I have a smallish garden with a hard-standing that will become a patio in the far left corner. I want to place 2 trees, one in front of the standing, one to the right (as you look at it from the house) so you'll look through the 2-3m gap formed by these trees onto the patio.
Now, should I get two similar appearance trees (if not identical) or go for 2 quite different ones?
Naturally both must have an upright habit and moderate overall height.
We have been thinking: Silver birch, white trunk variety Silver birch, red trunk Mountain ash ..for examples
I'd go for different trees, so that their periods of interest aren't exactly the same.
We have a silver birch, a yellow berried sorbus (TBH I wish now we'd got normal red mountain ash), and have recently got a whitebeam, which is also in the sorbus family but looks quite different, larger silvery green leaves - as the guy in the nursery who advised us said, its a pretty tree.
If I was getting two trees at the same time I'd consider fruit trees too - many aren't self-fertile so rarely a good idea to get just one.
Mountain ash is rowan. Its a small tree versus an oak or beech. Silver birch is probably about 50% bigger than rowan, but some of the red (or lovely chestnut) trunked birches are usually quite a bit smaller.
I'm rubbish at imagining what 6x12m looks like so don't know if they are the right scale but presumably the OP has/will look at mature trees of the types mentioned.
Cherry can be nice but they tend to be a bit wide for their height.
A lot of people with kids won't want laburnum because of the poisonous seeds - not that I've ever heard of a kid eating them.
One other thing to take into consideration - ask advice at the nursery - is what the roots are like. Some trees really shouldn't be planted near houses, and so presumably could affect the patio. We were told the whitebeam had non-spreading roots so was good.
I'd get two trees in completely different colours, and plant the taller one at the back. So if you're having a silver birch, then maybe get a red japanese maple, or a yellowy ginkgo biloba (not sure how big they get eventually but very pretty), and I'd also put some contrasting grasses underneath in blue/green, black, yellow/green etc, preferably with interesting seedheads.
I've got 5 trees along the back of my small garden for privacy and they are all different. We also have a Sorbus aria - very pretty and upright and I also have several cherries and a Robinia which is very attractive. All are suitable trees for a small garden and according to the garden centre have roots that are not too invasive.