How to Repot an Orchid

Yes, you can do this. It's not rocket science. Repotting is fun. And your orchid will thank you, especially if it's been two or more years since it was repotted. Never repotted an orchid before? We can fix that. Come on into our greenhouse and I'll show you how.

1. Gather your materials.  A good basic orchid mix consists of equal parts fir bark, charcoal and sponge rock (aka coarse perlite). You can buy these products online from OFE International and Tropical Plant Products. They also sell high quality ready-to-use packaged orchid mixes. Grower's Tip: The organic component -in this case the bark- can make or break the quality of an orchid mix, because that's the part that breaks down with repeated watering. The bark should be Douglas Fir or Pinus radiata, and should be mold-free. Pinus radiata (sold as Orchiata) and kiln-dried Douglas Fir bark (sold as Rexius bark) last longer than regular Douglas Fir bark. Fir bark often needs to be rinsed beforehand in order to remove dust and sediment.

2. Select a plant. The best time to repot an orchid like Cattleya is when the new shoot is about the length of your pinkie finger. The new shoot indicates that the plant has started a new cycle of growth, the perfect time to provide new roots with fresh medium. We repot every two years, because that's the lifetime of fir bark mixes in our greenhouse. Any longer is asking for trouble -a waterlogged mix that kills roots. Grower's Tip: Keep your eye on that new shoot while repotting! It is as fragile as new asparagus and if you break it, you lose an entire season's growth, including the flowers.

3. Invert the plant, tap the rim of the pot against the table and remove the plant. Keep the new shoot well away from the table when you do this. Grower's Tip: Water your plant the day before to make it easier to dislodge.

4. Remove the old mix. Hold the plant by the pseudobulbs (not the roots!) with one hand and gently prod the mix with your other hand in order to loosen it. Grower's Tip: Expect to find new yellow-tipped roots emerging near the base of the new shoot. Be careful not to break them.

5. Remove the dead roots. Healthy roots are white and firm. Dead roots are grey/black and squishy. You can use pruners for cutting, but remember that viruses in plant sap can be spread by using the same tool on consecutive plants. Grower's Tip: That's why we use one razor blade per plant. We wrap used blades in duct tape before discarding them. When I divide a large plant, I use a kitchen knife and sterilize it with a propane torch between plants. Grower's Tip #2: Notice the new shoot face up on the table? Don't rest the plant on its new shoot. Grower's Tip #3: Orchid roots can absorb tannins from the bark in the mix and appear brown on the surface. A brown root can be healthy. When in doubt, cut a cross section--a healthy root will have a white core.

6. Wash the roots. I like to do this under a gentle stream of water at the sink. It gently removes the old bark hiding in inaccessible places. And it often reveals more dead roots that need to be cut away. If the roots are healthy you don't need to remove all the mix --only about three quarters. If the roots are in poor shape, remove as much old mix as possible. Grower's Tip: This is a great time to observe how your plant is constructed. Notice how the vertical shoots (the pseudobulbs) are connected by a horizontal stem (or rhizome, pronounced rye-zome). This will become important in a few minutes.

7. Choose a pot size based on the size of the root mass, not the top growth. One inch bigger all around is plenty. Orchids like to attach their roots to their surroundings. Let them. Grower's Tip: A step up in pot size isn't always necessary. Sometimes fresh mix and a clean pot of the same size is all that's needed.

8. Center the new shoot in the pot. See how I'm holding the older part of the plant against the rim of the pot? That's because I want the new shoot in the center where it will have plenty of room to grow over the next two years. Looks asymmetric, right? Absolutely. The new shoot goes in the center. Hold the base of the new shoot about a half inch below the top rim. That's your imaginary fill line.

9. While holding the plant in place with your left hand, add mix with your right hand, small amounts at a time.

How to Repot Stanhopea

September and October are Stanhopea repotting season for us. Every grower has their own repotting technique, but I thought you might want to take a look behind the scenes at ours.

Orchids that are flourishing don't generally appreciate the root disturbance that repotting can inflict. Stanhopeas are no exception. We repot when: 1) The plant has overgrown the pot; 2) The medium needs to be replaced, either because it has deteriorated -after about two years- or because it is inappropriate for our growing conditions; or  3) The plant is in trouble. Signs of trouble include desiccated leaves and shriveled or rotting pseudobulbs.

The stanhopeas above, which we received last week from Andy's Orchids, fall into the second category. Andy grows his stanhopeas in a medium that works well for him, but turns to mush in our greenhouses during our hot & humid summers.

We repot our orchids when the new roots and shoots appear. For most stanhopeas, that's in late summer and early fall. In the photo above, you can see the new shoot on the Stanhopea graveolens in the foreground. Now is the time!

Because our plants are far from the main potting bench in the headhouse, I set up a temporary potting bench in our back-up greenhouse. It's just a pair of plastic sawhorses supporting a 5' rectangle of plywood. Potting materials include net baskets, razor blades and one of our favorite orchid media, a mixture of long-fibered premium moss and coarse tree fern fiber. The plants were watered the previous day in order to soften the potting medium.

