In general, many gardeners can make the mistake of thinking that because they have acid soil they will not be able to grow plants in it without first lowering those acid levels. But that is not the case, there are many acid-loving plants. In this article we will see what you should take into account when fertilizing these acid plants. We will see how and when you should fertilize this type of plants.
If the soil in your garden does not have the acid levels necessary to grow these types of plants, there are ways to increase the acid levels. One way is to use acidic fertilizers, so I’m going to list some of the best acidic fertilizers you can use in your garden.
1. What is acid soil?
Among the important characteristics of any soil you will always see that is the pH, which is a parameter that indicates if your soil is acid, neutral or alkaline. We speak of a soil as acid when its pH is less than 7.
Nutrients normally found in acidic soils are metals such as aluminum, zinc, iron, manganese, and copper. While the nutrients that are most important to our plants, such as phosphorous, calcium and magnesium, are generally found in low amounts.
In general, acid soils only bring us negative consequences for plants. Among the most unfavorable consequences are:
- Low productivity and crop yield.
- Impediment to the correct absorption of water and nutrients.
- Impact on the process of biological nitrogen fixation in legumes.
1.1 What causes soil acidity
Soils can lower their pH, that is, increase their degree of acidity, in many ways. Among the most common causes that favor these acidic soils are the following:
- Due to the washing that is generated with the rain that displaces the soil bases. This phenomenon is stronger in high areas, slopes and sloping terrain.
- The use of ammoniacal fertilizers react with the substrate and when nitrified, positively charged ions are released. This problem usually appears due to some agricultural practices.
- By decomposition of organic matter, which in its process generates organic acids, which affects the pH of the soil. This is normal in black soils rich in organic matter.
- Mining residues, with the oxidation of pyrite, increase the chances that a soil will acidify.
- The absorption of nutrients by plants can reduce some minerals and leave those that form acid soils.
- Acid rain, a serious environmental problem, causes substrates to acidify.
2. List of acidic fertilizers
As you well know, a fertilizer is responsible for providing nutrients to plants, those that specifically help provide nutrients to plants in acid soils are known as acid fertilizers. This is because, depending on the pH levels of the soil, some nutrients may be more or less easy for a plant to extract.
Acidic fertilizers can be separated into two quite different groups. A first group that acts by lowering the pH of the soil (increasing acidity) thus allowing the release of certain nutrients. While the second group directly provides nutrients that are not released in alkaline soils, and are needed by an acid-loving plant.
2.1 Commercial fertilizer
Within the market there is a large number of acid fertilizers available, in any case I have selected four fertilizers of this type available on Amazon:
- Dr. Earth Organic 4 Azalea/Camellia/Rhodendron: Provides continuous nourishment for several months. Makes the soil more acidic; 100% natural and organic. Eight select strains of ecto and endend mycorrhizae contribute to drought tolerance, increased nutrient availability and increased plant yield.
- Down to Earth Acidic mix 4-3-6: A natural fertilizer blended especially for acid-loving plants like rhododendrons, azaleas, camellias, hydrangeas, blueberries, raspberries, strawberries, potatoes, and other plants that need a low pH. To encourage lush flowers and fruit, apply Acid Mix in early spring for vegetative growth and again when flowers appear. Fall applications can help promote root growth and increase resistance to extreme winter temperatures.
- FoxFarm Happy Frog: This fertilizer is specifically formulated for use on Azaleas, Rhododendrons, Camellias, Hydrangeas, Evergreens, Blueberries, Raspberries, Strawberries, and all other acid-loving plants. Mycorrhizal fungi are included to help increase root efficiency, which can improve nutrient uptake and water uptake. OMRI Listed
- Jobe’s fertilizer spikes: This is a fertilizer spike format specially designed for acid-loving plants. Unlike surface-applied fertilizers that can be washed away by rain or irrigation, Jobe’s spikes work underground at the roots. They slowly release nutrients where plants need them most, promoting healthy growth and beautiful blooms. Specially formulated, pre-measured spikes deliver fast, easy, mess-free fertilizer.
2.2 Compost for acid loving plants (Ericaceous compost)
Compost for plants that love acid soils is known as ericaceous compost, and this name is directly related to the definition of plants in the Ericaceae family. That family of plants, as you might imagine, thrives in acidic soil.
The term ericaceous is something merely anecdotal that I found interesting to point out. But the important thing is that you know how to prepare this type of compost. You will see that the process of making any organic compost does not change much.
Follow the steps below to prepare the best Ericaceous compost:
- Look for organic matter with high acid content. Some examples are; coffee grounds, oak leaves, pine needles, citrus fruits, finely chopped onions, sawdust from freshly cut wood, used tea bags, etc.
