The Relationship Between Orchids and Sunlight, and Key Light Points for Care

TheCymbidium goeringii (spring orchid)and Cymbidium faberi (summer orchid) we grow are terrestrial orchids that obtain energy through the photosynthesis of their green leaves to sustain and continue life and reproduce. The power source is sunlight; through the chemical action of chlorophyll in the orchid leaves, sunlight absorbs carbon dioxide and releases oxygen to increase the nutrients the orchid body needs. The pseudobulbs and roots carry out digestion and decomposition at night, converting carbon dioxide into sugar, which then forms various needed proteins; through the flow and pressure of water and air, these are transported to all parts of the plant, enabling it to grow and swell. Day after day, the potted orchid is thus able to grow shoots and bloom. This is roughly the relationship betweenorchidsand the sun. Another relationship between the sun andorchidsis the temperature it brings to the orchid body.Cymbidium goeringii (spring orchid)and Cymbidium faberi (summer orchid), after growing in nature for hundreds and thousands of years, also have a close relationship with sunlight and temperature. General experience: at 20-25 degrees, under direct sunlight, the chemical reaction between the chlorophyll in the orchid leaves and light is very fast, and the grass grows vigorously. Above 30 degrees, the chlorophyll in the grass leaves automatically decreases, the leaf color becomes lighter, and a visible gray film gradually forms to reflect sunlight and prevent scorching. This condition can only be maintained for a relatively short time; if it lasts too long, starting from the leaf tips, the whole plant gradually withers and dies, especially older grass, which first turns yellow and then scorches. Below 20°C, orchid leaves can also automatically regulate the amount of chlorophyll, increasing chlorophyll to absorb more sunlight, so as to absorb more carbon dioxide and ensure the nutrients needed for the orchid body's growth. This function was formed byorchidsgrowing for many years under trees, among forests, and among grasses. Therefore, besides loving sunlight, orchids are also shade-tolerant. But orchids ultimately rely on sunlight as their power and on the temperature brought by sunlight to grow and reproduce. The fine-leaved varieties oforchidscan, under shaded conditions, tolerate high temperatures of 45 degrees for a short time; if the time is long, the leaves will scorch. When there is sunlight, they can also tolerate low temperatures of -5 degrees for a short time, but humidity is an important condition. Because orchids are shade-tolerant and can grow at low temperatures, in winter they need full sun, and also need temperatures above 5 degrees and scattered light to regulate the amount of chlorophyll, their own nutritional field. Orchid leaves in shady places are often greener than those receiving more sunlight. People have grasped this physiological characteristic oforchidsand, through years of accumulated experience, incultivationmanagement mostly take shading measures in summer; orchid pots can be placed outside in sunlight, and when above 30 degrees, they can also be placed indoors in shade. Although indoor scattered light is weak, orchids can still be grown well. For orchids on a south balcony, in summer after 9 o'clock and before 17 o'clock, under well-ventilated conditions, bamboo blinds or commercially available black shade nets of 70% or more can be used for shading, and the same applies to various orchid sheds. When shading, the blinds or nets should not be laid on theorchid grass, so as to avoid the heated blinds or nets scorching theorchid grass. Shading materials should preferably allow some light through; about 30% light is beneficial toorchid grass. Light can not only raise temperature, but also prevent the breeding of fungi, bacteria, and viruses; leaving gaps in the blinds or nets helps ultraviolet rays kill pathogens and viruses. Sunlight and temperature have a great influence on the reproduction oforchids. For example, if there is no sunlight for a long period in winter and the temperature is relatively low, winter buds will not be formed; if no new grass emerges in spring, the year's grass increase rate will be affected. The fundamental source of color in all things in the world is sunlight. A rainbow divides into seven colors, and the seven colors can change in countless ways; the original colors of orchids are composed of ever-changing primal light. Therefore, sunlight also has a direct influence on the colored flowers of orchids. Those growing and cultivating leaf-variegated orchids and colored-flower orchids should study sunlight to some extent. Examples are as follows: Green orchids should be exposed to less sun, and 0.2%-1% ferrous sulfate, or 2% edible vinegar, should also be applied. Applying less phosphorus fertilizer can deepen the green color and prolong its duration. This is the reason why Jiangsu and Zhejiang orchids and huilan have many green flowers and traditionally are mostly grown in shade. White flowers should be exposed to less sun, and 0.3%-0.5% clear limewater can be applied. Crystal orchids, Youlan, and Lingcao can only receive scattered weak light. For other white-flower grasses, when flower buds appear, dark paper can be rolled into a tube shape to cover the buds until flowering. Silver-edged variegated orchids should also be exposed to less sun. Yellow flowers should be exposed to more sun, and 0.2%-0.5% sulfur water should be applied. If yellow leaf-variegated orchids receive little sunlight, they may show white variegation color. Red flowers should be exposed to more sun, and 0.5% nitric acid or urea should be applied, with less potassium fertilizer. Pink flowers should be exposed to more sun, and 1%-3% superphosphate should be applied. Purple flowers should be exposed to more sun, and 0.3%-0.5% alum water should be applied. Regarding the discussion of shading, in summary, most colored-flower and leaf-variegated orchids need strong sunlight; placed in a sunny orchid shed below 30 degrees, they may not need shading, using granular medium, with one heavy watering at 10 a.m. each day and another heavy watering at 2 p.m., pouring over the top and soaking both grass and pot to cool them. Emptying the pot at night will neither burn the orchid grass nor stop the orchid grass from growing at night. Watering cool at the high temperature of 10 o'clock, then watering cool again at 2 p.m. when the temperature has just risen, with no further temperature rise at night and no remaining water in the pot, is very beneficial to orchid grass growth. This method is not suitable for potted grass that has not been hardened off; only grass that has been exposed to wind, rain, and sun can be treated this way, and it should not be used for green-flower grass, white-flower grass, white leaf-variegated grass, or diseased and weak grass. When the temperature is higher, or when one is not very confident, short-term shading protection can also be used, but green-flower grass accounts for the majority, so shading is still needed. (Guan Wenchang, Zhu Hexing)