Many plants actually depend on a cold period of some length and intensity before they will grow. The reduced temperatures are a trigger for their growth mechanisms. The early spring bulbs are classic examples, such as snowdrops, crocuses, daffodils and - best of all from my point of view - wild garlic.
In fact, some plants won’t grow at all if winter temperatures aren’t low enough – it’s very difficult to get winter aconite to flourish in London, simply because it’s too warm in winter.
Nonetheless, there will always be a few plants in flower through the depths of winter because they are:
- normally in flower at that time
- growing in a heat island like London, or
- reflecting the borderline effects of climate change.
Some plants and insects are now on show through all twelve months, including the white dead-nettle, Lamium album. Our largest native bumblebee, the buff-tailed bumblebee, Bombus terrestris, now flies all year – I saw one last January!