I can't think of a single tree that will stop growing at 5-6 feet high. The questions are, how small a tree are you prepared to call a tree, and how often are you prepared to replace it?

I think an acer which you can successfully keep to a size you like would be a good choice. A member of GOY, Four Seasons, has a wonderful garden which featured on a TV programme last autumn, does this with great success. Amelanchier Canadensis is a smallish tree. How big is your front garden as that will be a consideration. Bushes and trees often grow to the size of the growing area. If you planted something with a root restricter in place that might help.

I planted two amelanchiers about 20 months ago. One is now 4 feet high, and the other is over 5 feet. If you chose one of those you would need to prune it to keep it to shrub size.

I note you say you want to plant in the centre of the lawn setting it in a corner might allow you to have a greater choice and make the garden look better than putting it in the middle. You could underplant with spring bulbs or primroses if you choose a deciduous (loses its leaves for the winter) tree to lengthen the period of interest. If there is something of interest for longer it will be less boring.

Hi all, thank you for your suggestions. I will be visiting the garden centre next weekend so will have a look at the ones mentioned. Scotsgran, i like your idea of underplanting, that would add some more colour to my boring lawn! Thanks again

Could I also suggest some of the sorbus. We have S. cashmeriana which is still only just 2 metres after around 15 years.

Magnolia stellata is a shrub more than a tree but grows to a size that might suit you.

To grow any of the acers, you would need to improve the soil to make it more moisture retentive, but they will be quite happy with the shade. Take a look at acer palmatum dissectum varieties as most of these stay small and can be underplanted with early spring bulbs

Acers won't survive in very dry soil so if you plant one you will need to add a lot of moisture holding material first - even gel crystals will make a difference, and remember to keep it watered in dry spells. I think magnolia stellata is a nice idea. Mine is underplanted with blue anemone blanda. The show doesn't last long but it lovely while it lasts. But you won't have year round interest with it, so perhaps its not the best choice for your garden. I reckon Moon grower might have the best answer.

I'm a bit puzzled Sorbus cashmeriana is said to grow to 30ft with a 30ft spread. That would be too big close to a house. It does depend on the growing medium. Can you keep it smaller by trimming it to size? I think it is a wonderful tree with its white berries. A golden yew or a holly which can be trimmed to size might be an option as long as you buy a female holly. I think we need to know the size of this front garden and how dry is the soil? Digging out a hole 2 - 3 times the root ball size and filling with the right planting medium will allow the tree to settle before its roots get to the original soil in the area around. Keep in mind that general purpose compost unless it specifically says it has no peat is still almost entirely peat and is a good option when trying to add moisture retaining material. All new shrubs and trees need to be watered copiously for the first season. It is a good idea when planting a new plant to make a little ridge about a foot out from and circling the trunk and fill that with water every day and allow it to seep down to the roots.