By. A. D., New-York

Dear Sir - The subject of live hedges is an interesting one to the farmer in some parts of the country, especially in sections where both stone and timber are comparatively scarce. It seems to be pretty generally conceded now, that the English Hawthorn, with which the farms are almost entirely fenced in Great Britain, is not adapted to this climate, so that we must look around for a substitute. In Delaware, I have observed that a native thorn called the New Castle, has been considerably employed for hedges. It makes a good and substantial fence, but I noticed on a recent visit to that state, that the use of it did not spread much among the farmers. On inquiring the reason, I was told that the plant was very liable to injury by the borer and an insect, and on the whole had not given satisfaction as a farm fence.

I have seen a hedge of the Osage Orange upon the boundary of a garden near Philadelphia. It is five feet high, well clipped, and presents a very handsome appearance when covered with its rich glossy leaves. Being very thorny, it makes a thorough barrier against man or beast. I see by the papers that this plant has come into use for farming purposes in Illinois - especially in some parts of the prairies, and that Professor Turner, of Jacksonville, has planted several miles of it. From my conversation with my friend at Philadelphia, I am led to think that it requires too much and too constant clipping - say twice or thrice a season, to suit the farmers generally in this country; though for gardens it is not easily surpassed.

I should be glad to hear your experience, and that of some of your readers who have planted hedges extensively, as to what will make the hardiest and best farm hedge, taking into account easy cultivation, durability, and adaptation to a variety of soil and climate.

I saw not long ago, a line of hedge which was made by planting the seeds of the Siberian Crab - a small ornamental variety of the apple, which is well known in the nurseries, and sought after for the beauty of its little fruit. The tree, naturally, is a small one, and has not exactly thorns, but branches which become somewhat thorny and resisting. It naturally forms a thicket with a good many branches, so that it takes and keeps the hedge form very easily. He sowed the seeds of these crabs in the garden, and when the seedlings were a year old he transplanted them into the row, where they were to grow as a hedge. They were set six inches apart, in a single row, and the tops were cut off within three or four inches of the ground the same spring they were planted. They made a fine growth, and the next spring were again cut down to within six inches of the ground. This made the hedge bushy and thick at the bottom.

The hedge is now five years planted. It has attained its proper size, and having been regularly trimmed every spring, has become one of the thickest and most impenetrable hedges I have ever seen. It requires trimming but once a year, and seems to me well able to take care of itself the rest of the time. Besides this, it has a fine appearance in the spring, when it is covered with blossoms, and in the autumn when it begins to bear considerable fruit. Would not the Siberian Crab or its seedlings, make a good farm fence?

The locust has been used by some persons as a farm fence, and it makes a loose barrier very quickly. But it is difficult to keep within bounds, and it is apt to throw up suckers and thus take up the ground wanted for tillage. The Three Thorned Acacia - though it does not sucker, and is abundantly thorny, does not grow thick enough to make a complete hedge without a great deal of clipping.

The Buckthorn has been highly spoken of, and it makes, I believe, a first rate hedge for the garden. But will it answer for the farm, and what is preferable to it?

Yours, etc. A. D.

New-York, Jan. 7,1851.