7 Best Fertilizer for Rhododendrons 2021 [Reviews & Guide]

Rhododendrons are low maintenance flowering plants that are praised for their spectacular clusters of blooms and glossy green leaves. Although they are light feeders, you should feed them to get the desired blooms.

Only proper feeding can add a new dimension to your garden or landscape with pink, red, white, yellow, and purple colored long-lasting, bigger, and vibrant blooms of rhododendron.

Remember; without fertilizer, they can produce blooms or poor sets of blooms but feeding wrong fertilizer makes the plant bushy without blooms and increases the tendency to develop the diseases.

Now the question; what is the best fertilizer for rhododendrons?

The acid mix fertilizer that is specially formulated for acid-loving plants like azaleas, rhododendrons, camellias, hydrangeas, and hollies. Also, the good rhododendron fertilizer has to contain a balanced ratio of NPK and other macro and micronutrients.

For your convenience, here I have reviewed the best fertilizer for rhododendrons that will help you to pick a good fertilizer for your rhododendrons.

So, without losing your valuable time, let’s get started-

In A Hurry? Here is the overall best fertilizer for rhododendrons(editor’s choice) that you can pick right now-

Best Fertilizer for Rhododendrons-Comparisons

FertilizerNPKFormTypePrice
Jobe’s Organics 9826 Fertilizer5-4-3GranularOrganic
Dr. Earth 703P Acid Fertilizer3-4-3GranularOrganic
Jobe's Azalea Fertilizer Spikes9-8-7SpikeSynthetic
Jobe’s Organics (08281) Fertilizer6-1-1PowderedOrganic
Espoma Holly Tone Organic Fertilizer4-3-4GranularOrganic
Miracle-Gro Water Soluble Fertilizer30-10-10PowderedSynthetic
Down To Earth Acid Mix Fertilizer4-3-6GranularOrganic

Best Fertilizer for Rhododendrons-Reviews

1.Jobe’s Organics 9826 Fertilizer

Jobe’s Organics 9826 FertilizerJobe’s Organics 9826 Fertilizer is the best organic fertilizer for rhododendrons that is specially formulated for acid-loving plants including azalea, camellia, and hydrangeas.

This fertilizer contains 5% nitrogen,4% phosphorus, and 3% potash for dark green foliage, healthy roots, and blooms. The good news; it has 3.9% water-insoluble and 1.1% water-soluble nitrogen and doesn’t contain any urea nitrogen.

You will be happy to know that;

Water-soluble nitrogen acts as a quick-release nutrient that feeds the rhododendron plants instantly and water-insoluble nitrogen acts as a slow-release nutrient that feeds continuously without the risk of burning.

Besides NPK,it has 7% calcium,0.5% magnesium,and 1% sulfur.Also, the fertilizer may contain some other micronutrients because it is formulated from some nutrient-enriched organic compounds such as feather meal, bone meal, poultry meal, and sulfate of potash.

As you saw, this fertilizer doesn’t contain any toxic chemicals that’s why it is OMRI listed organic fertilizer for organic gardeners and it is completely safe for your health and plants.

And the most likable feature of this fertilizer is-

It contains Biozome; a natural and healthy mixture of beneficial bacteria, Mycorrhizal fungi, and Archaea, and it improves soil structure, root growth, and makes the plant disease, insect, and stress-resistant.

To apply this fertilizer to your rhododendrons-

Sprinkle 1 ½ cups of granular fertilizer per foot rhododendrons plant spread or 16 inches diameter of a plant pot. Mix gently on the surface soil and water the plant. Repeat the application 4-6 weeks later for beautiful blooms of rhododendrons.

 

2.Dr. Earth 703P Organic Azalea, Camellia, Rhododendron Acid Fertilizer

Dr. Earth 703P Organic Acid Fertilizer

Here is the another best organic fertilizer for rhododendron from Dr. Earth brand. It is specially formulated fertilizer for acid-loving plants like azalea, camellia, rhododendron, and so on.

As a plant food, it contains 3% nitrogen,4% phosphate, and 3% potash to promote foliage growth and flowering.

