Deflasking Orchid Seedlings

From the National Capital Orchid Society Bulletin
Volume XLIX Number 3
September 1995

Editor's Column

Cheaper! Better selection! More fun! Suspense! These are reasons orchid growers raise seedlings from flask. This issue of the Bulletin focuses on techniques used for deflasking orchids--removing seedling orchids from their bottles. This is a cost-effective and enjoyable way to increase your collection. Unlike the process of putting the seed into bottles, taking the seedlings out of bottles requires no special equipment and only a modicum of expertise.

Orchids in flask may be shipped across international borders with little or no paperwork, so being willing to deflask seedlings greatly increases your possible sources of orchids. If you have produced your own orchid seed, you can find a lab to flask the seed for you, returning the flasks when the seedlings are ready to be removed Seedlings in flask are a relatively inexpensive way to obtain some plants that are otherwise very expensive. The quality of seedlings may vary--you could produce an award-winner! This information in this Bulletin comes from a variety of sources. All of these growers have different specialties and requirements, but even two growers deflasking the same seedings may use completely different techniques. Many of the folks who contributed have very strong opinions--and some of them are mutually exclusive! Choose one of these methods, and give it a try.

-Lisa Thoerle


Fred Paget, California

Fred has grown orchids since 1965, in several different parts of the country including New England, where our periods of membership in the Massachusetts Orchid Society overlapped briefly. Fred was president of the San Francisco Orchid Society and the Marin Orchid Society. His specialty is color varieties of species and the Catasetinae. He lives in Mill Valley, among 900 square feet of greenhouses.

The methods I have seen used and use myself are quite straight forward. The seedlings are removed from the flask. Some people break the flask to extract them but I use fairly wide mouth jars--Mason jars-and pull out the clot of plants and agar with a wire hook. Then I wash off the agar in a coarse sieve--about 4 meshes to the inch--with plain water. The plants are then pulled apart and sorted with the largest plants in one pile: and the medium in another. Many discard the runts as they probably won't grow anyway, but I have heard it said that some of the best variations start as runts and I usually save them.

Seedling medium is usually fine bark hereabouts but I like to add a little rockwool and some charcoal and perlite. In Hawaii they use something like "mud" (peat based mixes). I use compots made from plastic bedding plant trays about 4 x 6 x 3 inches deep. This is usually big enough for me but the commercial growers here in California use a larger flat that is about 2 feet square. I have watched the seedling people at Rod McLellan's, where they have four workers going steadily all the work day. They get very good at tucking neat rows of seedlings into flats of dry mix. I have never enjoyed doing it that way and ran across a method that I call the quicksand method, I use a basin of water with about 3 inches of water. The flat is filled with mix and put down into the basin. The water soaks up from below and sort of floats the medium. It is like quicksand You can grasp a seedling with tweezers and lower it into the medium and it goes right in. This makes it easy to make neat rows of seedlings and long roots can be spread out After the seedlings are in and labelled, the water is drained by lifting the flat carefully out of the water and then it is watered with your favourite fungicide for stem rot and damping off. The new compots are placed in a warm spot with moderate light. I use a heated mat set at 85 degrees F. under them and make sure they never dry out entirely. There is a Mee fog nozzle aimed at them in my growing area I have seen some enclosed clear plastic boxes used in a couple of nurseries. They are good if you have low humidity in you growing area. The young seedlings get another shot of fungicide after 2 weeks and those growing in mud generally continue to apply a fungicide every two weeks. After they start growing well in a few months they can come out of the seedling area to make room for more seedlings. You now have compots and what you do with them is another story.


Gerardus Stadl, California

Gerardus is a noted grower and hybridizer of cool- growing orchids, and is currently president of the Pleurothallid Alliance. He is a retired biochemist who now devotes his time to his business Peninsula Hybrids, in Palo Alto. I use his method, with some variations, as do a number of other growers I know. I have employed it for everything from pleurothallids to Laelias, Dendrobiums and Catasetums. I use vented vegetable storage bags and allow the seedlings to drain completely before inserting them in the bag, and I allow the foliage to dry before sealing the bag. The following description is adapted, with permission from The Pleurothallid Alliance newsletter.

