Using Ammonium Sulfate Fertilizer on Perennials
Using Ammonium Sulfate Fertilizer on Perennials
Ammonium sulfate fertilizer is a type of fertilizer that has both nitrogen and sulfur. These two nutrients are essential for the growth of plants. On the one hand, nitrogen helps promote leaf growth and enhances the overall vitality of the plant. On the other hand, sulfur is critical for forming amino acids and proteins in plants.
Ammonium sulfate is a kind of water-soluble fertilizer that plants easily absorb. It can provide stable nitrogen and sulfur for perennials and hydrangeas growth. Nitrogen can make these plants grow lush, and sulfur can thicken their roots and make their flowers more colorful. In addition, it can also lower the pH value of the soil, making hydrangea show blue flowers.
Ammonium sulfate fertilizers are not necessarily white powders. Ammonium sulfate produced by different brands will vary in shape and color. However, ammonium sulfate must contain nitrogen and sulfur.
Ammonium sulfate fertilizers are not necessarily white powders. Ammonium sulfate produced by different brands will vary in shape and color. However, ammonium sulfate must contain nitrogen and sulfur.

1. Benefits for Perennials

Nitrogen can make perennials grow strong and have gorgeous flowers. Ammonium sulfate is a source of nitrogen. So, it can promote perennial growth and enhance these plants' disease resistance.

1.1 Enhanced Growth and Vibrancy

  • Strong stems: Plant cells need the help of nitrogen to form cell walls. Ammonium sulfate provides nitrogen to the plants, which makes the stem of a plant stout and promotes their growth.
  • Healthy leaves: Nitrogen can promote the production of chlorophyll, which makes the leaves green. Plants grow fuller and healthier when they have enough nitrogen. This is because nitrogen helps the growth of leaves and makes plants better at photosynthesis.
  • Vibrant flower blooms: Nitrogen can promote flower growth and enhance its color. Therefore, ammonium sulfate can increase the number of flowers in perennials and make them eye-catching.

1.2 Enhanced Root Development

Sulfur is vital stuff in synthesizing proteins and amino acids in plants and helps promote plant root growth.
Although ammonium sulfate has less nitrogen than ammonium nitrate and urea, it is still suitable for perennials. It has sulfur that helps to keep plant roots healthy and strong. In other words, it can make plants absorb water and nutrients from the soil more quickly. So, plants can better survive in harsh conditions like lack of water or bad weather.

1.3 Reduce Fungi

As plants grow, harmful fungi might infect them. These fungi can harm the plant's growth and cause diseases like powdery mildew, wilt disease, etc.
Ammonium sulfate has free ammonia that can inhibit the sprouting and survival of fungi. Fungi grow slower and have a lower chance of sprouting when there is a higher concentration.

2. Color of Hydrangea

The pH of the soil can impact the color of hydrangeas. In acidic soils with a pH of less than 7.0, the plant absorbs aluminum ions from the soil, causing the flowers to turn blue. On the contrary, hydrangeas will produce pink blooms in soil with a pH greater than 7.0.

2.1 Using Ammonium Sulfate to Lower Soil pH

Ammonium sulfate can break down into ammonium and sulfate ions in soil. Plants are selective in their absorption of nutrients. The amount of ammonium ions absorbed by plants is more than that of sulfate ions. There will be more sulfate ions in the soil, which will make the soil acidic.
Therefore, ammonium sulfate can change the pH of the soil and make hydrangea bloom into blue flowers.

2.2 Before You Dive In

Although ammonium sulfate can make the soil acidic, you must proceed carefully.
I will test the pH of the soil before using ammonium sulfate. This will help me determine the current acidity level of the soil. This critical step will decide whether or not I should use it or how much I should use. If the soil is too much acid, it can damage hydrangea and prevent it from absorbing nutrients properly.

2.3 Alternative Paths to Blue

While ammonium sulfate is one way to make hydrangea flowers turn blue, there are other methods. I also use aluminum sulfate or grow hydrangeas in naturally acidic soil to change the color of the flowers. No matter which method I choose, the first thing I need to do is ensure plant health and safety.

