Walnut, Juglans regia, L.—From Europe and Asia. Does not exceed 25 metres in height, but is a metre and more in diameter. Grows as a forest tree, but is very suitable for stocking mixed woods in the 2nd, 3rd, 5th and 6th regions. To be sown in rows, in holes or in nursery beds and planted out when a year old. As the seeds keep their germinative power for a month only, they must be sown immediately or placed in layers. The wood, which is greatly prized, is one of the best known and valued.
Paradise Tree, Melia azedarach, L.—Southern Asia. 15 metres in height by 0·60 metre in diameter. A good auxiliary species for mixed woods and timber for cutting in the 3rd, 4th, 6th and 7th regions, where the eucalyptus does not freeze.
Negundo Fraxinifolium, Nutt.—From North America, growing well in the 3rd, 4th, 5th, 6th and 7th regions, where it attains a height of 10 to 15 metres by 0·50 metre in diameter. It is a good kind for mixed woods and timber for cutting. The seeds are sown immediately on ripening. It is also grown from grafting twigs.
Fir, Picea excelsa, Linck.—From Europe, where it attains a height of 40 metres. The few specimens we know do not allow of our expressing any opinion, based on practical experience, about the possible merit of this splendid tree in our woods in the 3rd, 5th, 6th and 9th regions, though its origin and growth give reason for hope. In Europe, in all the plantations we know of in Germany, England and France, the fir is one of the best cold, storm and drought-resisting trees.
It is sown in rows, in furrows 2·50 to 3 metres apart, according to the soil. It may be planted alone or alternately with birch trees.
Pines.—The kind best known and cultivated here are the Pinus austriaca, P. insignis and P. Pinaster. Without questioning the specific designation applied to certain kinds of pine trees, we may say that P. insignis grows luxuriantly in the 4th, 5th and 7th regions, forming dense woods; the P. Canariensis, not quite so hardy, does not flourish so far south, the other kinds may be grown in those as well as in the Riparian austral and maritime regions, where they may prove very useful, as well as the varieties P. maritima, P. laricio, etc.
Plane Tree, Platanus orientalis, L.—From Europe and Asia Minor. It grows to 40 metres in height by 1 or 2 metres in diameter. It is the favourite for avenues; grows taller in the woods, but its foliage is not so luxuriant. Propagated from grafting twigs to be planted 50 centimetres apart in rows 2·50 metres apart. To be thinned out when two years old, leaving the latter distance between them and filling up the gaps with those taken out. Its wood is useful for many purposes, though not first class.
Poplar, Populus.—We have many large plantations of the Lombardy poplar, P. Nigra, L., Canadian poplar, O. Canadensis, Michx., and the Swiss, Virginian and some of the Carolina poplar, which is the male plant of the same species. Some plantations of the silver poplar, P. alba, P. euphratica and P. simoni, have also been planted.
All may be utilized as auxiliaries in planting mixed woods and timber for cutting. They are very hardy, and the wood is used for packing-cases, boxes, etc. They are planted from grafting twigs 50 centimetres apart, in rows of 2 metres, to be thinned out when necessary.
White Acacia, Robinia pseudo-acacia.—North American. Grows to a height of 25 metres by 0·60 metre in diameter; when dry, the wood is excellent, and is used for coach-building, cabinet-making, etc. It grows well, especially in mixed woods, as the saplings are utilized. In timber plantations it must be planted singly as it overruns the ground in a short time. To be sown in rows 25 or 30 kilogs. to the hectare, without any mixture. From the strongest and straightest specimens stock trees are chosen, the others are cut down to the ground every two, twelve or eighteen years.