34 THE UNHEATED GREENHOUSE 



HALF-HARDY PLANTS 



It is customary to count as half-hardy many of the soft- 

 wooded plants which are used for summer bedding, such as 

 Pelargoniums, Heliotrope, Ageratum, Cupheas, and the like, 

 but it is a misleading term as far as the unheated greenhouse 

 is concerned, for in no part of the British Isles will these 

 survive a winter out of doors, and they might perhaps be 

 more accurately described as sub-tropical. It is true that 

 Pelargoniums of certain sorts thrive all the year round in 

 sheltered spots in the Isles of Scilly, but whole hedges of 

 them were cut down to the ground-line in a disastrous winter 

 some years ago when there was a most unusual visitation of 

 10 of frost. It is also true that they will exist under glass 

 in a low temperature, but it must always be above 40 Fahr., 

 for they quickly damp off unless there is enough warmth to 

 keep them in a growing state, while to have zonal Pelar- 

 goniums in bloom during the winter requires not only a season 

 of special preparation beforehand, but a temperature equal to 

 summer heat ; hence it is plain that they cannot be recom- 

 mended for the cold greenhouse. 



Ordinary greenhouse plants, again, such as Libonia 

 floribunda, Bouvardia, Chinese Primula, and even Persian 

 Cyclamen must be put out of our thoughts, though the last 

 two do excellently well in the windows of light warm rooms. 

 It must therefore be clearly understood that by " half-hardy " 

 in these pages it is intended to express the degree of hardi- 

 ness which will pass safely through an ordinary winter in the 

 Isle of Wight or in Devon and Cornwall, and which is able to 

 endure a trifle of frost for a short time in a dry, still atmo- 

 sphere without permanent injury. But even for half-hardy 

 plants like these the mere shelter of glass will not suffice, 

 because the advantages of climate afforded by the South Coast 

 are exceptional, and therefore if we decide to grow the more 



