This week as part of the RHS's Grow at Home this Autumn Campaign,
We're celebrating autumn foliage. We'll be sharing tips on the plants to choose for your gardens,
how to grow them at home and of course highlights from the five RHS Gardens. It's early in the season and
a lot of the colour from trees and shrubs is still to come, but did you ever wonder where
that colour comes from? Well thankfully science has the answer and it's a lot to do with the British
weather. Well these leaves may look green but inside the fiery colours of autumn are hidden.
That's because they're masked by the green pigment, chlorophyll. Chlorophyll is the one that makes
energy for the plant from the sunshine in the process of photosynthesis. At this time of year
deciduous trees and shrubs start to shed their leaves in preparation for winter. The chlorophyll
is broken down and reabsorbed as a plant nutrient. As this happens, the colours underneath are revealed.
Carotenoids are both orange and yellow and they had a role in photosynthesis.
And ye, you guessed it, it also makes carrots orange. The second pigment is
anthocyanin and that's purple and reds. They were both products of photosynthesis.
These also make red wine red and blueberries blue, but it's pretty slim pickings at this time of year.
Different concentrations of these pigments result in different dual light colours in
autumn, but the intensity is very much due to the weather conditions take anthocyanins for
an example, high light levels from sunshine mean that things like apples go red and you can see
that red is on the top and when you look at the fruits they've got a sunny side and a dark side.
Low but not freezing temperatures increase the levels of anthocyanins
and inhibit sugars being taken out of the leaves and these are converted into pigment.
And finally, low rainfall is thought to make for higher levels of anthocyanins,
as the surplus sugars are not converted into pigments.
Well the weather in Britain is generally dull overcast and cool so hardly ideal for the best
displays, unlike the conditions that you get in New England in America where they get amazing
autumn colour. Climate change too is making us wonder how will autumn displays change,
we know we're going to get wetter winters and drier summers but it's likely the variable
conditions will make our autumns even more variable in terms of their autumn colour.
So the ideal conditions for dazzling autumn displays
are dry sunny autumn days with no wind and cool nights.
Well of course gardeners aren't going to let the weather stop them and certainly when you come to
an RHS Garden you'll see some amazing autumn colour. At home though if you want more autumn
color it's about choosing the right plants and putting them in a sunny spot. This is one of my
first and favourite choices it's a little cherry tree called prunus 'Kojo-no-mai', bright orange in the
autumn, just coming now, and of course in spring masses flowers so it's a two season wonder.
Euonymus europaeus or the spindle bush is a great shrub for small gardens.
It has this fantastic red foliage, pinkish hue. and you get orange berries as well.
My final choice is a hydrangea. Most will colour up pretty well in autumn but this one is really
good, it's the oak-leaved hydrangea, hence the shape and it's Hydrangea quercifolia.
This one's quite a big specimen, but you could equally keep it down to about 1.2 meters or so
and so ideal for a smaller garden. It'll even colour up quite well in shade, this one too.
Well that's just three options. Of course there's plenty more
inspiration on the RHS website and if you go to the RHS Plants website
you can buy them too. Well this autumn we hope you enjoy growing at home, whatever the weather.