h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I want a tree in my garden, specification as follows (apologies for the formality but I'm an engineer by trade):

Dimensions: Should top out at about 10-12 feet, or be capable of being cropped to this height.
Ancillaries: don't want any rubbish dropped from it (it will overhang a small pond), so no blossom or fruit and preferably evergreen.
Shape: mushroom-shaped top end, to provide semi-shade to plants and pond below, i.e. not a conifer.
Environment: good soil, a bit limey, full sun (Southern England), fairly sheltered spot.

Any gardeners out there? Ideas would be very welcome.
TIA

dunno, but as an engineer, with those exating specs, I'm sure oyu could knock something up wwith a bit of 2x4 and superglue some leaves on it.

Mmm, not a bad idea, but I doubt it would meet all the functional requirements.

One thing you should also consider is how long you want to wait before the tree or shrub reaches full height, and how long you want it to last at that height.

Fast-growing trees tend to grow tall. A little acer that might reach 10-12 feet max might take 15 years to reach that height.

That's about the total of my gardening knowledge.

Good point. I guess the idea of a tree that grows to 10 feet in a year and then stops is pretty unrealistic . Acers are nice, I could always buy a half-grown one.

My parents have an Acer in a big pot in the back garden - I think it's grown upwards about 15cm in a year, and it was just over 1.25m high from the base of the pot when they bought it from B&Q. Hope that's some help on the Acer front I think it's deciduous, so it may not be good to put over a pond.

Apart from that, I'm not a gardener at all so I can't say anything else . The only bit of gardening I can reliably do is hack plants to bits!

Oops - forgot to add, a medium conifer might be an idea. (NOT a Leylandii ) Well, the dwarf ones seem to stop at a certain height, anyway.