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  • The Low Down

Tree sign language: early fall colour

Deciduous trees, ice-cream stands and marinas close each fall for the same reason: as daylight dwindles and cold creeps in, they become less profitable. When their income dips below the cost of doing business, a wise proprietor turns out the lights and locks the doors until spring.

Some holdouts stay open longer — perhaps they have a better location. But the establishments which just scrape by at the height of summer will close shop at the first whiff of autumn.

Trees whose leaves show colour ahead of their same-species peers are doing so because they are barely breaking even. The solar-powered sugar factories we call trees are prudent savers and meticulous accountants. As a rule, they don’t live beyond their means. In addition to sunlight, they need carbon dioxide, enough water and nutrients, and their roots need oxygen.

Each spring, deciduous trees withdraw money from the bank – starches out of trunk and root tissue – and invest in a solar array, known as leaves. After replenishing its starch-bank for the cost of making leaves, tree expenses i