How to grow orchids from seeds – kitchen style

Introduction

These extremely simplified guidelines aims at getting you started. We have home gardeners, amateur biologists and schools in mind when writing these guidelines. Since this blog aims at gardeners in the tropics and in Chiang Mai in particular, there will be some information of local interest, but any keen gardener anywhere will find these guidelines useful. Once you grasp the fundamentals you can always develop, improve and adapt techniques. Please share your experience with us!

Golden rules for an orchid gentleman or gentlewoman:

1. Do not steal orchid fruits (capsules), seeds or any plant material from the national parks. Only purchase orchid species from CITES certified dealers, or use seeds from plants already cultivated in nurseries.

2. If you wish to provide native orchids for forest restoration, always collaborate with the authorities, national parks AND the scientists. Do not mess up the ecosystem by introducing foreign species, garden hybrids or strains from 2000 km away. Always document what you do, publish the details on internet for others to access if necessary.

Pollination

The purpose of a flower is sex. When male flower pollen is transferred to a flower’s female stigma, you get fertilization almost like when an animal sperm fertilizes an animal egg. The result of the fertilization is a fruit which contains the seeds. The seed contains a plant embryo, equivalent of an animal foetus. The elaborate shape and fragrance (often undetectable to humans) of an orchid flower is aimed at attracting special insects, the pollinators. When the pollinating insect tramples around to investigate the flower, it transfers pollen.

1. Always check if the pollinator is already inside your garden. If so, there will be fruits formed without your assistance. Help science by documenting the pollinator (photographs of visiting insects, or catch it and send it to an entomologist). If we know what insect, we may also know what host plant is used by the insect’s larva. Remember that many pollinators are active at night. Publish your discoveries on internet and please tell us!

 2. If there is no natural pollination, open the lid of the column and transfer the pollinia to the stigma. If the flower is big you can use your fingers, otherwise a toothpick is useful. Cross pollination between different orchid individuals is better than self pollination.

Orchid pollinia.

In this picture the orchid’s lip has been removed, and we look at the orchid flower from below. The uncovered pollinia appear as yellow ‘eye-like’ structures on top of the column. The mouth-like structure below the yellow pollinia is the stigma, the female part. It may have different morphology in different genera. To pollinate the orchid, transfer the pollinia to the stigma.

Harvesting of fruits

An orchid fruit (a capsule) is usually formed quickly but may take many months to mature. Harvest when yellow or brown and almost cracking open. If you live in the orchid’s home country and follow its natural cycle, take a note when the orchid fruit is mature. This is probably the best time for germination (regarding temperature).

Do not discard surplus fruits. If you live in the orchid’s home country, then open the fruits and tie them to a stone and use a sling shot to shoot them up in the tree crowns on a windy day. Select a national park, a botanical garden, a park, your own garden or a friend’s garden. If you live abroad, donate the seeds to a seed swapper:

Terrestrial orchids

Epiphytic orchids

You can also check the Orchid Ark’s species list. If you have a Thai orchid not included in the list, we should be grateful if you shared seeds.

A ripe fruit of Vanda liouvillei, opened by hand.

Storage of seeds

Dry the capsule indoors and then use a pair of forceps to transfer the interior of the orchid capsule to a small container such as an eppendorf tube. Preferably the seeds should be stored in the fridge, but here in the tropics it is so moist a lot of condensation may form in the cold which lead to growth of moulds. The drier the longer they keep. Some may last a year, some may last ten years. For successful seed germination, act quickly, do not postpone transfer to growth media!

Submerge the small seed containers (e.g. eppendorf tubes plugged with cotton plugs) in oven-dried rice kept in a larger containers such as kilner jars.

After drying the capsule the orchid seeds appear as dust on your fingers.

Transfer the content of the orchid capsule to an eppendorf tube or any small container.

Media making

40 g of mashed peeled banana (equivalent to half a small banana).

100 ml of fresh, peeled and crushed tomatoes (equivalent to 2 ordinary tomatoes).

10 g of agar (powder is preferable, strips have to be cut in tiny pieces).

20 g of sugar.

1.2 g of thiamine (vitamin B1 from the pharmacy, 12 tablets 100 mg each, pound in a mortar first).

