How to choose orchid pot drainage layer materials? Key points explained at once

OrchidsWhen potting, some materials are often placed at the bottom of the pot as a drainage layer to facilitate drainage and airflow. There are many kinds of materials that can be used as a drainage layer. Commonly used ones include sand, coal cinders, crushed brick, foam plastic blocks, etc. These drainage layer materials each have their own strengths and weaknesses, with both advantages and disadvantages. Some have more disadvantages than advantages, while others have fewer disadvantages and more advantages. In many years ofgrowing orchidspractice, the author has tried all of these drainage layer materials. Below is a discussion of the properties of these drainage layer materials. Sand: Using sand as a drainage layer is a "traditional" practice. For drainage layer sand, it is best to choose clean river sand that contains no salt or lime. River sand is divided into coarse and fine grades, and the size of its particles is inversely proportional to its water retention capacity. Advantages of river sand: stable physical and chemical properties, low price, easy to obtain, and coarse sand has relatively good drainage performance. Disadvantages: no microporosity, contains no nutrients, and poor fertilizer retention. Because fine sand has small particles, when used as a drainage layer, poor drainage at the bottom of the pot is commonly seen in practice. The author uses "sand heads" instead of coarse or fine river sand as a drainage layer, and its drainage and air permeability are even better. So-called "sand heads" are the leftover sand grains after sieving river sand used in construction, with particles roughly between the size of a mung bean and a soybean. Coal cinders: Coal cinders are lightweight, do not compact, are widely available, allow air and water to pass through, retain water and fertilizer, contain minerals, and because they have been burned at high temperature, they are sterile and pest-free and not likely to trigger orchid plantpests and diseases, so people also often use them as an orchid pot drainage layer material. However, coal cinders contain relatively few nutrients and are easily crushed under pressure, thereby reducing drainage and air permeability, so the coal cinders in the drainage layer often form a state of prolonged wetness that is hard to dry. Through repeated comparative testing and verification, the author finds that coal cinders are not an ideal choice as a drainage layer material. Crushed brick: Crushed brick has a wide range of sources, is easy to obtain, easy to process, reusable, and has excellent water absorption, drainage, and air permeability, so it can be considered a relatively good drainage layer material. However, crushed brick is heavy, contains no nutrients, and also has poor fertilizer retention. After bricks are broken and processed, they generally have sharp edges and corners, which can easily cut orchid roots. The crushed brick particles used as a drainage layer should not be too small; it is best to process them into brick particles about the size of a broad bean so as to better facilitate drainage and air permeability. Foam plastic blocks: Using foam plastic blocks as a drainage layer works well and has been widely used by people in recent years as a good material for orchid pot drainage layers. Foam plastic blocks have many excellent properties: lightweight, good for water passage, air permeable, warmth-retaining, do not press orchid roots (orchid roots can penetrate the foam plastic blocks), can give off an odor that repels insects and prevents disease, and are easy to separate from old pots when repotting. When foam plastic blocks are used as a drainage layer, orchid plants are less likely to have root rot, the germination rate is high, roots are white and long, and leaf variegation is easy to produce. The shortcoming of foam plastic blocks is that they lack organic fertilizer, which can be improved through fertilization. Practice has proven that foam plastic blocks used as a drainage layer should be processed into small pieces half an inch square; too small is no good, and too large is also no good. The main function of filling an orchid pot with drainage layer material is to facilitate water discharge and air circulation. However, some factors can reduce these two effects, and corresponding measures must be taken to overcome them. Measure one:When orchidsare planted and soil is being added, people often shake the orchid pot or pat the outside of the orchid pot so that the potting soil fits tightly against the orchid roots. If the growing medium used is dry, the fine medium in the middle and upper parts of the orchid pot easily sinks down to the bottom of the drainage layer as the orchid pot is shaken, causing the original gaps among the drainage layer materials to become smaller and reducing drainage and air permeability. A "finger-pressing method" can be used instead, but heavy pressure should not be applied, to avoid crushing and injuring orchid roots. Alternatively, spray the dry plant material to be used with water until slightly moist before use, which can also achieve the effect of reducing the sinking of fine medium. Measure two:When orchidsare watered, the fine medium in the upper and middle parts of the orchid pot will sink to the bottom of the pot due to the gravity of the watering. A plastic window screen mesh can be placed over the top of the drainage layer material to block the fine medium from sinking. According to observation, when orchid roots extend and grow to the plastic window screen mesh, they will pass through the mesh openings, pushing the screen threads outward in all directions, and will not affect the extension and growth of the orchid roots. The window screen mesh should be made of plastic, not metal. (Zhang Bingfu, Longyan, Fujian) Mailing address: Dongxiao Overseas Chinese Federation, Longyan City, Fujian Province Postal code: 364012