lo March, 1910.] Prickly I 'car. 189 



Resistance of Prickly Pear to Drought and Cold. 



Tiie idea that this plant wiil grow and thrive in the most arid districts 

 is a common, but quite mistaken one. A generation ago, an ingenious French- 

 man proposed to render the Sahara desert capable of supporting life by plant- 

 ing Pricklv Cactus over it. Experience has shown, however, that the plant 

 Avill only grow in really arid districts when irrigated, and where water 

 is available vastly better plants can be grown. The plant does not resist 

 frost at all well and is, in fact, a sub-tropical one. Dr. Griffiths shows 

 ■only a relativelv small area of land on the south-west and .south coasts 

 of North America, including California and Florida, where he considers 

 the plant might be profitably grown. Victoria would not come under this 

 zone, although parts of New South Wales and of Queensland, where 

 various P.rickly Pears are well known pests, would present a similar 

 range of conditions to^ the zones marked for the cultivation of the plants 

 in the United States. 



Tne following is a quotation from page 17 of the latest Bulletin, 

 January, 1909 : — 



The writer believes that the plants will grow under cultivation, without irri^M- 

 tion, on the Gulf coast of Texas and in California from the Sacramento Valley 

 south. Under the influence of the ocean, they may get along with neither cultiva- 

 tion nor irrigation, but in the interior vallevs they will have to be carefully 

 cultivated in order to conserve the moisture after the rains cease in the spring. 

 Experience has proved this at Chico, California. In the great arid interior region 

 •extending eastward from the southern Sierras, the Prickly Pears will have to be 

 irrigated before thev will make any growth worth while. 



The statement which the writer made in a previous publication applies with 

 equal force here and will bear repetition. The Prickly Pear plants are adapted 

 to a region having a considerable rainfall too irregularly distributed for ordinary 

 crops. They must have water to grow and a considerable amount of it. They 

 are the camels of the vegetable world. Thev must have water, but they can get 

 along for long periods without it. 



It must be remembered that, in the matter of arid regions, the United 

 States falls far behind Australia, having no districts which can be com- 

 pared with the deserts of Central Australia, so that there is no reason to 

 iear the plant establishing itself in pest fashion in Central Au.stralia. 

 In fact, districts with an average annual lainfall below 16 to 20 inches 

 may disregard the plant as a possible serious pest, since it can never exhibit 

 the luxuriance of growth shown in warm countries with a higher rainfall. 



On page 31 of the 1908 Bulletin it is stated that " the experiments 

 have been done on land having a rainfall of 16 to 40 inches per annum 

 (average 28 inches), the temperature minimum averaging 22° F. and the 

 rainfall being rather irregular " though less so than over the greater part 

 of Australia. 



Where there is a good, but somewhat irregular, rainfall, deeply-rooting 

 perennial fodder plants which draw water from the deeper layers of the 

 soil, will give better results than plants like Prickly Cacti which get 

 over temporary drought by storing water and checking transpiration. 

 Plants which check their transpiration also check their growth when the 

 temperature is most suitable for it, whereas the deeply -rooting fodder plant 

 will usually grow mo-st actively during Avaim drv spells and so makes the 

 most of everv opportunitv. 



Summarizing the remaining data given bv Dr. Griffiths: — The cost 

 of planting an acre of Prickly Cactus was ^i i6s. 8d., and would be at 

 least double .this in Au.stralia. (The cost of eradicating* it when once 

 established mav vary from jQ^ to ;^io per acre.) The cost of cultivation 

 and of preparing it for food bv cutting and burning is not given. 