900 ml of tap water (should be distilled water if your tap water is dirty or above pH 7).

Prepare the ingredients separately.

Mix all ingredients evenly using a household mixer.

Transfer the medium, while stirring, to the clean flasks. 1-2 cm depth is usually enough.

Close the lids softly so that air can go out (or they will explode in the oven).

There are three simple ways to sterilize the flasks:

1. Place the bottles on a tray in a pre-heated oven 150-180°C. Wait until you see bubbles and then sterilize for another 10 minutes. For this technique you can not use plastic lids.

2. Put the bottles with media in a big pan with boiling water just above the agar level. Put on the lid and leave for 30 minutes. Although you only reach about 100°C, this may in many cases be sufficient. Hospital sterility may not be the goal here, and we do not expect tough bacterial spores. The goal is mainly to kill fungal spores and most bacterial cells.

3. Transfer the flasks to a pressure cooker and when steaming, leave for 20 minutes. With a higher pressure the boiling temperature is higher, and so even bacterial spores will die. This is the best option, although maybe not always necessary.

Let the flasks cool down until the next day and then tighten the lids. If you tighten immediately you may have more condensation as you trap hot air which contains more humidity than cool air, and there will be a low pressure inside causing difficulties to open the lid, which in turn may result in contamination when trying to open. Store the bottles in clean plastic bags to avoid contaminating spores covering the surface. If the media start cracking or shrinking, they are too old and you should discard, clean and reuse again.

You could sow the orchid seeds as soon as the medium is not hot any more, but it is better to wait 5-6 days to check that the flasks are not contaminated by fungi which may kill the plants.

Agar at Rimping Supermarket in Chiang Mai, Thailand.

Vitamin B1 from Chiang Mai University pharmacy.

A mixer is good for making a smooth medium.

The nutrient medium is sterilised inside the growing flask.

Sterilization and sowing of orchid seeds

Select a clean working place indoors, such as a metal bench (not wood) free of debris and preferably cleaned with 80% alcohol. Use clean hands and clean clothes. Do not bend over the bottles. If the growing flask contains a lot of liquid on top of the medium, pour it out first.

Of course a professional laminar flow bench is preferable. It has walls and the sterilized air flow blowing against you makes it hard for outside spores to enter the growing bottle. A laminar flow bench is a big investment for a home gardener. Some simply use a fish tank (40 cm wide) which can be cleaned with alcohol. Turn it so the opening faces you and the glass wall becomes a barrier against airborne spores. In reality, using many duplicates, Eric has managed transplanting sterile tissue samples while working in hotel rooms on a simple table. The crucial point is those few seconds when the lid is open to add the orchid seeds. The golden role is to minimize the exposure time and to aim at highest cleanliness as possible. Take what you have and try. Surprisingly often you are successful without the expensive equipment.

Mix 9 parts distilled water + 1 part bleach (household, 5-6% NaOCl depending on brand, I used Rimping ‘Haiter’ Bleach) + 1 drop detergent as many seeds repel water. We call this the sterilization liquid.

Prepare 80 ml of sterile water per orchid fruit (boil water in containers like when you make the medium). Let the water cool down to room temperature.

Prepare a disposal vessel for excess liquids.

If you have a syringe go to A1. If you have no syringe go to B1.

A1. Add the contents of one fruit into any vessel that will fit your 20 ml syringe.  Eric uses 50 ml plastic Falcon tubes. They do not need to be sterile, as the sterilization liquid will take care of that.

A2. Add 10 ml of the sterilization liquid and mix gently. Wait 5-10 minutes.

A3. If the seeds are heavy they will sink to the bottom and using the syringe you suck out and dispose the majority of the sterilization liquid before adding 20 ml sterile water. Suck up the seeds and the sterile water in a 20 ml syringe. Let the syringe stand up with the tip upwards for 15 minutes while the seeds sediment.

A4. Press out excess fluid with one move without stirring the seed sediment, and fill the syringe with new sterile water. Repeat 3 times.

A5. Before transfer to the growing vessel, concentrate the seed solution by minimizing the amount of sterile water. 4 ml remaining liquid is fine, and then you shake the syringe to stir up and mix seeds. Add a preferred amount (Eric uses five droplets) to each flask with nutrient medium.

