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Elisabeth C. Miller Library

Keyword: Orchidaceae (Orchid family)

Deciduous or evergreen Dendrobium?

I just got a Dendrobium, it is Dendrobium eima x impact. The
flowers are pink and white. I was wondering how I can tell if it is a
deciduous one or an evergreen one. I still have months before winter,
but want to make sure I give it the rest it needs when the winter does
get here.

 

There are deciduous and evergreen types of Dendrobium. Unfortunately, I could not find information about the variety you are growing. If yours has soft canes, it is deciduous; hard canes are characteristic of the evergreen type. Here is information from Orchids Made Easy:
“Dendrobiums are separated into two main groups: hard-caned and soft-caned.
Hard-caned Dendrobiums have tall pseudobulbs that are very thin and their leaves are generally a little darker in color than the soft-caned. Hard-caned Dens are evergreen and often keep their leaves for many years before they drop them. Hard-caned Dens grow spikes from the top of the cane and produce gorgeous flower sprays.

“Soft-caned Dendrobiums have leafy pseudobulbs that are long and slim. Their leaves are generally a little lighter in color than the hard-caned Dens. They grow leaves along the length of the cane and the blooms sprout from the individual stems that are along the cane itself. Soft-caned dendrobiums are deciduous and drop their leaves
when the weather gets cold.”

The American Orchid Society has a guide to growing evergreen Dendrobium for beginners.

There is also good general information on caring for orchids in the Brooklyn Botanic Garden guides on the subject. Generally, winter is the time to hold back on watering a bit, but also be careful about the plant’s need for humidity–our heated homes in winter can be exceedingly dry. According to Orchids by Joyce Stewart (Timber Press, 2000), most orchids prefer 65-75% humidity during the day. She recommends “damping down last thing at night” during the winter (using a spray bottle or mister), if you have heat on in your house overnight.

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Sahlab and other edible orchids

When I lived in the Middle East, there was a warm drink we enjoyed called sahlab (spelled with variations in different countries, such as salep in Turkey) that is made from dried powdered orchid roots and milk. It can be sweetened, flavored with rosewater and sprinkled with cinnamon and finely chopped pistachios. The powder made from the roots was ubiquitous in markets in my country, but is hard to find here. I don’t know which kinds of orchids are used traditionally. Do all orchids have tubers that are edible (or drinkable)? Are there Pacific Northwest native orchids that could substitute for the wild orchids used in Middle Eastern sahlab?

 

The use of orchid tubers, whose stored starches are nourishing both to the orchid plant and to humans, goes back many centuries, and over time, sahlab/salep in one form or another migrated across Europe. In the Middle East, people typically use tubers from wild native orchids. In Israel, the family Orchidaceae is referred to as Sahlavim [plural], and the genus Orchis is called Sahlav. In Greece and Turkey, the drink is often made from the tubers of Orchis mascula, Orchis militaris and Anacamptis morio. Other sources include Dactylorhiza and Ophrys species. By the 18th century England, salep or ‘saloop’ was made from Orchis mascula, and was sold by street vendors as a lower cost alternative to tea and coffee. It also went by the name ‘dogstones’ because of the tubers’ resemblance to testicles. In his 1640 book Theatrum Botanicum, John Parkinson lamented that “our pharmacists are wont to adjudge every sort of orchid root an aphrodisiac,” possibly a throwback to the notion that a plant’s appearance indicates its medicinal uses (the Doctrine of Signatures).

An important consideration is the conservation status of some orchids, including species which have been harvested for making sahlab. CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, restricts importing all orchids, because of the difficulty in distinguishing one from another, especially by looking at tubers alone. This may account for the scarcity of sahlab powder.

Many orchids have edible properties–just think of vanilla, made from the pods of Vanilla planifolia. It is hard to say which locally native orchids have tubers best suited to making sahlab, and harvesting wild orchids is problematic from a conservation standpoint. For clues about edible uses of orchids in this country, I
searched the Native American Ethnobotany Database. Numerous tribes (including some in the Pacific Northwest) have used a wide variety of orchid species for edible, medicinal, and spiritual purposes. Those which grow here include: Corallorhiza maculata, Goodyera oblongifolia, Platanthera dilatata, Platanthera stricta, and Spiranthes species. Goodyera, for example, is mentioned in Erna Gunther’s Ethnobotany of Western Washington as a tonic among the Cowlitz.

Rather than try to find or grow and harvest orchids to make your own sahlab, the best thing would be to look for prepared sahlab powder that is made from sustainable sources.
Excerpt: “Salep can be produced sustainably, and the species of orchids that yield the best salep (Orchis mascula, Orchis militaris and Anacamptis morio) can be cultivated. Local propagation and sustainable cultivation alleviate harvesting pressure on wild orchids but subsequent trade poses challenges in the context of national and international legislation, such as CITES.”