1. To remove the plant, invert the pot and tap the rim against the edge of the potting bench.

2. Gently remove the old medium around the exterior of the root mass, small bits at a time so as to not break the new roots.

To remove the old medium from the center of the root mass, hold the plant by the pseudobulbs (not by the roots!), and wash the roots gently under running water. Remove about three quarters of the medium. It's not necessary to remove every bit unless you see rotting tissue. Rotting roots and pseudobulbs are easy to see after washing and can be removed with a razor blade.

3. Choose a pot size based on the size of the root mass. For a plant this size, we want a pot about an inch wider than the root mass on all sides. And, for a Stanhopea, choose a basket with openings that allow the downward-growing spikes to emerge from the root mass.

Behind the Scenes: Repotting

Orchid repotting starts early here--in February. The catasetums and their relatives (Mormodes, Cycnoches, Clowesia) are always first off the mark, producing new growth before any other group of tropical orchids. For these guys, there is a window of opportunity for repotting, an optimal time between the appearance of the new shoot and the maturing of the new pseudobulb, that lasts only about a month. After that it's too late. If we miss that window, we have to wait another year.

Because the Catasetinae repotting season coincides with Orchid Daze, sometimes it's a race to finish repotting them before the window slams shut. As you can see in the photo above, I'm running late on repotting: the basal part of the new new shoot on our Mormodes has already begun to thicken and the new roots are at a dangerously fragile stage in their development. They break so easily!

We have been growing our catasetums, cycnoches and mormodes in a bark based mix (which they prefer here) in net pots with large openings. To keep the bark from emptying out the bottom, we have been lining the net baskets with moss--with unhappy results. The moisture in the sphagnum produces a spectacular growth of mold on the bark. Eww. Time for a new approach!

First, I wash the root mass to gently remove some old potting medium and to expose the roots. It then becomes easy to see that many of the roots attached to the older pseudobulbs have died. This is typical. Catasetums have a strongly annual growth cycle and put a tremendous amount of energy every year into new root and shoot production. Many of the older roots shut down at the onset of dormancy. I cut those away with a clean razor blade.

This year I'm using using net pots with smaller holes. No moss is needed as a liner. That should eliminate the mold problem. The new net pots are manufactured for hydroponic growing.

Next, I center the new shoot in the pot, with the older growths against the side. I hold the plant in my left hand as I fill the pot with mix using my right hand. The potting medium is equal parts fir bark, charcoal and sponge rock. We make the mix ourselves from the individual components.I like to rinse the bark under running water beforehand to remove the dust and sediment sized particles.

The label and data card goes on last. Labels are always attached to the pot with telephone wire --plastic coated 22 gauge copper wire. We can't risk losing the data.

An afternoon's repotting. There will be more next week!

February Orchid Care vol. 2

orchid care calendar

February

There will come a day in late spring when it feels like nearly every plant in our collection needs repotting right now and I start to feel like a cook in a busy restaurant on a Saturday night, plating at full tilt, my hair in flames. But we're not there yet. It's early. A few orchids --the ones that flowered in late autumn and early winter-- are starting to stretch out some tentative root tips. They're just asking to be repotted.

1. Repot Angraecum sesquipedale.
If you stopped by in December you may remember Angraecum sesquipedale, Darwin's Orchid aka the Star of Bethlehem Orchid. We have a dozen young plants that we purchased a year ago from Kalapana Tropicals. In a year or so we will install them in the Madagascar bed in the Orchid Display House. Right now we are repotting them. Pull up a chair if you would like to watch.

Our plants arrived in pots made of biodegradable rice hulls. I like these pots--they are nicely proportioned, have terrific drainage and show no sign of breaking down after numerous waterings. Unfortunately at present they are only available directly from the manufacturer and with a dauntingly large minimum order (in the thousands). Hilary, our Assistant Horticulturist, breaks the pot (above) in order to extract the plant without damaging the roots.

Next, she removes the old mix --a bark+charcoal+ perlite mixture-- from around the roots. Angraecums love this classic orchid mix. But we are going to change the mix because we are changing pots.

Bath time for our orchid. Washing the roots accomplishes two things: it removes the sludgey remains of the old mix; and it allow us to see the roots better.
Next, Hilary directs a sharp stream of water at the lower surface of the leaves to remove a few scale insects.

I'm happy to see a healthy root system with firm white roots and green root tips.  Brown mushy roots are removed with a razor blade.

Losing orchids in solid plastic pots to root rot during Atlanta's long sweltering summers has taught us the value of net pots and open baskets for greenhouse use (but definitely not for windowsill use). In these pots a mixture incorporating long fibered premium sphagnum works well because it doesn't sift through the drainage holes. We add a little coarse tree fern fiber to give Angraecum sesquipedale the extra aeration it needs. This sphagnum+tree fern mixture is just one of three main orchid mixes that we use.

Hilary holds the plant with one hand and uses the other to wrap the root ball loosely with the moss mixture. Working with this mixture can feel a little strange at first when you are not accustomed to it-- like creating a bird's nest. But it's really very easy. Hilary is being very careful to hold the plant gently so as to not break the root tips.

