As the annual Asters differ from our wild Asters and were introduced from China, they should properly be known as China-asters, Callistephus chinensis. From a violet colored Daisy-like flower with a yellow center, the China aster has been bred to assume a multitude of forms and colors. Previous to 20th century, the China aster was not considered a cut flower but was grown only for garden decoration. A few years later, with the production of the early sort, Queen-of-the market, and the Comet and the Branching China-asters, this flower began to exhibit its rapid development, its long stems, and its large flowers.
The principal types of China aster popular for the garden may be classified into two groups: The flat-rayed or “petal” Asters and the tubular or quilled Asters. Among the earliest are Queen-of-the-market, Early Wonder, Early Express, followed by the Royal group, then the King. Of these, the Tall Branching Asters, the Crego Giants (an improved Comet), the American Beauty, California Giants, Heart of France, and the Ray are the most popular for cut flowers, but all the other groups-dwarf and tall-are interesting for the garden. Notice illustration below, which depicts some of the distinct types. Seed catalogs list most of them in their various colors.
A new type of China aster promises to be included in every catalog, known as Sunshine. The flowers are 4 inches to 6 inches in diameter. The centers are quilled, golden in color, merging toward the outside of the flower into white. The outer petals are mauve, dark blue, dark red, and the more or less pastel tints-coral to silver lavender.
CUT FLOWERS. As a cut flower the China aster is highly popular and generally admired for its colors-rose-pink, white, violet, purple, red, light pink and lavender. The commercial demand is more for white and rose, the lighter pinks and purples are not as popular. It has splendid keeping qualities, but vases used for it should be thoroughly cleaned afterward because of the odor, which is usually generated by China-aster stems kept for a long time in water. It is well to remove all leaves from the part of the stem that will stand under water. A few drops of formaldehyde will keep the water from becoming foul. The stems are long and in most cases strong enough to hold the heavy flowers erect. The flowers stand rough usage, too, a quality greatly desired in blooms used commercially.
The following discussion applies to outdoor culture. Florists are growing China-asters more and more each year in greenhouse in Summer. More perfect and long stemmed flowers develop in greenhouse.
SOWING DATES. The earliest are first sown Feb. 20 in a greenhouse. Second lot sown March 1 in the greenhouse or hotbed.
Crop for late bloom May 1, in seedbed. This late sowing gives later blooms, which are more in demand and less susceptible to disease.
One ounce of seed contains 10,000-12,000 seeds; at least 5,000 plants can be expected from this amount.
1. Sterilize seed with organic mercuric compounds such as to prevent stem rot and damping-off.
2. Where to Plant clean soil for seed sowing, i.e., soil that you are certain does not harbor diseases. Regarding the sowing of seeds, it is best to use a shallow flat. “Seedlings will grow in ordinary garden soil to a size large enough to transplant; but it is well to add one-fourth well-rotted manure and enough sand to prevent the soil from becoming hard. Fill the flat half or two-thirds full, water thoroughly, and finish filling with soil just moist enough to handle nicely. The wet soil in the bottom will furnish enough moisture so that the boxes will not have to be sprinkled until after the seedlings are up. Sow the seed in rows 2 inches apart, cover with fine sand and press firmly.” Note the advice to water before sowing the seed and to cover the seed with sand.
YOUNG PLANTS. The seeds will germinate in a little over a week and the seedlings should be kept in full light, so that they may be sturdy rather than tall and leggy. When they need water give it, but do not sprinkle the plants each day, as this encourages the destructive damping off fungus. As soon as several true leaves have grown, the seedlings should be transplanted to other boxes. Userich soil in the bottom of the flats and ordinary soil above as further protection against disease. Set the seedlings 2 to 3 inches apart.
Crowding, too much water, or drought will check the plants, and nothing lessens the future blooming quality of the plants as much as a check. If the young plants are given a little cool air each day, or if a cold frame is available so that they may be gradually hardened off, they will stand some frost when finally set out into the garden.
PLANTING. The best soil for China-asters is a sandy loam, but a heavy soil will also produce good flowers. If the spot where they are planted has been manured and limed the previous year, it is better than to apply manure just before setting out the plants. Plants set in dry weather should have the roots puddled.
