Many products are available to help to boost lawn health and garden production, and 13-13-13 fertilizer is one of the most popular. While it’s not the best choice for every garden need, I’ve found that triple 13 fertilizer is a convenient product to have on-hand for various uses.
13-13-13 fertilizer is excellent for feeding both new and existing lawns, fertilizing trees and shrubs and general use in the vegetable and flower garden. Triple 13 is a salt-based fertilizer that breaks down quickly, making the nutrients available to your plants fast. Quarterly reapplications are usually needed to maintain soil nutrient levels.
In this post, you’ll find out where triple 13 fertilizer is best put to use and how to apply it effectively and safely.
Let’s get started!
- 13-13-13 fertilizer is a good all-purpose formula for lawns, gardens, trees and shrubs.
- It’s a fast-acting formula that requires reapplication every couple of months to maintain results.
- Some plants may need a more targeted fertilizer for best growth and production.
- Triple 13 fertilizer is best applied in warm months, not in cold or overly dry soil.
What Is 13 13 13 Fertilizer?
Triple 13 fertilizer is a chemical fertilizer with equal amounts of the three macronutrients:
- Nitrogen (N)
- Phosphorus (P)
- Potassium (K)
All plants require these key nutrients in some amount, and fertilizer packages often abbreviate the formula using the nutrients’ chemical symbol: NPK.
A bag of fertilizer with the ratio 13 13 13, also known as “triple 13,” includes 13% of the total pound weight of the bag devoted to each nutrient.
The values indicate the proportion of nutrients present relative to the bag’s total weight.
- A 100-pound bag of 13-13-13 fertilizer contains 13 pounds each of nitrogen, phosphorus and potassium.
- A 50-pound bag of 13-13-13 fertilizer contains 6.5 pounds each of nitrogen, phosphorus and potassium.
- A 20-pound bag of 13-13-13 fertilizer contains 2.6 pounds each of nitrogen, phosphorus and potassium.
When all numbers in a nutrient profile are the same, like 13-13-13, 5-5-5 or 19-19-19 fertilizer formulas, it indicates a balanced level of each nutrient.
What Is 13-13-13 Fertilizer Good For?
13-13-13 fertilizer is good for a variety of plants and crops, including these:
13-13-13 fertilizer for grass does wonders- since it’s a fast-acting formula, it’s great for quickly greening up your lawn. Reapplying the fertilizer every 12 weeks or so is effective for maintaining a consistent green color.
Vegetables usually demand a pretty high supply of nitrogen, phosphorus, and potassium, and triple 13 fertilizer can be a good choice for all-purpose feeding.
Triple 13 is a good all-purpose option for boosting garden soil nutrients pre-planting and during the mid-season when soil nutrient levels may start to become depleted.
Phosphorous is key for strong roots and new cell production needed for a lovely show of flowers, and 13-13-13 fertilizer provides a nice boost.
Trees and Shrubs
Ornamental trees and shrubs benefit from a balanced diet of nitrogen, phosphorous and potassium provided by a 13-13-13 formulation.
One exception is evergreens, which benefit from a more targeted formula. For more details, visit our post on fertilizers for arborvitae.
13-13-13 fertilizer is an excellent choice for feeding your fruit trees. Typically, feeding twice annually is a good strategy.
Where to Avoid Using 13-13-13 Fertilizer
While a 13-13-13 formula helps provide an overall nutrition boost, it shouldn’t be your go-to for all your vegetable garden crops. Many veggie plants go through a flowering and fruiting stage, and they need more phosphorous and potassium at these times.
Stacie Krljanovic, head groundskeeper and consultant at Patio Productions, recommends a more tailored fertilizing strategy for garden favorites, like tomatoes and peppers. “It is important to choose a fertilizer that is formulated specifically for the plants you are growing. For example, vegetables such as tomatoes and peppers typically benefit from a higher amount of phosphorus, which helps with root development and fruit production.”
Stacie continues, “If you are looking for a fertilizer specifically for vegetables, you may want to consider using a fertilizer that is formulated for vegetables or that has a higher percentage of phosphorus, such as a 10-20-10 or 5-10-5 formula. It is also a good idea to have your soil tested before applying fertilizer, as this will help you determine which nutrients are lacking and how much fertilizer to use.”
There are a few other instances when 13-13-13 fertilizer isn’t a great option:
- Acid-loving plants such as azaleas or rhododendrons: these plants require a fertilizer with a lower nitrogen content.
- Cold or dry soil: soil conditions like these can cause the nutrients to leach out of the soil before plants can absorb them.
- Aquatic plants: the nutrients can pollute nearby water sources.