Deflasking of any orchid seedlings is a handicraft that can only be learned through experience with older plants of the same type in order to get conditions right. One must learn to deal with the heartbreaking experience of seeing young seedlings shrivel up, get grazed over by snails and slugs, or mysteriously disappear through very fast-acting watermolds (Pythium and Phytophtora species). The conditions required to prevent shrivelling after transfer from flasks, namely high humidity, appear to be at odds with the prevention of molds, which would require low humidity. Seedling plants can shrivel to a crisp in less than a day when humidity is low. Part of the reason for this is probably that roots formed in agar appear not to function properly in a very different growing medium such as Sphagnum moss. The combination of all these factors has led to the formulation of a deflasking system for pleurothallids that is nearly foolproof, in my hands as well as those of others who have followed it exactly.

Step 1: Seedlings are taken out of the flasks and washed in a Natriphene solution (one tablespoon per gallon of water) until most of the agar is washed off, Excess liquid could be drained. but adhering liquid should be left on. (Natriphene is a broad spectrum fungi-bactericide with little phytotoxicity). Please note that Natriphene in water is not compatible with most other chemicals, including detergents, spreader- stickers, and Physan.

Step 2: Long-strand sphagnum moss is soaked in a Physan solution (one tablespoon per gallon of water). Excess liquid can be squeezed out, making the moss easier to handle. Physan is not only another general fungi-bactericide, but also a very good wetting agent which helps condition the moss. Although New Zealand sphagnum moss is tops, we use the less expensive Wisconsin sphagnum with good results. However, beware of other types of green tree or sheet mosses, as they are generally unsuitable. The Physan treatment also helps to diminish the threat of the pathogen Sporotrichum schenkii which may occur in the moss. For the same reason, it is wise not to inhale dust from untreated dry moss.

Step 3: Each seedling is carefully wrapped in a few strands of moss, so that nine seedlings fit in a 2 1/4 inch square plastic Anderson pots (two-thirds of the pot is already filled with sphagnum moss, preferably with a drainage additive such as shredded tree fern fibre prior to accommodating the wrapped seedlings on top). The filled community pots are then dipped again in Physan solution to saturation and placed, with some of the solution still dripping out, in gallon- sized Ziploc plastic freezer bags. The significance of this size of pot is that a row of four fits snugly in a one gallon bag, The bags are then hung over a wire in the greenhouse, out of direct sunlight, and can be left alone for two months. During this period new root growth takes place without danger from fungi, snails, slugs or insects.

Step 4: Compots with seedlings taken out of the bag after two months have moss-adapted new roots and turn out to do fine in the usual greenhouse climate. There is little benefit in leaving the seedlings in the bags long than two months, because they are starving for nutrients at this point. The compots are good for another year of growth before transplanting into individual pots. The individually wrapped seedlings are easy to separate for transplantation, Particularly when working with hybrid seedlings, it helps in keeping individual seedling clones separated.

Of course, if you are already blessed with 100% humidity in your greenhouse, you-may find this method somewhat superfluous. In that case, however, think of your peace of mind when you don't have to worry about any predators or diseases far at least two months. However, using the bag method without the fungicides is courting disaster. Physan is readily available, but Natriphene presents a problem, because the manufacturer has suspended sales pending renewal of EPA permits. Other fungicides specifically suitable for watermolds may also work (this list does include leaf spot fungicides such as Benomyl (Benlate), which may be entirely ignored by this kind of fungi, so read the label carefully) but we cannot make a recommendation at this point. Be particularly apprehensive about products in emulsified form, because the organic solvents used in these are most likely detrimental in a closed system from which they cannot quickly evaporate.

In my experience, most seedlings of other alliances, such as Odontoglossums and Cattleyas, don't seem to benefit as much from the bag treatment as Pleurothallids do. However, the two months of bagged security may still be a benefit. In our experience, many small and intermediate size Masdevallia seedlings, particularly hybrids, can bloom after about one year out of flask with optimal care, a fact that certainly serves to make our orchid friends green with envy.