Set the plants at least a foot apart. Where space is at a premium, the plants may be set in beds and spaced 12 inches apart each way. Keep them cultivated and well watered. The feeding roots are usually near the surface of the soil so that cultivation should be shallow.
SHADING. Regarding the shading of China-asters, in The Florists’ Review, remarks that: growing China-asters under cloth shades is a great deal like growing Asters in the greenhouse, and there is always a question as to whether or not it pays. That depends, as with all other crops, on the kind of crop you get and the kind of market you have for the crop. There is no doubt that it has its advantages. In the first place, the cloth shades the plants from the heat of the sun, which is a big advantage with China-asters, and growing them under cloth has its advantages over growing them in the greenhouse, because the former method allows more circulation and freer evaporation, reducing to a minimum the danger of damping-off and retarding the development of fungus, which is so liable to reduce the yield of a crop grown under glass.
The supports for the shade should be put up just as soon after the plants are established as convenient Any width of bed may be covered and 1×2-inch lumber is heavy enough to use. We should advise using a frame around each bed any desired length and in width anywhere from 20 to 50 feet, with height sufficient to clear at least six feet, so that a man can walk under the frame for cultivation and for picking flowers.
The use of side muslin’s would depend on whether a grower is bothered by beetles or other insects (tarnished plant bug and leafhopper). In some sections you cannot grow China-asters on account of beetles. If the muslin is put on early enough and side cloths are used one will, of course, have protection from beetles such as cannot be secured any other way. At any rate, the covering should be put on before the hot sun sets in; certainly before the buds appear.
It does not pay to go to the expense of covering plants that will not return the maximum yield for the plants that are cultivated. If an upright type of plant is used, such as Perfection, it will permit much closer spacing than if the branching type is used, and a great many more flowers can be picked to the square foot. If I were growing Asters under cover,
Or you could use the Dutch bed system and set the plants about 15 inches apart each way, with an 18-inch walk every six feet. If cross-pieces are used every four or five feet and the muslin sewn together on the edges, the first length of the muslin being attached to the frame on one side, it can then he rolled over the entire bed like an awning and rolled back again at any time desired. Of course, it would have to be put on in overlapping sections as far as the length of the piece would be concerned, so that each 12 or 15 feet of length could be rolled across separately.
The amateur can easily shade China-asters by planting them among corn or setting them in a naturally partially shaded spot, although not one in which the food and moisture is robbed by large trees.
WATERING. When a method of irrigation is provided the flowers produce longer stems and are larger. So that overhead watering is highly profitable to the commercial grower who must not let his crop be ruined by a dry season.
INSECT ENEMIES. Tarnished plant bug. The tarnished plant bug is so small that it would hardly seem able to do much damage, but it is the most serious China-aster pest during the hot, dry weather. It punctures the growing tips of the plants so the growth is deformed and dwarfed. The flowers open one-sided so that when “stung” they are malformed. A tobacco spray and the dusting of the plants with airslaked lime or tobacco dust is often moderately effective in keeping the bugs in check, but as they are rapid fliers they are seldom killed or completely controlled. The bugs do not work in the shade so that sometimes the plants are not troubled when grown in the greenhouse, under trees or when protected with cheesecloth screens.
Cutworms, grasshoppers. Cutworms cut off the plant at the surface of the soil. Grasshoppers eat the flowers and foliage. Spraying with arsenate of lead will help to control them, as will also poison bait.
Blister beetles, black beetles. One of the worst pests of the flowers is the large fat-bodied, bluish-black blister beetle. They appear about the time of the mid-season flowers. In limited quantities, they can be jarred into a can of kerosene. They drop as soon as touched or disturbed. To prevent the infection becoming serious the plants may be sprayed from the start with any spray, which contains pyrethrum extract. This is superior to arsenate of lead.
Boot lice. Some sickly China-asters are not diseased but are affected with root lice which sap the strength of the plants, but which may sometimes be controlled by tobacco stems placed around the plants. It is not safe to plant China-asters two successive years upon soil infested with these pests.
DISEASES. Yellows. This is a disease, which cause one-sided flowers, yellowish in color and leaves, which are golden.
