What are the effects of high alkalinity in potting soil on plants?
This article introduces the effects of high alkalinity in potting soil on plants and related methods to improve the alkalinity of potting soil for green plants and flowers. Let's dive into the details provided by the editor.
Most plants in the south prefer slightly acidic soil, and this is also true for ornamental flowers (especially gardenias, camellias, azaleas, jasmines, and Michelia). At the very least, neutral soil is required for normal growth. What dangers can arise from excessively alkaline soil?
In the north, both tap water and garden soil from outside tend to be slightly alkaline, which makes it difficult for southern plants to thrive. In addition to improving the alkalinity of potting soil, humidity is also a major concern for growing southern plants in the north.
1. The dangers of alkaline potting soil to plants?
Once the soil becomes alkaline, plant growth is restricted because the sodium and hydrogen content in alkaline soil is higher, which can prevent plants from absorbing calcium and magnesium. A deficiency in calcium and magnesium can cause leaves to turn yellow and the plant to become weak and slender, with symptoms such as dry, yellowing leaves and stunted growth.
Moreover, the activity of microorganisms is also limited in alkaline soil. For fruit and vegetable plants, this can lead to reduced yields, while for ornamental plants, it results in fewer flowers, increasingly slender growth, and eventually, a stop in growth.
2. How to completely improve alkaline potting soil?
If the potting soil of your potted plants has become alkaline, it is difficult to improve it using various sulfate fertilizers or acidic fertilizers because the alkaline substances remain in the soil and do not volatilize; they only gradually seep to the surface of the soil and other areas.
If the soil is already alkaline, the best method is actually to change the soil. This involves removing the original soil, pruning the plant's branches and leaves to reduce water loss, and then transplanting into a new pot. This is usually done in spring or autumn, avoiding the extremely hot summer and the cold winter, which can thoroughly improve the alkalinity of the potting soil.
If your potted plants are not doing well, with weak growth, flowering initially but not later, continuous yellowing leaves, and eventually stopping growth, it could also be due to poor soil.
3. Using acidic soil to grow flowers
Most gardening enthusiasts grow flowers on balconies or rooftops, where the amount of sunlight is fixed. What we can improve is providing the plants with suitable potting soil and reasonable watering. We can start from these two aspects to improve the pH level of the potting soil.
High alkalinity in potting soil affects flowers
You can test the pH level of the potting soil in advance
When potting plants, you can use slightly acidic soil, including common types like peat soil, grass charcoal soil, decomposed leaf soil, and compost soil, which are all slightly acidic. When growing flowers indoors, it is generally recommended to mix peat soil with perlite.
If planting succulents, you can mix in 40% to 50% of particle stones, such as common materials like volcanic rocks, red jade soil, light stone coal cinders, etc.
4. Precautions when using base fertilizer
If the environment is good, such as on a balcony or rooftop with good ventilation and plenty of sunlight, you can add a little well-rotted manure, such as sheep manure or earthworm manure, at the bottom of the pot. These types of manure have a gentle nutrient content, and you should ensure that the plant's roots do not come into direct contact with the fertilizer to avoid fertilizer burn.
If growing flowers indoors, it is not recommended to use manure but rather slow-release fertilizer, which can be mixed into the soil or sprinkled on the soil surface without being buried at the bottom of the pot. Since its nutrients are released slowly, the fertilizer will gradually渗透 into the soil during regular watering. If the slow-release fertilizer is directly sprinkled at the bottom of the pot, its nutrients will be washed away by water, and the plants won't be able to absorb them.
5. Watering and potting soil pH
Improving the pH of the soil is not enough; you also need to start with daily watering. Many gardening enthusiasts in the north know that most tap water in the north is slightly alkaline, which is disadvantageous for plants.
If tap water is used for a long time to water plants, it can easily lead to alkaline soil, and the surface of the potting soil may develop a white alkali deposit. This is even more evident when using red pottery pots, where white alkali substances seep out from the surface due to the numerous pores, and the alkali substances accumulate over time.