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caring for Dendrobium orchids

I have a couple of Dendrobium orchids, and one other that I don’t know the name of. Both the Dendrobium have lost all their leaves, and I’m worried that they will die if they are not repotted soon. There is white fuzzy mold growing in the potting mix (which is just bark) of at least one of them, and I researched a little online and found that it is a common kind of snow white fungus (that may not be the right name) that is common to orchids in general.

I’m worried about root rot, and I’m wondering what I can do to try to revive these two orchids back to blooming. I read that soaking the roots in hydrogen peroxide can often help kill the fungus and then repotting thereafter can possibly revive them. What would you suggest for a repotting mix, and do you have any tips on reviving orchids once that have lost all their leaves?

The roots seem to still be intact, and do not appear to be rotted, as far as I can tell. I’m also wondering about good types of greenhouses/shelters to keep them in, as well as heaters to keep them a little warmer in the house — they seem to be having a harder time with the 60 degree temperatures that my apartment tends to be. Any advice you could give would be great!

 

Some Dendrobium are deciduous, so your plants are likely acting exactly as they should. However, now that they’ve lost their leaves, you should restrict watering them through the winter, watering them only enough to keep them from shriveling, until flower buds form. Then, resume watering again. The species of Dendrobium that are deciduous require night temps of 50-55 degrees F during the winter.

Dendrobium grow well in Osmunda fiber, a potting medium, or bark if they are carefully staked, though they shouldn’t be re-potted or divided until new growth starts. Also, Dendrobium with 4 or 5 shoots will grow well in a 4-5 inch pot, so you don’t necessarily need to increase the pot size when you do re-pot your plants.

If you cut back on the water you give your Dendrobium through the winter, you shouldn’t have to worry about root rot/fungi, especially if you repot them when new growth appears.

The advice above is taken from Home Orchid Growing (by Rebecca T. Northen, 1990, pp. 209-212).

Orchid Growing Basics (by G. Schoser, 1993, pp.40-45) shows some ways you can create a good place for orchids inside your home. For Dendrobium, placing the plants in a window with southern exposure, a grow light that will give them 12 hours of light each day, and humidity (Schoser recommends standing the pots on upsidedown flower pots in a tray of water) seem to be the most important considerations.

The Miller Library has many, many books on orchid growing.

Also, you might want to investigate the Northwest Orchid Society.

encouraging orchids to bloom

All but one of my orchids are blooming this season! What could be the cause of the one orchid not blooming?

 

First of all, congratulations that you have all but one of your orchids
blooming. Orchids are plants with very particular needs, as you well know. I
have found two possibilities as to why your one orchid will not grace you with
its flowers: light and space. However, there are other possibilities as well,
which I will try to address.

Perhaps this one plant is not receiving the amount of sunlight it needs to bloom
and the others are. Are all your orchids the same species or variety? If so, are
they all in the same area of your house; i.e. same window? If they are not the
same species or variety, then they may require different amounts and levels of
intensity of light. Are they growing in a window with natural light or are you
growing them under artificial light? If you are using artificial light, orchids
do require dark as well as light. Orchids “should not receive more than 14 hours
of artificial light a day. More than that will prevent them from blooming.”
(Orchid Growing Basics by Dr. Gustav Schoser, Sterling Publishing Company, 1993)

Are you using a fertilizer? If so, and the first number is a lot higher than the
second or third (such as 15-5-5), it is likely that the plant is receiving too
much nitrogen. This will do wonders for the green leaves but nothing to promote
flowering. A fertilizer with the numbers closer together (such as 10-12-10) will
be more balanced and would be recommended. Are you monitoring the temperature?
“The effects of temperature changes are most clearly observable in the Cymbidium
orchids. Flower production begins when daytime temperatures are about 68 degrees
and nighttime temperatures are around 50-57 degrees. Phalaenopsis schilleriana
and its hybrids will only bloom when the nighttime temperature is under 68
degrees for at least 2-3 weeks.” (Orchid Growing Basics)

Here is an excerpt from a frequently asked question and answer web page from a
commercial grower: beautifulorchids.com.

Q: I am growing my phalaenopsis orchid in the house but they never bloom. What can I do?

A: The most common reason for any orchid not to bloom is insufficient light.
Move your phalaenopsis plants to a window where they will receive strong, but
indirect light (near a south-facing window is ideal). You might also try
lighting your plants with a fluorescent light fixture placed about 1-2 feet
above the foliage. Give up to 12 hours of supplemental light per day.
Phalaenopsis will also develop flower spikes in response to a cool period of
about four weeks with night temperatures of 55F. After the cool treatment, raise
the night temperature back to the normal 60-65F minimum. See if these changes to
your growing conditions help to stimulate your plants to bloom.