Also, this fertilizer doesn’t contain urea nitrogen and the total amount of nitrogen is coated for slow release that feeds your plant continuously.

And good news; the fertilizer is formulated from some organic ingredients such as feather meal, cottonseed meal, fishbone meal, alfalfa meal, kelp meal, and kelp flour. All the ingredients are natural sources of macro and micronutrients and as you saw, it is free from toxic chemical that is also certified by OMRI.

This fertilizer also contains a natural and healthy blend of beneficial bacteria with ecto and endo mycorrhizae to improve soil and plant health and make the rhododendrons disease and stress-resistant. Also, it has  11% humic acid as a stress reviver.

To get a healthy rhododendron with lots of blooms-

Sprinkle 2 tablespoons of this granular plant food per gallon of potting mix or 2 cups per inch of trunk diameter. Work gently on the surface soil, water the plant, and reapply 2 months later.

 

3.Jobe’s Azalea, Camellia & Rhododendron Fertilizer Spikes

Jobe's Azalea, Camellia & Rhododendron Fertilizer Spikes

If you are looking for the easy to use best fertilizer spikes for rhododendrons, then you may pick the Jobe’s Azalea, Camellia & Rhododendron Fertilizer Spike that is specially formulated for some acid-loving plants including rhododendrons, and azaleas.

According to the NPK ratio, It contains  9% nitrogen,8% phosphate, and 7% potash to promote foliar growth, root development, and produce beautiful and vibrant blooms.

And good news;

It is urea free fertilizer and the total amount of nitrogen is ammoniacal nitrogen that helps the soil to reduce soil pH and feeds the plant more gently with no risk of burning.

You know spike fertilizer has a lower chance to wash off with surface water and it feeds the plant slowly. There is no exception to this fertilizer. 

It also acts as the best slow-release fertilizer for rhododendrons and to feed the plant slowly, it contains 4% slow-release nitrogen,3% slow-release potassium, and 3% slow-release potash that can feed your rhododendrons up to 8 weeks.

It comes in easy to spike form. Simply push a spike per foot of plant diameter into 1-2 inches below the soil near the rhododendron stem. Now water the plant and repeat the feeding after 1-2 months.

 

4.Jobe’s Organics (08281) Holly, Azalea & Rhododendron Fertilizer for Acid Loving Plants

Jobe’s Organics (08281) Holly, Azalea & Rhododendron FertilizerJobe’s strikes again with the best water-soluble fertilizer for rhododendron named Jobe’s Organics (08281) Holly, Azalea & Rhododendron Fertilizer. It is also an organic fertilizer for acid-loving plants.

As the primary nutrients, it has 6% nitrogen,1% phosphate, and 1% potash. As you saw, it contains a lower amount of phosphate and potash than other fertilizers.

Yes, it’s true, it contains a lower amount of phosphate and potash but that doesn’t mean it is poor in NPK. Why am I telling you like this?

Because it is a water-soluble fertilizer but a small portion of the nutrients is coated for slow release. As a result, the nutrients release slowly without the chance of leaching loss.

In contrast, other water-soluble fertilizers come with a quick-release formula. So, the plant takes the required nutrient instantly and others pass out through the water.

Good news; this fertilizer also contains a small portion of quick-release nutrients for instant feeding.

This OMRI listed organic fertilizer is formulated from some organic ingredients such as soy protein hydrolysate, kelp, soft rock phosphate, and sulfate of potash and all the organic ingredients provide the plant some micronutrient and growth stimulator.

You know; all jobe’s organic has a healthy and natural blend of bacteria, Mycorrhizal fungi, and Archaea that is called Biozome and it helps to improve long-lasting soil health and makes the plant resistant.

To feed this water-soluble fertilizer to your rhododendron-

Pour 1 scoop (1 tablespoon) into a gallon of water. Mix well and spray on the plant foliage and soil. Repeat feeding after 7-14 days for more blooms.

 

5.Espoma HT18 Holly Tone Fertilizer

Espoma HT18 Holly ToneEspoma HT18 Holly Tone Fertilizer is the best natural acid fertilizer for rhododendrons. Besides rhododendrons, it can also be perfect for acid-loving plant like plumeria, azaleas, holly, amaryllis, bayberry, blueberry, andromeda,  camellia, hemlock, hydrangea, etc.

