Growing Pleione from Seed - Part 2
2. Sowing & Replating
I find the best time to sow is November or December (northern hemisphere). The exact techniques used may be quite varied between different people, but I will describe here how I do it. To describe the process in detail would take too long here, so what follows is an outline. It might be summarised as seven steps:
1. Prepare the medium
2. Sterilise everything
3. Sow the seed
4. Provide light & warmth for germination
5. Replate on to stronger medium
6. Replate again on to final medium
7. De-flask and plant
Let us examine each step in turn:
I find the best time to sow is November or December (northern hemisphere). The exact techniques used may be quite varied between different people, but I will describe here how I do it. To describe the process in detail would take too long here, so what follows is an outline. It might be summarised as seven steps:
1. Prepare the medium
2. Sterilise everything
3. Sow the seed
4. Provide light & warmth for germination
5. Replate on to stronger medium
6. Replate again on to final medium
7. De-flask and plant
Let us examine each step in turn:
1. Preparing the medium to sow on
Under natural conditions, most orchid seeds are only able to germinate if they form a symbiotic relationship with a fungus, which provides various nutrients the seed needs. This means that orchids cannot be simply sown in a pot in the normal way. Techniques have been developed which can supply these nutrients artificially by way of an artificial growing medium. This medium is prepared and poured in to flasks (jars) and on it the seed is sown. For flasks I use honey jars for sowing, and taller jars (from cooking sauces) for replating. It can be difficult to find suppliers of media but some orchid nurseries sell it. On artificial media of this sort, all kinds of organisms can grow, especially fungi and bacteria. These can overwhelm or kill the germinating seeds, so you have to sterilise the medium before use and keep it sterile during the sowing operation.
I like to make up the media several weeks before I actually intend to use it. Then, if any jars are not perfectly sterile, they will show contamination by the time you want to use the jars and so the contaminated ones can be rejected. In outline, making up media involves:
♦ Dissolving the powdered media in water, including any additives required.
♦ Bringing to the boil.
♦ Testing and adjusting the pH
♦ Pouring into jars. About 0.5 to 1 cm depth for sowing or 2 to 3 cm depth for replating.
♦ Sterilising the jars in a pressure cooker at 15 psi for 20 to 25 minutes.
I have tried various media, including both commercial media and homemade stuff. I find I get the most reliable results by sowing on HALF-STRENGTH Sigma P6668 orchid maintenance medium. When making up this medium I add 7g per litre of Agar. The Agar turns the solution into a gel, rather like when setting a jelly. The dissolved medium is brought to the boil. Then I use pH test papers to measure the pH of the medium and adjust it to pH 5.7 (using a 2.5% solution of potassium hydroxide) before pouring it into the jars. The lids are put on LOOSELY ( to allow air to expand and escape during cooking) and then the jars placed in a pressure cooker and cooked at 15 psi for 20 to 25 minutes. Then the pressure is released, the jars removed and the lids immediately tightened. They are then left to cool and set.
Under natural conditions, most orchid seeds are only able to germinate if they form a symbiotic relationship with a fungus, which provides various nutrients the seed needs. This means that orchids cannot be simply sown in a pot in the normal way. Techniques have been developed which can supply these nutrients artificially by way of an artificial growing medium. This medium is prepared and poured in to flasks (jars) and on it the seed is sown. For flasks I use honey jars for sowing, and taller jars (from cooking sauces) for replating. It can be difficult to find suppliers of media but some orchid nurseries sell it. On artificial media of this sort, all kinds of organisms can grow, especially fungi and bacteria. These can overwhelm or kill the germinating seeds, so you have to sterilise the medium before use and keep it sterile during the sowing operation.
I like to make up the media several weeks before I actually intend to use it. Then, if any jars are not perfectly sterile, they will show contamination by the time you want to use the jars and so the contaminated ones can be rejected. In outline, making up media involves:
♦ Dissolving the powdered media in water, including any additives required.
♦ Bringing to the boil.
♦ Testing and adjusting the pH
♦ Pouring into jars. About 0.5 to 1 cm depth for sowing or 2 to 3 cm depth for replating.
♦ Sterilising the jars in a pressure cooker at 15 psi for 20 to 25 minutes.
I have tried various media, including both commercial media and homemade stuff. I find I get the most reliable results by sowing on HALF-STRENGTH Sigma P6668 orchid maintenance medium. When making up this medium I add 7g per litre of Agar. The Agar turns the solution into a gel, rather like when setting a jelly. The dissolved medium is brought to the boil. Then I use pH test papers to measure the pH of the medium and adjust it to pH 5.7 (using a 2.5% solution of potassium hydroxide) before pouring it into the jars. The lids are put on LOOSELY ( to allow air to expand and escape during cooking) and then the jars placed in a pressure cooker and cooked at 15 psi for 20 to 25 minutes. Then the pressure is released, the jars removed and the lids immediately tightened. They are then left to cool and set.