John Law Arizona

John has been growing orchids since the early 1970s, when we both lived in Chicago. He is Professor of Biochemistry at the University of Arizona. Tucson, and lives in Tucson. He has two greenhouses and specializes in growing species, and has a singularly amazing specimen plant of Cymbidium canaliculatum 'Sparkesii'.

Getting plants out of a flask can be a challenge. I find a carving knife or a metal spatula sometimes does the trick. I wash the plants in warm water, which helps remove the agar. I dip them in a fungicide solution. I prefer Natriphene or Captan. Then I lay them out on damp newspaper.

I usually pot in a seedling mix consisting of 4 parts fine seedling bark, 1 part fine charcoal, and 1.5 parts milled sphagnum. I fill the pots or flats with this mixture. Then I plunge the pots or flats into a tray filled with fungicide solution. It should be deep enough so that the potting mix becomes a loose Slurry in the pots or flats. This makes it very easy to put the seedling roots into the medium. A pencil or bamboo skewer or chopstick aids in the placement process, When the seedling have been planted, lift the pots or flats out of the solution and the mixture will sink to the just the right depth.

I brought some plastic trays that have matching clear plastic covers, from Mellinger's. I put newly planted flats or pots into the trays (I have drilled holes in tray for drainage) and cover with the plastic cover. I keep the seedlings under fluorescent lights for the first 3 weeks. Cheapest tubes are fine. After the first week, I replace the original cover with one that has 6-half inch holes cut into the sides to provide ventilation. At the end of the second week, I replace with a cover which has half the top cut away. At the end of the third week, the seedlings are ready to be uncovered. I water carefully while the seedlings are in this seedling potting mixture. I dig down into the mix, and when it is dry half way down, I water. Between waterings, I mist the seedlings at least once a day, occasionally with weak fertilizer solution. When I see good new root growth, I move plants to a regular potting medium or mount them.


Steve Saunders, Nova Scotia, Canada

Steve is an Internet correspondent who is past president of the Canadian Orchid Congress, an association of orchid societies across Canada, as well as being past president of the Orchid Society of Nova Scotia. Steve successfully grows Pleurothallids, Odontoglossums, Cymbidiums, Paphiopedilums and others under a variety of conditions, including under lights, on windowsills, in a hobby greenhouse and outdoors.

When I deflask seedlings Phalaenopsis, Cattleyas, Paphiopedilums, Oncidiums, Odontoglossums, Masdevallias and others), I leave the seedlings soaking in water as I plant I don't add any fungicide, it doesn't seem to help. As I deflask, I am most careful with the roots. The secret of orchid growing is to grow roots well. The leaves and flowers are easy after that!

I use a perlite-rockwool based medium for everything. I favour perlite in the mixture, using two or three parts of that to one of rockwool. This medium is fine and retains moisture--and seedlings' roots need the moisture. They have just come from a moist medium, so be sure to keep their new medium moist!

I prefer to pot the seedlings individually, especially Paphiopedilums, in small pots rather than compots. Because I use an inorganic potting medium, I don't have to repot the seedlings for some time, so this works well. With some drainage chips on the bottom, I place some medium in the pot put the seedling in and then carefully cover the roots.

I stand the potted seedlings together on a standard 11 x 22 inch nursery tray with a clear plastic dome top. This dome is essential since the seedlings are used to high humidity. Usually they get some bottom heat, from heating cables or from fluorescent lights in a lower tier. I am very careful not to overwater the first few weeks, because rot can be a problem. A fine mister every three or four days works well. Misting the inside of the dome is helpful, also, to keep the humidity high. I water with dilute Dynagrow fertilizer every two or three weeks. I'm always careful to water first and then apply fertilizer, especially with seedlings.

The trick seems to be to keep the air humid and the potting medium damp but still "airy". If you do this correctly, you'll avoid rot and desiccation, and the seedlings will grow!


Bob Hamilton, California

Bob is Internet correspondent who lives in Berkeley. He specializes in growing Odontoglossums and related hybrids an intergenerics. He is experimenting with the use of colchicine to increase ploidy, thereby assuring chromosome pairing during meiosis, to extend the useful breeding life of crosses from disparate parents.