According to the NPK ratio of this fertilizer, it has 4% nitrogen,3% phosphate, and 4% potash. Great news; it has 2.5% water-insoluble nitrogen slow-release nitrogen to feed the plant continuously. Also, it contains quick release nitrogen for instant feeding.

Besides NPK, it also contains  3% calcium,1% magnesium,5% sulfur, and some macro and micronutrients to encourage flowering and produce healthy blooms.

It is an OMRI listed organic fertilizer that is formulated from feather meal, alfalfa meal, bone meal, poultry manure, greensand, sulfate of potash, and elemental sulfur.

Also, this fertilizer has beneficial soil microbes to promote the soil and plant health and it contains % humic acid to protect the plant from environmental stress like water and heat stress.

It comes with granular form. To feed this holly tone to your rhododendron-

Sprinkle 1 cup for 1 foot of branch spread for in-ground rhododendron bush and 1 tablespoon for 3 inches pots. Mix with the top soil and water the plant.

 

6.Miracle-Gro Water Soluble Azalea, Camellia, Rhododendron Plant Food

Miracle-Gro Water Soluble Azalea, Camellia, Rhododendron Plant FoodHere is the Miracle-Gro fertilizer for rhododendrons, azaleas, camellias, and some other acid-loving plants. It is a water-soluble acid fertilizer. Let’s see what’s inside this best plant food for rhododendron

To promote green foliage, healthy roots, and blooms, it has 30% nitrogen,10% phosphate, and 10% potash. You will be happy, the heavy ratio of NPK feeds your plant instantly and gives you a healthy plant quickly.

But one thing I didn’t like, It contains a large amount of urea nitrogen. Urea nitrogen feeds the plant aggressively that may burn the foliage because of overfeeding. So, follow the label direction to avoid overfeeding and get quick results.

The best part of this fertilizer;

It is enriched with some micronutrients.As a micronutrients,it contains  0.02% boron,0.07% copper,0.325% iron,0.05% manganese,0.0005% molybdenum,and 0.07% zinc.

Good news;

Most of these nutrients have a chelated coat that protects the nutrients from different types of soil reaction and keeps them always available for plants.

You know, it is a quick-release fertilizer and you need to apply it frequently to get better and quick results.

Mix 1 tablespoon fertilizer for outdoor rhododendrons and ½ teaspoon for indoor rhododendrons into a gallon of water. Pour the solution around the plant base and repeat the application after 7-14 days.

 

7.Down To Earth All Natural Acid Mix Fertilizer

Down To Earth All Natural Acid Mix Fertilizer

Down To Earth All Natural Acid Mix Fertilizer is the another best natural fertilizer for rhododendrons, azaleas, and some other acid-loving plants. It is the OMRI listed organic fertilizer that you may feed your rhododendrons without the risk of damage or burn.

As the primary nutrients,it contains 4% nitrogen,3% phosphate,and  6% potash.Good news; it has 0.4% water-soluble 3.6% water-insoluble nitrogen.You know water-soluble nitrogen feeds the hungry plant quickly and water-insoluble nitrogen feeds slowly and continuously.

This fertilizer is formulated from some natural ingredients such as cottonseed meal, fishbone meal, langbeinite, rock phosphate, and kelp meal and it contains some soil microbes to improve soil health and stress tolerance of the plants. Also, it has 2.5% humic acids for protecting the plant from adverse environmental conditions.

Sprinkle 1-2 tablespoons for one gallon of potting mix or 1 cup for an established rhododendron. Mix with the top soil, water and get a healthy plant with lots of blooms.

 

When to Fertilize Rhododendrons?

Rhododendrons don’t need extra food all year long. If the soil conditions are good, you don’t feed too much. Only the rhododendrons need fertilizer in active growing seasons.

Apply fertilizer to your rhododendrons in spring to a week before the first frost. You can also feed if you notice any nutritional deficiency symptoms on the plants.

How Often Fertilize Rhododendrons?

The schedule of applying fertilizer to the rhododendrons depends on the type of soil conditions and fertilizer. You need to apply more frequently the quick release, water-soluble fertilizer than slow-release fertilizer.

