Chipping and twin scaling
Twin scaling and chipping are techniques to improve the rate of snowdrop propagation, usually performed by experts or experienced amateurs. With care, anyone might perform the technique however.
As an example of an exceptional rate of increase made possible by twin scaling: Alan Street from Avon Bulbs found the first bulb of the cultivar ‘Midas’ in 2011 (1). This was a particularly large bulb, from which he managed to grow 20 new bulbs within 2 years. Chipping these 20 bulbs yielded another 300 bulbs after 2 more years, which were chipped again to allow the bulbs to go on sale in large numbers in 2017.
Twin scaling involves cutting a bulb into multiple sections. As a snowdrop bulb consists of a base, which is actually a modified stem, and a scale, which are actually modified leaves, this is similar to allowing a new shoot to emerge from a tree axil.
It is important to perform the technique sterilly. To this end, a scalpel and tweezers can be sterilized in a flame, such as those of a camping stove. Plastic gloves can be used. When wearing the gloves, they can be carefully sterilized in a solution of 70% alcohol (for example bio-ethanol for the barbecue mixed with normal tap water). A chopping surface can also be sterilized with 70% alcohol or by heat-sterilizing it before use.
Each bulb segment needs to be large enough to provide enough energy/starch for a new bulblet to grow, so take care not to cut segments too small. Depending on the bulb size, 4 to 32 twin scales might be achieved. Chipping involves making the cuttings even smaller, but will leave each bulblet with less starting energy/starch.
Materials and methods
– plastic gloves
– glass or plastic container, e.g. a shot glass
– plastic bags
– Camping stove
– 70% alcohol
– systemic fungicide of preference
Bulbs should be take out of the soil after going dormant in Mai-June, depending on the species and location. Carefully clean the bulb by removing the tunic and roots by hand, washing in water with soap and rinsing of with normal tap water. Presterilize the bulbs in 70% alcohol while shaking them in a glass container during 1 minute.
Sterilize tools in the flame. The cutting surface and gloves can be sterilized with 70% alcohol. Prepare a working solution of your fungicide of choice, as per manufacturer’s instructions.
Take the cleaned bulbs to the cutting surface, and cut away the basal plate until white tissue can be seen (discard this lower part of the bulb). This is also the time to remove any damaged, unhealthy or discoloured parts of the bulb. Then cut off the top of the bulb. Don’t throw the top away, it can also grow bulblets! Continue to cut the remainder of the bulb vertically into 4 or more equal sized segments, taking care to include a bit of the basal plate with each segment. For twin scaling, make sure each segment has at least 2 bulb scales. Gather these segments and place them into the fungicide working solution during 15-30 minutes.
In the mean time, add and mix about 80ml of (pre-)heat-sterilized water to 1L of vermiculite or perlite. Add the vermiculite to the plastic bags, due to the nature of manufacturing of plastic bags, these should be sterile already.
After the 15-30 minute fungicide treatment, wash the twin scales once more in 70% alcohol over 1 Minute, then add the twin scales to the plastic bag and seal it. Store the bag (with a label of the cultivar) at a dark location with a temperature of approximately 18° Celcius (64,4° Fahrenheit). Bulblet growth should commence after 4-8 weeks, depending on the variety. If fungal infection occurs, a re-treatment can be attempted with fungicide. After at least 3 months, in September/October, twin scales can be planted (also see the guide on growing in pots). Sections without bulblets should be discarded. Pay attention: some bulblets will only produce leaves in the second year.
1. Val Bourne. Hot on the trail of those elusive gold snowdrops. 27th of january 2017.