Advantages of Foliar Fertilization for Orchids and Points to Note

Orchid (scientific name: Cymbidium ssp.): epiphytic or terrestrial herb, with several to many leaves, usually borne at the base of the pseudobulb or on the lower nodes, two-ranked, strap-shaped or rarely oblanceolate to narrowly elliptic, the base generally with a broad sheath that clasps the pseudobulb, with a joint. The raceme bears several to many flowers, in colors of white, pure white, white-green, yellow-green, pale yellow, pale yellow-brown, yellow, red, blue-green, and purple. Among the traditional famous flowers of China, "orchid" refers only to certain terrestrial orchids distributed among the Cymbidium species in China, such as Cymbidium goeringii, Cymbidium faberi, Cymbidium ensifolium, Cymbidium sinense, and Cymbidium kanran, namely what is commonly called "Chinese orchid". This type of orchid is very different from tropical orchids with large, brilliantly colored flowers; it has no showy, gaudy appearance and no huge flowers or leaves, yet it possesses a simple, quiet, elegant, and noble temperament, which fits well with the aesthetic standards of Eastern people. It has a cultivation history of more than one thousand years in China. According to records, as early as the late Spring and Autumn period, King Goujian of Yue had already planted orchids on the hills of Shaoxing, Zhejiang. After the Wei and Jin dynasties, orchids were already used to adorn courtyards. In ancient times, people at first mainly collected wild orchids; as for artificial cultivation of orchids, it began in the imperial palace. After the Wei and Jin dynasties, orchid cultivation expanded from the imperial palace to the private gardens of the scholar-official class, and was used to adorn gardens and beautify the environment, as described in Cao Zhi's poem "Autumn Orchids Cover the Long Slope." It was not until the Tang dynasty that the cultivation of orchids and Hui orchids developed to general gardens and flower growers, as in the lines written by the great Tang poet Li Bai, "The secluded orchid's fragrant wind travels far, the hui grass's flowing fragrance reaches its roots."

Advantages of Foliar Fertilization for Orchids

1. Direct nutrient supply, preventing potting soil from compacting. Certain nutrient elements such as iron (Fe), manganese (Mn), and zinc (Zn) are easily fixed after being applied to the potting soil, greatly reducing their availability. If changed to foliar fertilization, it can prevent the potting soil from compacting and also increase fertilizer efficiency.

2. Nutrients circulate quickly, with results visible in a short time. Foliar spraying of fertilizer takes effect faster than root fertilization and can ensure timely nutrient supply. Practice has shown that foliar spraying of urea can take effect in 1 to 2 days, while applying it to the potting soil requires 5 to 6 days. As another example, phosphorus fertilizer can take effect with 1 foliar spraying, but root fertilization requires 10 days to take effect.

3. Saves fertilizer and does not harm roots. The amount of fertilizer used for foliar spraying is generally only about 20% of the amount used for potting soil fertilization. Taking the spraying of "Huabao" as an example, 1 gram of Huabao dissolved in 1 liter of water (that is, diluted 1000 times with clean water), sprayed on both the front and back of orchid leaves, uses a small amount; only 1/5 of the amount used for watering the potting medium is enough. Foliar spraying of trace element fertilizers not only saves dosage, but also avoids the harm to orchid roots caused by uneven application to the potting soil.

4. Makes up for the deficiency of stopping root fertilization. During the hottest days of midsummer and the severe cold of deep winter each year, root fertilization must be stopped, but this does not mean the orchid plants do not need nutrients. At such times, the safest measure to supplement nutrients is foliar fertilization. Foliar fertilization can be carried out all year round; choosing slightly cooler weather in summer and mild times in winter for foliar fertilization can achieve better results, thereby making up for the deficiency of stopping root fertilization.

5. Saves time and reduces the number of sprayings. Foliar fertilization can be carried out together with procedures such as insecticide and sterilization. In the foliar fertilizer solution, adding an appropriate amount of omethoate (to kill scale insects, etc.) and 75% chlorothalonil (for sterilization) not only applies fertilizer but also kills insects and sterilizes, thus saving time and reducing the number of sprayings, achieving twice the result with half the effort.

Points to Note in Foliar Fertilization for Orchids

1. Non-water-soluble fertilizers cannot be used. For different fertilizers of the same nutrient element, the speed of foliar absorption differs. For potassium fertilizers, the fastest absorbed by leaves is potassium chloride, followed by potassium nitrate, and then potassium dihydrogen phosphate; for nitrogen fertilizers, the fastest absorbed by leaves is urea, followed by nitrate nitrogen fertilizers, and then ammonium nitrogen fertilizers. Fertilizers used for foliar spraying can only be water-soluble; non-water-soluble fertilizers cannot be used.

2. Pay attention to solution concentration and reaction. The principle is to appropriately increase the solution concentration on the premise that the leaves are not harmed by fertilizer, as this can improve penetration efficiency and give better results, but appropriate moderation must be observed.

3. Time for moistening orchid leaves. Generally, the fertilizer solution is required to keep orchid leaves moist for 30 minutes to 1 hour, so that absorption is fast and the effect is good. If it dries quickly, the effect will be very poor. If it is exposed to rain shortly after spraying, the effect is also poor, so foliar spraying should be done on the evening of a clear day or in the early morning when there is dew, and windless weather is better.

4. Spraying sites must be reasonable. Stomata are the portals for gas and water exchange during plant photosynthesis and respiration, so the foliar spraying sites must be reasonable. For example, about 85% of the stomata on Cymbidium goeringii leaves are on the underside, with only 15% on the upper side, so when fertilizing, special attention should be paid to spraying the underside of the leaves. Other varieties of Chinese orchids are roughly the same, and emphasis should be placed on spraying the underside of the leaves.

5. Water quality must be clean. The water used to dilute fertilizer must be clean; cloudy water containing impurities cannot be used. If tap water is used, it must be stored for more than one day until the chlorine has dissipated before use.

6. A single fertilizer must not be used for a long time. Different fertilizers should be sprayed at different growth stages of orchids; a single fertilizer must not be used alone for a long time. For example, in spring when new orchid shoots emerge, nitrogen fertilizer should be the main type, such as urea and Huabao (No. 5); from the beginning of July to the end of August, to promote flower bud formation, phosphorus fertilizer should be the main type, such as Huabao (No. 3) and potassium dihydrogen phosphate.