1174- ARBORETUM AND FRUTICETUM. PART 111. 



reader will bear in mind, differs from an ericetum, in containing all the plants 

 of the order Jricaceae, while an ericetum, or heathery, is limited to the 

 species of the section .Ericeae normales. 



All plants which require peat soil do so in consequence of their having 

 hair-like roots ; and, in the culture of the ligneous Jricaceae, as of all plants 

 whatever in peat soil, to insure success, it is essentially necessary to keep the 

 soil in an equable degree of moisture. The reason is, that plants having hair- 

 like roots never extend these to any great distance from the stem, or main 

 root ; and, consequently, that they draw their nourishment, or what, in a 



Sactical sense, is equivalent to it, their moisture, from a very limited space, 

 ence, no plants suffer more from drought than the -Ericaceae, whether in 

 the open air in beds, or in the green-house in pots ; and no plants are more 

 difficult to recover after they have sustained injury from being kept too dry. 

 Hence, in very hot summers, the rhododendrons, azaleas, and other shrubs 

 of this order, which grow in common garden or shrubbery soil, are frequently 

 killed to the ground, without shooting up again the following year, as is th*e 

 case with the shrubs of most other orders, killed down by drought. Every 

 American garden, therefore, ought to be laid out in some situation, and, ac- 

 cording to some principle, not only favourable to the retention of the natural 

 moisture of the soil, but also favourable to the application of moisture arti- 

 ficially. A level surface at once supplies both the conditions to a certain 

 extent ; and a level surface, sunk 5 ft. or 6 ft. below the surrounding surface, 

 supplies both in the most perfect manner. The advantage of placing an 

 American ground in an excavation some feet under the surrounding surface 

 is, that the soil in the excavation will always be moister than that of the sur- 

 rounding surface, in proportion as the one is lower than the other. The soil 

 in such an excavation will also be found cooler than that of the general sur- 

 face, though both may be alike exposed to the direct rays of the sun. These 

 results may not at the first sight appear obvious ; but they take place in con- 

 sequence of temperature and water having both a continual tendency to 

 come to a level. 



An ericacetum ought, therefore, to be laid out in an excavation, the sur- 

 face of which is reduced to a perfect level, in order to gain all the advantages 

 of moisture and coolness which the natural situation affords : and, to admit of 

 supplying water artificially to the soil in the beds in the most economical 

 manner ; and, at the same time, in the manner best adapted for the plants, the 

 excavation should be intersected with drains at regular distances ; all these 

 drains communicating with a main drain in the centre, and this main drain 

 communicating with the' source of the water, which should be so arranged as 

 to be turned on and turned off at pleasure. The drains may be laid out in 

 parallel lines, 10ft. or 12ft. apart, and 2ft. or 3ft. under the surface; and 

 they may be formed of bricks, laid without mortar, 9 in. deep, and 4>i in. wide. 

 The main drain in the centre, with which they communicate, may be a foot 

 wide, and a foot deep. The bottom of all the drains ought to be on the same 

 level. The water may be admitted to one end of the main drain by various 

 means. If conveyed under ground in a pipe, that pipe should be 3 ft. or 4 ft. 

 under the surface, so as not to be injured by frost ; and the stopcock may be 

 reached from the surface through a vertical shaft of 2 in. or 3 in. in diameter, 

 formed by brickwork, and closed at the surface by a brick or stone, so as not 

 to appear unsightly. If the water is supplied from a pump on the spot, that 

 pump need not lift the water higher than the upper surface of the drain ; and 

 it may easily be contrived with a removable handle, so as to have no appear- 

 ance of a pump, except when it is in use. Where the water is supplied 

 by water-carts, or from a pond at a short distance, it is only necessary to pour 

 it into the main drain through a funnel carried up in masonry or brickwork 

 to the surface, from the centre of the main drain, having a stopper of brick or 

 stone to put on when not in use. 



Water may be supplied artificially to an ericacetum by surface drains ; but 

 these will not apply so well as under drains, in cases where the garden con- 