Yellows has proved one of the most baffling of plant diseases, it is hard to determine whether bacteria too small to be seen even through a microscope were the cause, or whether the disease was due to some disturbed physiological condition with the plant.
As the China-aster was found to be particularly susceptible to yellows, the Boyce Thompson Institute chose this plant for its series of intensive experiments, which have resulted in discovering what is believed to be the germ carrier of the disease. Dr. L. O. Kunkel, plant pathologist of the Institute, has proved that one certain insect known as a “leafhopper” always transmits the yellow disease. Although it is not yet known just what the leafhopper transmits or how he does it, Dr. Kunkel found that when a diseased plant and a well one were imprisoned in a small glass house the contagion did not spread from one to the other unless this particular insect was present. Other insects of similar species were tried in the glass house; but though they might hop and scurry from the sick plant to the well one the latter never contracted yellows until the leafhopper was introduced.
One of the striking things about the transmission of yellows is its similarity to the transmission of yellow fever and malaria in man, which is effected by means of the mosquito. The Boyce Thompson experiments in this field are being continued and it is possible that their results will throw light upon human as well as plant diseases.
From Wisconsin Horticulturist.
PREVENTION. (1) Plants for setting out should be grown in the house or greenhouse. The leafhopper, which spreads the disease, does not live indoors, nor in proximity to buildings; plants set near walls or buildings are more apt to be free from the disease than if planted in the open.
The disease-free leafhoppers get the yellows virus by feeding on biennial and perennial host plants. Several weeds belonging to the genera Sonchus, Erigeron and Chrysanthemum are some of the wild plants in which yellows most often pass the Winter and in which it first appears in the Spring. Aster leafhoppers after feeding on such plants become disease carriers and retain the virus as long as they live. The number of leafhoppers that feed on these wild weeds must be relatively small. They transmit the disease early in the Spring to a few annuals, such as the China aster, the Ragweed (Ambrosia artemisiaefolia), and the Daisy Fleabane (Erigeron annuus). Large numbers of young leafhoppers hatch from the eggs deposited in these diseased annuals. They feed on the diseased plants, become virus carriers, and when adult, spread yellows far and wide. There is evidence that the leafhoppers do not range in large numbers over distances of more than a mile under ordinary conditions of food supply. Severe cases of yellows are local and occur where large numbers of insects have been reared on diseased plants.
(3) After the plants are established outdoors, watch for the ones with leaves growing vertically (like Cos Lettuce leaves) as these are infected plants and should be pulled up and destroyed.
(4) Bordeaux mixture seems to repel the hoppers but its utilized is not of itself a guarantee of yellows free plants.
(5) The leafhopper is merely the medium through which the disease is transmitted; it carries it from a diseased plant to a healthy one; therefore if we eliminate diseased plants, which includes certain weeds, we lessen the probability of infection. China-asters grown in plots surrounded by cultivated fields are less subject to severe infection than China-asters grown in the vicinity of pastures, meadows, wastelands, or other weedy places. If we could screen the plants all through the growing season we might expect plants 100 percent disease-free.
Stem-rot. If the season has been a wet one the stems of China asters almost in the blooming stage often become black just at the surface of the soil. Gardens once infected often become so bad that it is best not to attempt to grow China-asters in them for several years. The spores are carried over from year to year. The scattering of wood ashes about the plants and the fumigating of the seed with a one percent solution of formaldehyde or the use of Semesan have been reported as effective by some gardeners, while others have found no satisfactory means of control.
Rust. Orange-colored masses of rust often appear on the underside of the leaves of plants, which may thereby be either checked or stimulated, into too active growth. Rusted plants of any sort are rarely curable; they must be pulled and burned. Spraying the young plants with Bordeaux mixture will prevent their infection. Note that the disease appears on the underside of the leaves; it is here only that spraying will be effective.
Summary of Important Points.
1. Careful culture from the time the seed is sown prevents damping-off. 2. Checking growth cause poor flowers and rust. 3. Shading plants prevent injury from the tarnished plant bug and yellows. 4. If plants are badly diseased, burn them and stop growing China-asters for a few years.
(From Greek for beautiful crown)