You know it's fall when...

The sun no longer wakes you at 5:30 a.m.

3 p.m. in the afternoon feels like it's about time to make dinner.

Most of the summer bloomers have died back and asters take over the garden.

The milkweed pods have exploded their seed, and the last clutch of milkweed bugs hurry to mature so they can fly away.

You see scenes like this on your walks through the "backyard".

Did you ever wonder what gives the leaves of some trees such spectalular color in the fall? Yes, it's those other pigments (i.e., light harvesting complexes) in the leaves that are unmasked once the chlorophyll has been ripped apart and its nitrogen transported back to the roots for winter storage. The yellow (xanthophylls) and the orange (carotenes) pigments and combinations of those two make the birch and aspen leaves yellow, some maples orange, and oaks orangy-brown.

But what makes sugar maples so red? It's not a pigment. It's the production of an anti-oxidant compound called anthocyanin, formed by excess sugar attached to a protein. The sugars are formed during photosynthesis on warm days, but fail to be transported out of the leaves during cool nights. So, fall temperatures and reduced daylength contribute directly to the glorious colors produced.



By the way, anthocyanins are also produced in ripening fruit, to signal that its ready to eat. Depending on pH and concentration of anthocynanins in the skin or flesh of the fruit, the resultant color may be deep red, blue, purple, or even black.