|Standard Cyclopedia of Horticulture|
Violet. One of the choicest of fragrant garden flowers. See Viola.
Comparatively few changes have taken place in the commercial cultivation of the violet within the past decade. The industry is more or less stabilized, and while there has been a tendency to increased planting of the single varieties, on the whole there has been no marked growth in the actual area under cultivation. The violet still offers some unique opportunities for the untrained lover of plants for the reason that it may be grown at less expense and with fewer and more simple houses and frames than almost any other of the major florist crops. While the violet readily responds to good treatment and to clean and healthy surroundings, its status is still relatively low owing to the fact that the risks of production are great, and this seems to develop a tendency toward carelessness on the part of those who take up the work as a business.
The cultivated varieties of the florist's violet are limited in number and probably all have been derived from the common sweet violet, Viola odorata, widely distributed over Europe and Asia. So far as known, no true varieties of the violet, either single or double, have originated in America. Of the double varieties and strains the most widely planted in this country are the Marie Louise (Fig. 3947) in its several forms, including Farquhar and Imperial; Lady Hume Campbell, Neapolitan (Fig. 3948), De Parme, Swanley White (Fig. 3949), and Madame Millet. For all practical purposes the culture of the double violet is confined to the Marie Louise, a true mauve in color, and the Campbell, a light mauve. The Neapolitan is a somewhat hardy type, but its color is too light for the market. The single varieties are coming to be important in the trade, and in the South and West are taking the place of the double sorts. South of Philadelphia, and north of Richmond, Virginia, the growing of any of the doubles is more or less risky, and it is in this territory and the Pacific coast that the singles are becoming so popular. The principal varieties are the Princess of Wales, Admiral Avellan, La France, California, and Baron Rothschild. The last is a promising variety, being a very free bloomer and a good keeper. The habit of this plant is compact and the foliage is of good texture, shape, and color.
Violets will grow and thrive in almost any good garden soil. The soil that will grow good strawberries or potatoes should, with proper care, grow good violets. Under such intensive cultivation as must necessarily be given the violet, it is important to give strict attention to soil preparation. Sod from an old pasture makes excellent soil for the crop, but care should be taken that it is not too heavy. A moderately sandy loam sod is best. This should preferably be cut in the fall and composted with well-decomposed stable-manure. Many growers use cow-manure, but no particular advantage has been observed in this material so far as the vigor of the crop is concerned. It is more difficult to secure and is not so easily handled; hence ordinary well-decomposed stable-manure is preferred. About one part manure should be used to four parts of soil, and a little extra work in thoroughly incorporating the manure with the soil always pays well. Some of the best growers make up the heaps by bringing the soil and manure together by means of wheelbarrows and then mixing by shoveling over the pile, as is done for concrete-mixing. When there are large quantities of soil to be mixed, the hauling can of course be done with wagons or carts. A one-horse cart makes a very convenient means of bringing the materials together. Before putting the soil into the houses or frames it should be turned and mixed again and for about every two or three thousand plants use a 200-pound bag of powdered quicklime. The lime may be sprinkled on the heap from time to time as the mixing takes place.
For all practical purposes the commercial cultivation of the violet is limited to growing in houses except in the South and far West, where for the most part they are grown in the open or in coldframes. There is still considerable growing done in frames, but there are so many inconveniences involved in this work that most of the frame culture has been abandoned for the cheaper forms of houses. Gradually, also, the method of growing the plants in the open field and later covering with frames is being abandoned. The violet is subject to so many diseases and troubles which are materially influenced by weather conditions that it is important to have control over at least the moisture conditions the greater part of the year. In house culture the crop is preferably grown in solid beds (Fig. 3950). Experience has shown that better and more flowers are secured by this method than by growing on benches. Then, again, there is the advantage of the long life of the solid beds and the lessened expense of the general work. Care should be taken not to have the beds too wide, otherwise it will be difficult to reach all parts of them from the walks. The best growers practise changing the soil each year. At least 5 inches of fresh soil should be put in before the young plants are set out. The time of planting varies somewhat in different parts of the country. Usually the flowers are not much in demand after the middle of April, so that in practically all the violet-growing sections preparations may begin at this time for clearing the houses and getting ready for the new crop. The plants, having been properly prepared, as will be described later, should be set 8 or 9 inches apart in rows 10 inches apart. This is the distance for the doubles. For the singles they are usually planted about 12 inches apart in the rows, the rows being from 12 to 18 inches apart. Most of the single varieties now under cultivation may be planted closer than this, say from 10 to 12 inches apart. After the plants are put out it is necessary that they should be carefully watered and all weeds in the beds kept down. It is desirable to keep the temperature as low as possible in summer. To this end the houses should be shaded. It is desirable to give plenty of fresh air, but care should be taken to have the top ventilators so arranged that the plants may be protected from rain. The violet requires considerable water, but no very rigid rules can be laid down as to the amount required. Every effort should be put forth to keep the plants in good growing condition without over-saturation of the soil. Early in summer the runners will begin to appear and these must be cut off as rapidly as the plants can be gone over conveniently. The object is to secure a good strong healthy compact plant and to induce free growth at all times, as with such strong free-growing plants developed by October 1 all the conditions will be at hand for the production of long-stemmed, good-colored flowers.
