Nobile Type Dendrobium Care
Nobile dendrobiums can be grown and flowered in the home or greenhouse. They do, however, have rather specific cultural requirements. When those requirements are met, they will produce a profusion of sweet-scented, long-lasting flowers that can appear from fall through spring.
Nobile dendrobiums can and should be grown outdoors in the summer, usually between the first of June and the end of September if you are in the far northern states. Check your local climate for frost dates. If there is danger of frost, bring them in. They should be grown in 30-50% shade or bright, filtered sun. In the fall, when you bring them in, place them in either an east or south window. South is preferable. Try to give them as much light as you can, just short of burning.
There is a direct relationship between light, temperature and water. In the spring and summer months when the plants are in active growth, the sunlight is strong and there is ample air movement, water when the mix approaches dryness but still has a bit of moisture left. In the fall (usually mid to late November) when the newest growths have matured and get their last terminal leaf and there is a small nubby area in the center at the base of the leaf, water only enough to keep the canes or pseudobulbs from shriveling. This could be every couple weeks. Do not resume normal watering (watering when the plant approaches dryness, every 3-5 days) until you see flower buds appear on the sides of the canes usually opposite where the leaves are. Water in the morning. Rain water, reverse osmosis or distilled water is ideal, but well or municipal water is fine if the pH is 7.5 or lower and there are not huge amounts of minerals in the water.
Fertilize with Grow More 20-10-20 or Green Jungle Orchid Food, especially formulated to work with rain, distilled, reverse osmosis water or water low in alkalinity. Fertilize with Green Jungle every time you water. (NOTE: If using sphagnum moss, fertilize with Green Jungle every third or fourth watering during the growing season.) Stop feeding around mid-September, otherwise you will have lots of growth but few, if any, flowers. You may also see new plantlets develop where the flower buds should be if the plant has too much nitrogen tied up in it. Resume feeding after flowering when new growths emerge at the base of the plant and you can see new roots. If new plants do appear on the sides of the canes and you want more, wait until the growths are 6-8 inches in size and the roots are at least 3 inches long. They can then be simply twisted or cut off the cane and potted up separately.
Nobiles need cool temperatures in the fall and winter months in order to develop flower buds. Therefore, when they are brought in, they must have cool night temperatures. To expect good bloom, night temperatures should be no more than 60°F until the buds appear. Day temps can be in the low to mid 70s. After the buds appear, you can keep them at 62-64° F at night and you should have blooms in January or February. At night one can even put them in the refrigerator until buds appear. These plants can even take cooler temperatures but really reduce watering as rot problems can result from cold, damp potting mix.
After the flowers have finished, you can trim the stems off close to the canes. After several years, some of the older growths may become woody, shriveled and yellow-looking. As long as you have three or more healthy canes and at least one with a full set of leaves, you can cut the old unsightly growths at the base. We do not recommend cutting all the leafless canes as they store energy and contribute to the front new growths' development. Canes that flower one year can often produce a few more flowers in a subsequent year. The 2-3" flowers are long-lasting (6-8 weeks) and are highly fragrant. With the right culture you can have literally 50 to 100 flowers per cane.
Repot every two years or as the plant outgrows the pot. Orchiata Bark ('Power'-medium grade) or New Zealand sphagnum moss or coconut chips also work well. The best time to repot (if needed) is after flowering in the spring when the new growths and roots appear. If there is a solid root mass, you won't need to try and dig out the old mix; simply pot on if that is the case. If the mix is old and crumbly or sour, carefully remove the bark or moss and rinse the root system. Any old hollow or decayed roots can and should be removed. If the plant is growing in a direction, put the oldest growth towards the edge of the pot and allow at least an inch or two between the newest growth and the edge of the pot so there is room to grow.