I grow plants in a greenhouse, so before taking plants from a flask I place flasks in the greenhouse in a shady location for 2-4 weeks. This is to help the plants acclimate to more light and greenhouse conditions before being removed from the flask. I then follow the steps listed below:

1) If the seedlings are in a necked bottle and have substantial roots, I wrap the flask in newspaper and break it with a hammer. The flat bottom is weakest, and therefore the easiest place to break the flask.

2) Plants with modest root systems can be "floated" out of a bottle by filling the flask with tepid water and using a wire hook to pull the clumps of seedlings out the top.

3) Rinse off all growing medium. Much of the medium can be "flicked" off by gently holding the plants and shaking.

4) If the roots are badly entwined, do not attempt to separate the tiny plants. Just place the roots as best possible in your seedling medium of choice. I recommend New Zealand sphagnum moss or fine bark with perlite.

5) If plants can be separated, sort them by size, removing any proliferants. Do not bother with the runts. Place seedlings on newspaper,

6) I use 4 x 6 inch shallow bulb pans (McConkey) for compots. I have found I can tilt these at 45 degrees and place a layer of damp medium down. I then add another layer of medium. The compot can be built up quickly this way. I place the largest ones in first progressing to the smallest.

7) Once filled, I turn the compot end-to-end and give it a few sharp taps to settle the medium. I place more as needed.

8) I have a "deck gun" on my kitchen faucet and use the attachment to hydraulically drive the medium against the plants.

9) MOST IMPORTANT! I place the completed compots under a 25 watt light bulb (about 18" away) and let the plants dry out overnight before placing the compots in the greenhouse. I grow compots in 400- 600 foot candles and do not water them again until the top of medium is dry.

10) I never use fungicide on seedlings. I cannot see where something from a sterile flasks benefits from a chemical drench of potentially phytotoxic material.

Given a sustaining environment, seedlings grow reliably. I have seen some growers use an anti-transpirant (water-soluble wax) effectively to prevent desiccation of new seedlings.


Harvey Brenneise, Michigan

Harvey is an Internet correspondent who lives in Berrien Springs, Michigan. Harvey specializes in growing Phalaenopsis and Paphiopedilums.

First, the flask-- I don't try to save glass flasks. It's quicker (and more fun--this is one of the best parts of the job!) to just smash it but be careful. You don't want glass everywhere. I simply put the flask in a paper bag, get a hammer and aim for the bottom of the flask. If you do it just right, the bottom drops off and you don't have a lot of slivers or smashed plants. This takes a little practice. It is easier to remove plants from some of the newer plastic flasks. I suppose if I recycled glass flasks I might not smash them, but as I'm not (yet) into breeding, I have no use for them.

Dick Wells of Hilltop Orchids recommends placing the just-deflasked seedlings into the following mix: 1 gallon of warm water, l/2 cup sugar, 1/2 teaspoon Truban, and 10 drops of Superthrive. You may leave the plants in this from 1 hour to 1 day. When ready to plant, though, be sure to rinse them thoroughly as you don't want sticky, sugary plants in the greenhouse.

For paphiopedilums and other orchids that I'm planting in a bark mix, I usually group them in clusters of between 3 and 6 plants in a 2 1/2" SVD (very deep) pot with mix all the way to the bottom. These are placed under lights and kept quite moist. As new mix often doesn't retain Water well, this may mean watering every day for a few days (especially if there's much air movement). It seems that often recently deflasked plants lose their "flask roots" and grow new roots in the medium they've being planted into, and if it's too dry, this is very difficult. Plants should be planted to the correct depth so that the new roots can emerge into the medium. For leggy paphs, this may mean removing the bottom leaves so that the roots can emerge from the "joints" where the leaves were.

I plant seedling phalaenopsis directly into a "mud" medium, but one that has been emended with perlite so it dries fairy quickly. I plant in small clay pots half full of Styrofoam peanuts. I make sure they are not planted too deeply, as this can lead to crown rot. Water as they dry out. Dick Wells plants 25-30 seedlings in a 6" pot.


NCOS Bulletin: Manuscripts and correspondence to Lisa Thoerle, 22341 Old Hundred Rd., Barnesville MD 20838 USA [(301)-972-7107 or MAHA0H06@sivm.si.edu]

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