Growing seedlings from flask

Buying flasks of orchids is an inexpensive way to build a valuable collection of rare plants with only a modest outlay. These flasks contain between 1 and 5 seedlings each, depending on their value. They need not be transplanted until spring next year, giving you time to read all about them. Meanwhile, here are a few tips to help you get the most out of every flask.

Choosing Flasks

When you have decided the type of species or hybrid you want, look carefully at the flasks on offer and pick one out that has separate plants with sturdy, evenly green shoots (and the first pseudobulb if possible) and roots visible in the agar gel. (Our flasks contain only natural, wild species.)


Stand the flask in tepid water to loosen the gel. Withdraw the seedlings complete with the gel disc and stand it in tepid water while you tease the seedlings apart. If they refuse to come out, wrap the flask in some sheets of newspaper, stand it on a solid surface and give it a tap with a hammer on the side edge of the flask base and if the washed roots will not separate, plant them as a clump and separate them when they are stronger. If you choose not to transplant until spring, watch out for mould on the agar gel surface; if that appears, you must transplant at once.

Potting up

Wash or dust your cleaned seedlings with a protective chemical like Physan or a fungicide like Captan; don't use systemic fungicides like Benlate. Wear protective gloves, as all chemicals are potentially harmful to you. Most seedlings thrive in groups in a community pot (up to five per pot) just slightly larger than the flask they came from. Use fine bark compost with charcoal and perlite, or, if you prefer, rockwool, and place the seedlings in up to their stem bases. Firm them in with more compost.

A warm, humid situation for the first 2-4 weeks gives the best chances for survival. A base-heated propagator is ideal, placed in a bright spot, but not in direct sunlight. After two weeks, prop the lid up and open the vents for air circulation. Air movement helps growth and prevents types of fungal rot. An inexpensive alternative to the propagator is a halved 2 litre clear plastic soft drink bottle.

What to expect

The plants will begin to grow in 2-3 weeks. Now you can begin to feed them with quarter strength, nitrogen-based fertilizer. But, in case the fertilizer accumulates, remember to flush the pots through with clean water before feeding again. Keep the pots moist and humid but never sodden. After some weeks they can be moved to a well-shaded place in the greenhouse where they will soon become established. You may decide to mount them on cork bark or wood, in which case add some moss around the washed roots and tie the plants on with strips of old tights. Keep in a shaded, humid place until the roots have grown and have become stuck to the mount.

What to Buy

Phalaenopsis species and hybrids are easy. Grow them at high humidity and in an open compost at 25°C taking benefit from bottom heat. Some flower a year later.

Cattleya species and hybrids are tough and survive well. From flask to flower will be from about 3 years. Treat as adult plants after a year out of flask.

Paphiopedilum (Slipper Orchids) are easy but sometimes slow to get going as their roots are easily broken during deflasking. They like to be potted close together and separated later.

Odontoglossum/Oncidium species and hybrids. You can expect some losses but flasks often have many seedlings. Best survival is in conditions of high humidity and good air movement which they need until the first pseudobulb appears. Flowering starts after 2-3 years.

Other Species. Survival is variable and you will need to read about each species' special requirements. Dendrobium nobile, Gomesa crispa, and Oncidium cogniauxianum are all reliable beginners' species, the latter two almost guaranteed to flower after 18 months.

by Dick Warren and Janet and Ian Plested.
If you would like a fuller account of 'Seedling Care', send 4 x 25p stamps to Equatorial Plant Co., Gray Lane, Bardnard Castle, Co. Durham DL12 8PD.


The North Hampshire Orchid Society is affiliated to The Royal Horticultural Society & The Orchid Society of Great Britain
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