2. Sterilise everything
All sowing and replating (which means moving seedlings from one flask to another) must be done under sterile conditions. Professionals work inside what is called a laminar flow cabinet - a working space that has filtered air flowing through and out of it to keep out airborne fungal spores and other possible contaminants. Amateurs can use a simple "glove box" - an old fish tank turned on its side for example, but for better results it is possible to cheaply fashion a makeshift laminar flow cabinet and this is what I did. First I bought a cheap, clear plastic storage box from the DIY store. I cut a hole in the lid and another in the base over which I glued a plastic grill. Then I bought an air purifier – machines which are sold for people with asthma or allergies. They filter the air in the room through a very high grade filter (called a HEPA filter) and blow out cleaned air with all pollen and other particulates removed – including most fungal spores and the like. With the box turned on its side, I connected the outlet from the purifier to the hole cut in the base, using a polythene bag cut into a tube. Here is the finished product:
All sowing and replating (which means moving seedlings from one flask to another) must be done under sterile conditions. Professionals work inside what is called a laminar flow cabinet - a working space that has filtered air flowing through and out of it to keep out airborne fungal spores and other possible contaminants. Amateurs can use a simple "glove box" - an old fish tank turned on its side for example, but for better results it is possible to cheaply fashion a makeshift laminar flow cabinet and this is what I did. First I bought a cheap, clear plastic storage box from the DIY store. I cut a hole in the lid and another in the base over which I glued a plastic grill. Then I bought an air purifier – machines which are sold for people with asthma or allergies. They filter the air in the room through a very high grade filter (called a HEPA filter) and blow out cleaned air with all pollen and other particulates removed – including most fungal spores and the like. With the box turned on its side, I connected the outlet from the purifier to the hole cut in the base, using a polythene bag cut into a tube. Here is the finished product:
Homemade laminar flow box
Once sterilsed and with the air filter turned on, this simple device creates a sterile environment inside the box in which you can work. Before starting the actual sowing, all the inner surfaces must be thoroughly wiped down with disinfectant. A 10% bleach solution is the most effective, but is not very pleasant to work with. I use Dettol (anti-bacterial formula) as an alternative. Any instruments used must also be sterilized with this or (even better) with Virkon, which can be bought from agricultural or equestrian suppliers. Always wear gloves (sterilise these too with the bleach) for the whole operation and a plastic coat is a good idea too. Sterility must be thought about at all times and good technique will help in this respect – this comes with practice and experience. Once I got good at keeping everything sterile I ended up with very few jars that got contaminated - less than 5% of them.
3. Sowing the Seed
The day before sowing, I prepare a solution of one teaspoon of sugar (sucrose) in 250 ml of water. That evening, I put a little seed into a small bottle, add some of the sucrose solution and give a good shake. The seed is left to soak in this overnight. I also put some tap water into jars and sterilise it in the pressure cooker. On the day of sowing, the sugar solution is removed with a pipette. The seed must then be sterilised. For this I use Miltons Fluid, sold for disinfecting babies’ bottles etc. Miltons is 2% Sodium hypochlorite. I dilute this at a rate of 10ml of Miltons made up to 50 ml with water. Wearing sterilised gloves, I use a pipette to add the diluted Miltons to the bottle of seed, filling it right to the top. The seed bottle itself is then dipped into disinfectant and wiped all over with it, then placed into the sterile cabinet - along with the jars of sterile water prepared the day before and all the jars of prepared sowing medium. Remember to wipe the jars all over with disinfectant before putting them in to the cabinet. Everything that goes in to the cabinet must be sterilised first!!
I leave the seed to soak for 20 mins in the Miltons - or 25 for seed I think may be fungosed. After this, the Miltons is removed with a pipette, carefully so as not to suck out the seed too! Some of the sterilised water is added in its place to rinse the seed. This is removed and a little more sterile water added. Next, remove the lids from the jars in which the seed is to be sown. Then the seed is swirled around in the sterile water and poured into the jars (using just enough water to be able to swirl around to distribute the seed evenly over the medium). Any excess can be carefully removed with a sterile pipette. Replace the lids, tightly.
The day before sowing, I prepare a solution of one teaspoon of sugar (sucrose) in 250 ml of water. That evening, I put a little seed into a small bottle, add some of the sucrose solution and give a good shake. The seed is left to soak in this overnight. I also put some tap water into jars and sterilise it in the pressure cooker. On the day of sowing, the sugar solution is removed with a pipette. The seed must then be sterilised. For this I use Miltons Fluid, sold for disinfecting babies’ bottles etc. Miltons is 2% Sodium hypochlorite. I dilute this at a rate of 10ml of Miltons made up to 50 ml with water. Wearing sterilised gloves, I use a pipette to add the diluted Miltons to the bottle of seed, filling it right to the top. The seed bottle itself is then dipped into disinfectant and wiped all over with it, then placed into the sterile cabinet - along with the jars of sterile water prepared the day before and all the jars of prepared sowing medium. Remember to wipe the jars all over with disinfectant before putting them in to the cabinet. Everything that goes in to the cabinet must be sterilised first!!