Another page on the same site more clearly defines good vs. bad light. They
explain that too little light may prevent the plants from blooming. They also
list specific orchids that prefer low light and those that prefer moderate to
high light.

The Brooklyn Botanic Garden All-Region Guides: The Gardener’s Guide to Growing
Orchids (2004) Handbook #178 has good information regarding light
requirements on a variety of orchids. It is noted in this book that “light is
undoubtedly the most important factor in determining whether or not an orchid
will flower.” The American Orchid Society’s page on “Light, the Key to Successful Blooming” should also be helpful.

Also, there is a possibility that the one orchid has outgrown its pot faster
than its companions and has a need for more space (and possibly more nutrients).
“Most orchids usually only bloom from new growth” (Your First Orchids and How
to Grow Them published by the Oregon Orchid Society, Inc 1988). “An orchid is in
need of repotting when the leading pseudobulb or growth has reached the rim of
the pot and there is no room for future development. (The Gardener’s Guide to
Growing Orchids by Wilma and Brian Rittershausen, David and Charles Publishers
2001) If you are getting new shoots but they are growing over the edge of the
pot and breaking off, this would also be a sign for the need to repot.

The Gardener’s Guide to Growing Orchids by Wilma and Brian Rittershausen, and The
Brooklyn Botanic Garden All-Region Guide and Orchid Growing Basics by Dr. Gustav
Schoser, offer good directions on repotting. The Schoser title even offers
recipes on how to make your own potting mixes.

propagating Phalaenopsis orchids

I have a question about a Phalaenopsis orchid. The orchid is a year old and at the top of last year’s flower stalk has grown a new set of leaves as well as roots. Can this be cut off and re-rooted? Also, after the blooms fade, do you cut the stalk off and if so, how far?

 

Here is some information on propagation of Phalaenopsis, from a commercial orchid grower:

“Phalaenopsis can be vegetatively propagated by cutting the flowering stem above a stem internode, the dormant growth ‘eye’ is covered with a triangular sheath. Cut, with a hot knife or shears, through the flower stem after the last flower has fallen. Then move the plant to a dimmer area. In most cases, new plants will start from the dormant ‘eyes.’ After the new plants initiate, the mother and ‘keikis’ (babies) can be move gradually back to higher light. When the keikis have 2-3 roots, the keikis can be removed, by slicing between the stem and the keiki, or cutting the stem above and below keiki’s attachment point. The new plant can now be potted up and grown on. If more flowers are desired, cut the stem as above, but do not move the plant. In the second method, the mother plant is topped. As a monopodial plant, Phals continue to grow vertically. In time, they discard their lower leaves. The leaves have served as a storage vessel of water and nutrients. The leaves have outlived their usefulness and are discarded. New roots are produced above the leafless stem, as the Phal continues growing vertically. The stem can be cut below the new roots. The top part, with leaves and roots, can be repotted after proper care of the cut. The remaining stub can be left as is, for a few days/weeks. Soon, new little plants will be found growing out of the old stub. These keikis can be repotted in the same manner as the first method. They will grow on and eventually bloom. If left on the stub, they will often bloom sooner, than if individually potted.”

The American Orchid Society has a video illustrating the potting of a keiki, as well as a host of other orchid care information.

You may find the following links to the Brooklyn Botanic Garden useful for general directions on orchid care. Here is an excerpt:
“Some species will also produce plantlets on the flowering spikes, complete with leaves and roots. These small offshoots can be pruned and planted, but keep in mind that transition from plantlet to flowering specimen is a long process requiring several years and lots of patience.” Here is another helpful link from the Brooklyn Botanic Garden website.

As for what to do with a spent flower stalk, here is what the Royal Horticultural Society recommends: “A flower spike can continue to bloom for up to three months. Once faded, cut the spike just above the second node (joint) beneath the spent flowers, and a flowering sideshoot may develop.”

Wild Orchids of the Pacific Northwest & Canadian Rockies

Wild Orchids of the Pacific Northwest cover A field guide “to assist the user in identifying” the wild orchids throughout an expansion of our region that includes Alaska and western Alberta and Montana. Author Paul Martin Brown, of the University of Florida, has a series of similar titles covering all of North America except for the southwest; however he has clearly spent considerable time in our region. Appendices brim with reference materials, many trying to untangle the nomenclature of our orchids, but more romantic is the “Orchid Hunting” section with tips such as “watch for small, shaded cemeteries along the way.” Essays such as “The Correct Name for the Northwestern Twayblade” add to this slightly eccentric but fun book.

Excerpted from the Fall 2007 Arboretum Bulletin.