Thursday, 29 September 2011

Indian summer or a double dip spring?


So is it the summer we missed in August, or a second spring? Either way Kew Gardens get another flush of flowers as well as spectacular autumn colours.

If you visit Wakehurst Place (pictured above) today, you'll get both at the same time! Head of Wakehurst Place, Andy Jackson, is particularly impressed by Viburnum plicatum ‘Mariesii’ which is in the middle of a second flowering flush while its leaves turn red.

It seems that the cool dry August (summer) followed by an unusually warm late September (autumn) has 'tricked' some plants into thinking it's time to flower again.

At Kew you can enjoy these unexpected flowers now, with peak autumn colour in about two or three weeks. That said, there is some brilliant red in my backyard and Ash trees in the Gardens proper doing their autumn thing.

No one is quite sure why things are different in Kew and Wakehurst, but we've had a slightly milder August here near London. The cooler evenings at Wakehurst may have brought autumn forward, running it into this second spring.

While there is some science in all this hypothesising, there is also a little autumn leaf reading. Do we really have four seasons (or is it five?) and are they changing with climate change? 

We know a little about autumn leaves and what makes them colourful. Good sunshine and cool nights means the green chlorophyll breaks down more quickly and the yellow and orange colours left in the leaves are more intense.
More of this hot dry weather concentrates the sugars in the leaves leading to greater production of red pigments – as sunscreen or to scare off insects while the tree withdraws all the good stuff back into the stem (see the link in paragraph above...).

Is there a down side to this gorgeous weather? Well horticultural staff at Kew Gardens just finished removing the cacti and succulents from the roundabout bed at the northern end of the Broad Walk. These plants would have a loved a few days of our Indian summer or even a little more spring before returning to our glasshouses for the winter.  

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