What Is 13-13-13 Fertilizer And When Should You Use It?


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Fertilizing your lawn annually helps keep it lush and green. Giving the grass more of the nutrients that it needs to thrive also allows it to grow quickly before weeds get a chance to pop up. So there’s more than one good reason to feed your lawn. In the quest for the perfect fertilizer for your front yard, you’ve probably come across 13-13-13. But what exactly is 13-13-13 fertilizer, and what can it be used for?

After reseeding your lawn, 13-13-13 fertilizer is a good choice because it gives the young grass the nitrogen, phosphorous, and potassium that it needs to sprout. This type of fertilizer can also be used to feed ornamental flowers and shrubs to support healthy foliage.

What do the numbers in 13-13-13 stand for?

Many commercial fertilizers have three numbers separated by hyphens. These numbers represent the percentage of nitrogen, phosphorous (also called phosphate), and potassium (also called potash) in the fertilizer. So 13-13-13 fertilizer has 13% nitrogen, 13% phosphorous, and 13% potassium. 

Nitrogen is essential for photosynthesis. Without it, plants turn yellow and develop anemic-looking leaves. Phosphorous is necessary for cell division and the growth of new tissue. This mineral helps plants get established quickly, and without it, plants become stressed. And potassium enables plants to utilize the moisture that’s in the soil, while also increasing drought tolerance.

While plants rely on a variety of vitamins and minerals in the soil to survive, N-P-K fertilizers provide them with the three things they need most. Applying the appropriate N-P-K fertilizer to your lawn helps it start out on the right foot so it can look great and grow well all season long.

Yellowing grass may benefit from 13-13-13 fertilizer.

Is 13-13-13 good for fertilizing your lawn?

When it comes to fertilizing your lawn, 13-13-13 is a fantastic all-purpose fertilizer for the task. Because it contains moderate amounts of nitrogen, phosphorus, and potassium, it works well on any lawn that needs a perk-me-up.

A 13-13-13 fertilizer contains an equal balance of nutrients. It’s ideal for a lawn that is well-kept. Regularly mowing, raking, and de-thatching your lawn, while necessary for its health, ends up taking away nutrients from the soil over time. Using 13-13-13 fertilizer helps to top off mineral levels, ensuring the grass in your yard has everything it needs to be at its best.

Another major benefit of 13-13-13 is that it breaks down quickly. If your lawn is looking a little sad, this fertilizer can make a big difference within about a week’s time. Compare that to some organic fertilizers which can take a few weeks before they even start releasing nutrients into the soil.

13-13-13 is an all-purpose fertilizer that works well for most lawns.

How can you tell if your lawn needs 13-13-13 fertilizer?

It’s always best to test your soil before applying 13-13-13 fertilizer. You can’t tell how much of which minerals are in your soil just by looking at it. And when you apply fertilizer without fully understanding your soil, you run the risk of doing more harm than good. 

Applying 13-13-13 fertilizer to soil that contains plenty of nitrogen could backfire. Have you ever noticed how the grass turns yellow and dies around freshly spread manure or dog poop? That’s because excrement is high in nitrogen, and too much nitrogen burns a plant’s foliage. Likewise, adding more phosphorous and potassium to soil that already has plenty can end up killing your lawn. 

On the other hand, if the soil in your yard is severely nutrient deficient, then 13-13-13 may not be strong enough to do the job. Extremely low levels of nitrogen, phosphorous, and potassium should be built up, ideally with organic materials like compost. But a fertilizer with a higher percentage of these nutrients, like 19-19-19, can be helpful, too. 

Does 13-13-13 fertilizer alter the soil’s pH?

You run the risk of altering the pH anytime you add something to the soil. It’s unavoidable, and not necessarily a bad thing. For instance, if your soil is too acidic, then adding wood ash, which is alkaline in nature, can help bump up the pH just enough to make the soil neutral and, therefore, hospitable to a wider variety of plants. 

The nutrients in 13-13-13 may alter your soil’s pH over time. Nitrogen, particularly if it’s ammonium-based, acidifies the soil. Phosphorous also has a tendency to lower the soil’s pH, though potassium’s effects are minimal. 

It’s worth noting, too, that your soil’s pH can impact how effective 13-13-13 is. If your soil is already somewhat acidic, you may need to add lime first to raise the pH before investing in other fertilizers. Adding acidic substances to already acidic soils acidifies things even further, to the point that the plants in your lawn and garden may have even less access to nutrients than they did before you fed them. 

Use an at-home soil pH test to gain a better understanding of your soil’s properties. When you have a good idea of what’s going on underground, you’ll be able to give your plants the things they need to stay healthy. 

When should you apply 13-13-13 fertilizer?

It’s best to apply 13-13-13 fertilizer every spring, just as the grass in your lawn is starting to sprout up. Young plants leech a ton of minerals out of the soil. Feeding grass at this time gives it the boost it needs to fill in quickly and grow nice and thick, covering your yard in a carpet of green.

This fertilizer is also a good one to apply after reseeding your lawn. Providing seedlings with an extra dose of minerals enables them to become established much more quickly. A heavy application after reseeding your lawn will encourage good growth. 