- Place a layer of garden soil about 5 cm high on top of the organic matter. Microorganisms found in the soil will help speed up the decomposition process.
- Perform the above procedure several times until it is at least 1 m high.
- The process will take several weeks, you can use the compost when it has a light brown homogeneous consistency. Never use compost without a proper decomposition process.
2.3 Organic fertilizer for acid loving plants
As with commercial fertilizers, when it comes to naming the organic fertilizers that you can use for your acid plants, the truth is that the list is quite long. But I can summarize it in the following four acid fertilizers:
- Coffee grounds: As I mentioned, coffee grounds are a good ingredient for creating Ericaceae compost, but it can also be applied directly to plants. Let them dry on a sheet of newspaper before applying.
- Vinegar: You can make a good acid fertilizer by mixing half a tablespoon of vinegar for every half gallon of water. Be careful not to apply this fertilizer near plants that don’t like acid soil. Or if you do, don’t do it too often, or you’ll end up hurting her.
- Use of pine needles: in acidic plants, mulch can be created with pine needles. Thus these will fulfill more than one function. They will act as fertilizer while better regulating soil moisture and temperature.
- Compost: obviously compost could not be missing among organic fertilizers. We have already seen how to prepare it in the previous section. 😉
If you are reading this post, you will probably be interested in learning about fertilizing these other plants.
3. Fertilizer for acid loving plants – How to fertilize
In plants that love acid soils, an important point before starting any fertilization plan is to check the pH of the soil. If the pH is high, that is, it already exceeds 5.5 or 6, the first thing we must do is lower this pH to acidify the soil. Otherwise, there would be many nutrients that the plants could not access.
3.1 How to lower soil pH
Acid-loving plants give us several signs that the soil is becoming alkaline. The first of the symptoms can be observed in the leaves, which take on a greenish-yellow color. If you do not act in time to lower the pH little by little, the plant will lose its foliage, which may end with its death.
In flowering plants such as hydrangeas it is also possible to detect a high pH in the flowers. For example when their color is light pink.
If you observe any of these behaviors you should buy a pH measurement kit and check the acidity. Then lower the pH with one of these methods.
- Iron sulfate: it is a short-term acidifier that provides extra amounts of assimilable iron. The dose to reduce the pH in 1 unit is 4 grams per liter of water, and it is recommended to apply it in irrigation.
- Nitrogen fertilizer with acid reaction: ammonium nitrosulphate, ammonium nitrate, monoammonium phosphate or urea. Its use is as a fertilizer, although as a secondary effect it acidifies the soil as it contains sulfur. In general, this type of fertilizer is not used to lower the pH, since its application in excess can cause phytotoxicity, also contaminating the subsoil.
- Organic matter: as we saw in previous sections, there is a lot of organic matter that has the ability to lower the pH. In general, it is usually a slower action method but with very good results in the long run.
- Elemental sulfur: once placed in the ground, elemental sulfur oxidizes very slowly to sulfuric acid. Procedure in which alkaline elements are neutralized. The dose that you must apply to reduce the pH by 1 unit is 1 kg of sulfur per m2.
Whichever method you decide to apply, it is never advisable to lower the pH too quickly. For example, if you have a pH of 7, you should not bring it to 4 in one application. It is best to go down 0.5 to 1 unit at a time.
3.2 How and when to fertilize acid loving plants
Once you’ve got the pH levels under control, the process of fertilizing an acidic plant doesn’t change much from fertilizing any plant. It is not the same fertilization process that an azalea needs as a hydrangea, a gardenia or a dogwood. I recommend that depending on the plant in question, specific reports that each one needs.
In any case, never forget to check the pH levels with each beginning of the season. Don’t wait for the earth to become alkaline to act. Since your acid plants will have to suffer for a while until you manage to acidify the soil. For this it is good that every year you apply ericaceous compost and you can also put mulch with pine needles.
Keep in mind that although these plants like acidic soils, it is not a matter of over-acidifying them. A pH of 4 or 3 is already starting to be too low a level. Tolerance to these levels will depend specifically on the plant.
If you are going to apply any of the commercial fertilizers that I recommend in previous sections, read the instructions for use carefully. Always try to use a lower dose of acid fertilizer than recommended in the instructions. As I always say, it is easier to solve a problem of a lack of nutrients than an excess of them.
4. How to make the soil acidic
Although we have already reviewed four ways to acidify the soil, I may not have gone into too much detail on the subject. And since I do not want any doubt to remain on this point, since it is vital to keep your acid-loving plants healthy, I have decided to select a video on this topic.
I hope you find it useful and you can review in a much more graphic way some of the points that we have seen in this article. The YouTube channel author of this video is Living With Nature channel, so you can visit it since it has very good gardening videos. 😉
If you are reading this post, you will probably be interested in learning about fertilizing these other plants.