4 BULLETIN 71, HAWAII EXPERIMENT STATION 



disadvantages associated with them. Experiments in vegetative 

 propagation, including several methods of grafting, of which 

 budding is considered a form, have been employed by the sta- 

 tion during the past 10 years. Since 1906, seed propagation has 

 been used mainly to develop rootstock plants on which to graft 

 desirable varieties. These have been grown from sweet oranges, 

 sour oranges, trifoliate oranges, rough lemons, pomelo of the 

 shaddock type, and tabog (Chaetospermum glutinosa), which is 

 of a different genus but of the same family. Tabog has been dis- 

 carded for use as a rootstock on account of its slow growth and 

 hard, close-grained wood. Trifoliate orange stock does not ap- 

 pear to have any material advantage for Hawaii. The use of 

 rough lemon and sweet orange stock has also been discontinued 

 because of a lack of resistance to gummosis. Sour orange and 

 shaddock stocks have been proved best, especially the latter 

 because of its great vigor, adaptability to grafting, and apparent 

 disease-resistant qualities. Several kinds of citrus trees that 

 were grafted on shaddock stock in 1921 reached bearing age in 

 1926. They have not transmitted any unsatisfactory characters. 

 The Cleopatra mandarin, which was highly recommended by the 

 late E. N. Reasoner of Oneco, Florida, as an excellent rootstock 

 for most citrus, has been introduced. 



Vegetative propagation of citrus requires considerable ac- 

 curacy and patience. The work includes the production of root- 

 stocks, the making of unions, and careful cultivation of the 

 grafted plants to sizes suitable for planting in permanent places. 

 It is a branch of horticulture which is usually, but not neces- 

 sarily, performed by experienced nurserymen. The details of 

 vegetative propagation adaptable to citrus in Hawaii have re- 

 cently been worked out at the Hawaii Experiment Station and 

 published in Circular No. 6, "Grafting Tropical Fruit Trees in 

 Hawaii," illustrated, and issued in April, 1933. 



CULTURAL REQUIREMENTS 



Temperature, Moisture, Soil, and Windbreaks 



The general requirements for all kinds of cultivated citrus 

 are practically the same. In many parts of Hawaii requisite 

 conditions of temperature, moisture, and soil for all species and 

 varieties of citrus are found, but in some places protection is 

 needed against strong winds. The most suitable growing places 

 range from near sea level to about 1,000 feet. In these belts 

 leeward slopes are preferable. In Hawaii the maximum tem- 

 perature seldom ranges above 85° F., and the minimum tem- 

 perature, at sea level, never falls below 50° F. In most parts of 

 the agricultural belt the average annual temperature is 74°, 

 with a daily average range of 11°. The average relative humid- 

 ity is about 72 per cent. Here moisture exerts the most marked 

 influence on citrus. Citrus may be grown with a rainfall ranging 

 from 50 to 150 inches per year. This amount is large as com- 

 pared with that required by other orchard crops, but it should 

 be remembered that the heavy foliage, which has no marked 

 rest period, transpires large amounts of water. However, in 



