Orchid Fertilization and Light Management Methods, reprinted from Orchid Treasure Trove

Fertilization and Light (reprinted from Orchid Treasure Trove) The relationship between fertilization and light is an extremely important issue in the process of fertilizing orchids that is often overlooked by people. Regarding fertilization, orchid enthusiasts pay great attention to issues such as the suitable temperature for fertilizing, what fertilizer should be applied during the vegetative growth stage, what fertilizer should be applied during the reproductive growth stage, which plants can tolerate fertilizer, which plants need lean cultivation, and the concentration of the fertilizer solution. Regarding light, orchid enthusiasts also pay great attention to issues such as the suitable light intensity for various types of orchids at each growth stage, how to shade, and how to supplement light. However, in the process of orchid cultivation, paying attention only to the above issues is still not enough. We often see that some orchids cultivated by orchid enthusiasts have very long leaves but very short roots, presenting a top-heavy state; some have only 3 or 4 seedlings planted in a large pot, with orchid leaves growing short and yellow, yet their roots are long and numerous, filling the entire pot, also presenting a top-heavy state. The important reason for these two poor growth conditions is that the relationship between fertilization and light has not been correctly handled. As everyone knows, light can promote the synthesis of sugars and amino acids in the plant body. During the day, the sugars produced by photosynthesis are stored in the leaves in the form of starch, and only during the dissimilation process at night are they moved downward. The strength or weakness of light will lead to strong or insufficient assimilation. If light is insufficient, the assimilation of the leaves will also be insufficient. Because nitrogen fertilizer is not well digested during the day, the accumulation of sugars and starch is small, and what descends at night is also small. Over time, orchid leaves will inevitably be wide and thin, with elongated and thin bases. The roots will be short and few, or even rotted. This is when the top-heavy phenomenon appears. After this situation occurs, the light intensity needs to be gradually increased, organic nitrogen (which can reduce sugar consumption during metabolism), cell activators, and cell enhancers should be continuously supplied, and water supply should be reduced. After new roots grow out, slowly return to normal management. If light is too strong, the assimilation of the leaves will also be too strong. Because excessive nitrogen fertilizer is consumed, the leaves become short, small, and yellowed. Because of sufficient sugars and amino acids, the pseudobulbs and roots grow excessively. When this top-heavy phenomenon appears in orchids, in addition to reducing light, sufficient inorganic nitrogen should be continuously supplied. Supplying inorganic nitrogen can reduce sugar content and also promote protein synthesis. Proper division or root thinning can also be done to increase the number of shoots. In this way, the new plants produced can return to normal. Practice has proven that only under conditions of sufficient light can orchids absorb nutrients, so when fertilizing orchids there must be sunlight, and the best time to fertilize is in the morning of good weather. When applying chemical fertilizer, the light intensity selected should be relatively higher; when applying organic fertilizer, it should be relatively lower. In addition to the light factor, if there are conditions such as the orchid pot being dry for a long time, too much stem fertilizer, or the placement position being too high, the top-heavy state can also appear; similarly, if the carbon dioxide concentration in the orchid room is too high during photosynthesis, causing high-carbon growth, the night temperature is too high causing respiration to be too vigorous, or there is nitrogen deficiency when growth is good, the top-heavy state can also appear. These issues should be discussed separately.