The basal plate of a bulb is really a modified stem from which the roots and leaves grow. If this stem is damaged either naturally or artificially then the bulb’s response is to produce new buds (bulblets).
Twin-scaling takes full advantage of this survival technique the idea being to cut the bulb into small sections (slices) each with a piece of basal plate and at least two scales to nourish the growing bulblet.
Ideally during the growing season it will be useful to make a note of the plants that you wish to propagate, choosing healthy plants and ones that display the correct characteristics for the type. (See Twin-Scaling Part 2 (1))
Twin-scaling can be performed successfully on bulbs that have a fungal disease which shows up as decay on parts of the scales, as long as all the decay is removed and the basal plate is sound. Bulbs which have a virus infection should not be used as the process will not eradicate the disease. I have tried experimenting with some and have found that most will develop a mould during the incubation period. Few have survived to maturity.
Twin-scaling should not be attempted until the bulb has gone completely dormant, that is, all the leaves have withered away, naturally. This will usually be the end of May or beginning of June. I normally start as soon as I can and continue until early July, so by allowing an incubation period of twelve weeks I can still complete the potting up process by the end of September.
Carefully lift the bulb(s), making sure that no damage is sustained. Assemble your bulb(s), ingredients and equipment together in a clean, sterile place and allow plenty of time.
Plan to keep a record of what you are doing for future reference. How many bulbs of each variety, condition of bulbs, how many chips, how many chips actually produced bulblets, how many bulblets grew into bulbs etc.
To save any cross contamination between bulbs go through the process on a per bulb basis.
Disposable gloves Plastic bags (approx 6ins x 12ins)
Water Elastic bands
Large Bowl Labels
Cling film Scalpel
Systemic fungicide Methylated spirit
Jug Small bowl(s)
Chopping board (marble or glass, not wooden)
- Wear gloves throughout.
- Boil water and leave to go cold.
- Place 1000mls vermiculite into a large bowl and add 80mls of water, mix well. It should feel just damp to the touch. Cover with cling film and leave to go cool. (When water is added to vermiculite it will generate heat). This quantity will be sufficient for three bulbs)
- Mix the fungicide with water in a jug according to the manufacturer’s instructions. I find that one pint will be sufficient for six small bowls as you only need enough in a bowl to just cover the bulb slices.
- Remove the tunic and roots from the bulb. This is easier if done under running water. If the bulb has any discoloured patches then remove the outermost
scale. Your aim is for a perfectly white, shiny bulb.
- Wipe the surface of the chopping board, scalpel and bulb with methylated spirit.
- Place bulb on the chopping board and trim down the basal plate until it is level with the outermost scale.
- Cut off the upper quarter of the bulb (the neck). (See Twin-Scaling Part 2 (2))
- Wipe both cut surfaces with methylated spirit.
- With the basal plate uppermost cut the bulb vertically in half, then half again, then half again, etc. The aim is to get a wedge-shaped slice of bulb with a piece of basal plate attached. Depending on the size of the bulb you would normally achieve either eight or sixteen slices.
- To stop at this point would be the process correctly termed “chipping”, to carry on and perform twin-scaling you need to cut each slice in half between the scales, aiming to keep two scales on each new slice.
- Stir the fungicide in the jug and pour a small amount into a bowl.
- Put the slices into the bowl and leave for thirty minutes.
- Put one-third of the vermiculite into a plastic bag.
- After thirty minutes pour the fungicide and slices into a sieve to drain. If the slices are excessively sticky (as in plicatus or plicatus hybrids) then rinse the sieve under the tap. Blot with a piece of kitchen roll.
- Drop slices into the bag of vermiculite, one at a time, giving the bag a little shake between each one. If the slices stick together there is a greater risk of mould developing.
- Grasp the bag near the top and seal with an elastic band, ensuring that there is a good air pocket. Do not blow into the bag.
- Label the bag with the name of the snowdrop, the date and number of slices. Put the bag into a warm (20c) dark place.
- Dispose of gloves and any used fungicide; thoroughly cleanse any utensils that have been used.
- Proceed from the beginning with the next bulb.
- The bags containing the slices will need to be checked regularly for any signs of mould developing. If any is found then remove the infected slices, re-soak the remaining slices in a fungicide solution for thirty minutes and put back into a clean bag containing fresh vermiculite.
- After a period of four to five weeks you should notice that the scales are splaying apart and tiny bulblets are forming between the scales. In the case of “chipping” more than one bulblet may form; some bulblets may even form on the scales themselves.
- After twelve weeks the slices that have produced bulblets will be ready for potting up. Discard any slices that are blind. (See Twin-Scaling Part 2 (3) & (4)).
- Choice of pots is a personal thing but choose pots where the slices will fit comfortably, without touching. I use either 7cm or 9cm square black plastic pots as these can be packed in tightly on the greenhouse shelving, so saving space. Only use clean pots; if re-using any pots then wash thoroughly in a weak bleach solution and remove any limescale.
- Choice of compost is again a personal thing but you are aiming for a well drained mix. I use 50% general purpose compost and 50% vermiculite.
- If the slices are the result of chipping and only one bulblet has developed then the excess scales are gently removed, leaving just two scales. If more than one bulblet has developed then I will leave all the scales intact.
- Half fill the pot with potting mixture, then add a layer of sand (approximately 2cm), lightly push the slices into the sand, basal plate down (like little flags), spray with fungicide and top up the pot with potting mix.
- Label the pot, e.g. with the variety and number of slices.
- Water the pot thoroughly; a weak solution of fungicide can be used if desired.
- I then place my pots in a shaded, frost-free greenhouse and therefore can not comment on the suitability of using a cold frame.
- Depending on the date they were first watered I would aim to give the pots another watering before mid-October. They are not watered again until growth appears.
- Hopefully tiny leaves will appear in the pots approximately the same time in the growing season that the mature bulbs would come into leaf. It is sometimes the case that small bulbs are produced even though there is no top growth, so check any pot before discarding the contents.
- During the growing season the pots need to be kept just moist, but avoid watering them if the weather is very cold or frosty.
- I find feeding them with a half strength tomato food at every other watering to be beneficial.
- After the leaves have withered in summer the small bulbs can either be planted into the garden or re-potted into clean pots with fresh compost, the same mix as before plus a pinch of blood, fish and bone, and grown on under the protection of a greenhouse.
- It may take between two to four years for the bulbs to reach flowering size, with a further growing year to reach their full potential.
The photos show the size of the bulbs after one growing season.
Colin Mason, the well known galanthus expert, offers to propagate bulbs by twin-scaling. A very useful service for anyone who has a cherished plant, which they would like to increase, but do not want to attempt this method of propagation themselves.