How to Grow and Care for Dendrobium Orchids

The Dendrobium genus is one of the largest of all orchid groups with nearly 2,000 species. Native to southeast Asia, these plants grow in all manner of climates—from hot, wet lowlands to high-altitude, cool mountains. Dendrobiums are primarily epiphytes, meaning they grow on other plants but don't take nutrients from the host. In nature, they're often found growing on tree branches. While the species vary in appearance, all of them are known for their profuse blooms that come in a variety of pastel tones. Some species bloom all along the lengths of their stems while others bloom just from the tops of the stems. Some are deciduous and drop their leaves in the fall, and some hold their leaves year-round.

Most species have a moderate to fast growth rate. The best time to plant is either at the very beginning of the growing season or after the orchid has finished flowering. 

Dendrobium Orchid Care

Dendrobium is a very large genus with hundreds of species, so it is difficult to generalize care needs since each species will have its own requirements. Generally speaking, though, the dendrobiums require relatively warm conditions, above 60 degrees but no more than 85 degrees Fahrenheit during the growing season. While some types of orchids require pruning to prompt reblooming, with dendrobiums, reblooming is likely to be prompted by a winter rest period, where the plant is kept at lower temperatures and water is withheld for three or four weeks. With some species of dendrobiums, only a single rebloom is possible, while other species may rebloom four or five times each year.

Dendrobium orchids make good houseplants and are fairly easy to grow, though they can be picky about their environment. Thus, paying close attention to their growing conditions is key for a healthy, well-blooming plant. In general, these orchids like small pots where their roots can be somewhat cramped, and they need to be by a bright window if you're keeping them indoors. Plan to water and feed your orchid often during the growing season but then back off in the winter months.

Light

In native settings, these plants grow well in partial sunlight. But indoors they'll likely need to be by your brightest window—preferably a south-facing window—to bloom well. The appearance of many tiny offshoot plants (known as keikis, pronounced "kay-keys") on relatively young, small canes can mean the plant isn't getting enough light. On the other hand, if you see yellow leaves, you might have given the plant too much direct sunlight.

Soil

Orchids don't grow in typical potting soil but rather in a special mixture that mimics their environment in the wild. Use a commercial orchid potting medium, which generally contains peat moss, perlite, or fir bark. Or make your own using those ingredients. Make sure the medium has aeration and is well-draining, so the roots aren't left in too much moisture for a lengthy period.

Water

During the growing season, these plants like moisture but shouldn't sit in a saturated medium. Overwatering can lead to root rot and ultimately cause the plant to yellow or wilt. To determine when you should water, simply stick your finger in the medium. If it feels wet, wait to water until it has dried out slightly. During the winter months, you can put a few more days in between your regular waterings, but don't let the medium dry out entirely.

Watering with distilled water or collected rainwater is a good idea, as tap water can cause salts and minerals to build up in the pot.

Temperature and Humidity

Dendrobium orchids like warm climates and grow best with daytime temperatures between 70 and 85 degrees Fahrenheit, with a nighttime drop of about 10 degrees. They might be able to withstand slightly cooler nighttime temperatures down to 50 degrees Fahrenheit, but prolonged exposure to cold isn't ideal. Many types, however, do require a winter rest period where the plant is kept at about 55 degrees for several weeks to prompt reblooming.

Dendrobiums prefer a humidity level between 50 and 70 percent (with a minimum of 45 percent). Brown leaf tips can be a sign that the air is too dry for your orchid.

Fertilizer

Feed regularly during the growing season with a balanced orchid fertilizer, following label instructions. At the end of the growing season, reduce fertilizer by about half.

Types of Dendrobium Orchids

Dendrobium orchids are classified into six distinct groups, each of which has different characteristics and care needs. It is important to understand what group your orchid falls into so you can give it proper care:

• Dendrobium phalaenopsis is the most popular group, comprising most of the commercial dendrobiums offered for sale. These are evergreen species that like warm conditions and usually bloom in the fall, with a spring rebloom possible if the plant is given a three- to four-week rest period at lower temperatures and drier conditions. Species in this group include. D. affine, D. biggibum, D. dicuphum, and D. williamsianum. They can be identified by the perky star-shaped flat-petaled blooms growing in the middle to end of a slightly curved cane.
• Dendrobium spatulata is another evergreen group, but comprised of species that may bloom several times a year. Species that fall into this group include D. antennatum, D. canaliculatum, D. discolor, D. gouldii, D. johannis, D. lineale, D. stratiotes, D. strebloceras, and D. taurinum. Unlike other groups, this group does not require the winter rest period to rebloom. These orchids are identified by their spiral, twisted, and curly-edged floral segments and asymmetrical flowers.
• Dendrobium is divided into two sections. Group 1 includes a select group of species with pendulous stems. They usually actively flower in summer and drop their leaves in winter. These orchids require a winter rest period with cooler, drier conditions. Species in this group include D. chrysanthum, D. friedricksianum, D. nobile, and D. wardianum.
  Dendrobium group 2 is comprised of species that are fully deciduous and should not be watered at all in winter. Species include D. anosmum, D. crassinode, D. falconeri, D. fimbriatum, D. findlayanum, D. heterocarpum, D. loddigesii, D. moniliforme, D. parishii, D. primulinus, and D. transparens.
• Callista group includes species such as D. aggregatum, D. chrysotoxum, D. densiflorum, D. farmeri, and D. thyrsiflorum. These need warm conditions in summer, but reduced temperatures and drier conditions in winter. Callista orchids have bright colors and canes with dense blooms.
• Latouria group includes species such as D. atroviolaceum, D. macrophyllum, and D. spectabile. These species need a winter rest period. Latouria orchids are characterized by large yellow-green blooms that have black or purple markings on the inside surface of the petals. They can also be hairy on the inner surfaces.
• Formosae group includes species such as D. bellatulum, D. dearii, D. draconis, D. formosum, D. infundibulum, D. lowii, D. lyonii, D. margaritaceum, D. sanderae and D. schuetzii. Orchids in this group generally require cool to moderate conditions year-round: 50- to 60-degree nights and days that are no more than 85 degrees Fahrenheit. The main identifying characteristic of this group is the fine black hair covering the canes.

