Citrus Rootstocks in New Zealand

New Zealand Journal of Agriculture, Volume 63, Issue 2, 15 August 1941, Page 148

Citrus Rootstocks in New Zealand

Citrus Notes

THE rootstocks generally used in 1 New Zealand at present are the sweet orange, the rough lemon (citronelle), the trifoliate orange (Poncirus trifoliata); and, to a limited extent, the sour orange Until the results of definite scientifically controlled experiments on a range of soil types are available, recommendations must ,be based on general observations. These indicate that the sweet orange is the safest all round rootstock. It is recommended for sweet, orange varieties and New Zealand grapefruit. Its chief weakness appears to be its susceptibility to collar rot. The trifoliate orange can be recommended for mandarins and for sweet orange varieties if the soil retains moisture during the summer months. In general,: trees budded on this stock should be planted closer together, 16 to 18 ft. should be adequate. The quality of fruit on this stock 'is outstanding. The rough lemon (citronelle) can still be recommended as the standard stock for lemons, including the hybrid “Meyer” lemon. The sour orange must at -present be classified with “Cleopatra” mandarin and double-worked stocks. as. worthy of trial, but it is not yet proved commercially. Throughout the citrus belt in New Zealand there are citrus trees of" good

quality, but it is essential that occupiers of properties should be conversant with such particulars in regard lIIIIIIIIIIIIII3IIHIIIIIIIIIIIIIIIII i tin i ii inulin iiiiiiiiiiiiiiiiiiniiiir

iiiiiiiiiiiiiiiiiimiiiiiii ii ii i ini i ii i ii i hi i ii in min ii 11 iiiiiiii to the trees as root stock upon which worked, name of variety, age, soil, and annual crop \ over a period of at least three or more years. • , In order that persons interested may learn to recognise rootstock and variety, the following hints are given. If the tree, especially orange, is very vigorous and upright in its growth, with little or no fruit for its age, and no union is visible, it, is probably a seedling. Poncirus trifoliata- (trifoliate orange) rootstock is - characterised by mottled bark and flanging. Rough lemon (citronelle) stock also ' exhibits

flanging but no mottling, and sweet orange as a rootstock is generally round and even. If a root is cut and the cut end, exposed to the air, it will generally break into foliage, and the characteristic orange, lemon, or trifoliate appearance will be recognised. ’ The recognition of varieties presents a greater problem, and will be dealt with in greater detail.

Lemons

Lemons, in order of their preference, under New Zealand conditions, are: — (1) Genoa. — thornless semi-dwarf tree well furnished with laterals. It is a good cropper all the year round. The fruit is exceptionally uniform in shape, being oblong and pointed at both ends, with very small pith and 7 to 10 regular sections. (2) Villa Franca. — This variety has the advantage of being an early bearer and also of bearing its main crop in summer. Its branches are shorter jointed and less drooping than those of Eureka, and the tree is thus better suited to exposed conditions. The fruit has a pointed apex and rounded base. There are 11 well-defined and regular sections, and there are generally more seeds present. (3) Lisbon. — A thorny tree of the short-thorned strain, vigorous grower, well furnished with fruiting laterals

and foliage. It \ tends to ripen its heaviest crop in September-October, and this, combined- with its thorny character, is a distinct - disadvantage. The fruit is oblong, with a very sharp pointed nipple. The rind z is fairly, smooth and sweet to taste. The /pith is small, and there are 10 to 11 small regular sections. Another strain of poorer quality is known as the longthorned type. (4) Meyer. is really a sweet orange lemon hybrid, but is becoming increasingly popular in domestic gardens. It is recommended to be planted at a distance of 15 ft. apart in commercial orchards. It is of a deep, golden yellow colour and beautiful texture, but shape, is more broadly oval than the usual lemon. One main crop ripening about May-June is borne. (5) Eureka. This lemon, although thornless,- is characterised by willowy growth and the bearing of fruit at the ends of the branches. There are two local strains, of which the “sweet rind” is the better. The other type sports freely, and often gives thick-skinned and irregular fruit of low commercial value. It is generally a shorter fruit, with a small nipple. The pith is small, and there are 10 well-defined and regular sections. Rough Lemon. This is quite different from the varieties previously

mentioned. It is often found at the old Mission stations, and is often miscalled the “Maori” lemon. It is extremely rough, the skin being wrinkled and in many . cases loose. The fruit has an open centre, and the juice is low in acid. The rind is of varying shades from yellow to orange when the fruit is mature. For culinary purposes it is inferior. , Its greatest value is as a source of seed for rootstocks. Ponderosa.— fruit is large and pear-shaped, and it is possible that it contains pomelo strain. The rind is rough, and there are 12 distinct sections and coarse grained greyish flesh. It is generally considered by commercial citrus growers to be a valueless novelty fruit. — This variety is seldom seen, but is oblong in form with short abrupt nipple. There are 12 regular sections, fine grained, greyish yellow flesh, small pith, and generally 12 seeds.

Limes

A fruit that is sometimes- confused with the lemon is the lime. The lime is not at present grown commercially in New Zealand, but occasional trees are found. Externally, the fruit resembles a fine-textured, small , lemon,, but the flavour of the fruit is distinct.

The leaf is smaller than that of the lemon, and has a small winged petiole. The commonest varieties are the Mexican and Tahiti lime. , The Mexican lime grows as a shrubby bush 10 to 15 ft. high, and has many small sharp spines. The fruit rind is smooth and very thin, with short pointed nipple, 10 sections, light greyish green flesh, open pith, and lime flavour. The Tahiti lime is a round-topped tree with drooping branches. In shape the fruit is larger than the Mexican, with a broad-based nipple, 10 sections, greenish flesh, open pith, and lime flavour. The Persian lime is probably identical with .Tahiti. - " Another citrus tree often called a lime is the Rangpur. It is sometimes used as a rootstock. The tree has the habit of the lime, but the fruit > is roundish and the nipple, if present, is short. The fruit is orange red. in colour, and the rind is inclined to be rough and separates from the pulp. It has seven ' sections, which' readily separate. The flesh is slightly, orange coloured, and the flavour of the juice is unlike the lime. (To be continued.) .

-A. W. M. GREIG,

Citri-

culturist, Auckland.

Reminders for the Month Complete the planting of citrus arid shelter trees. , Turn under leguminous or other cover crops. ■■ ■ / i Apply the .spring dressing of manure. Overhaul the spray equipment. Harvest sweet orange varieties when mature. Harvest N.Z. grapefruit for dessert purposes if sufficiently tree-ripened.