The Best Fertilizers for Blueberries: The Ultimate Resource

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Many of us associate summertime with the sweet smell and taste of fresh blueberries. Growing your own blueberries isn’t very difficult, and fertilizer is absolutely necessary to get the best yield out of your blueberry bushes.

The best fertilizers for blueberries add macro and micronutrients to the soil and simultaneously lowers the pH to optimal levels. Ensure it contains nutrients like iron, magnesium, and sulfur, and opt for a type that releases nutrients gradually to avoid fertilizer burn. 

In this article, I will give all the information you need to know when it comes to feeding fertilizer to your blueberries. After helping you learn the best way to feed your blueberry bush, I’ll also go over a few natural (non-industrial) options you may want to consider. 

Nutrients the Blueberry Plant Needs To Thrive

Just as humans need a variety of vitamins and other micronutrients to reach our healthiest state, plants also have their specific nutrient requirements. 

Blueberry plants need nitrogen (N), phosphorus (P), and potassium (K), just like most other plants. Fertilizers typically show a ratio of these three nutrients as NPK followed by a number. Look for a fertilizer with equal amounts of NPK (ratio 1:1:1) for blueberries. 

Tip: I’ve written in-depth articles about why plants need nitrogen, phosphorus and potassium. Check them out!

Blueberries also need iron, magnesium, and sulfur to grow well and bear fruit. If you notice that your fertilizer doesn’t add enough magnesium to your blueberries. Lack of magnesium leads to interveinal reddening, meaning the leaves first start to turn yellow and then red. This process typically starts from the bottom of young shoots. So if you see these symptoms, you can supplement the soil with additional magnesium by adding Epsom salts (found over the counter at most pharmacies).

It’s better for your blueberry plant to use a fertilizer that releases nitrogen gradually over time. Also, avoid fertilizer brands that include chlorides and nitrates because blueberry plants favor their nitrogen source in the ammonium form. 

Additional Info: Check out my articles about fertilizers high in nitrogen and potassium.

The Effect of Soil pH on Blueberry Bushes

Plants absorb all their nutrition through the root structures embedded in the soil. You should know that different plants have different requirements for soil. Blueberry bushes tend to grow more foliage when the soil is at a slightly acidic pH (4–5.5). 

The soil’s pH level is important because it is part of the environment surrounding the root structures. As such, the acidified soil puts the roots in the optimum conditions to absorb a healthy dose of nutrients the plant needs to grow.

What Happens When the pH is Neutral or Alkaline?

Blueberry bushes planted in neutral-pH soil tend to develop yellow leaves and show signs of stunted growth. More often than not, the bushes do not ever bloom or bear fruit. While neutral pH is the optimal level for many other plants, blueberries are an exception.

The yellow leaves in a blueberry plant are a sign of iron deficiency because the neutral or alkaline soil does not allow the plant to absorb sufficient amounts of iron. The condition is called iron chlorosis and can be a seasonal problem because soil pH can become alkaline in early spring. Iron chlorosis has other causes, but pH imbalance is more likely. 

Reasons for Applying Fertilizers to Blueberries

To grow big, juicy blueberries, regularly adding fertilizers to the soil is a must. Adding fertilizer is especially important if your blueberry bush has been in the same spot for several seasons. The nutrients in the soil deplete with every fruiting cycle, and the pH value also changes over time.

There are two different types of fertilizers for blueberries: 

  • Nutrient-rich fertilizers 
  • pH correcting fertilizers

I’ll get into more detail about each type below, but remember that the best option is always a pH-correcting fertilizer because it is an all-in-one solution that is easier to apply. You only need to buy one product, and there is no need to figure out how two different products work with each other.

Nutrient-Rich Fertilizers 

The most common type of fertilizers added to help boost growth in blueberry bushes are ones that supply and replace nutrients in the soil. 

As plants grow in a plot of soil, they suck up all the nutrients (metals, macro and micronutrients, trace elements, etc.) in the soil. A nutrient-rich fertilizer replaces the various nutrients and trace elements in the soil to ensure that your blueberry bush gets the nutrition it needs, especially the big three macronutrients like nitrogen, phosphorus, and potassium.  

pH Correcting Fertilizers

Most plants thrive within a specific range of soil pH, so fluctuations in the soil pH impact the growth of your plants and even the yield. Fertilizers that correct pH will increase it by adding basic (alkaline) chemicals or lower the pH by adding acidic materials. 

For blueberries, you will typically need to lower the pH to mimic the acidic soil environment in which blueberries evolved to grow. 

Of course, before you add pH-correcting fertilizers to your soil, you will need to check your soil pH using a home testing kit. The process is relatively simple, and you might have tried experiments with similar dip-sticks in science class. You can get them fairly cheap here on Amazon or other online retailers like Walmart.

Blueberries generally favor a pH of 4 to 5.5. If the pH of your soil is within that range, you won’t need to correct it. However, if the pH value has shifted, leaving your soil more alkaline, then you need to add a fertilizer that will make the soil more acidic, like ammonium nitrate. 

Fertilizers that affect the pH value create the perfect environment within the soil by providing a balance of required nutrients at an appropriate pH to increase the absorption of said nutrients.

