CITRUS FRUITS.

New Zealand Herald, Volume LXIII, Issue 19419, 30 August 1926, Page 14

CITRUS FRUITS.

SELECTION OF STOCKS. THE BEST VARIETIES, AFFINITIES AND USES. B7 B:. R, . BRIGHT, AVONDALE. The principal root stocks that are used for the budding and grafting ol citrus fruits throughout tho world are the Poncirus Trifoliata, Sour Orange, Rough Lemon and Sweet Orange. It has been found necessary to work upon different stocks to suit varied soils and climatic conditions, as not all stock or roots will suit all soils, therefore it is obvious that to plant a tree in a light soil, that prefers a heavy one, spells failure, or vice versa. Growers, when ordering citrus trees, should always make known to nurserymen, the nature of their soil, whether light or heavy. This is most imperative, in that it enables the nurseryman to choose the stock that will suit the particular soil. Ihe two stocks that will meet the requirements of our New Zealand climate are the Sour Orange, or Wild Sevillo, and the Poncirus Trifoliata, or deciduous wild orange of Japan,, the former for light to medium soils, the latter for medium to heavy soils that ure too wet for tho former. The sour orange stock' is undoubtedly the best all-round stock, and the most universally used, and its claims are frost resistance, deep-rooter, great surface feeder, and it has a root sya';em par excellence. It is claimed that the varieties worked upon this root keep their juice longer into tho summer than on • any other stock, owing to tho fact that the sour orange is a late maturing variety; likewise more resistant to collar-rot, or mal-de-goma, a gum disease, than either Rough lemon or Sweet orange stock, but less resistant tnan Poncirus Trifoliata. ' Tho Rough Lemon as Stock. In Australia the Rough lemon iB the principal stock used; being a gross-feeder it stands the dry climate, whereas in New Zealand, owing to the wet conditions, it is less suitable, except in fairrly dry situations. In our nursery the Rough Lemon has proved a far more vigorous stock than the Sweet orange, but somewhat tender to frost. All varieties oi Citrus trees thrive well upon it, excepting Golden Nugget Navel, and Parker's seedling mandarins. These tiro lack affiinity and are . easily broken off., and, furthermore, this same lack of afiinity prevents them attaining a large size. The Sweet orange stock is mainly used in New Zealand. It gives perfect affinity, to all varieties worked npon it, being more hardy to frost than the Rough lemon, the seed of which is more difficult to procure j hence the general use of Sweet orange stock. t

The Poncirus' Trifoliata is a deciduous wild orange, indigenous to Japan; it is the hardiest of all citrus stocks. As an indication of its hardiness it is claimed that it will withstand the winters of New York, U.S.A. Citrus trees worked upon it are made more hardy and frost-resis-tant, owing to ths dormant nature of the root in winter, while those worked' upon Sweet orange and liough lemon stocks are more likely to be perpetually growing, owing to the nature of the stocks. Poncirus Trifoliata is essentially a heavy land stock, possessed of a fair amount of moisture, typical of our gum lands. On light,, dry soilß it is a failure. This has been proved both in Florida and California, and also in Avondale, as we have in our nurseries both heavy and light soils, thereby enabling us to make a thorough test. Citrus varieties worked upon Poncirus Trifoliata attain a much higher colour and come into bearing earlier than any other root or •stock. From one to two years will-see most varieties in bearing upon it, thus bringing in a new era in citrus culture, v i - . V ,

The. early fruiting on •' this stock is brought about by the diverse nature between stock scion or variety worked,upon it,' illustrating -the rule, the nearer the relation between stock and variety, the longer they take, to come into • fruiting and the more distant the relationship the quicker they come into bearing. This holds good with other fruits as well as citrus fruits, but it must bo borne in mind that when using a stock or root that is widely separated by relationship from those to be worked upon it, one must expect some varieties to prove an 'absolute failure through lack of affinity, for in the use of such stocks we get three phases, viz., perfect affinity, partial affinity, and no affinity, -the results of which are strong growth ,weak growth, and no growth. The Question of Affinity.

While dealing with this subject, it may be well to draw attention to the April issue of the New Zealand Journal of Agriculture, in which are many interesting illustrations of Citrus trees grown on different stocks, showing instances of partial affinity; also adverse soil conditions. Sea page 222, fig. 3 Eureka on Poncirus Trifoliata, only partial affinity, and on see page 222, fig. 3 Eureka oh Poncirus Trifolita, perfect affinity. Note the difference in growth between the two varieties; both are growing in adverse soil conditions for this stock being in dry and sandy soils. ' These illustrations '■ with my own experience prove conclusively that affinity counts first, while soiL conditions come necond, but given perfect affinity with ideal soil conditions, the results will be all that could be desired. The Poncirus Trifoliata is the earliest of all citrus varieties to mature its own fruit; therefore all varieties worked upon it will ripen earlier than on other stocks. Poncirus Trifoliata and Sour orange used jointly as stocks for working of same variety will carry over a much longer ripening period. The heavy and precocious cropping of varieties worked upon Poncirus Trifoliata is really phenomenal, as was borne out by the one-year-old trees exhibited at the Auckland Winter Show. It is to be regretted that nurserymen in the citrus-growing districts of Auckland have been unable to offer citrus trees worked on the Sour orange stock, this being brought about through the difficulty in purchasing seed which has to come from Florida. The distance is too far, and most of the seed perishes in transit, thus putting it beyond a business proposition.