You should apply slow-release fertilizer once in a month and water-soluble quick-release fertilizer once per 7-14 days. But the best idea is to follow the label directions of your fertilizer.

How to Fertilize Rhododendrons?

Fertilizing the rhododendrons is not a difficult task. Follow the simple steps and feed your plants correctly.

Step 1: Pick the Best Plant for Your Rhododendrons

Rhododendrons love synthetic, organic, granular, spike, or water-soluble fertilizer. So, pick any type of fertilizer from the reputable brand for your rhododendrons.

Step 2: Choose the Best Time to Fertilize the Rhododendrons

Applying fertilizer in hot and sunny weather can damage your plant. So, you should apply fertilizer to your rhododendrons in calm and cool weather.

Morning and evening are the time when the weather remains calm and cool. So, apply fertilizer in the morning or evening.

Step 4: Measure and Prepare a Solution for Rhododendrons

Measure the fertilizer according to the label directions.No need measure if you pick the spikes fertilizer for your rhododendrons. Prepare a solution by mixing the pre-measured fertilizer into water. Avoid pre-mixing if your fertilizer isn’t water-soluble.

Step 5: Fertilize your Rhododendrons

Water-soluble fertilizer: Pour the pre-mixed solution around the base of the plants. Soak the rhododendrons foliage if the solution is permissible to apply on foliage.

Granular fertilizer: Sprinkle the pre-measured granular fertilizer around the base of rhododendrons. Mix with the surface soil and water thoroughly.

Spike fertilizer: Take one or more fertilizer spikes according to the plant diameter and push the spike into the soil near the stems.

Homemade Fertilizer for Rhododendrons

Items Required:

  1. Epsom Salt (Magnesium)
  2. Eggshells (Calcium)
  3. Coffee Grounds(Nitrogen)
  4.  Banana Peels (Potassium)
  5. White Vinegar(Decrease soil pH)
  6. Watering can

Steps:

  1. Dry and grind the banana peels and eggshells.
  2. Mix crushed eggshells, crushed banana peel, and coffee grounds equally.
  3. Sprinkle ½ -1 cup of mixed fertilizer around the plant base.
  4. Pour 1 teaspoon of white vinegar and Epsom salt per gallon of water and mix properly.
  5. Apply the pre-mixed water to the plant.

How to Make Soil Acidic for Rhododendrons?

Rhododendron is an acid-loving plant. You need to make the soil acidic to grow them successfully. You can decrease the soil pH by adding coffee grounds and white vinegar.

Also, you can add some soil acidifier(our pick: Jobe’s Soil Acidifier) to make the soil acidic for rhododendrons.

Frequently Asked Questions

#Are coffee grounds good fertilizer for rhododendrons?

Yes, coffee grounds are good for rhododendrons. They provide nitrogen to the rhododendrons. Also, they make the soil acidic and create a healthy environment for the rhododendron plants.

#Do rhododendrons like acidic soil?

Rhododendrons like to slightly acidic soil(pH 4.5 to 5.5) to thrive and blooms. If the soil is not acidic, the growth of the plants will stunt and yellow leaves appear.

#Is Epsom salt good for rhododendrons?

Epsom salt is also known by Magnesium sulfate. It can provide magnesium to the plant and you know magnesium is the essential plant nutrients that can protect the plant from chlorosis.

#Is bone meal good for rhododendrons?

Bone meal is the natural source of phosphorus and phosphorus is the primary plant nutrient to promote the flowering of rhododendrons.

#Do rhododendrons like horse manure?

Horse manure provides nitrogen to the plant that makes the plant bushy. So, it is not good to apply horse manure to flowering plants like rhododendrons. Also, it may contain weed seeds.

Conclusion

Rhododendrons and Azaleas are plants belonging to the same family. Many gardener claims, they are the same because of the same food habit and behaviors. But they have differences too.

Both are easy to grow flowers. Just plant them in well-drained soil and feed good fertilizer to thrive and blooms.

I hope you found the best fertilizer for rhododendrons here. Tell me what is your favorite fertilizer for rhododendrons.

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