3. Safe Application

When it comes to gardening, Ammonium sulfate is a valuable fertilizer. However, it is crucial to use it properly to ensure the safety of plants and the environment.

3.1 Clear instructions

Follow these simple guidelines to apply ammonium sulfate fertilizer to your garden safely.
  • Dilution rates:
When diluting ammonium sulfate, I will follow the instructions on the product packaging. The amount of water I need to mix with the product may vary depending on the brand and what I want to do with it. I usually mix 1/3 tablespoons of ammonium sulfate with one gallon of water, which works well for my plants.
  • Frequency:
How often I use ammonium sulfate depends on the instructions and your soil test results. Generally, I only spray once or twice on leaves during the hydrangeas growth season.
  • Application Method:
I spread the diluted fertilizer evenly around the bottom of the plant or foliar spraying.
Some people put aluminum sulfate in the soil and thoroughly water the plant, but I choose not to do this. I don't think this is suitable for flower planting. This method wastes water and fails to ensure rapid plant absorption.
However, no matter the method, be careful not to let the fertilizer touch the root directly.

3.2 Addressing Safety Concerns

Wrong use of ammonium sulfate may cause plant burns and safety risks. To minimize these risks, follow these guidelines:
  • Avoid Over-Application:
Excessive use of ammonium sulfate can burn the roots and leaves of plants. At the same time, do not use ammonium sulfate for plants in hot weather and dry climates.
  • Environmentally friendly:
Avoid using ammonium sulfate near streams, ponds, and other water sources to minimize runoff pollution. Calculate the application amount as accurately as possible to reduce waste. Replace part of ammonium sulfate with organic matter, such as compost or manure.

4. FAQ

Q: What types of plants are ammonium sulfate suitable for?
A: Ammonium sulfate is suitable for plants that like acidic soil.

Q: How long can the efficacy of ammonium sulfate last?
A: Ammonium sulfate contains 21% nitrogen and 24% sulfur. Generally, its nutritional supply can last for 4 to 6 weeks.

Q: What are the cons of ammonium sulfate fertilizer?
A: Ammonium sulfate can cause harm if wrong used. It can burn plants, make the soil too acidic, and pollute the environment. Therefore, using it with care and according to the recommended guidelines is crucial.

Q: Is ammonium sulfate harmful to pets (cats or dogs)?
A: Yes, don't let your pet near ammonium sulfate. Prevent your pet from eating it.

5. Conclusion

When we use ammonium sulfate fertilizer correctly, it has many benefits for perennials and hydrangea. It can provide plants with nitrogen, promote perennial root health, and improve disease resistance. For hydrangea, it can make hydrangea bloom blue flowers.
Before using ammonium sulfate, we need to check the pH of the soil and read the instructions carefully. In the process of use, we should avoid polluting the environment. This will help us use the product effectively and safely.
Please leave a message if you want to share any questions or planting experience with me. I wish you every success on your gardening trip.
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  • JONES, L. H., & SHIVE, J. W. (1923). Influence of Ammonium Sulphate on Plant Growth in Nutrient Solutions and its Effect on Hydrogen-ion Concentration and Iron Availability. Annals of Botany, 37(147), 355–377.
  • Powlson, D. S., & Dawson C. J. (2022). Use of ammonium sulphate as a sulphur fertilizer: Implications for ammonia volatilization. Soil Use and Management, 38, 622–634.
  • Lewis AH, Marmoy FB. The effect of ammonium sulphite on plant growth. The Journal of Agricultural Science. 1933;23(1):1-5. doi:10.1017/S0021859600052850

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My name is Arthur Mo. I am a gardener who loves gardening so much. I graduated from Ocean University of China. After I returned to Japan, I began to learn how to cultivate hydrangeas and daisies. Mr. Mitsuhiro (my master) taught me to sow, cut, fertilize, and manage diseases and pests. For nine years, I have been sharpening my planting skills. In 2022, my family and I moved to Florida. The warm climate of Florida gives me the impulse to continue cultivating hydrangeas and daisies. I began my gardening trip in my backyard and unswervingly contributed my efforts to these plants. I love these plants deeply, and at the same time, I also thank my family, my master, and friends for their understanding and support.

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