Are Coffee Grounds Good For Blueberries? ☕

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Coffee grounds don’t just provide a delicious beverage; they can also be used to provide nutrients to your garden. But the strong acidic content means that they won’t be suitable for all species. So, can you use coffee grounds for blueberries?

Blueberries prefer the acidic soil conditions that coffee grounds can create. They will also benefit from the high nitrogen levels. Coffee grounds can be added to a blueberry patch through mulching, diluting the grounds in water, or sprinkling some onto the soil.

Coffee grounds and blueberries will make a wonderful pairing. But you still need to be careful about how you use the grounds. Too much, and the soil can become too acidic. Keep reading to learn how to use coffee grounds to help your blueberries thrive.

Table of Contents

Why Use Coffee Grounds with Blueberries?

To understand why coffee grounds are so beneficial, we need to understand the soil conditions that blueberries require.

First, they will need acidic soil. Blueberries will often do best if the soil pH is between four and five. This is lower than most other plant species. Because they are acidic, coffee grounds can help reduce the soil pH levels to create a more suitable growing environment for blueberries.

The other reason why gardeners prefer to use coffee grounds is their high nitrogen levels. Blueberries require a fertilizer containing high nitrogen levels while low levels of nitrates. This is something that coffee grounds can provide. Furthermore, coffee grounds can take a while to break down, slowly releasing nutrients into the soil.

There are a few other soil conditions that a healthy blueberry plant will need; these are:

Well-drained area

Location that gets full sun and is protected from the wind
Organic material, like manure, should be mixed into the soil.

Of course, not all plants will benefit from the use of coffee grounds. If you apply this type of mulch to the wrong type of plant, you can cause substantial problems. The acidity can lead to stunted growth and lower fruit yields. If you want more information, check out this post on the plants that don’t like coffee grounds.

Signs Of High Soil pH

One of the biggest concerns is that the soil pH levels will be too alkaline for blueberries to thrive. In this case, it will be difficult for the blueberry plants to get the nutrients they need from the soil. Here are a few signs that the soil is too alkaline for blueberries:

Yellowing leaves
Stunted growth

Lack of fruit
Weaker shoots might die during the winter months

The longer your plant stays in these soil conditions, the weaker it will become as it cannot absorb the nutrients it needs to grow.

The good news is that there is a simple way of determining whether the soil is suitable for your plants. You can perform a pH test. You should be able to find this at your local hardware store. It’s fairly simple to use and should contain the necessary instructions.

There are a few other reasons why your blueberry bushes might be struggling; these include:

Iron deficiency. This occurs when the leaves turn yellow, but the veins remain green.

Magnesium deficiency. In this case, the edges of the leaves will develop a reddish, yellow tinge.

You can perform soil tests to see if these deficiencies are responsible for your blueberry plant’s struggle.

How To Use Coffee Grounds With Blueberries?

There are a few methods that you can use to add coffee grounds to the soil. Let’s look at some of the options that you can explore.

Mixing The Grounds Into The Soil

The first option to consider is mixing the grounds into the soil. It’s best to do this before you plant out the blueberries. Here are the steps you will need to follow to do this:

Sprinkle a handful of coffee grounds onto the soil. Make sure to spread them out throughout the garden patch.
Use a shovel to mix the grounds with the top four inches of soil

Water them in, and you can also cover the area with a hessian sack. This will encourage worm activity, which helps break down the grounds and release the minerals into the soil.

After you’ve done this, you’ll need to wait for the grounds to be broken down. This can take from six months to a year.

You should be very careful about applying coffee grounds on established plants. This is a very powerful type of fertilizer, which has the potential to acidify the soil too much and cause harm to your plants. Furthermore, the grounds can clump together. This can stop the water from getting through, dehydrating the plants. Therefore, you should also only sprinkle the grounds around established plants.

If you want, you can sprinkle some grounds around the edge of the blueberry garden patch. This can act as a natural form of weedkiller.

Adding Coffee Grounds To Compost Piles

One of the best ways to dispose of coffee grounds is by adding them to a compost pile. In this case, you’ll need to be careful about the ratio of coffee grounds to kitchen waste. You will need one part coffee ground for every four-parts kitchen waste. Green materials, like leaves or grass clippings, can count towards the kitchen waste portion. This ensures that you aren’t overpowering the compost pile.

There are a few general principles to keep in mind when you are composting. For example, you will need to keep the pile moist. You should also keep turning the pile regularly. This will encourage microorganisms, like worms, to help break down the materials and extract the nutrients.

If you want to know more about the process of creating a thriving compost pile from kitchen waste, you might want to check out this video.

