We are now only a couple of weeks away from the spring equinox. The significance of this for gardeners is that even if we have an unusually cold spell of weather like this week with snow being forecast, the daylight hours are nonetheless steadily increasing and with them the pace of plant growth. More daylight hours means more time when plants can photosynthesise, make sugars and grow.
It is interesting to consider that in our particular geographical location, London, that by midwinter 21st December, we have around 8 hours daylight and 16 hours darkness. By the spring equinox on 20th March this has shifted to 12 hours daylight and 12 hours darkness, and then by the midsummer solstice 21st June we have around 16 hours of daylight and 8 hours of darkness. Not surprisingly these seasonal variations affect plant growth.
If we set this in a broader context of gardening and food growing in other parts of the world, different patterns emerge depending on the garden’s latitude (its north-south location in relation to the equator). If you were gardening in a land lying across the equator such as Brazil or Kenya you would have very little seasonal variation in daylight hours, with 12 hours daylight to 12 hours night time all year round. However if you were gardening up near the poles, say in the northern part of Norway or Canada you would have something more akin to a two season year with the sun not setting around mid summer, ‘the land of the midnight sun’, and the sun not rising around mid winter.
Not surprisingly these seasonal variations in light levels are something that affects food growing practices around the world. Not only this but some
plants can ‘read’ these seasonal variations and map their patterns of growth and flowering against the lengthening or shortening of day light hours. Gardeners call this photoperiodism.
