Is it a shrub, is it a tree, no it's …

[french frank]

Trees can be weeds, which are after all simply plants in the wrong place. I still think it could be a birch seedling, and they do grow quickly. I've just chopped one down that had outgrown its welcome(and the space available); It was no more than 3 years old and was getting on for 5' high and 3' across, the 'trunk' was about 1" diameter at its thickest, just above the soil.

The birch theory was attractive because of the recently dead one, a mere 12ft away next door, casting its last desperate seed to perpetuate life :-). But it is very slender.

[Serial_Apologist]

The birch theory was attractive because of the recently dead one, a mere 12ft away next door, casting its last desperate seed to perpetuate life :-). But it is very slender.

If it is a tree, it will only grow to a certain size if kept in a plant pot, owing to root restriction. Plant it out and watch it flourish - but first get some advice on what it actually is, ff. Take it down the local nursery or garden centre: someone there should know.

[greenilex]

Kalinka perhaps?

[oddoneout]

The birch theory was attractive because of the recently dead one, a mere 12ft away next door, casting its last desperate seed to perpetuate life :-). But it is very slender.

Even fully grown birch trees are not chunky so slenderness, in itself, does not signify, but seedling and very young trees are in any case slender. Bulking out comes with increasing maturity. In the course of my garden volunteering I often have to remove seedling oaks(result of jay activity) and although the leaves may be not too dissimilar in size and form from those on an adult tree, even after several years growth the stems won't be more than about a quarter inch thick -the roots are often bigger than the top growth at that stage though so removal of such a seemingly insubstantial thing can be more of a job than at first thought, especially if the aim is to replant.
I think the survival instinct is to grow upwards as quickly as possible to gain maximum light.

[Serial_Apologist]

Even fully grown birch trees are not chunky so slenderness, in itself, does not signify, but seedling and very young trees are in any case slender. Bulking out comes with increasing maturity. In the course of my garden volunteering I often have to remove seedling oaks(result of jay activity) and although the leaves may be not too dissimilar in size and form from those on an adult tree, even after several years growth the stems won't be more than about a quarter inch thick -the roots are often bigger than the top growth at that stage though so removal of such a seemingly insubstantial thing can be more of a job than at first thought, especially if the aim is to replant.
I think the survival instinct is to grow upwards as quickly as possible to gain maximum light.

I found an oak sapling popping up in a box container the other day, and decided to pull it up. Fortunately the soil was loose and the sapling came out in its entirety. I was surprised to discover that although it had only grown to about 6" above soil level, the roots were a foot long. The small girl from next door was fascinated to see the acorn still attached, halfway down.

[french frank]

even after several years growth the stems won't be more than about a quarter inch thick

That sent me scuttling for my Vernier gauge. The stem is 4.5mm thick just above the bottom most branch (now removed).

There are birches with cordate leaves, but I think these are too elongated for a silver birch - which is what my neighbour is/was. It will certainly need to be repotted again soon. Currently attempting thaumaturgy on a potentilla cutting.

[Serial_Apologist]

That sent me scuttling for my Vernier gauge. The stem is 4.5mm thick just above the bottom most branch (now removed).

There are birches with cordate leaves, but I think these are too elongated for a silver birch - which is what my neighbour is/was. It will certainly need to be repotted again soon. Currently attempting thaumaturgy on a potentilla cutting.

I reckon you're rather enjoying the mystery of not knowing what it is, ff.

[french frank]

I reckon you're rather enjoying the mystery of not knowing what it is, ff.

But if it plans on growing to 20ft tall I won't have room for it in the back yard, which is about 15' x 15'.

[oddoneout]

But if it plans on growing to 20ft tall I won't have room for it in the back yard, which is about 15' x 15'.

Well, that rather depends on whether you want anything else in the yard..... However,growing in a container and judicious pruning can postpone the inevitable, and if it is a birch of some kind then it is not a dense shade maker. I currently have a winter flowering cherry in a large tub on my patio; it's awaiting(3 years now poor thing!) its permanent position becoming available, but even if I only had the 14' x 16' patio as my outside space I would still keep it as it offers so much, not least height which helps to open up a cramped space.

[doversoul1]

Could it be this?

https://en.wikipedia.org/wiki/Amaranthus_palmeri

I was given a couple of seedlings which, I was told, would make lovely salad leaves. I planted them in a flower bed and they are now looking like small trees.

[oddoneout]

Could it be this?

https://en.wikipedia.org/wiki/Amaranthus_palmeri

I was given a couple of seedlings which, I was told, would make lovely salad leaves. I planted them in a flower bed and they are now looking like small trees.

No! Various forms of amaranthus are indeed useful culinary plants, and some can make sizable plants - I grew some called Magentaspreen which got to 5 or 6 foot with pretty magenta (would you believe!) flushed crystalline coated leaves - but trees they are not.

[gradus]

The later photo of the plant up-thread looks a bit like an abutilon.

[french frank]

I don't think it's either amaranthus or abutilon - the leaves are too hairy. A Woodland Trust man suggested, from the photos, a Downy birch which is a 'pioneer species'. But failing that, 'a non-native shrub'

It is now 26" tall and its habit certainly looks 'tree-like', slender branches coming off the main stalk/trunk rather than a bush. I don't suppose I'll know until it produces a flower and fruit.

[gradus]

I don't think it's either amaranthus or abutilon - the leaves are too hairy. A Woodland Trust man suggested, from the photos, a Downy birch which is a 'pioneer species'. But failing that, 'a non-native shrub'

It is now 26" tall and its habit certainly looks 'tree-like', slender branches coming off the main stalk/trunk rather than a bush. I don't suppose I'll know until it produces a flower and fruit.

You're probably right but the picture of an abutilon grandiflorum reminded me of your original photo: httpshttps://www.google.co.uk/search?q=abutilon&source=lnms&tbm=isch&sa=X&ved=0a hUKEwi9p7na1O_cAhUpJsAKHaqXAnIQ_AUICigB&biw=1536&b ih=710#imgrc=cG3wYQ9oSQjHbM:&spf=1534356849950

[french frank]

You're probably right but the picture of an abutilon grandiflorum reminded me of your original photo: httpshttps://www.google.co.uk/search?q=abutilon&source=lnms&tbm=isch&sa=X&ved=0a hUKEwi9p7na1O_cAhUpJsAKHaqXAnIQ_AUICigB&biw=1536&b ih=710#imgrc=cG3wYQ9oSQjHbM:&spf=1534356849950

I shall be very happy if it gets flowers like that! I really don't want a tree that will grow to 50 feet in my back yard. This is 'im now: