Dendrobium Culture Sheet
How to grow Dendrobium orchids.
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Dendrobium orchids require medium to high light to grow and flower, but avoid direct sun. This is slightly less light than is required for cattleyas, but more than is required for phalaenopsis and paphiopedilums.
Window: Place dendrobiums in a bright east, west, or south window, but watch for signs of developing sunburn. This will appear initially as a yellowing or tan patch facing the source of light. A sheer curtain can be used to protect from sun damage.
Artificial light: High-pressure sodium lights, fluorescent and compact fluorescent lights, and LED lights can all be used to grow dendrobium orchids. Place dendrobium orchids closer to the middle of the growing bench, and move plants with lower light requirements closer to the ends.
Outdoors: Like most orchids, dendrobiums benefit from being moved outdoors after nighttime temperatures remain above 60 degrees. Plants may need to be acclimated gradually to brighter conditions, and should be kept out of hot sun.
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Dendrobium orchids thrive in intermediate to warm temperatures. A combination of bright light and excessive heat may result in sunburn, which will appear initially as a patch of yellow, tan, or white discoloration, fading to light tan and forming a dry patch. Check plants regularly for sunburn. Temperature requirements may vary for different species, with some requiring cooler temperatures, such as Dendrobium cuthbertsonii.
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During active growth, dendrobium orchids want to be watered heavily on watering day, and then approach dryness before being watered again. Once growth slows in fall and winter, dendrobiums should be allowed to just dry before watering. Some species, and their hybrids, require a dry rest to properly flower. To water at a sink, run a tap of room temperature water, and hold the pot in the water, moving it so that the entire pot is thoroughly flushed with water to thoroughly drench the medium. Allow the pot to drain, and place back into the growing area. This is an ideal time to check for sun damage, pests, and other developing problems.
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Formula: Dendrobium orchids benefit from a balanced fertilizer, such as 10-10-10. The formula of fertilizer required will change depending on the amount of dissolved minerals in your local tap water. Water with high total dissolved solids (TDS) will require fertilizer without these additional minerals, or it may burn the roots. Water with low dissolved magnesium and calcium will require a formula that supplements these essential minerals. The Chicago municipal water supply is very good for growing orchids.
Schedule: Most orchid growers follow a “weakly-weekly” fertilization schedule, and will use ¼ of the package recommended strength, every time they water. Some growers will decrease or discontinue fertilization from late fall to early spring, or when the plant is not actively growing, while other growers may feed evenly year-round. Some growers report success switching to a “bloom booster” formulation in the months leading up to that orchid’s blooming season. Flush the pot with plain water without fertilizer once every month to avoid the buildup of fertilizer salts.
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Some dendrobiums will require regular watering all year round, while others will require a dry rest of several months to properly flower. Do not remove old growths which have dropped their leaves. Many dendrobiums will bloom from old leafless pseudobulbs. A very small drizzle of water can be applied around the edges of the pot, or mist applied to pseudobulbs in the early morning, to prevent excessive shriveling. Maintain the dry rest until buds appear in spring. Some species may require a dry rest between Thanksgiving and Valentine’s Day, such as Dendrobium nobile, Den. chrysotoxum, and Den. bigibbum; while others may just require more pronounced drying between watering, such as Den. spatulata, Den. antennatum, and Den. Hibiki. Some varieties may also require cooler temperatures during this period. Dendrobium varieties that naturally drop their leaves in fall are more likely to require some form of dry rest.
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Use a coarse, free draining potting medium like fir bark or a fir bark mix. Some growers have success using lightweight expanded clay aggregate (LECA) or Hydroton in a container that keeps a small reservoir of water, in a method called semi- hydroponic. For small plants, or varieties that require some form of dry rest, planting in sphagnum moss may allow more even distribution of traces of water. Dendrobiums like to be tight in their pot, so use a pot just big enough to hold the roots.
Care requirements created with information from the American Orchid Society, and Illinois Orchid Society growers.
