I have one of these, planted about 2 years ago, so still small, say
18". It is still very green. A friend who lives on high ground in
mid-Cornwall also has one, long established, a magnificent example of
why they're called 'Burning Bush'.

What triggers the colour change before leaf-fall? Is it cold weather
(we've not had any frost here yet, but they have in mid-Cornwall I
believe), or is the colour effected by age of the plant or soil
chemistry or type (pH, light sandy or heavy clay etc. They are on wet
acid soil tending to boggy in places)? Are there selected cultivars
that are better than the standard type for Autumn colour?

--
Chris

Gardening in West Cornwall, very mild, sheltered
from the West, but open to the North and East.

On 23/10/2021 09:47, Chris Hogg wrote:
> I have one of these, planted about 2 years ago, so still small, say
> 18". It is still very green. A friend who lives on high ground in
> mid-Cornwall also has one, long established, a magnificent example of
> why they're called 'Burning Bush'.
>
> What triggers the colour change before leaf-fall? Is it cold weather
> (we've not had any frost here yet, but they have in mid-Cornwall I
> believe), or is the colour effected by age of the plant or soil
> chemistry or type (pH, light sandy or heavy clay etc. They are on wet
> acid soil tending to boggy in places)? Are there selected cultivars
> that are better than the standard type for Autumn colour?

You've probably got Euonymus alatus 'Compactus', as that seems to be the
form which I've seen in most garden centres I've been in in the last
couple of years.

Mine started changing colour a couple of weeks ago, but it's generally a
slow process. I'm sure it's triggered by temperature, and possibly day
length. We had a near frost here a couple of nights ago (min 2.4°C), but
as yet it doesn't seem to have accelerated the colour change. I doubt
there's any input from soil chemistry or type.

--

Jeff

On 23/10/2021 12:16, Jeff Layman wrote:
> On 23/10/2021 09:47, Chris Hogg wrote:
>> I have one of these, planted about 2 years ago, so still small, say
>> 18". It is still very green. A friend who lives on high ground in
>> mid-Cornwall also has one, long established, a magnificent example of
>> why they're called 'Burning Bush'.
>>
>> What triggers the colour change before leaf-fall? Is it cold weather
>> (we've not had any frost here yet, but they have in mid-Cornwall I
>> believe), or is the colour effected by age of the plant or soil
>> chemistry or type (pH, light sandy or heavy clay etc. They are on wet
>> acid soil tending to boggy in places)? Are there selected cultivars
>> that are better than the standard type for Autumn colour?

I believe it is triggered on temperature and even for the same species
different cultivars can have radically different thresholds. One of my
blueberry bushes has been bright red for nearly a month now but the
other is still green. They are next to each other an in identical pots
and soil. The more sensitive one has slightly larger berries and fruits
ripen sooner on it. But they have very different thresholds for turning.

It has been a good year for my Japanese acers. A cool dry Autumn without
strong winds so far means they are brilliant red (or yellow) now.

> You've probably got Euonymus alatus 'Compactus', as that seems to be the
> form which I've seen in most garden centres I've been in in the last
> couple of years.
>
> Mine started changing colour a couple of weeks ago, but it's generally a
> slow process. I'm sure it's triggered by temperature, and possibly day
> length. We had a near frost here a couple of nights ago (min 2.4°C), but
> as yet it doesn't seem to have accelerated the colour change. I doubt
> there's any input from soil chemistry or type.

Most of them are temperature based (not necessarily a frost but some
threshold temperature that varies even with specific cultivar).
Reabsorption of the chlorophyll ready for winter leaves the other
pigments and leftovers visible in the leaves.

--
Regards,
Martin Brown

On 23/10/2021 13:28, Martin Brown wrote:

> It has been a good year for my Japanese acers. A cool dry Autumn without
> strong winds so far means they are brilliant red (or yellow) now.

Mine have hardly changed. There is a bit of colour on 'Senkaki', and
some of the others have a few leaves which have started to colour, but
most haven't.

The best autumn colour by far (it's now lost most of its leaves), was on
a Crepe Myrtle - Lagerstroemia indica 'Braise d'Été'. Unfortunately it
didn't flower this year as August was too cool. Looks like I'm also
going to miss out on the Hibiscus (moscheutos) 'Galaxy' F1 flowers this
year. The buds have yet to open and the leaves have already turned
yellow and dropped.

--

Jeff