258 



ACCLIMATATION OF PLANTS. 



with animals — remove them from 90 de- 

 grees to 30 degrees in the same hour, and 

 mischief must ensue. 



The hardening off", as it is called, of all 

 plants raised in heat, for planting in the 

 open air, is quite requisite on all occasions, 

 from the common annuals to dahlias. All 

 are in practice submitted to the same pro- 

 cess : first, by admitting more air than 

 usual ; then by removal to a cooler situa- 

 tion ; lastly, perhaps to a cold frame which 

 will merely keep out frost ; although these 

 things are to be planted out in our warm 

 spring months, as the temperature is in- 

 creasing instead of declining. 



The reasoning of Mr. Johnson is good, 

 and his advice is good, for on account of 

 the much greater facility for cultivating 

 hardy plants, the more we have capable of 

 enduring our winters the better. " Hence," 

 says the author of the " Principles of Gar- 

 dening," " hence it is very desirable that 

 an extended series of experiments should 

 be instituted, to ascertain decisively whe- 

 ther many of our present green-house and 

 stove plants could not endure exposure to 

 our winters, if but slightly or not at all pro- 

 tected. It may be laid down as a rule, that 

 all Japan plants will do so on the southern 

 coast counties of England, but it remains 

 unascertained to what degree of northern 

 latitude in our island this genial poiver of 

 eiidurance extends.'''' This last remark is in 

 character with a practical man, for in truth 

 that is the only inquiry to conduct : no pos- 

 sibility of changing the power of endurance 

 exists ; all we have to do, is to see what 

 power the plant has, and there ends our 

 task ; we can then assign the plant to its 

 proper station. Mr. Johnson says, "We all 

 know the larch was once kept in a green- 

 house, and within these few months, such 

 South American plants, as TropoRolum pen- 

 to.phyllwn and Gesnera douglasii, have been 

 found to survive our winters in our garden 

 borders. Very true, ; but the larch was no 

 more a green-house plant for that fact, nor 

 does the mere fact of surviving our winters 

 in our garden borders in Scotland and Suf- 

 folk, or in Herefordshire, prove a jot towards 

 the two plants being hardy. We remem- 

 ber very well seeing Tacsonia pinnatistipu- 

 la flowering on TAvickenham Common, in 



front of a cottage, by the side of Tropmolum 

 aduncum, in the middle of January, yet the 

 former is a tender plant, whatever the lat- 

 ter may be ; but the winter accommodated 

 itself to the plant, not the plant to the win- 

 ter. 



A registering thermometer alone can set- 

 tle the question, as to how much frost the 

 plant endures, or whether it endures any, 

 and the thermometer ought not merely to 

 be out of doors in the open air, but it should 

 hang where the plant is ; for we have seen 

 the dahlia in full flower in one place, and 

 cut down to the ground in aiiother, not one 

 hundred yards oft'. And then again it has 

 to be considered whether a sudden change 

 has not done more towards killing a plant, 

 than the intensity of the frost ; for it must 

 be admitted that rapid changes from heat 

 to cold, and vice versa, do more mischief in 

 our winters than the actual cold would, if it 

 came gradually and went gradually. We 

 think nothing of the mere fact of plants 

 once considered tender, being found hardy, 



Mr. Johnson says : " Another fact is, that 

 many tropical plants, of every order and 

 species, have been found to require much 

 less heat, both during the day and during 

 the night, than gardeners of a previous cen- 

 tury believed. Other plants than those al- 

 ready noticed have passed from the tropics 

 to our parterres, and even to those of high- 

 er northern latitudes. The horse-chestnut 

 is a native of the tropics, but it endures un- 

 injured the stern elements of Sweden. Au- 

 cuba japo/iica, PcEonia moutan, we all re- 

 member to have passed from the stove to 

 the green-house, and now they are in our 

 open gardens." 



All this is very true, but it does not show 

 that the nature of the plants, or their pow- 

 ers of endurance have changed one degree, 

 or even a shade of one. It is said further 

 on : " Then, again, there is no doubt that 

 all the Coniferas of Mexico, which flourish 

 there at an elevation of more than 8,000 

 feet above the sea coast, will survive our 

 winters in the open air. Among them' are, 

 Pimis llaveana, Pinus teocote, Piims patula, 

 Pinvs hartwegii, Cupressus thwifera, Juni- 

 periis flaccida, Abies religiosa, and some 

 others." 



Perhaps the learned author will some of 



