The Magazine of Botany and Gardening, 1836

There is a grub that is sometimes very destructive to crops of onions. The ravages of this insect may very easily be perceived by the onion blade assuming a glaucous green colour, and soon after changing to yellow. But if charcoal dust, (which is the refuse that is left at the bottom of a charcoal pit, after the charcoal for use is taken out), be spread upon the top of the ground intended for onions, about half an inch thick, before the seed is sown—the ground being previously well dug and manured—and the top soil mixed with the dust, not the least sign of infection will afterwards appear.

The charcoal dust ought to be kept quite dry, which may easily be clone by placing it in a round heap, and covering it closely with turf.

The application of this material has also been found effectual in preventing the clubbing in the roots of cabbages, &c.

Besides the defending of onions against the ravages of the grub, it has been found that the transplanting of onions greatly promotes their growth. All know the effect of the process in the case of leeks, and that these are scarcely thought marketable when they have not been so reared. Why should not the transplanting of onions be equally beneficial? It is practised in Portugal. There they sow the onion seed in November or December, on a moderate hot bed, covered with a few inches of rich good mould, in a warm situation, merely sheltered from their slight frosts by mats. When about the size of a large swan's quill, or about April, they are transplanted on a rich light mould, well manured with old rotten dung, the plants at the distance of about nine inches each way, generally in beds, for the convenience of access, laying the plants flat, covering lightly the beard, and part only of the bulb, with rich mould, well mixed with two-thirds of old rotten dung; watering if the weather is dry, until they have taken root; subsequently now and then breaking the earth by lightly hoeing, and keeping them perfectly clean from weeds. There, they have often the means of watering by irrigation, and if so upon rich soils, the onions grow to a very large size, particularly when the water runs through small heaps of dung. When this is practised, however, or much water given, the onions do not keep so long as in other circumstances. When ripe, the onions are drawn gently from the ground, a twitch is given to the tops, after which they are left to season, where they grew, for a few days. Ere being housed, they are bound into ropes with dry straw, and not permitted to sweat in the heap. Their preservation depends much on their being dry and good when housed, and on their not being bruised. The onion most esteemed in Portugal is thus treated and reared.