Shallots are planted in the same way as onions, and so also are the members of the family called potato onions.” Both of these produce offsets to the bulb, which form the season’s crop. Tree onions, another type of onion sometimes grown as a curiosity, form bulbils on the stems, instead of flowers; these, if left, gradually weigh down the stem to soil level and root there to form new plants.
Soil should be well cultivated, but need not be so rich as for onions. It is an advantage if a plot can be chosen that has been manured for the preceding crop. In any case, apply a mixture of 3 parts of superphosphate, 2 parts of sulphate or muriate of potash and 1 part of sulphate of ammonia, at 3 oz. per square yard, prior to planting. This is done as early in February as the weather will allow. Good bulbs saved from the previous crop are pushed firmly two-thirds their depth into the soil. They should be spaced 6 in. apart in rows 9 in. apart. The bulbs should be ripe and ready for harvesting at the end of June. A week or so before this, draw the soil away from the clusters of bulbs so that they are exposed to the light and can swell readily. After lifting with a fork, lay the clusters on the surface or in a frame for a few days to dry off. Then separate the bulbs and store them in a in a dry, cool place. Native de Niort is the most shapely variety but Giant Red and Giant Yellow crop more heavily.
Foes are as for onions, but virus disease is also sometimes very troublesome.
Leeks, also members of the onion family, are grown in a little different manner. They are usually sown under glass in March, set out in the nursery in April, and planted in prepared trenches, or in heavily manured soil, in June or July. For success rich soil is essential, and it is common on poor soil to open wide, deep trenches, and to fill in a 4 or 5 in. layer of animal manure at the bottom. Then, as growth develops, the earth from the sides of the trenches is gradually drawn up against the plants, with the result that the lower portion of the leaves becomes blanched. It is this lower portion that is cooked for the table, and it is essential that there should be a good length of blanched growth, of good substance. Quite satisfactory leeks for ordinary purposes can be grown if a wide hole is made for each by working a dibber round and round in the soil, refilling the hole with rich, sifted soil, so that the surface is just a little lower than the surrounding ground. Seeds can be sown direct on this prepared site, and thinned to leave one strong seedling, the soil being hoed up round the plant as it develops. It should be noted that whereas celery plants are allowed to grow to full size before they are blanched by earthing, leeks are earthed in stages as they grow.