Natural Fertilizer Options for Blueberries 

If you’re not fond of adding fertilizers made in an industrial setting and prefer a more natural approach to gardening, there are still options you can look into. People have been adding “natural fertilizers” to their gardens for centuries, and so can you. Not only are natural options better for the environment, some people feel that they are more effective than chemical fertilizers. 

You might want to consider a few options when feeding your blueberries.

Sources of Nitrogen: Blood or Fish Meal

Blood meal and fish meal are old-school sources of nitrogen that have a proven track record. They are a powdered form of dried animal blood or fish and are exceptionally high in nitrogen.

Some people might feel that these options are very pungent when handling them, but the smell is not noticeable if you add mulch on top. Blood meal and fish meal are also very eco-friendly fertilizers because they cut down on waste. 

Making your own is a lengthy process, but you can find these in gardening and pet stores. If you decide to make fish or blood meal, ensure that everything is sterilized to avoid rotting your plants.

Potassium and Phosphorus: Seaweed and Bone Meal

Remember that plants need three primary nutrients: N, P, and K. We’ve covered nitrogen already, but for natural sources of potassium and phosphorus, you’ll need a bone meal and seaweed powder. 

As you can expect, seaweed powder is simply dried and ground seaweed. Bone meal is cooked and dried bones that are also ground to a very fine powder. It also contains waste from slaughterhouses. 

Again, it’s better to buy these, but it is certainly possible to make your own. If you decide to make a bone meal, make sure all your equipment is sterilized properly. 

Acidifying the Soil: Coffee Grounds and Sphagnum Peat Moss

Lastly, you’ll need a natural way to lower the pH of the soil around your bush. You can achieve this using a very cheap and eco-friendly option: coffee grounds. Simply sprinkle the remnants of your daily brew as you would regular fertilizer. 

If you aren’t a coffee drinker (or you don’t have access to coffee grounds for some other reason), you may consider purchasing Sphagnum peat moss. You may be familiar with the Sphagnum moss plant found in bogs and other wetlands. The decayed remains that have been dried thoroughly are known as sphagnum peat or peat moss and can be used to acidify your soil.

You can grow sphagnum easily and dry it yourself or purchase peat moss at any gardening store.

Tips on Feeding Fertilizer To Your Blueberries

Now that you know what kind of fertilizer you need to get the most out of your blueberry bushes, it’s time to move on to how you will feed the bush. Feeding refers to adding fertilizer to your plant to provide it with more nutrition so that it can grow better and you can enjoy more fruit in the coming season.

In order to successfully feed your blueberry plants, you should pay close attention to the following factors:

  • Technique
  • Timing
  • Quantity

Applying Fertilizer

It isn’t very difficult or time-consuming to apply fertilizer correctly. The most important thing to remember is that you need to apply the fertilizer evenly and avoid dumping it all in one lump. Try to cover the base of the plant (where it shoots out of the ground) and extend all the way towards the edge of the canopy. 

Because blueberry plants do not have very deep roots, too much fertilizer in one spot poses a risk of salt burn. Also, you should not dig around the bush to avoid damaging the roots. If you have mulch on the soil, remove as much of it as possible before applying the fertilizer to ensure it reaches the roots. 

After feeding your plant, make sure you water them well. 

Pro Tip: If you find that removing the mulch is difficult or not feasible, you can simply double the amount of fertilizer instead.

The Best Time To Feed Your Blueberries

I generally recommend that you feed your blueberries in the early spring and then once more in late spring. This timeline gives your bushes time to absorb the nutrients long before they are in their active growth stage during the summer.

At the very least, add fertilizer once a year for older plants. I highly recommend feeding new plants twice for the best results. If you’re only feeding your blueberry plants once, do it during the early spring before the leaves have grown in.

There are also a few signs you can look for in your blueberry plants that indicate it’s time to add fertilizer. Here are some:

  • Interveinal chlorosis: yellow or pale green leaves with bright green veins. 
  • Poor growth: the plants are not lush and are spotted with yellowing and reddish leaves. They may also be stunted (shorter) than typical blueberry bushes.
  • Low yield: fewer blueberries than in previous seasons.

Avoiding Over-Fertilization

To avoid adding too much fertilizer to your blueberries, this is a round estimate of how much you should use every year. As mentioned earlier, you may double this amount if you add the fertilizer on top of mulch that you do not want to remove.

  • For younger plants, add up to a half cup of fertilizer per year for every plant. 
  • If your blueberry bush is mature (over three years old), you can add 2 to 3 cups per year for every bush. 

If you follow the right technique mentioned above, you’ll find yourself using roughly the same quantities.

Although feeding your blueberry bushes is a great way to care for your plant, it takes time for the effects to show. Fertilizer shouldn’t be considered a quick fix; you shouldn’t add it to the soil without checking for signs of nutrient deficiency.

Be patient after adding your fertilizer, and trust in the process. You’ll need to wait until late in the spring to notice a marked difference in your plants, and only then will you be able to decide whether to feed them again.

Over fertilization can cause salt burn and nutritional imbalance, negatively affecting your plant. Additionally, avoid adding fertilizers to your bush in autumn. Give the plant time to recover from the active growth phase of summer and go into dormancy during the winter.

Final Thoughts

Blueberries provide the best yield when provided with the right type of fertilizer regularly. Make sure the fertilizer acidifies the soil and supplements it with macronutrients and micronutrients like sulfur and magnesium, and you’ll see the difference in your bushes quickly.

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