This seems to be a difficult to control plant. If I know what it is, maybe I can find the best way to deal with it. Many thanks.

Overall yellowing from older leaves, and purple colored stem could be from a certain nutrient deficiency too. Sorry I have no idea of the identification.

Try on Acer negundo- bozelder maple. Opposite compound leaves, coming up from the maple seeds that blow around, there would be a big one somewhere nearby.
Maples can make plenty of seedlings, anywhere they can blow. If they start in a crack they can be hard to pull. Cut them off, they may grow new shoots..

bunnydefluff said:Overall yellowing from older leaves, and purple colored stem could be from a certain nutrient deficiency too. Sorry I have no idea of the identification.

Its going dormant.

I believe the Box Elder ID is correct though.

bunnydefluff said:Overall yellowing from older leaves, and purple colored stem could be from a certain nutrient deficiency too. Sorry I have no idea of the identification.

In colder climates it is very common for plants/shrub/trees to go yellow in the autumn prior to the leaves dropping off.
It may be a very healthy mystery plant...just deciduous.

sallyg said:Try on Acer negundo- bozelder maple. Opposite compound leaves, coming up from the maple seeds that blow around, there would be a big one somewhere nearby.
Maples can make plenty of seedlings, anywhere they can blow. If they start in a crack they can be hard to pull. Cut them off, they may grow new shoots..

In UK Acer negundo is not very common...bit special.
Certainly would not expect to find seedling.
If sold in a garden centre it would be as a proper tree with a trunk.

I have struggled to see the pics clearly but cannot make out clear detail.
To compare I attach a couple of pics to show the leaves of Acer negundo Kelly Gold

I tend to believe it to be Box Elder too, but in the picture it is hard to see the leaves and their arrangement clearly. It is a common tree here.

I first thought of Plearandra but nope, it's not that one. It looks so familiar, like I know I've seen it somewhere before but I wasn't thinking of Acer species; I was thinking of something that is often sold as a houseplant. Is it something you acquired as a container plant or something that grows in the landscape in your area?

Thank you Silversurfer and Daisy for telling me the going dormant mechanism.

You're welcome! A little more explanation: In fall deciduous trees prepare for winter by sending as many nutrients as possible to the roots for safe keeping before dropping their leaves. The first thing to happen is the chlorophyll in the leaves is broken down so the leaves lose their green color. As other chemical changes occur, more colors show and the cool nights and warm days of fall enhance the effect. Deciduous trees are first class recyclers and the resulting show is sometimes awesome.

I walk by a little Box Elder tree about once a week. It has turned a really pretty pastel pink with a hint of yellow. My dogwood is red and purple.

I agree with the box elder ID. Thanks very much to all for your input!