When she has created a mass about an inch smaller in diameter than the pot, she lowers it into the net basket. Notice that she hasn't tried to force all of the aerial roots into the basket.

Hilary then adds small amounts of mixture between the roots and pot until the plant stands upright. It's important to not pack the roots too tightly. Small air pockets are okay.

The moss mixture will last about two years if it is not over-fertilized or over-watered. Nice job, Hilary.

When to Repot Your Orchid (Part 2)

Now that you know how often to repot your orchid you may also wonder when.
Q: When is the best time to repot my orchid?

A:  At the start of a flush of new root growth.

Why?
Because an orchid establishes very quickly in a potting medium during the part of its annual growth cycle when its roots are actively growing. In nature that span usually coincides with the onset of the rainy season.

Many people are surprised to learn that tropical orchids have an yearly cycle of growth, flowering and rest--a cycle similar in some ways to the yearly growth cycle of temperate zone perennials, but more subtle. Orchid roots do not grow continuously throughout the year.

How do you know when a potted orchid is producing a flush of new roots? They are not always visible.
It's pretty easy, actually, to tell indirectly. Look for a new vegetative (leaf-producing) shoot on your plant. Most orchids produce new roots right around the time the new vegetative shoot appears. Think of the new shoot as a green flag signaling that it's time to repot. I have trained my eye to spot new shoots as I scan our orchid collection. When the new shoots are the size of my little finger, it's time to repot.

A new shoot on Laelia purpurata indicates that it's time to repot.

Is it bad to repot during those months when the orchid's root system is not growing?
It can be. If you damage the root system--and it's hard not to inflict a little bit of breakage during repotting--you can impair the orchid's ability to take up water. It could be months before new roots replace the broken ones. In the meantime your plant may start to decline.

Two new shoots on a Dendrobium Red Emperor 'Prince' that is ready for repotting.

A green flag: the new shoot of an Oncidium intergeneric at the start of its growing cycle. 

Be careful not to confuse a young flower spike and a new leafy shoot! Some orchids produce a flower spike that emerges near the base of a mature shoot--in the same neighborhood as the new vegetative growth. A young spike and a young leafy shoot can look very similar early in their development. If you're not sure it's best to wait. Within a couple of weeks it should become obvious.

What about orchids like Phalaenopsis (above) that don't produce a new shoot? When do I repot my Phalaenopsis?
The best time to repot Phalaenopsis (and other monopodial orchids) is within a month or two after flowering.

Coming soon: a review of commercial potting mixes for orchids.

When to Repot Your Orchid (Part 1)

Q: When should I repot my orchid? Does it matter when?
 Absolutely!

However, there are two ways of interpreting when:
Frequency How often does an orchid need to be repotted? and
Timing During which stage of the orchid's annual growth cycle should repotting be done?

The next two posts will address these questions separately. Today's post tackles the first: How often should I repot my orchid?

You don't need to repot your orchid every year. At the Fuqua Orchid Center we strive to repot our orchids every two years as a general rule. But that is just a general rule. Sometimes one or three years is more appropriate. When I am evaluating our plants with regard to repotting there are always three questions I ask:

1. Is the orchid about to overgrow its pot?
The Oncidium intergeneric (above) has two new shoots (pointing leftward). They look fine now, right? But imagine how they will look next year at this time in the same pot when those two shoots have matured into fat round pseudobulbs. Pretty crowded. Now is the time to repot!

2. Has the orchid's health declined (shriveled pseudobulbs, wrinkled or yellowing leaves) or has it overgrown the side of the pot?
The Laelia (above) should have been repotted two years ago. Yikes. If we wait another year it will be in a serious state of decline. As it is, this plant is so overgrown that it needs not just repotting, but dividing as well--major surgery which could have been prevented had we repotted it in a timely fashion. This plant needs emergency intervention!

Cattleya Mix. Brand new (left) and after two years (right).

Premium Sphagnum Mix. Brand new (left) and after two years (right).

3. Has the potting mix broken down?
Question 3 is especially important. The quickest way to kill your orchid is to let the soil mix break down. Here's what you need to know:

• Most orchids available commercially are tropical in origin, and the majority of tropical orchids are, in varying degrees, epiphytic--they live in trees. Their roots are often exposed to brief drenching rainfall, wind and drought on a daily basis. They are not covered in wet soil.
• In cultivation orchid roots need a potting mix that allows some air circulation. That's why the best orchid mixes are chunky and coarse in texture.
• A high quality orchid mix--either the classic bark/charcoal/perlite type or the newer premium sphagnum variety--lasts about two years, depending how much warmth and moisture it is subjected to.
• Over time bark and sphagnum break down, and if watered at the same rate they become increasingly waterlogged. Ask yourself: Does the mix take a lot longer to dry out than it used to? Is the moss now dark brown or covered with green moss? Is the bark soft and crumbly and dark brown? Time to replace it!
• A constantly saturated potting mix will kill your orchid.

The bottom line: repot your orchid about every two years.

A 'yes' answer to any of the 3 questions above means that your plant is a good candidate for repotting. But maybe not immediately! In order to time your repotting correctly, see my next post.