From the plant's point of view, the primary function of a pot is to provide a stable and healthy environment for its roots. Dendrobium orchids are predominantly epiphytes, meaning they naturally grow attached to trees. Their roots are adapted for rapid water and nutrient uptake and require exceptional aeration. They are not designed to be buried in dense, water-retentive soil. Therefore, the pot must facilitate a cycle of quick drainage and then allow air to circulate through the potting medium. A pot that is too large holds moisture for too long, suffocating the roots and leading to fatal rot. Conversely, a pot that is too small may dry out so rapidly that the roots become desiccated and cannot function. The ideal pot size is one that allows for 1-2 years of growth, typically leaving about an inch (2-3 cm) of space between the edge of the root mass and the pot's rim.
The material of the pot directly influences the root zone's moisture and temperature. Unglazed terracotta or clay pots are porous, allowing water and air to pass through their walls. For a Dendrobium, this means the potting medium dries out more evenly and quickly, which is beneficial for growers who tend to overwater. However, this also means more frequent watering is required. The porous nature also helps keep the roots cooler. Plastic pots, on the other hand, are non-porous. They retain moisture for a longer period, which can be advantageous in drier climates or for growers who struggle to water frequently. The plant's perspective here is one of consistency; the choice between materials should be made based on which environment provides a more stable moisture level for its specific growing conditions.
Regardless of material or size, a pot is a death sentence for a Dendrobium orchid if it lacks adequate drainage. From the root's perspective, being submerged in stagnant water is catastrophic. It immediately cuts off the oxygen supply, causing the velamen (the spongy root covering) to break down and rot. This rot can quickly spread to the rhizome and pseudobulbs, killing the plant. A suitable pot must have multiple large drainage holes in the bottom to allow water to flush through the medium completely. Some specialized orchid pots also feature slits or holes on the sides to further enhance air circulation around the roots, mimicking their natural aerial environment.
Dendrobiums often develop tall, heavy pseudobulbs (canes) that can make the plant top-heavy. The pot must provide a stable base to prevent the plant from tipping over, which could break new growths or roots. A wider, heavier pot, like a clay pot, can provide this stability better than a lightweight plastic one. Furthermore, these orchids grow from a rhizome that typically extends horizontally. Therefore, a pot that is wider than it is deep is often more suitable than a deep, narrow pot, as it accommodates the plant's natural growth direction and provides space for new leads (growths) to develop.