B1. Add the contents of one fruit to any tall thin vessel like a perfume bottle.

B2. Add 10 ml of the sterilization liquid and mix gently. Wait 5-10 minutes.

B3. If the seeds are heavy they will sink to the bottom and you pour or suck out the majority of the sterilization liquid. If the seeds are light they float, and then you pour the top layer into a new sterile bottle. Add 25 ml of sterile water and repeat 3 times.

B4. Remove most of the sterile water and shake the seeds with the remaining water, and transfer a small amount of liquid (5 droplets to 1 ml) to a flask with nutrient medium.

Remarks:

The sterilized seeds must be sown immediately.

Remember that some orchid seeds are light, som are dark. There is usually some unimportant sterile tissues from the capsule floating at the top. To see the actual seeds you look into the liquid after mixing. It is important to ascertain if they sediment or float upwards. In the rare case they do neither (same density as water) you need to start all over and change the density of the sterile water by adding some sugar before boiling.

Inside the 20 ml syringe you can see the  sedimenting orchid seeds (Vanda liouvillei).

Incubation

Some seeds germinate after a few days, some germinate after many months. Keep the bottles in the light shade outdoors if you live in the tropics, or in a ventilated room with light ramps and a temperature set for the species (default is 25°C). The ventilation may be needed to lower the temperature in the room.

Reinoculation

If the plants grow slowly the agar may eventually start looking cracked due to water losses. The gas exchange is also poor and may stunt plant growth. If you observe this, simply transplant the plants to new flasks with fresh medium (use the same aseptic environment as when you inoculated the seeds). Before opening the old flask, surface sterilize it by wiping it with clean paper soaked in 80% alcohol or bleach.

Transplanting to a dry and unsterile environment (deflasking)

When the plants are large enough to handle and with several visible roots then it is time to adjust them to the outer world. Remove as much agar as you can mechanically and swirl for some while in water to remove sugars which may attract moulds and bacteria. To make sure your precious orchids do not dry out immediately after leaving the flask, transfer them to a plastic box with household paper or sphagnum moss in the bottom. Put the box in a moist environment such as a shaded nursery. Spray water on the paper and the orchids but do not cover the box (plants need light!). Check on your orchid babies frequently and make sure rain can not drown them. After one week you can mount them to any substrate you prefer (plastic net, concrete, hardwood, hanging basket, sphagnum moss or coconut husks) and let them gain size in the shaded and moist nursery.

Final position in the garden or forest

Pots are fine in a nursery, but a natural look is more appealing in your garden, or maybe you wish to contribute to the national park? Then you need to attach the orchids to a tree. This should be done in the rainy season only, as a gradual adaptation to the new environment is essential. Use a string made of natural fiber (which will break without strangling the branch) and tie the orchid to the tree, facing east or north. Do not attach it below eye height as standing moist air near the ground may cause a rot in the rainy season, or they may burn due to fires in the dry season. Select deciduous trees for sun loving species and evergreen trees for shade lovers.

 Remarks:

Why can’t I just throw the seeds in a pot of soil like with ordinary seeds?

Orchid seeds are very special. They are tiny to enable long-distance dispersal and to get high up into trees with the help of the wind. Most orchid seeds are between 0.3 and 0.8 mm, but including the exceptions the range is 0.15-6 mm. To become tiny the orchid seeds hardly carry any extra nutrients, in contrast to larger seeds which have picnic bags of either protein (soy bean), oil (canola) or carbohydrates (rice). In larger seeds of other plants there is a large multicellular plant embryo for quick growth, while in the orchid seed the embryo is minuscule. Depending on species and growing conditions an orchid fruit (a dry capsule) may contain between 1500 to 3 million seeds. To compensate for the small size and lack of nutrients, the orchids parasitize on fungi. Orchid seeds landing on a tree trunk are attacked by fungi, and in some cases the seeds are killed, in some cases the seeds kill the fungus and then the orchid starves to death, in some cases the orchid does not allow the fungus entrance and it will die too, but in a small fraction of cases, the fungus repeatedly attacks the orchid while the orchid repeatedly degrades and consumes the tissues of the fungus. This parasitic symbiosis is called orchid mycorrhiza. A seed which dies in one situation, may survive in another situation. That is why genetic diversity and large numbers of seeds are crucial. When we grow the orchid seeds on the nutrient medium, we offer the nutrients otherwise provided by the fungus, and we have a greater rate of germination and development since there is no battle between organisms.

