How to grow orchids from seeds: These extremely simplified guidelines are aimed at getting you started. We are “home gardeners” and “amateur biologists” and with these guidelines you may want to try. Once you grasp the fundamentals you can always develop, improve and adapt your techniques. 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 or capsule which contains the seeds. 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 to the stigma. If there is no natural pollinator, you can open the lid of the column and manually transfer the pollinia to the stigma. The uncovered pollinia appear as yellow „eye-like‟ structures or yellow balls on top of the column. 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 and in this way you may get winning offspring from the seed. The mouth-like structure below the yellow pollinia is the stigma, the female part. It may look different in various genera. To pollinate the orchid, transfer the pollinia to the stigma. If you are doing cross pollination you will transfer the pollinia of one plant to the stigma of another plant. Harvesting 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. 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 glass container such as an eppendorf tube. You can get suitable small glass jars or tubes from your chemist. Preferably the seeds should be stored in the fridge, but be careful that condensation does not form in the cold which may lead to growth of moulds. The drier the capsule, the longer they keep. Some may last a year, some may last ten years. For successful seed germination, act quickly; do not postpone the transfer to the growth media. Submerge the small seed containers (e.g. eppendorf tubes plugged with cotton plugs) in oven-dried rice kept in larger containers or bigger jars to promote drying. After drying the capsule the orchid seeds will appear as dust on your fingers. Transfer the content of the orchid capsule to another eppendorf tube or any small glass container. Media making recipe 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). You can buy these at a Chinese shop and is called agar-agar powder – various brands exist. 20 g of sugar. 1.2 g of thiamine (vitamin B1 from the pharmacy, 12 tablets 100 mg each, pound in a mortar first to powder). 900 ml of 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/blender. Transfer the medium, while stirring, to the clean sterilised flasks. 1-2 cm depth at the bottom of the flask is usually enough. As to flasks, you can use an old marmalade or jam bottles made of glass with a metal screw cap. Close the lids lightly (not tight) 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 cannot use plastic lids; or 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 is not the goal here, and we do not expect tough bacterial spores. The goal is mainly to kill fungal spores and most bacterial cells; or 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. Note that 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, but 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. The crucial point is those few seconds when the lid is open to add the orchid seeds. The golden rule is to minimize the exposure time and to aim at highest cleanliness as possible. Use what you have and try. Surprisingly often you are successful without the expensive equipment. Now prepare sterilization liquid: Mix 9 parts distilled water + 1 part bleach (household, 5-6% NaOCl) + 1 drop detergent, as many seeds repel water. Prepare 80 ml of sterile water per orchid capsule (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 (a small bucket will do). Transfer seed to medium: If you have a syringe, follow procedures A1-A5. If you have no syringe, follow procedures B1-B4. A1. Add the contents of one capsule into any vessel that will fit your 20 ml syringe. 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 form 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 transferring to the growing flask containing the medium, 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 little amount (about five droplets) from the syringe to each flask with nutrient medium. B1. Add the contents of one seed capsule 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 a flask with nutrient medium. Remarks: The sterilized seeds must be sown immediately. Remember that some orchid seeds are light, some are dark. There usually are 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. 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 a warm environment, or in a ventilated room with light lamps and a temperature set for the species (default is 25°C). The ventilation may be needed to lower the temperature in the room. Re-inoculation If the plants grow slowly the agar may eventually start looking cracked due to water loss. 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 towel 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. To get the plants out of the flask you may need to gently break the glass. Remove as much agar as you can mechanically and swirl for a 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 damp paper towel or sphagnum moss in the bottom. Put the box in a moist environment such as a shaded nursery or a protected spot in your shade house. 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 cannot drown them. After one week you can pot them in community pots in a very fine medium and let them gain size in the shaded and moist nursery. Transfer them individually to small seedling pots when they have grown enough. 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. Because they are so tiny the orchid seeds hardly carry any extra nutrients, in contrast to larger seeds which have picnic bags of 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 and 3 million seeds. To compensate for the small size and lack of nutrients, the orchids parasitize on fungi. 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. 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 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.
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