need to know about tomato fertilizer, read my article.
Berries are not usually fertilized with 13-13-13. Read my article for everything you need to know about blueberry fertilizers. Blackberries should be fertilized with 20-20-20. Triple 13 does not have enough nutrients for them.
For trees, apply three pounds per 1000 square feet of canopy. Spread the fertilizer directly under the drip line. For fruit trees, including pear trees, you should use 10-10-10 instead. Triple 13 is intended for ornamental trees, not fruit trees. For pecan trees, use 16-4-8 instead.
Triple 13 fertilizer is not intended for lawns. A better choice would be 16-4-8. Grasses like Bermuda grass and ryegrass, along with the other grasses used for lawns, need more nitrogen and less phosphorus and potassium than 13-13-13 offers.
Always water your plants after applying fertilizer. Granular fertilizer requires water to activate it and send the nutrients into the soil.
Liquid 13-13-13 fertilizer is not usually used. Spring fertilizers need to be slow-release so they last well into the growing season, and liquids are not slow-release. Liquid triple 13 is not practical because of the large amount of liquid needed and the frequent applications required.
Where Do I Buy 13-13-13 Fertilizer?
Triple 13 fertilizer can be bought at garden supply stores online, such as Amazon. This fertilizer is sometimes carried by big box stores such as Tractor Supply and Home Depot.
My 13-13-13 Fertilizer Recommendations
Control Release Plant Food 13-13-13 contains all twelve of the nutrients plants need to grow and thrive. These nutrients are encased in a coating that slowly dissolves, releasing the fertilizer over three to four months, so you do not have to fertilize your plants as often. Control Release Plant Food 13-13-13 is best on bulbs, ornamental plants, and bedding plants. It is not organic.
For landscape beds, simply spread four pounds of Control Release Plant Food 13-13-13 per hundred square feet, then work into the top two to three inches of soil. Repeat every three to four months. Water the plants after you fertilize them.
For container plants, use 1/8 teaspoon per inch of pot diameter or ½ teaspoon per gallon of pot. For sensitive houseplants, use half of the recommended amount. Water the plant after you fertilize it.
Groundwork 13-13-13 All-Purpose Fertilizer works for vegetables, ornamental trees and shrubs, perennials, bulbs, and annuals. This triple 13 does not have any extra nutrients added, so supplies nitrogen, phosphorus, and potassium only. It is a synthetic granule.
For new plants and vegetables, apply two pounds per 100 square feet of garden. For established plants, use one pound per 100 square feet of garden. Water the fertilizer in.
For evergreen trees, spread 1 ¼ pound per 1100 square feet of bed in early spring. Do not use it on flowering trees. Water the fertilizer in.
For deciduous trees, use in early spring or in the fall after leaf drop. Drill two-inch holes six to eight inches deep and two to three feet apart around the outer dripline. Using one to two pounds of fertilizer per inch of trunk at chest height, distribute the fertilizer in all the holes, then fill in the holes. Water the fertilizer in.
Elegant Garden 13-13-13 General Purpose Fertilizer is a good general-purpose triple 13 with iron and calcium in it. The granules contain fast-release fertilizer to give your plants the nutrients they need in the spring to start growing. Use on bulbs, ornamental trees and shrubs, perennials, and annuals. This product is not organic.
For landscape beds, use a half pound of fertilizer per 100 square feet of landscape bed. Make sure that none of the granules touch the plant stems and foliage. For trees, apply a half pound of fertilizer per inch diameter on the trunk at chest height. Spread it evenly under the canopy of the tree. Water the plants after you fertilize them.
Elegant Garden 13-13-13 General Purpose Fertilizer does not have instructions for container plants. I would recommend using another product for them that does, such as the Control Release Plant Food 13-13-13 mentioned above.
What Are the Ingredients in Triple 13 Fertilizer?
The exact ingredients in a triple 13 fertilizer depend on the brand. Each bag of triple 13 is guaranteed to have thirteen percent nitrogen, thirteen percent phosphorous, and thirteen percent potassium.
Some brands also include other nutrients that plants need. In addition, some manufacturers put soil microbes and nutrients for soil microbes in the fertilizer to help make the nutrients more available to the plants.
Finally, some manufacturers include proprietary ingredients to help plants use the nutrients in the fertilizer. The rest of the fertilizer is filler to make it easier to spread and compounds to retard spoilage.
Some triple 13 fertilizers are organic, but they are difficult to find. Most triple 13 fertilizers are conventional.
Liquid formulations of triple 13 are also difficult to find. Granular formulations are generally slow-release, so they last a long time.
13-13-13 Versus 10-10-10 Fertilizer
While triple 13 and triple 10 are both balanced fertilizers, they are not interchangeable. You use a balanced fertilizer, where all the numbers are the same when your soil test reveals equal levels of nitrogen, phosphorus, and potassium.
Triple 10 is an excellent all-around fertilizer for ornamental plants, vegetables, trees, and shrubs. Triple 13 helps ornamental plants bloom, so it is primarily used on annuals, perennials, bulbs, and ornamental trees and shrubs to give them the nutrients they need to wake up in the spring and start blooming.
Triple 13 can be used throughout the growing season to give these plants the nutrients they need.
Frequently Asked Questions
How long does it take triple 13 to work?
Triple 13 usually takes a week to start working because it takes that long for the coating to dissolve enough to release the first nutrients.
How long does triple 13 fertilizer last?
Most formulations last six to eight weeks before you need to apply more fertilizer. Do not reapply the fertilizer to lawns until fall, and only apply triple 13 twice per year to turf grass.
Is 13-13-13 good fertilizer for fall?
Triple 13 may be applied to annuals until they are killed by the cold. This fertilizer should not be used on perennials, shrubs, or trees within a month of the average first frost date. Triple 13 can be applied to turf grass in the fall, but only once.
Will 13-13-13 fertilizer kill weeds?
No, triple 13 fertilizer will not kill weeds. Some products include a weed killer and triple 13 fertilizer, which will kill weeds, but triple 13 alone will not kill the weeds.
Will 13-13-13 fertilizer burn grass?
If you exceed the amount listed on the fertilizer label, you can burn your grass. In addition, if you apply triple 13 to your grass more than twice a year, you can burn your grass.
Will 13-13-13 fertilizer cure my sick plants?
If your plants are sick because they lack nitrogen, phosphorous, or potassium, triple 13 will help. If your plants have a disease or pests, triple 13 will not help them.
In conclusion, 13-13-13 fertilizer is a fertilizer that contains thirteen percent nitrogen, thirteen percent phosphorous, and thirteen percent potassium. The fertilizer may contain other nutrients or proprietary ingredients to help the plant use the nutrients in the fertilizer. Some triple 13 fertilizers are organic, while most are synthetic. Granular fertilizers are best for ornamental plants because they are slow-release and will last several months before you have to reapply them. Apply in early spring to wake up your ornamental trees and shrubs, bulbs, annuals, and perennials. You can also use triple 13 as the initial fertilizer when planting vegetables.