Here are some things to keep in mind when you are applying the compost to the blueberries:

Provide a healthy level of mulch, around four inches

Keep the mulch away from the main stem of the blueberry plant
Water the mulch after you have applied it

Steeping Coffee Grounds In Water

The next option to consider is steeping the grounds in water. Here are the steps you’ll need to follow during this process:

Use a ratio of one cup of coffee grounds to every two and a half gallons of water
Mix the grounds into the water.
Leave them overnight, giving them time to steep

Sieve the water with a cloth to remove the grounds
Apply to your blueberry patch

This is one of the mildest ways of using coffee grounds, and you should be able to apply this mixture to most types of gardens. The downside is that you will only be able to use a small number of grounds at a time. Though grounds are best used fresh, you can store them in an airtight bag.

Feeding Grounds To Your Worms

If you have a worm farm, you might want to regularly add a few coffee grounds. Mix this in with some of your other kitchen waste. The worms will then do their part to break down the grounds.

It should be noted that worm castings tend to work best in alkaline soils. So, it’s important to avoid adding too many coffee grounds. Furthermore, the castings tend to be alkaline or neutral. But this isn’t likely to significantly impact your blueberry patch.

How Often Should You Apply Coffee Grounds?

This will depend on the method you use to add the grounds to your garden. If you plan on mixing it into the soil, you will need to apply it at least six months before you plant the blueberries to give the grounds some time to break down.

Here are some other guidelines to keep in mind:

Directly applying the grounds. You can do this once every two to three months as long as you have an established blueberry bush.
Mulching. You can apply this once a year. This should be done during spring, giving your berries the nutrients they need to grow and bloom.

Worm juice/ steeped coffee grounds. You can provide this once a fortnight, particularly when your plant grows strongly during the spring months.

Other Ways To Increase Soil Acidity

As we discussed earlier, one of the biggest issues is alkaline soil, which can cause major problems for blueberries. Coffee grounds are a good way of lowering the pH of the soil. But they aren’t the only option that you have available. Here are some methods you can use to make the soil more acidic:

Using ericaceous compost. If you are planting your blueberries in a pot, you might want to consider using ericaceous compost. This will already be acidic. Most of the time, it will already have a pH of four to five, so it’s ideal for planting your blueberries. Over time, though, you might need to use coffee grounds to maintain the low pH levels.

Sprinkling sulfur. You should be able to find this at your local hardware store. This is a powerful way of lowering the soil pH levels. Though you will need to be careful about the way you use it. The downside is that this can take a long time to deliver results. It’s recommended that you wait a year before you plant the blueberries. You will need to sprinkle the sulfur between the plants if they are already planted.
Iron sulfate. This is a milder version of sulfur. This additive can also be used as a method for treating iron deficiency.
Acidic mulch. Ingredients like pine needles can be a great way of lowering the pH level of the soil. You can also make your own homemade acidic mulch by adding coffee grounds.

Sphagnum peat moss. Not only will this help acidify the soil, but it will also improve the water retention rate.
Diluted vinegar. This is a fast solution to this problem, but it won’t be suitable over the long term. Plus, you will need to be careful about how you use it. If the vinegar solution is too strong, it can kill the blueberries. You should aim to use one tablespoon of vinegar, diluting it into 15 gallons of water. Then, you can apply it to the soil.

It’s best to make sure that you are regularly checking the pH level. Sometimes, the amendment can take a few days to change the soil pH level. However, if you lower the pH too much, the blueberries will be unable to absorb soil nutrients.

If the pH level drops below four, you should stop the measures you have taken to acidify the soil. Then, you will need to sprinkle some dolomitic lime around the area. This will help to raise the pH back to the right levels.

Once the soil is at the right pH level, it should be fairly easy to maintain it. You will just need to use some coffee grounds or mulch to keep the ground acidic. It’s best to perform a pH test every three to six months to monitor progress.

Other Ways Of Adding Nitrogen

If you suspect that low nitrogen levels in the soil might be causing the problem, coffee grounds can be a good solution. But there are a few other options that you can investigate; these include:

Bone meal
Fish meal, which will need to be diluted in water
Manure, particularly chicken waste

It’s best to perform NPK tests while you are adding these fertilizers. This allows you to tell when to stop.

Conclusion

There aren’t a lot of plants that can tolerate the use of highly acidic coffee grounds. But blueberry is a notable exception. This species requires low-pH soil to thrive and will benefit from the high nitrogen levels found in the grounds. So, if you have any leftover coffee grounds, feel free to incorporate them into your blueberry patch.

Sources

https://extension.uga.edu/publications/detail.html?number=C1163

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