This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Under these names Richardia aethiopica or R. africana is best known to the trade. It is a tuberous-rooted plant, 2-3 ft. high, with large green broadly arrow-shaped leaves, and is highly esteemed as a market plant on account of its large pure-white bell-shaped spathes, popularly known as "flowers". Arum Lilies are chiefly remunerative at Christmas and Easter time when they are in much request. To have the plants in flower for Christmas, the rootstocks should be potted up afresh in July or August. They may be left in the open air till September, when it becomes advisable to place them under glass. A temperature of 55° F. by night and 60° F. by day will suit the plants until about the middle of November. The temperature should be regular and not fluctuating too much by day and night, as nothing interferes with the development of the spathes so much as an irregular temperature at this period. From the middle of November onwards the temperature may be raised to about 70° F. by night and 75° F. by day, and the plants may be kept clean by occasional syringings with tepid water. In the event of aphides appearing a quassia and nicotine solution may be used for syringing, or the houses may be fumigated or vaporized.
A rich gritty loam with a little leaf mould or well-rotted manure suits Arum Lilies well. The pots should not be too large - 5 in. or 6 in. being the sizes most favoured. Stock is readily increased when repotting by detaching all offsets and potting up separately into pots according to size. When flowering is over, the plants may be moved to cooler quarters, and when all danger from frost is over in spring they may be placed out-of-doors in warm sunny spots to rest. Many growers plant them out of the pots in the open ground during the summer; others leave them in the pots, and excellent results are produced by both methods. In the mildest parts of the kingdom, such as Cornwall, the Scilly Islands, and the south and west of Ireland, Arum Lilies may be grown in the open air all the year round. Besides the ordinary variety there is a dwarf-growing form called "Little Gem", and another called "Childsi" - both much smaller than the type. There is also a strong-growing variety called Nicolai, 4½ - 5 ft. high, which has spathes 1 ft. or more across - probably much too large to be popular with market growers.
ARUM LILIES GROWN FOR MARKET BY THE EDITOR.
Next to the white Arum Lily, the yellow-flowered one called Elliot-tiana (fig. 261) is most extensively grown - more by nurserymen, however, than by market men. It resembles the ordinary form in shape and size, but the leaves are decorated with silvery semi-translucent blotches, and the spathes are of a bright golden yellow. It requires to be grown in greater heat, and is readily reproduced from seeds, from which flowering plants develop in about three years. There are several other Richardias, but they are chiefly grown in small numbers for private trade.
Fig. 261. - Richardia Elliottiana.