Vitamin B1 (thiamine)

This vitamin is important in all cells for carbohydrate metabolism. It is probably present in the orchid mycorrhiza in nature, but due to heat sterilization we lose so much thiamine there is no native source rich enough. 100 g of whole-wheat flour contains 0.55 mg of thiamine. 100 g yeast extract=0.9 mg thiamine. Mushrooms 0 g. We need 1200 mg/litre medium. That is why it is better to use a pressure boiler than the oven, due to the lower temperature.

Temperature during media making

If you put the flasks on a stand in a pan with boiling water you reach 100°C if you boil at sea level. At higher altitude the water boils at a lower temperature. Boiling is normally sufficient to kill the fungal spores, the main enemy of orchid growers. If this results in sterile flasks and eventually orchid seedlings, fine, but in some environments there are bacteria which do not die unless you reach 120°C. The pressure boiler allows a higher boiling temperature. If you put the flasks in the oven at 150-180 °C you may experience more destruction of vitamin B1 resulting in stunted growth.

Costs for making 1 litre of medium in Chiang Mai, Thailand (August 2011):

Two tomatoes 0-12 Baht (39 Baht for one package with 7 tomatoes. Big Rimping).

Half a banana: 0-2,5 Baht (29 Baht for one package with six bananas. Big Rimping).

Agar 20 Baht (48 Baht for a package of 25 g. Big Rimping).

Sugar 0.5 Baht (27 Baht for a package of 1000. Big Rimping.).

Thiamine 12 Baht (1 Baht for each tablet of 100 mg. University pharmacy).

Water 0-1.3 Baht (29 Baht for one crate of 20 1-litre bottles. Home delivery).

Total cost 32.5-48.30 Baht/litre. The lower cost applies if you use your own water and garden fruits.

As to flasks, you can use an old marmalade bottle made of glass with a metal screw cap. New empty bottles can be bought at Rimping for 80 Baht each. Professional Schott Duran glass bottles with blue plastic caps (which can stand a pressure cooker but not the oven) can be bought from Union Science. There is one store almost opposite to the Chiang Mai University pharmacy, just west of Wat Suan Dok temple. Cross the street from the pharmacy and walk back almost to the canal road and you will see it on your left hand. A 100 ml bottle cost 108 Baht. They have chemicals, syringes, pipettes, gloves and other things too (phone 053-808858). On the same side of the street there is a peculiar shop with second hand bottles, a cheap alternative.

Other useful websites

The Hardy Orchid Society Seed Bank

Ionopsis ‘Propagation from seed’

Olivia’s Spanish orchid seed germination:

Plant tissue culture & Orchid seed sowing for hobbyists

Seed swaps – epiphytic orchids

Seed swaps – terrestrial orchids

Seed sterilization (Spanish)

Seed sterilization (SIGMA ALDRICH)

YouTube Orchid Seed Flasking – Part 3 (2011)

About the authors

Eric Danell has a PhD in plant physiology from Uppsala University, Sweden. He is a co-founder of the Orchid Ark and is the senior scientist at Dokmai Garden, Chiang Mai, Thailand.

Brett Maloney from Australia is an experienced orchid seed grower who co-founded the Facebook orchid seed swap. He is currently located in Thailand.

Martin Shim is a Malaysian horticulturist with a BSc From University of Guelph, Canada. He lives and works in Kota Kinabalu, Borneo. He is an experienced orchidologist and engaged in orchid conservation.

Ketsanee Seehamongkol is the president of Dokmai Garden and a co-founder of the Orchid Ark in Chiang Mai, Thailand. Her practical approach is important to small scale cultivation.

Olivia Vila from Spain has a lot of experience from home cultivation of orchids and her practical approach is important to adapt a lab environment. She has published a lot of her invaluable experience on internet.

Did you like this blog? Kindly help us by clicking ‘LIKE’ on our website!

Photograph: Cleisostoma fuerstenbergianum is native to Thailand.