Diseases

Stemrot (Rhizoctonia) is the common wet stemrot which does perhaps more damage than all the other diseases combined, and it is also more difficult to control than any of the others. Its presence does not manifest itself until its damage is wrought, and the plant is seen to wilt and die. The cause of the disease is a fungus which exists in the soil, and which will lie dormant in the soil for several years if there are no plants to attack. Hence no carnations should be planted for several years in soil which is known to have this fungus present.

Species of Fusarium cause a slow rot of the heart of the plant; the treatment is same as above.

Carnation-rust (Uromyces caryophyl-linus) is more common than stemrot, but not nearly so destructive. A slight swelling of the outer tissue of the leaf is the first sign of its presence. Later on this bursts open, releasing a brown-colored powdery substance, comprising the spores by which the fungus is propagated. Keeping the foliage dry and the atmosphere buoyant and bracing will prevent the appearance of this disease. Spraying with bordeaux mixture has been found effective in combating this disease after it has gained a foothold.

Fairy-ring (Heterosporium echinula-tum) is perhaps the most destructive of the spot diseases. It is brought on by a humid or foul atmosphere, and must be fought with remedies which will produce the opposite in atmospheric condition. Bordeaux is the standard remedy for all spot diseases.

Carnation flower showing a well shaped calyx that will seldom burst.

Fig. 815. Carnation flower showing a well-shaped calyx that will seldom burst.

Bench rot may be caused by any one of a number of organisms attacking the ends of the cuttings in the propagating-bench. It is frequently a very serious disease. The fungi most frequently causing the trouble are in the sand and under the ideal conditions of temperature and moisture of the propagating-bench spread very rapidly. The use of clean sand, free from all organic matter, and the securing of new sand for each lot of cuttings and cleanliness in the propagating - house will help to control this trouble.

Insect Pests

A green plant-louse (Myzus persicae) is frequently troublesome on carnations. It also attacks a large number of greenhouse and garden plants as well as several fruit trees. Nicotine applied in one of the many forms will destroy it. Spraying and vaporizing are both employed successfully as preventives of the attacks of aphids.

Thrips (Heliothrips haemorrhoidalis) are equally destructive and more difficult to control. The same treatment as for aphis is suggested. Sweetened paris green used as a spray is also effective (three gallons of water; two pounds of brown sugar; two table-spoonfuls paris green).

The punctures made by thrips and plant-lice cause yellowish spots on the leaves, a diseased condition known as stigmanose.

Red-spider (Tetranychus bimaculatus) is found mostly where plants grow near steam-pipes, where ventilation is poor, or in houses kept too dry. Persistent syringing with water will usually destroy them if the spray is applied to the under surface. Use much force and little water to avoid drenching the beds. Sulfur as a dust or in water will also destroy them.

The carnation mite (Pediculopsis graminum) injures the buds by transmitting the spores of a fungus (Sporotrichum pose) which causes them to decay. The injured buds are easily recognized and should be promptly gathered and burned to prevent further spread of the trouble.

Raising New Varieties

It is a long way from the undeveloped five-petaled carnation (Fig. 813) of early days to the perfectly formed full bloom of today. This filling out of the bloom has evolved gradually, and has been assisted by cross-fertilization and selection by the carnation-breeders through the many years in which the flower has been cultivated. This crossing, which has been the means of perfecting the American strain of the perpetual-flowering carnation, has been prosecuted continuously ever since the arrival of the first plants in this country. Many men have found both pleasure and profit in the work, and those with scientific inclination will find no subject more interesting. Not only have the blooms become larger, but the color has varied widely, the "substance" has been much improved, the calyx has been developed for non-bursting (Figs. 814, 815), the keeping qualities of the flowers have been improved, and the stems have been lengthened.

The operation of pollinating the bloom, or transferring the pollen from one flower to the stigma of another, is a simple matter, and is perhaps of less importance than other parts of the work of producing desirable new varieties.

Carpenteria

(after Professor Carpenter, of Louisiana). Saxifragaceae. Ornamental shrub cultivated for its large fragrant white flowers.

Evergreen: leaves opposite, petioled, usually entire: calyx 5-parted; petals 5; stamens numerous; ovary almost superior, 5-7-celled; styles 5-7, connate at the base, with linear-oblong stigmas: fruit a many-seeded dehiscent caps, with numerous oblong seeds. - One species in Calif.

This is a highly ornamental evergreen plant, with rather large opposite leaves and showy white and fragrant flowers in loose and terminal corymbs. Hardy only in warmer temperate regions. It requires a well-drained, light and sandy soil, and sunny, somewhat sheltered position; it especially dislikes moisture during the winter, and its perishing is more often due to an excess of moisture than to the cold. Propagated by greenwood cuttings under glass in summer, and by suckers, which it produces freely; also, by seeds sown in spring.

Californica

Torr. Shrub, 6-10 ft.: leaves elliptic-lanceolate, entire or remotely denticulate, bright green above, whitish-tomentose beneath, 2-4 in. long: flowers pure white, 2 1/2-3 in. diam., fragrant; petals orbicular, concave. June, July. B.M. 6911. Gn. 31:100; 34, p. 75; 36, p. 26; 54, p. 248; 76, p. 376. G.C. II. 26:113; III. 40:6, 7; 44:112. R.H. 1884, p. 365. J.H. III. 29:251; 45:107; 59:61. M.D.G. 1913:121. G.M. 31:25; 40:300. G. 29:695. Gn.W. 4:569. Alfred Rehder.

The Fig. 816 is a section of a flower showing the reproductive organs; a shows the pod which encases the ovules or forming seeds, b. From the tip of the pod rises the style which has usually two, but frequently three curved ends, or stigmas, c. When the stigma is in the proper stage to be fertilized, which is indicated by the fuzzy appearance of the upper part, the pollen, which is the powdery substance released by the anthers, d, is applied to the fuzzy parts. To prevent self-fertilization, these anthers should be removed from flowers intended to be pollinated, before the pollen is released. Within one to three days, if fertilization has taken place, the bloom will wilt, the ovary will begin to swell and within a week the seed-pod can be seen to increase in size. As soon as the bloom has wilted, the petals should be removed and the calyx slit down the sides to prevent water from standing inside the calyx and causing the pod to decay. In six to eight weeks the seeds will be ripe and should be sown at once. Each seed may prove to be the beginning of a variety which will be one of the milestones of progress in the improvement of the carnation.