POTATOES.

(Solanem tuberosum).– Potatoes are a crop which, though extremely valuable, are generally cultivated in larger gardens. The reason is that they occupy a good deal of space, time and attention, and the crop when it is grown hardly seems worth all that has been expended on it.
In a garden of a fair size, however, it is usual to grow potatoes, and particularly the early varieties, partly because the quality of newly- dug potatoes is so superior to any that can be obtained from the markets. Potatoes are not grown from seed but from what are usually called "seed potatoes" or sets. New varieties are raised from seed by specialists, but as in the case of many seeds, the seedlings vary so greatly in quality, that possibly only one in a thousand is any use at all. The supplies of seed potatoes offered are grouped into three divisions: early varieties, mid-season varieties, and late or main crop varieties. The early potatoes are sown first, and mature earlier than the others because their season of growth is shorter. They do not crop so heavily, and partly because of this they do not need to be planted quite so widely in the rows.
Soils.– The best soil for potatoes is that of a rather light nature, but potatoes will grow on any kind of ground. A good crop can be expected from any well-cultivated plot. It is a favourite practice in breaking up new ground to plant a crop of potatoes the first season, partly because the potato is not averse to newly-broken soil, and partly because the cultivation of the potato is one of the most effective ways of cleaning the plot of weeds. The regular hoeing-up which is done for the potato crop, destroys the weeds during the summer months, and leaves the plot clean in autumn.
Sprouting the Tubers.– Potato tubers received as seed potatoes should be roughly about the size of an egg, and weigh about 2 oz. each. When they are received by the grower, they should be set to sprout in trays as soon as possible. Tests have been made with seed potatoes by setting some to sprout immediately they have been dug at the end of the season, and leaving them in the trays exposed to light and air (but of course kept away from frost) during the winter months. The result in such cases has been that fewer but sturdier sprouts have appeared on the tubers than when the potatoes are stored in the usual way, and set to sprout later in the winter. In any case, tubers should always be sprouted several weeks before they are planted. The method is to pack them closely together on trays with the rose end uppermost. The "rose" end is the end where the eyes are gathered in a cluster. At the other end of the tuber there is usually a single mark where the tuber was at one time joined to the stem-root.
For ordinary outdoor culture the ground should be trenched and left rough until about the middle of March. By this time the seed tubers will have several stout shoots on them about 1 or 2 in. in length. Two shoots should be left on each tuber, unwanted shoots being rubbed off. The best way to plant is to open out trenches across the plot with a spade. throwing some old, well-decayed manure into the trench and setting each tuber on to this. Failing old, decayed manure, leaf-mould, or similar humus-containing soil can be used.
The tubers are set with 2 ft. 6 in. between the rows and about 15 in. between each potato, in the case of early varieties. Later crops are set with 3 ft. between each tuber, and the rows are spaced anything up to 4 or 5 ft. apart. The tubers are immediately covered with from 4-6 in. of soil and as soon as the tops show through (which will probably be sometime before the season of frost is over), the soil is drawn up with a draw hoe so that it is banked over the growing shoot. This protects it from late frosts.
In the case of very early crops some growers cover the early potatoes with twiggy branches or litter to protect them. It should not be necessary to earth up early potatoes again. In fact, no further attention need be given until the crop can be lifted. (This can usually be judged by the development ot flowers on the tops of the potatoes.)
With late crops, some growers make a practice of earthing them up in two operations. The reason for earthing-up is chiefly that it keeps light away from the tubers. The tubers are actually underground stems and have a tendency in many cases to run along the surface of the soil rather than to bury themselves deeply below the top. The result is that sunlight reaches some of the tubers, and turns them green. Green potatoes are neither wholesome nor appetizing.
Spraying.– The most troublesome disease of potatoes is the ordinary potato blight. It is advisable, wherever potatoes are grown, to spray as a preventive against this. Bordeaux Mixture is used for the purpose, and one spray should be given about the middle of June, another in July and, in some cases, a third application in August. Spraying is only practised on the later varieties of potatoes, not on the first early crops. It is important that the spray should reach both upper and lower surfaces of the leaves, if there is the slightest indication that the potato blight is already present.
The Wart disease of potatoes is another disease and in this disease the young shoots, when they are about 1 in. long, become coloured dark brown and often misshapen. The tuber later becomes withered in appearance, with unsightly looking crusts or scabs. Tubers are disfigured by black unwholesome looking scabs which gradually spread and affect the whole tuber. There is no known cure for this disease. If it does put in an appearance potatoes must not be grown on the plot for several seasons. If there has been any trouble from wart disease in the district, only potatoes which are guaranteed to be immune to the disease should be grown. Fortunately, many of the most popular varieties offered in catalogues now are immune.
Potato Scab, which is more unsightly than harmful, is sometimes troublesome to the grower. The easiest way to treat it is to scatter flowers of sulphur in the trenches at planting time. Another cure recommended is to dip the seed potatoes in formalin solution before planting (1 pint formalin to 20 gall. of water). Potato Leaf Curl is another fungus disease, but regular sprayings with Bordeaux Mixture will prevent its appearance. The Colorado Beetle will not, it is hoped, prove a serious menace to British growers, but every gardener should keep his eyes open for its appearance.
Forcing Potatoes.– Where a

is made up, potatoes can be forced, to provide a very early crop. They need, however, 15-20 in. between the rows, about 1 ft. between each tuber. They are planted carefully and given a good watering when the weather is warm, and earthed up a little as in the case of outdoor tubers. As the tubers are planted in autumn, from the middle of December onwards the potatoes produced will be considerably earlier than the main supplies grown outdoors. Careful attention must be given throughout growth to matters of ventilation and regulation of the heat of the hotbed.
Potatoes for Exhibition.– In cultivating potatoes for exhibition the usual method as already outlined is adopted, but extra care should of course be taken in the preparation of the soil. Leaf-mould and old mushroom-bed manure thrown into the bottom of the trench and also used to cover the seed tubers after they have been planted, gives them a good start. Throughout the season dressings of soot are given from time to time. A useful fertilizer to use as required along the rows is made by mixing 5 lb. superphosphate, a lb. sulphate of ammonia and 3 lb. kainit, using this at the rate of 3 oz. of the mixture per yard of row. When the potatoes are lifted, tubers of even size, not too coarse, with clean skins, and "eyes" as few and as shallow as possible, should be selected. They should be shapely and not deformed. Do not wash them until the last minute, and stage them as fresh as possible.
Varieties.– Constant cultivation appears to weaken any strain of potato. That is why new varieties are constantly coming on to the market and why the new varieties are for the most part more expensive than those which have been in commerce for a number of years.