The violet may be propagated in a number of ways. One of the common practices is to divide the crown. This is usually done in spring after the flowering season is over. The plant is lifted and the soil shaken off, and then it may be readily pulled apart and the small plants either set in beds or flats. This method has objections because a great many plants or crowns so separated are hard and woody, and they will refuse to grow into good vigorous healthy crowns. A second and more desirable method is carefully to select young and vigorous offshoots and root these in the ordinary way in sand. Following the second method the young plants can be secured from time to time during the late winter without disturbing the main plants. If proper care is exercised and good selection made, another good supply of stock may be readily available early in March, and selections may be made from these for the planting, which is performed the latter part of May.
Comparatively little attention has been given to proper houses for violet-culture. Almost any kind of house is believed to be suitable, hence the crop has not had the advantages that more favored ones like the rose and carnation have had. Any good type of well- lighted, well-ventilated house will suffice. For beginners and those who have not a large amount of capital to invest, one of the most economical and satisfactory houses is an ordinary even-span type, 12 feet wide. The height of such house from the bottom of the walk to the ridge is 7 feet. The height of the side from the top of the plate to bottom of gutter is 20 inches. The walls can be easily boarded up with rough lumber and then covered with rustic siding. One walk 14 inches wide is made through the center of the house. This gives two beds, each 5 feet 5 inches wide. Such beds are a little wide for conveniently reaching the plants from the walk, but by means of a board to be hooked onto the heating pipes, all plants may be conveniently reached. Coldframes for violet-culture are simple in construction. They are of the usual type, being 6 feet wide, 12 inches high in front, and 16 to 18 inches high at the back. Ordinary 3 by 6 sash may be used. These frames may be made any length in locations where the soil is porous and well drained; the frames may be lower than the surrounding soil. This gives some advantages in winter although it is back-breaking work at any time properly to care for the plants and pick the flowers in such frames.
In sections where the climate is comparatively mild, violets may be planted directly in the open ground and the frames, which may be movable ones, may be set over the plants about the middle of September. Violet houses do not need much heat, merely enough in fact to keep out the frost. The tendency is to overheat and there are probably more good crops spoiled by too much rather than too little heat. Hot water is usually depended on for heating both houses and frames. For the average houses a boiler capacity of 1,200 to 1,500 square feet will be required for every 10,000 plants. With the present cost of materials and labor it is safe to figure the cost of a plain style of house such as already described at about 50 cents a plant. A house 12 feet wide and 100 feet long will hold about 2,000 plants and should cost complete from $850 to $1,000.
Marketing is one of the most important factors connected with commercial violet-growing and is seldom understood in all its details. The grower should be thoroughly familiar with the many needs and requirements of the market and be able to supply these demands, for upon his ability to do this depends largely his success or failure from a financial standpoint. Violets are prized chiefly for their delicate perfume, and as this diminishes in proportion to the length of time they are picked, the best market, other things being equal, is the one which requires the least possible delay between picking the flowers and placing them in the hands of the customer.
The crop may be disposed of at retail or wholesale or through a commission merchant. Each method has its advantages and disadvantages, and in deciding which one to adopt the grower must be guided by existing conditions. He must in any event have a thorough knowledge of the requirements of the market as regards quality of the flowers, size, shape, and arrangement of the bunch, and should at all times exercise the utmost care in picking, packing, and shipping, so that the flowers may reach the customer in the best and most attractive condition. The kind of bunch varies from year to year, and each large city is likely to have its own style. The various styles are wonderfully exacting in their requirements and great skill is required to bunch the flowers properly.
The cultivated violets are subject to a number of diseases, each of which is characterized by one or more distinct symptoms. The principal diseases are as follows, their destructiveness being in the order in which they are discussed:
Spot disease (Alternaria violae) (Fig. 3951), also called leaf-spot, leaf-rust, and smallpox, is the most widespread and destructive known in America. It attacks principally the foliage, normally producing definite circular whitish spots, frequently with concentric rings, of a darker shade, very often with a light central portion resembling the bite or sting of an insect. Cercospora violae. Phyllosticta violae, Septoria violae, and the like, produce spots very similar in outline and appearance to those caused by Alternaria violae, but only under conditions peculiarly favorable to these fungi do they cause any serious loss.
