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Trees and shrubs for open allees must meet the one requirement ofbeing close growing and columnar in their habit. An open allee maybe developed with rapid-growing material as well as with slow-grow-ing material, and the time required is less than two-thirds as long asthe time required to develop a pleached allee of the same height.Six to ten years may be required to develop an open allee eight to tenfeet in height. The scale of the allee, whether wide, with a tall border on either side, or narrow, with a lower border, governs the type ofmaterial which should be selected. Here again, with such plants asthe thorns and elms, a larger specimen may be used with a high head,and the smaller specimens may be planted between and on either sideto produce the mass of foliage at the bottom. An illustration of this isshown in plate No. XXVIII on Page 190. This interesting open allee ofthorns and flowering dogwood is planted according to the followingmeasurements. The distance between the middle line of each row ofthorns is twenty-two feet six inches. Each row was originally plantedwith high-headed thorns at a distance of four feet six inches apart in therow. Equally spaced at a distance approximating one foot six inchesapart, small specimens two feet to three feet high were planted in asingle row at a distance of one foot six inches on either side of the mainrow of thorns. These small thorns were for the purpose of producing afoliage effect beginning at the ground and extending into the higherheads of the larger thorns. The width between the rows of floweringdogwood is eight feet and the distance between each flowering dog-wood plant in each row is eight feet. The width of the walk in thispicture is four feet. It is very essential to use types which have abranching habit to the extreme base of the main trunk if a perfectopen allee is desired. |
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