Because 13-13-13 is fast-acting, it should be reapplied regularly. You’ll know it’s time to give your lawn another feeding when the vibrant color starts to fade. If you notice your grass is turning yellow or brown even after you’ve applied a fertilizer, test the soil before fertilizing again to address any nutritional imbalances. 

It’s best to fertilize your lawn in spring.

What else can you use 13-13-13 fertilizer for?

While 13-13-13 is traditionally applied to lawns and large grassy areas, like golf courses, it can also be used to feed the plants in your landscaping. This fertilizer has enough nitrogen and potassium to help your garden plants stay green. Plus, the added phosphorous provides flowering plants like hydrangeas with the extra nutrition they need to bud out and reproduce. 

If you notice your shrubs are underperforming and the flowers you planted earlier in the year still haven’t become established months after transplanting, that’s a good sign they need more nutrition. An equal dose of nitrogen, phosphorous, and potassium will help these plants develop healthy roots and turn the sunlight and water they receive into the energy they need to survive. 

You can also use 13-13-13 to feed the veggies in your garden. Apply this fertilizer in spring to support crops throughout the flowering period. The more flowers they produce, the more fruits you’ll have to pick at harvest time. 

You can also use 13-13-13 to feed flowers, like hydrangeas.

How should you apply 13-13-13 fertilizer to an established lawn?

A walk-behind broadcast spreader is all you need to apply 13-13-13 on your lawn. Simply fill the spreader with the fertilizer and wheel it back and forth until the whole lawn has been covered. There’s nothing to it.

It’s standard practice to apply 10 pounds of fertilizer for every 1,000 square feet in the spring. Never apply fertilizer to wet grass. Water droplets catch the fertilizer, causing it to cling to the plant and burn the foliage. For best results, apply 13-13-13 fertilizer in the afternoon, when the morning dew has dried up. 

After the initial fertilization, you can scale back on the amount of fertilizer you use. Apply 7 pounds of fertilizer for every 1,000 square feet to your lawn every 8 to 10 weeks. Be sure to water your lawn after applying the fertilizer, or apply the fertilizer before scheduled rainfall. Water activates the fertilizer, allowing it to seep into the soil. 

Note: always read the instructions before applying a commercial fertilizer. This will maximize your chances of success, and prevent damage to your local ecosystem. 

Regular feeding keeps an established lawn healthy.

How should you apply 13-13-13 fertilizer to a newly seeded lawn?

If you’ve just reseeded your yard, then the grass’s nutritional demands will be greater than that of a more established lawn. You’ll need to drastically increase the amount of fertilizer you use to ensure the seed has everything it needs to sprout up evenly, so there are no bare spots. 

Apply 5 pounds of 13-13-13 fertilizer for every 1,000 square feet of a newly seeded lawn. Apply the fertilizer before the grass begins to sprout, and avoid fertilizing if the grass is damp. Use a broadcast spreader to apply the fertilizer, then use a garden hose or sprinkler to water it down. 

Once your reseeded lawn has started to come in, decrease the amount of fertilizer you use in your applications. Use 7 pounds per 1,000 square feet every 8 to 10 weeks. Regularly feeding a new lawn is key to developing a solid root system, so be sure to stick to your fertilizing schedule.

Apply 13-13-13 using a walk-behind broadcast seed spreader.

How should you apply 13-13-13 fertilizer to your flower beds?

Obviously, you can’t roll a broadcast spreader through your flower beds. You’d trample them into the dirt. It’s not good for ornamental plants to get fertilizer on their leaves, anyway, so use gloves to scatter 13-13-13 around the base of the plants, and work it in with a weed fork. Follow the instructions on the bag to determine how much fertilizer your plants need. One or two tablespoons is usually enough for small plants, but larger ones may need ¼-cup or more. Once the fertilizer has been applied, water the plants thoroughly. As with your lawn, you’ll need to feed the plants every 7 to 10 weeks. 

Use a weed fork to work 13-13-13 into your flower beds.

Will applying 13-13-13 fertilizer to your lawn harm your trees?

It’s perfectly safe to apply 13-13-13 around the trees in your lawn — in fact, they’ll probably benefit from it, too. Like other plants, trees rely on nitrogen, phosphorous, and potassium to produce energy and to create healthy, vibrant foliage. When applying 13-13-13 fertilizer to your lawn, there’s no need to try to avoid the trees. Just remember to water around them, as well, so the fertilizer doesn’t burn their roots. 

It’s safe to use 13-13-13 around trees.

More tips for applying 13-13-13 fertilizer

Fertilizing annually restores minerals that were lost during the previous season. Plants benefit from regular feedings. Just be sure to wear long sleeves and pants when applying fertilizers, and avoid inhaling them or getting them on your skin, as they can burn. You should also avoid applying fertilizer near ponds and streams. Excessive nitrogen and phosphorus can lead to eutrophication, a burst in phytoplankton activity that can have devastating consequences for the agricultural industry and your local ecosystem as a whole. 

By applying 13-13-13 fertilizer properly and only when necessary, you can help the plants in your lawn and garden reach their full potential. 

About The Author
Michelle Sanders is an outdoor enthusiast who is passionate about teaching others how to observe and support their local wildlife. She enjoys gardening, birdwatching, and trying (in vain) to get butterflies to land on her.

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