CHAP. LXIX. .ERICA^CEiE. 1103 



a freer circulation of any superabundant moisture which may be given, through 

 the mass." (Treatise, &c, p. 25.) Mr. Bowie, also, recommends small stones 

 and fragments of garden pots to be mixed with the soil in which heaths are 

 grown : but the practice seems to have been first introduced (probably before 

 1820) by Mr. James Niven, who was many years a collector at the Cape, and 

 who died at Pennycuick, near Edinburgh, in 1827. (See Gard. Mag., vol. ii. 

 p. 255.) The thorough drainage of the pots or tubs, the judicious mixture 

 of lumps of freestone with the soil, and the addition of thoroughly consumed 

 cow-dung, seem important points in the culture of Cape heaths in pots, and 

 afford equally important hints for their culture in the free soil, either against 

 a conservative wall, or in beds in the open ground, with temporary coverings 

 of glass or boards during winter. 



The Treatment of Cape Heaths as half-hardy Shrubs is a subject on which 

 we can derive but little assistance, either from books, or from the experience 

 of practical men. Mr. M'Nab is of opinion that, in the climate of Edinburgh, 

 the Cape heaths ought never to be taken out of doors, but should be kept 

 in the house, even during summer, giving them plenty of air, and keeping them 

 cool during winter. It is commonly supposed, he says, that turning heaths 

 out of doors, for four or five months in summer and autumn, makes them 

 hardier, and enables them better to stand the winter ; but he very properly 

 differs from this opinion, finding from experience that, when heaths and other 

 green-house plants are kept in the house during summer, the young wood gets 

 better ripened, and is, consequently, better able to resist cold in winter. The 

 greatest care is requisite to keep the house in which heaths are grown well 

 ventilated ; for which purpose the glass of the roof and sides should be 

 made to open ; and the plants should never be so near as to touch each other 

 with the extremities of their shoots: on the contrary, they ought always to be 

 at least 3 in. or 4 in. apart, in order to admit of a free circulation of air round 

 each. " Except in cases of high wind or heavy rain, both top and front 

 lights should be open night and day ; and, besides watering the earth in the 

 pots freely when they require it, the plants should be well watered over- 

 head with the garden engine every day ; and, if the weather be hot and 

 dry, this operation should be performed twice every day ; namely, both morning 

 and evening." " The chief objection," Mr. Marnock observes, " to heaths 

 and other green house plants being kept in the house in summer is, that, 

 being exposed to the sun, the earth in the pots becomes dry, and the extremes 

 of heat and cold, wet and dry, to which the roots are thence subjected, cause 

 the plants to assume a brown and unhealthy appearance ; and, generally, the 

 leaves on the lower branches to fall off. These evils may, however, be effec- 

 tually prevented by using double pots ; the empty pot which is intended to 

 form a screen for the other which contains the plant, being sufficiently large 

 to receive the latter within it, so that the tops of both are nearly on a level. 

 1 have practised this mode for the last three years, both with stove and green- 

 house plants ; and, during the dry summer of 1832, I had at Bretton Hall at 

 least 100 of the latter in pots, protected in this way." {Gard. Mag., vol.x. 

 p. 32.) When heaths are attacked by aphides, which they very seldom 

 are, a little tobacco smoke for two nights in succession will destroy them. 

 It is always better to apply the smoke two or three times, if necessary, in 

 small quantities, than the same quantity of tobacco all at once, because there is 

 less risk of injuring the plants. When heaths in pots happen to be frozen 

 during winter, there is nothing more injurious to them than the application 

 of fire heat to such an extent as to thaw the soil. All that ought to be 

 done is, by covering the sashes with mats, or by other means, to prevent 

 the increase of the frost, and leave the soil to be thawed by the natural re- 

 turn of genial weather. In the Botanic Garden of Edinburgh, we believe, fire 

 heat, or artificial heat of any kind, is seldom or never applied to the heath- 

 house. Some valuable remarks on this subject, by Mr. Marnock, the curator 

 of the Sheffield Botanic Garden, will be found in the Gardener's Magazine, 

 vol. x. p. 31. 



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