Spring is in the Air

Today is the first day of spring. At least it is the first day meteorologically, which is based upon the annual temperature cycle and fixed on 1st March, in order to have a clear date demarcating the seasons and to keep records for observation and statistics. The astronomical first day of spring is actually on 20th March this year, and is determined by the Earth’s orbit in relation to the sun. Either way, it feels like life is beginning to break through the ground, as many annual, biannual and perennial plants start to put in an appearance in parks and gardens, raising everyone’s spirits.

The timing of the appearance of plants in spring, along with other life-cycle events, such as leaf bud burst, flowering, and fruiting, is known as phenology. These events are the result of responses to environmental conditions such as variations in temperature. These are what give us in temperate climate, the seasons that we recognise, and enjoy for all their differences.

But signs of phenological change have been noticeable in the deviation of plants from their typical growth patterns, in parallel with increasing temperatures, over the past four decades. The timing of leaf appearance and flowering have generally advanced by several weeks, equal to 4-5 days per 1º Celsius rise in temperature. In Britain it has been noted that annual plants are flowering before perennials, and insect pollinated plants before wind pollinated ones.

The changing climate for gardeners isn’t just a matter of things getting warmer, and therefore using plants from hotter regions in gardens and parks. This is the message too often put out there by gardening organisations, and it is misleadingly simplistic. Because it ignores the fact that there will be ecological consequences produced by asynchronous events. It is likely to cause competitive discrepancies between different plant species within plant communities, as well as disrupting the cycles of mutual interactions between plants, insects and animals in ecosystems.

These things will have knock-on effects for us, and other species, in many different ways. We just don’t know what many of them may be at the moment. Obviously species adapt to changes in circumstances, that’s how evolution works, but the rate of change happening at the moment is unprecedented, and therefore worrying. We are already seeing many species of plants and animals going extinct.

So while the start of spring is surely something to celebrate, we need to be mindful about doing all that we can to address the climate and extinction crises we are facing. As gardeners, plants are our allies, so let’s learn from what they are doing, and what they are telling us about how the world is changing.