Just as pH balance is essential to our own wellbeing, it plays a key role in the health of our houseplants too. Soil pH determines how effectively a plant can absorb the nutrients it needs to grow and flourish. Bottom line? Even a well-fed plant can struggle if the pH is off. In this post, we’ll dig into what soil pH is, why it matters and how to create the right conditions for your plants to thrive.
Understanding Soil pH
Plants receive 14 of their 17 essential nutrients from soil. If soil pH is out of balance – too acidic or too alkaline – the ability to absorb these nutrients can be compromised. Alkaline soil locks up a plant’s key nutrients, making them inaccessible to the plant, while acidic soil causes nutrients to leach out too quickly, before the plant can absorb them.
The pH scale ranges from 0 to 14. A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline. Most potting soils are standardized to be neutral (7) or even slightly acidic (6.5), and the majority of potted houseplants thrive in this soil. But there are a few exceptions. Flowering plants such as Rhododendrons, Camellias and even Blueberries, for example, are acid-loving plants, which means the right potting mix —one that is acidic— is key to their survival. On the other end of the spectrum, it’s much less common for indoor houseplants to prefer alkaline soil, but plants like the African Violet, Aloe Vera and Lavender can tolerate it.
Understanding your plant’s ideal conditions can help you ensure they remain healthy and prevent common issues that can otherwise go undetected.
Identifying Imbalances in Soil pH
Identifying whether your plant’s soil pH is out of balance can be difficult if you’re relying solely on your plant’s visible symptoms. Leaf discoloration, falling leaves and stunted growth– these are all signs of low soil pH, but they can also be signs of other deficiencies or disease. That’s why testing is key. At-home pH testing kits are widely available, easy to use and provide results within minutes. The good news is, if your plants are healthy, there’s no need to test your soil. But if your plants are suffering and you can’t figure out why, testing the pH could give you some answers.
Treating Your Soil
While you may be doing all the right things to care for your houseplant, an imbalance in soil pH may be out of your control. Soil pH can shift over time due to various external factors–particularly indoors. The most common cause? Hard water. Tap water high in calcium carbonate can slowly raise your soil’s pH, making it more alkaline after a year or two of regular watering. This can be a challenge for acid-loving plants. To make your soil more acidic, try one of the following methods, and retest your soil each year:
- Soil sulfur: Sprinkle soil sulfur on the surface of your plant once a year and water thoroughly. This method is ideal for mature plants that are already potted.
- Peat moss: Naturally low in pH, peat moss is great for acidifying soil. You can repot your plant in peat moss at any time, but this is generally easiest with new or young plants.
By contrast, overly acidic soil in houseplants is very rare, but it is seen outdoors in landscaping environments due to excessive rain or acidic fertilizers. To raise pH and balance out the acidity, you can add calcium carbonate (lime) to the soil and water it thoroughly.
Help Your Plants Help Themselves
Ultimately, when it comes to balancing soil pH, keep in mind that healthy soil supports self-sufficient plants. Within a narrow range, plants with a thriving microbiome can regulate their own soil pH without any external support or intervention. By using a potting mix rich in biological activity–for example, through compost, worm castings, or a premium living soil–you’re creating a strong foundation for your plants to better care for themselves, while decreasing the risk of unbalanced soil pH.
If you’re concerned about your plant’s soil pH, ask yourself: is your soil healthy? Does your plant have a strong microbiome? If so, sit back and let your plants do the work to find neutral ground.