I enjoy gardens but admit to being clueless about them so I had to look up the word espalier, used in the description of Abbey-Mill Farm in Chapter 23. I did have an idea about apple trees. (;D) The obliging Dr. Johnson says:

Espalier: A tree planted and cut so as to join others. (A Dictionary of the English Language by Samuel Johnson, John Walker, Robert S. Jameson, 1828)

From the Espalier page at Wikipedia: An espalier collects almost as much sunlight as a regular tree, yet has far less mass. This makes them ideal not only for decorative purposes, but also for gardens in which space is limited. They may also be planted next to a wall, which can reflect more sunlight and retain heat overnight, or be planted so that they are facing south (or North South of the equator) and absorb maximum sunlight. These two facts allow an espalier to succeed in cooler climates, where a non-espaliered tree of the same variety would fail. They also mature fruit more quickly. (http://en.wikipedia.org/wiki/Espalier)

The Espalier page at Wikipedia has two nice photos of espaliered fruit trees (address above) and should it please you, a photo of an espaliered apple-tree taken at Barrington Court in Somerset can be seen at: http://en.wikipedia.org/wiki/Image:Espalieredpear.jpg

(The address says pear but it looks like an apple tree to me—I leave it to you to decide. LoL!)

She went, however; and when they reached the farm, and she was to be put down, at the end of the broad, neat gravel-walk, which led between espalier apple-trees to the front door, the sight of every thing which had given her so much pleasure the autumn before, was beginning to revive a little local agitation…

The quarter of an hour brought her punctually to the white gate again; and Miss Smith receiving her summons, was with her without delay, and unattended by any alarming young man. She came solitarily down the gravel walk -- a Miss Martin just appearing at the door, and parting with her seemingly with ceremonious civility. (Chapter 23)

The entrance of Abbey-Mill Farm sounds charming—entering through a white gate to traverse a broad neat gravel-walk between the espalier apple-trees to the front door paints a delightful picture in my mind. I note that it is described as neat. The neatness I think reflects the Martins attentiveness to their home but it seems to me espalier apple-trees are not only sensible but also ornamental. Abbey-Mill Farm with its two parlors and handsome twelve-person summer house in the garden for summer tea parties does not seem to be the utilitarian home of an awkward and abrupt farmer whose future person, according to Emma in Chapter 4 is quite grim:

"But there may be pretty good guessing. He will be a completely gross, vulgar farmer -- totally inattentive to appearances, and thinking of nothing but profit and loss." (Chapter 4)