The common snowdrop, Galanthus nivalis, is one of our tiniest spring bulbs. Its appearance in January fills me with delight; here comes spring. They are pretty adaptable, tough little things, but really thrive on dampish, heavy-ish clay soils. Too much sunlight makes the flowers go over fairly quickly, so they tend to last longer in flower in a shady spot. If you can recreate their ideal habitat, at a hedgerow bottom, with plenty of leaf mould, they will romp away and reward you with their prolific naturalisation.
Snowdrops increase naturally by forming offsets or bulblets from the main, parent bulb each season. Left undisturbed, snowdrops will double in quantity each year, (under ideal conditions of course.) So your investment of 100 snowdrop bulbs this spring increases thus:
year 1 = 100 bulbs
year 2 = 200 bulbs
year 3 = 400 bulbs
year 4 = 800 bulbs
year 5 = 1600 bulbs
year 6 = 3200 bulbs (just in time for the 2012 Olympics)
Not a bad investment. Left to their own devices clumps of snowdrops may become overcrowded and take longer to develop to flowering size. Especially if left in a bucket for a year... After the flowers have gone over, and when the leaves are dropping yellow at the tips, lift the clump carefully and separate the bulbs. Separate the parent bulbs from the offsets, and replant the larger bulbs individually about 2" apart. Scatter the offsets amongst the replanted clump, again about 2" apart and the same depth as the parent bulb. This level (in the parent) is indicated by the colour change between the green top-growth and the chlorotic, yellow-green leaf bases that were underground. Water well in, and lightly feed with a high-potash, low-nitrogen dressing.