- Houseplants: the high percentage of nutrients in triple 13 is too intense for indoor potted plants. Use a 1-1-1 or diluted 4-4-4 concentration instead.
When to Apply 13-13-13 Fertilizer
The best time for the 13-13-13 fertilizer application rate to be effective is when the soil is warm and moist, usually during the spring or summer months.
It is crucial to adhere to the instructions on the fertilizer bottle to avoid harming your plants from over-fertilization.
How to Use 13-13-13 Fertilizer
The 13-13-13 fertilizer application rate depends on the space, timing, and the type of plants you aim to fertilize. Most triple 13 fertilizers are in granular form, but there are a few liquid formulas as well, so I’ll cover those too.
How to Apply Granular Triple 13 Fertilizer
The first step in applying granular triple 13 fertilizer is determining how much you need. This will depend on the size of the area you are treating and the type of plants you are fertilizing.
Triple 13 for Lawn Care
Lawn care is the most popular way to use triple 13. Since it’s a fast-acting formulation, it should provide a quick boost of green to your grass.
Always refer to the package directions for specific application doses and frequency, but these numbers can help provide a rough idea:
- For an established lawn, apply 10 pounds of triple 13 fertilizer per 1000 square feet just before the start of the growing season.
- For a brand-new lawn at the start of the growing season, apply 15 pounds of triple 13 fertilizer per 1,000 square feet. Since triple 13 is a fast-acting (and therefore fast-degrading) formula, you’ll need to repeat the application every 8-10 weeks, using about 10 pounds of fertilizer per repeat application.
After calculating how much to use, sprinkle fertilizer out across the area to be treated. Depending on the area you’re fertilizing, you can use a small shovel or a broadcast spreader.
After application, water the area thoroughly to ensure that your fertilizer is absorbed into the soil, where it can do its job.
Triple 13 for Vegetable and Flower Gardens
Apply about 1 pound of 13-13-13 fertilizer for every 100 square feet of vegetable and flower beds. Early spring is a great time for a general soil boost, especially if a soil test indicates low overall nutrient levels.
For a general application, use a broadcast spreader evenly sprinkle the granules by hand. Rake them into the soil and water the area well.
For mid-season fertilizing, apply a top dressing over the desired areas roughly every 3-4 months during the growing season. Always make sure to water the fertilized plants well after applying.
Triple 13 for Trees and Shrubs
Apply a top dressing around the bases of trees and shrubs at the rate of 1 pound per 100 square feet.
Use a broadcast spreader or sprinkle the fertilizer by hand, starting near the trunk and going all the way to the drip line. Avoid putting the fertilizer directly on any exposed roots- aim for the soil instead.
After application, water your trees/shrubs thoroughly.
How to Apply Liquid Triple 13 Fertilizer
Most 13-13-13 fertilizer formulas are granular, but a few companies produce liquid formulations. These are typically highly concentrated, and they’re meant for large-scale foliar applications to help plants recover from stressful conditions.
Dilute the triple 13 fertilizer according to the package directions for the total area you plan to treat. Add the prepared fertilizer to a backpack or handheld sprayer and apply to the desired plants, spraying it directly onto the leaves.
This video from MIgardener has a helpful demonstration of foliar fertilizing:
Early morning is the best time to apply foliar fertilizers. Do not apply during the late morning or mid-day- the sun’s harsh rays can quickly scorch wet leaves.
Using Triple 13 Fertilizer Safely
Whenever you’re working with 13-13-13 fertilizer (or any fertilizer), you risk health problems if you don’t take the proper precautions.
Use sturdy gloves (chemical-resistant rubber ones are the best), a dust mask and protective goggles.
I didn’t realize that fertilizer is as potentially hazardous as it is for longer than I care to admit, but it’s worth knowing about. Salt-based fertilizers contain nitrogen in the form of nitrates, and when your body is exposed to them in large enough quantities, it can cause health problems, including:
- Skin/mucus membrane irritation
- Reproductive problems
According to WebMD, the greatest danger is ingesting nitrates, which you probably won’t be doing while working with fertilizer. But there is also risk from direct skin contact and inhaling dust, so it’s always better to play it safe and use the proper protective gear from the get-go.
Frequently Asked Questions about 13-13-13 Fertilizer
Fertilizing our gardens and lawns is a big part of keeping them healthy and thriving. In my experience, 13-13-13 fertilizer is a handy multi-use formula that works well for grass, trees, shrubs, flower beds and general start-of-season vegetable gardens.
I’d love to hear from you! Do you have any other questions about tripe 13 fertilizer, or maybe you’ve got some application or use tips to share that you’ve picked up along the way? The best way to learn is from others in the gardening community, so please share your thoughts in the comments!