How to Grow and Care for Dendrobium Orchids

The Dendrobium genus is one of the largest of all orchid groups with more than 1,500 species. Native to southeast Asia and the Pacific, 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. If cared for properly, a dendrobium lives for decades.

Dendrobium Orchid Care

• Use a small pot when planting so the roots are somewhat cramped, and fill it with commercial orchid potting medium.
• Keep the orchid in a spot that receives bright light for at least 6 hours daily.
• Place your dendrobium orchid in a spot with temperatures above 60 degrees but no more than 85 degrees during the growing season.
• Water and feed your orchid often during the growing season but then back off in the winter months.

Light

Select your brightest window—preferably a south-facing window—for the orchid to bloom well. The appearance of many tiny offshoot plants (known as keikis, pronounced "kay-keys") on relatively young, small canes indicates that the plant isn't getting enough light.

Soil

Purchase a special orchid growing mixture when potting or repotting that mimics their environment in the wild. 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

Watering is most crucial during the growing season and you should use distilled water or rainwater to prevent minerals and salts from building up in the pot. Simply stick your finger in the medium to determine when you should water.

If it feels wet, wait to water until it has dried out slightly. During the winter months, space the watering out more without letting the medium dry out entirely. Overwatering leads to root rot and ultimately causes the plant to yellow or wilt.

Temperature and Humidity

Keep dendrobium orchids warm with daytime temperatures between 70°F and 85°F, with a nighttime drop of about 10°F.

Many types require a winter rest period where the plant is kept at about 55°F for several weeks to prompt reblooming.

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

Fertilizer

Feed the orchid 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

The numerous species in the Dendrobium genus are divided into several sections and subsections based on both their floral and vegetative characteristics. They either flower in summer, drop their leaves in the winter, and require a cool, drier winter rest period; or they are fully deciduous and should not be watered at all in winter.

• Dendrobium phalaenopsis and their hybrids (also known as phalaenopsis-type dendrobium hybrids or, short den-phals) are some of the most common dendrobiums offered for sale. These evergreen orchids 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.
• Dendrobium spatulata are commonly known as antelope orchids because their unusual, twisted petals are spirally twisted like antelope horns. The orchids bloom several times a year and do not require the winter rest period to rebloom. These orchids are identified by their spiral, twisted, and curly-edged floral segments and asymmetrical flowers.
• Callista orchids are a section comprising about 10 of the most desirable D. species. They have bright colors and canes with dense blooms. Species include D. aggregatum, D. farmeri, and D. thyrsiflorum. They need warm conditions in summer but reduced temperatures and drier conditions in winter.
• Latouria orchids are a section of about 50 species with large yellow, white, or green flowers. The blooms have black or purple markings on the inside surface of the petals. Species includeD. atroviolaceum, D. macrophyllum, and D. spectabile.
• Formosae orchids have fine black hair covering the canes. This section comprises about 30 species, including D. bellatulum, D. draconis, and D. sanderae. The plants require cool to moderate conditions year-round: 50- to 60°F nights and days that are no more than 85°F.
  

Pruning

These plants generally send up at least one new upright cane each year. After the flowers fade, clip them 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 is the case with other types of orchids.

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 sharp 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 an orchid potting medium.
4. Press down the potting medium firmly, and wait one week to water it thoroughly.

Tip

Old canes sometimes flower or produce tiny offset plants, calledkeikis, that you can use to grow another orchid.

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.

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 the potting mix has broken down and loses aeration. 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 varies 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°F is often ideal, before returning them to the normal pattern of 60°F to 65°F nights and 75°F to 85°F 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, which will ultimately cause the plant to yellow or wilt.

Petal blight, a fungal disease, sometimes causes 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 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 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°F —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:

Yellow or Spotted Leaves

Yellow leaves are usually caused by too much water or too much direct sunlight. However, the leaves of some deciduous species develop spots and turn yellow just before they are shed for the winter so the yellowing is part of the natural life cycle.

Burned and Brown Leaves

Browned edges on leaves are typically 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.

From: thespruce