Root-rot (Thielavia basicola) is very troublesome and destructive in some localities, especially to young plants that are transplanted during hot dry weather. It causes the browning or blackening of the parts attacked and the final death of the plant.
Wet-rot (Botrytis sp.) attacks leaves, petioles, flower-stalks, and flowers, causing a moist or soft rot. It is sometimes very destructive, especially with large plants growing in a damp stagnant atmosphere, where there is insufficient ventilation and light.
Leaf-fading or yellowing is induced by a variety of conditions, but as yet little that is definite has been ascertained regarding its cause.
It is difficult to exterminate any of the diseases named after they once gain a foothold. However, they can be held in check and often entirely prevented by selecting and propagating exclusively from strong vigorous disease-resistant plants, and by keeping them in the best possible growing condition. Careful attention must be given to watering, cultivation, and ventilation, and the dead and dying leaves and all runners should be destroyed as fast as they appear.
Although violets are attacked by a number of insects and other related enemies, only a few do sufficient injury to warrant discussion here.
Aphides (Aphis sp. and Rhopalosiphum violae) are generally known as the green and the black aphis or the green- and black-fly. They cause the young growing parts to curl and twist, resulting in a stunted ill-formed plant. They work their way into the young, unopened flower-buds, and, thrusting their bills through the overlapping petals, feed on the juice. Each puncture produces a greenish white blotch on the petal, and the flower becomes dwarfed, distorted, and worthless for market. Aphides can be easily controlled by fumigating with hydrocyanic acid gas, and this is now in general use. To each cubic foot of space in the house or frame use .15 gram of 98 per cent cyanide of potash for double varieties and .10 gram for single varieties. Handle the cyanide and gas with utmost care, as both are very poisonous. Divide the total amount of cyanide into as many equal parts as there are jars used, which latter should be one for every 50 to 75 lineal feet of a house 12 to 18 feet wide. Put each part into a two-pound manilla paper bag and this into a second bag. Attach each package to a string or wire so arranged as to allow it to be lowered from the outside of the house into its respective jar. Pour into each jar an amount of water about equal to the bulk of cyanide in the bag, add commercial sulfuric acid until steam is evolved, then from the outside lower the bags into the jars beneath. Fumigate double varieties thirty minutes and single varieties twenty minutes, after which open ventilators from outside, leaving them open at least sixty minutes before entering the house. Aphides may also be combated by using tobacco in some one of its many forms, but tobacco is likely to weaken the leaves and make them more liable to the attack of fungi, and on this account is very objectionable.
Red-spider (Tetranychus telarius) lives on the under surface of the leaves, and, when present in sufficient number, causes considerable damage. It is widely distributed on a great variety of plants, and when established in the violet-house is most difficult to combat. It can be held in check, and often the plants may be kept entirely free from it, by frequent syringing with clear water under a pressure of twenty to thirty pounds to the square inch. Care must be taken to syringe early in the morning and on bright days, so that the plants may dry off before night. Neglect may be the means of inducing disease.
Eel-worms, or nematodes, are sometimes very injurious to the violet. A common species attacks the roots, producing galls and distortions that check the growth of the plants. These may be controlled by judicious soil selection, the freezing of the soil in winter and the use of good clean grass sod. A very destructive nematode, Apheleuchus olesistus, that appeared in this country twelve or fifteen years ago, is rapidly becoming one of the serious enemies of the violet. This nematode attacks the crown-buds, causing the plants to "go blind." Rigid selection of stock is the only remedy. Every "blind" crown plant should be taken out and destroyed. Extreme care should be exercised in bringing in new stock. Nearly all imported plants are more or less affected with the pest. The bud nematode does more injury in this country than abroad. This may be due to the fact that while the pest has been imported, its enemies have not been brought in. Some very promising investigations are now being made by N. A. Cobb, of the Bureau of Plant Industry, United States Department of Agriculture, of a race of predaceous nematodes which destroy immense numbers of the harmful kinds.
In some parts of the country the larvae of gall-fly (Diplosis violicola), violet sawfly (Emphytus canadensis), greenhouse leaf-tyer (Phlyctoenia rubigalis), and several species of cutworms (Agrotis et al.) injure the plants to some extent by feeding on the foliage. Fumigating with hydrocyanic acid gas is the best means of combating them.
Under certain conditions slugs, snails, sowbugs, and the like, do considerable damage, especially to the flowers. They also can be controlled by the hydrocyanic acid gas treatment.
Pests and diseases
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963