I leave the seed to soak for 20 mins in the Miltons - or 25 for seed I think may be fungosed. After this, the Miltons is removed with a pipette, carefully so as not to suck out the seed too! Some of the sterilised water is added in its place to rinse the seed. This is removed and a little more sterile water added. Next, remove the lids from the jars in which the seed is to be sown. Then the seed is swirled around in the sterile water and poured into the jars (using just enough water to be able to swirl around to distribute the seed evenly over the medium). Any excess can be carefully removed with a sterile pipette. Replace the lids, tightly.
4. Provide light & warmth for germination
The jars are then put on shelves under fluorescent lights, which are on for 14 hours and off for 10 each day. Temperature is kept between 18 and 25 centigrade. For this stage, I bought cheap plastic shelving and fitted lights under each shelf:
The jars are then put on shelves under fluorescent lights, which are on for 14 hours and off for 10 each day. Temperature is kept between 18 and 25 centigrade. For this stage, I bought cheap plastic shelving and fitted lights under each shelf:
Shelving with added lights for germinating & growing on
Germination is usually fairly rapid - most are obvious after between 1 to 3 weeks, though some can take much longer.
5. Replate on to a stronger medium
I replate (which simply means moving the seedlings to a new jar) approximately 2 months after sowing (so mid Jan to mid Feb roughly depending on when I sowed and how quickly they germinated. They should have small shoots about 3 to 5 mm high at this stage). For this first replate I use honey jars again and the same media but a bit stronger - 60% strength and I add 80g per litre of pureed banana and 25 ml per litre of pineapple juice, again adjusting the pH to 5.7 (Before adjustment this media is quite acidic and it usually takes about 6 ml of the potassium hydroxide to get to pH 5.7). The replating is done inside the sterile box again, remembering that the inside of the box must be sterilised first and everything put in it must be sterilised too.
To do the replating I use a spatula. I cut a "v" shape in the end of it which helps. Replating is then simply a case of lifting small clumps of seedlings with the spatula and transfering them to the new medium. The young plants remain on this medium until they go dormant later in the year. Here is what a group of flasks looks like towards the end of their first year in flask:
I replate (which simply means moving the seedlings to a new jar) approximately 2 months after sowing (so mid Jan to mid Feb roughly depending on when I sowed and how quickly they germinated. They should have small shoots about 3 to 5 mm high at this stage). For this first replate I use honey jars again and the same media but a bit stronger - 60% strength and I add 80g per litre of pureed banana and 25 ml per litre of pineapple juice, again adjusting the pH to 5.7 (Before adjustment this media is quite acidic and it usually takes about 6 ml of the potassium hydroxide to get to pH 5.7). The replating is done inside the sterile box again, remembering that the inside of the box must be sterilised first and everything put in it must be sterilised too.
To do the replating I use a spatula. I cut a "v" shape in the end of it which helps. Replating is then simply a case of lifting small clumps of seedlings with the spatula and transfering them to the new medium. The young plants remain on this medium until they go dormant later in the year. Here is what a group of flasks looks like towards the end of their first year in flask:
Pleione seedlings at end of year 1
I then put the flasks in a fridge (not freezer!!) to keep them dormant - they start growing again fairly soon after if you don't do this and so end up growing out of season.
6. Replate again on to the final medium
I keep them in the fridge until the start of the following year and I then do a second replate in Jan or Feb. For this second replate I use taller jars (jam jars or cook-in sauce jars) to accommodate the leaves, which will grow much taller in their second year. For this second replate I use a different media - Sigma P1056 at full strength and add 50 ml per litre of pineapple juice, again adjusting pH to 5.7. They go back under the lights for the rest of the growing season. Here is what they typically look like at the end of this stage:
I keep them in the fridge until the start of the following year and I then do a second replate in Jan or Feb. For this second replate I use taller jars (jam jars or cook-in sauce jars) to accommodate the leaves, which will grow much taller in their second year. For this second replate I use a different media - Sigma P1056 at full strength and add 50 ml per litre of pineapple juice, again adjusting pH to 5.7. They go back under the lights for the rest of the growing season. Here is what they typically look like at the end of this stage:
Pleione seedlings after two years in flask
When they go dormant in the autumn they go back in the fridge for the winter, until spring.
7. De-flask & plant
I remove them from the flasks in Spring and wash off the medium. They look like this:
I remove them from the flasks in Spring and wash off the medium. They look like this:
Deflasked Pleione seedlings
In a closer view you can see the new shoots ready to grow on some of them:
Deflasked Pleione seedlings ready for potting
Once potted you can expect your first flowers, typically, three to five years later.