What are Sheaths?
Encourage Blossoms in Cattleyas
When you have a Cattleya orchid (or any another orchid that produces sheaths), it can be a little worrisome to know when a flower spike is going to appear. In this article, you’ll learn about sheaths, what their purpose is, and what to do if the bud never bursts through the sheaths to produce that beautiful blossom that you’ve anxiously been waiting for.
What is an Orchid Sheath?
" Cattleya warneri" by chipmunk_1 is licensed under CC BY-SA 2.0
A sheath is a protective covering, like a leaf pocket, that forms on the end of a pseudobulb.
It shelters the fragile orchid bud that is forming inside of it. Since the flower buds are so tender, they’re easily damaged.
Ants, mealybugs, thrips, spider mites, and other pests love to chew on the flower buds, since they are extremely rich in nutrients, water, and minerals. Buds tend to be the most tender part of the orchid, too.
Insects aren’t the only damaging agent that can destroy the flower bud.
Low humidity, high sun exposure, low temperatures—all these can cause bud blast if the bud is endangered, and not properly protected from harm. The sheath totally envelops the bud, until the orchid bud is strong enough to grow on its own.
To better shield the flower spike, since the blossom is the only way to guarantee reproduction, the orchid develops a paper covering over the bud.
Which Orchids Produce Sheaths?
Cattleyas aren’t the only orchids that produce sheaths. Laelias and Paphiopedilums also form orchid sheaths. You will find this similar behavior in orchids that have pseudobulbs.
Most all sympodial orchids (which produce pseudobulbs) will have sheaths to guard either a new leaf or a flower bud. On Cattleyas, the sheaths are paper thin, and usually brown, but sheaths on other orchids can be thick, leathery and quite large.
How Long Does it Take for the Bud to Appear After a Sheath is Formed?
This is a hard question to answer, since there are so many types of orchids. For example, the Cattleya Labiata will produce a sheath, and within one month the bud will had burst the sheath and be blossoming. Yet the Cattleya Mossiae will take up to 5 months of impatient expectation to see a flower after the sheath has formed.
Patience is always the answer when it comes to sheaths.
What’s a healthy sheath color?
We tend to think that brown is related to a dead plant, but healthy sheaths can be all kinds of colors: green, yellow and brown. So when you see the brown sheath, don’t think the bud has died and snip it off. It could be that is the normal color of the sheath. You can lose many buds this way, when even though they are taking a long time to produce, they still are healthy.
Photo by Kelly Kiernan on Unsplash
Bud Blasting or Blind Sheaths
The bud can die within the sheath, which is called a blind sheath.
A blind sheath is when a sheath doesn’t produce a bud, or the bud dies while inside the sheath. This is very common to happen when the orchid hasn’t yet produced it’s first blossom.
The orchid is geared up to form a flower spike, but for some reason, the flower doesn’t ever leave the sheath and dies. This is so normal, it’s almost expected.
The second year the orchid blossoms, it should penetrate the sheath and produce that gorgeous flower that we all love and admire.
How is a blind bud different from bud blasting? Bud blasting is a little different—it’s when the bud has already left the sheath and dies after it looks like it will produce a flower, but doesn’t. There is an entire article about Bud Blasting,
if you want to look more into buds dying before flowering.
Why do Blind Sheaths Occur on Cattleyas?
One common theory for the blind sheaths is that newly acquired plants just don’t have the energy stored up in the pseudobulb to produce a flower spike. If the orchid senses that it won’t be able to accomplish its goal, it will abort the mission.
As for enough energy, I wish I could say to upgrade the fertilizer. But if you haven’t been fertilizing all year long and start now, chances are slim. High nitrogen fertilizers will suppress blossom formation in the long run. It’s great for leaves, but it focuses so much on leaves that the roots and flowers take a hit.
Fertilization Tip: For more about fertilizer and how to fertilize, there are two options: (1) this article will explain the 5 different methods that can be used and has recommended products for each one, (2) I’m currently working on a mini-guide that talks all about fertilization and should have it available to download for free in a few weeks. So please check back if it’s not available when you’re reading this. If you want to, leave a comment in the box below and I’ll email it to you when it’s ready.
Back to the reasons why buds die inside the sheaths: it could also be problems during transport. Sometimes you can buy a healthy orchid, but transport is often cruel. Outside temperatures are extremely harsh. The short time in freezing weather is enough for the cold to pass through the sheath and destroy the bud. Cattleyas are a little better at handling temperatures, but they aren’t indestructible, so take extra precautions.
Not enough humidity is another possible cause. This does go hand in hand with proper watering, even though they are separate topics. If you underwater, the pseudobulb will wither and dry up, and the energy it has won’t be placed into flowering, but into surviving.
But humidity is another dragon of its own: the leaves need humidity during the day so they won’t lose water when they perform gas exchange. If the humidity is too low, the buds won’t from, since they require tremendous amounts of water. (That’s also why insects like to chew on buds inside the sheaths.)