Species falling outside these groups include D. linguiforme, D. tetragonum, D. gracillimum, and D. cuthbertsonii. With these, it's generally safe to allow them to dry out and go dormant in winter, providing them with moderate temperatures during their growing season.

Pruning

These plants generally send up at least one new upright cane each year. After the flowers fade, they can be clipped off where they join the canes, but don't cut off old canes, as they store nutrients and water to keep the orchid healthy. Clipping this stem off does not promote reblooming, as it does with some other types of orchids.

Old canes also will sometimes flower or produce tiny offset plants, called keikis (pronounced "kay-keys"), that can be potted on their own after they develop roots.

Propagating Dendrobium Orchids

If your plant has at least four canes bearing healthy leaves, you can divide it. Here's how:

1. Use a large stiff knife to cut through the rhizome and root mass, attempting to keep the root mass as intact as possible.
2. Remove all the growing medium from the root mass, and then cut away any long dangling or dead roots.
3. Put the plant in a pot close to the size of its root mass, and cover the roots with orchid potting medium.
4. Press down the potting medium firmly, and wait one week to water it thoroughly.

Another propagation method is to simply prune away the small offset plants (keikis) that sometimes appear at the base of old, mature canes and replant them in their own pots. However, these offsets will take longer to become mature, flowering plants than if you create larger divisions.

How to Grow Dendrobium Orchids From Seed

Seed propagation of orchids is not recommended, since it requires carefully controlled conditions and laboratory precision. In the wild, orchid seeds germinate through a complex symbiotic relationship with soil fungi, and duplicating this process artificially is tricky and prone to failure when attempted by amateurs. Thus, propagation is usually done by division (see above), a much easier method.

Potting and Repotting Dendrobium Orchids

Dendrobiums grow well in any well-draining container filled with commercial orchid potting mix, which is usually a bark-based medium. Repotting is usually needed every two to three years and is best done in the spring. Repotting is needed if the plant outgrows its pot, or if the plant has broken down the potting mix. Choose a pot large enough to accept four to six new canes, then slide the plant out of its old pot, rinse off the root ball, and plant in the new pot with fresh bark-based potting mix, spreading out the roots as you fill the pot.

Overwintering

Proper overwintering strategy can vary somewhat depending on species, but generally speaking, dendrobiums should be given a cooler, drier, rest period during the winter. Three or four weeks spent at 55 degrees Fahrenheit is often ideal, before returning them to the normal pattern of 60- to 65-degree nights and 75- to 85-degree days.

Common Pests & Plant Diseases

Mealybugs are the most common pest for dendrobium orchids, often hiding in the junction where leaves meet the canes. A good treatment is to spray with a homemade concoction consisting of equal parts water and rubbing alcohol, with a few drops of dish soap added. Large infestations may require spraying with a commercial pesticide formulated for houseplants.

Diseases are not common with dendrobiums, but excessive watering may cause root rot. Petal blight, a fungal disease, can sometimes cause spotting on the flower petals. Affected blossoms should be removed.

How to Get Dendrobium Orchids to Bloom

For most types of dendrobium orchids, the long-lasting sprays of flowers remain in bloom for roughly six to eight weeks, and they can make excellent cut flowers. Spring and summer are the most common bloom seasons, though in optimal conditions, some types might bloom multiple times per year. If blooming seems suboptimal, try providing your orchid with more light. Improper temperatures can also cause orchids to be shy about blooming. These plants also need regular feeding during their active growing season.

Reblooming

Getting dendrobium orchids to rebloom usually depends on giving them a rest period with lower temperatures—three to four weeks at 55 degrees Fahrenheit—and less water. This is not true of all species. For example, the Dendrobium spatulata does not require a winter rest period to bloom and orchids in the Formosae group may need only a shorter winter rest period than others needing longer respites.

Common Problems With Dendrobium Orchids

Dendrobiums are regarded as one of the easier orchids to grow, but you may run across these issues:

Yellowing, Spotted Leaves

Too much water can cause yellowing leaves, but with some deciduous species, it is natural for leaves to develop spots and turn yellow just before they are shed for the winter.

Burned Leaves

Browned edges on leaves can be caused by too much fertilizer or by growing medium that has become saturated with salts and minerals from tap water. Most likely, though, is sun scald caused by too much exposure to direct sunlight. If these plants are kept in south- or west-facing windows, it is a good idea to use a sheer white curtain during the summer months to diffuse the sunlight. Dendrobium orchids will tolerate partial shade and some direct sun, but bright indirect light is better.

Low humidity can also cause leaves to dry up and turn brown.