The writer has had no experience in propagation except in the way of propagating the Otaheite variety as a house plant. But the results obtained by varied plans of propagation have been studied in the orange-growing centres of Europe, California, Florida, and Cuba, and the decisions of experts and growers have been compared.
As with other orchard fruits the best results have been obtained in growing uniform, vigorous, and healthy trees by using stocks for budding grown from seeds of fruits near to Nature. In California, strong, vigorous stocks have come from seeds of the primitive oranges of Tahiti, and also from the sour oranges yet found around the old missions. In north California, hardy dwarf stocks have been used grown from the varieties imported by General Chabot from north Japan. And also the relatively hardy and primitive Citrus trifoliata has been used quite extensively. The rough lemon also seems to give additional hardiness and inherent vitality to varieties worked upon it.
Since the freeze of 1894-95 in Florida and the Gulf States, the main stocks used have been the rough lemon and Citrus trifoliata. But farther south the sour-orange seedlings are mainly used. Those who have had a long experience in propagating the northern orchard fruits are surprised to find the citrus fruits so tenacious of life and easy to propagate in so many ways. Aside from liability to fatal injury by severe cold, we have no northern fruit tree so tenacious of life. Even where the top is wholly killed by fire or freezing and the roots show no sign of life or growth for a year or more, vigorous sprouts will finally appear. It is even said that trunks of quite old orange-trees that have lain as ballast in the holds of vessels for a month or more have grown into fine trees when planted as pollards. By cutting back the tops quite severely, large trees are planted successfully with roots cut so short that northern men are certain they will fail to grow. It also layers as easily as the grape, and often shoots resting on the ground will take root. When on own roots it is also propagated from root-cuttings (50. Propagation by Root-cuttings). Summer layering (52. Summer Layering) is also practised successfully, and this is a principal method of propagation by the natives of Cuba.
Where the Otaheite orange is used for stocks it is mainly propagated by mounding (51. Rooting Sprouts by Mounding). It also grows well from cuttings of the young wood with a heel of the two-year-old wood planted in the dormant period. But in propagating by mounding, layering, or cuttings, it must be remembered that the orange must have water. If neglected in a dry time they will fail, Skilful propagators even insert buds in the top of a long cutting which is planted with the bud just above the surface in boxes of earth kept well watered. In this case the buds remain nearly dormant until the cuttings take root. But all these methods are confined to home-growers.
The commercial method is to grow seedlings in beds in well-prepared and rich soil. From the beds they are transplanted to nursery rows and budded when the bark peels well, as we manage the stone fruits at the North. The transplanting of the seedlings from the bed requires care, as the stocks have a full supply of leaves for rapid evaporation. A moist soil and cloudy weather are requisite for success in planting.
Some growers familiar with northern methods plant the seeds in well-prepared rich soil in the nursery rows early and bud the same season, as practised at the North with the peach and plum (74. Budding the Same Season the Pits are Planted). This plan gives trees large enough for orchard planting in less time than the common plan, but the root system is not so good if the tap-roots are not cut, as noted in section (74). In budding, the old plan was to shove the bud upward, as practised sometimes in spring-budding at the North (76. June Budding). But those who practise the usual plan of shield-budding have quite as good success and the bud can be inserted lower down.