Insufficient light is the next reason that an orchid bud will die within its sheath. Even though the orchid believed it could produce a flower spike, it just doesn’t have the energy to do so, because the lighting is not bright enough to have sufficient photosynthesis. Make sure your species of Cattleya, Laelia, or Paphiopedilum is getting enough light.
Thrips and other pests can often be a cause. If you have analyzed the roots, the leaves, and everything seems to be fine, then look for pests and insects. Once infested, they can be dealt with. It just takes careful observation, the application of either soapy water, a soft toothbrush, neem oil, diamentaceous earth or whatever your most recommended for your specific pest.
And the last possible reason is that the bud is just too weak to break through the sheath.
Again, this goes back to proper fertilization, lighting, lack of humidity…or maybe a combination of all of them.
What Can Be Done to Prevent Bud Blast Inside of Sheaths?
Make sure you read up on how to care for your orchid. I have a complete guide for Cattleya care here,
but if you’d like, but there are so many specific species, that it’s best to find the complete orchid’s name, or ID, and do a search on the net.
"[Central America] Guarianthe × laelioides 'Brechts' CCM/AOS (Lem.) Van den Berg, Phytotaxa 239: 67 (2015)" by sunoochi is licensed under CC BY 2.0
for most Cattleyas, temperatures need to range about
50ᵒ F to 60ᵒ F
during the night
70ᵒ F to 80ᵒ F
during the day
(10ᵒ C to 15ᵒ C
during the night and
21ᵒC to 26ᵒC
during the day).
your Cattleya needs to be a bit on the wet side, more than a Phalaenopsis, but still needs to dry out between waterings. Air circulation
is fundamental. Keep on a fan at all times, to guarantee that the roots air dry and keep the humidity circulating. Lighting:
this is probably the main problem in blind sheaths and why they don’t ever evolve. Improper lighting. It’s so common to see many guides saying to keep indoor lights on for some many hours a day, but forget that our world rotates. We have seasons. Each season has a longer or shorter light period. The closer you are to the equator, the less this is visible.
I can really vouch for this, since I have lived so many years in Brazil and when I recently moved to Kansas suffered during the low light during winter. Wow—never thought sun was so vital to my exitance until winter came. I take my hat off to you guy more north than I am. How do you manage?
during the winter, cut lighting down to 10-12 hours a day. Gradually raise this threshold an hour or two in during until you keep the indoor lights on for 16 hours a day during summer. Cattleyas require bright light, but around 70 to 80% shade.
Cattleyas also require a dry and cool winter rest. This is their dormancy period. Again, research your specific orchid species to find out if she blooms twice a year or just once. Each orchid has a different period of bloom and to shove them all into spring and summer is bad advice. Humidity
of around 50%. Yes, you will need a humidifier. The average indoor home ranges around 33% in relative humidity (rH) and much less during winter. If you don’t have one, this article has 5 suggestions for humidifiers all under 120 dollars.
You can’t get this through a humidity tray (sitting on pebbles), since they work to raise the rH about 2%.
Again, this is a very slim summary of the detailed article about Cattleyas. Do your research, because proper care can prevent the buds from dying within the sheaths, if your orchid is mature.
When Should I Cut Open a Sheath?
Sometimes you’ll be patiently waiting (more like impatiently waiting) for the sheath to break through the sheath, but it never does. The sheath then withers from vivid green to yellow, and finally shrivels into a papery brown.
There are several articles that recommend slicing the upper part of the sheath open, to help the bud leave and continue its growth. If this doesn’t happen, it ends up rotting inside the sheath and dies. I’ve personally never done this, but there’s a first time to everything.
You can squeeze the sheath with your fingers to find out if the sheath has a bud in it. Be extremely careful to only cut open the sheath and not slice through the bud. Sometimes even dry paper sheaths will contain healthy buds, but they just need a little extra care. Slicing the top of the sheath open, by making a tiny slit in the top is ideal.
Ideal, except for one thing: now you have to be extra careful when watering. With this new opening, water will seep into the sheath and form a pool. Perfect for root, bacteria, and mold.
When Can I Tear Off the Orchid Sheath? Or Even Should I?
When you repot your Cattleya, or any other orchid that produces sheaths, you can tear away the old papery sheaths. They do nothing for your orchid besides house pests, insects and water, which leads to a whole new problem. Never pull off sheaths that offer resistance: you should be able to effortlessly pull back the dead, dry sheath.
Some orchids have thicker sheaths. If they have produced a blossom, they won’t blossom again. You are free to cut away the sheath with a razor blade. Don’t zig-zag the cut, but make a smooth, surgical slice. It should be dead, so this might be hard.
In any case, don’t cut the pseudobulb, or cut into live orchid tissue. If you happen to do that, stop immediately, and apply cinnamon.
If you have any other questions, please write them in the comment box below. If you want to read more about sheaths, this article from the New York Botanical Gardens
talks a little about sheaths.