12 



The Weekly Florists' Review. 



—. April 2, 1908. 



appearing during the last week or ten 

 days before the cuttings were taken out. 

 We had the same experience, too. This 

 year we are not troubled so much, but 

 we notice it appear just after the cut- 

 tings are potted.-. In tUat.oase it can 

 be controlled better, because after a 

 few days in the pots the sun can be 

 allowed to shine on the plants, and other 

 remedies can be applied which cannot 

 be applied to advantage in the cutting 

 bench before the cuttings are well rooted. 

 Cardinal was another bad one, and also 

 Adonis. 



I hardly think you should blame the 

 propagator altogether. I would advise 

 picking off all affected leaves and burn- 

 ing them. Then dust the plants with 

 dry-slaked lime and keep the foliage as 

 dry as practical. The plants, if they 

 possess any vigor at all, should soon 

 grow out of it. Do not overwater the 

 plants, A. F. J. B. 



LEAF SPOT ON CARNATIONS. 



Would you kindly tell what disease 

 causes the brown spots on the leaves 

 of the enclosed plants and starts to 

 dry up the plant? The variety is Han- 

 nah Hobart, and the disease is begin- 



ning to spread to others as well. How 

 could I fight it? A. A. 



The specimen forwarded showed an 

 aggravated casre of carnation leaf-spot, 

 or Septoria Dianthii. All plants as badly 

 affected as the specimen would best be 

 pulled up and burned, as they are full 

 of the disease and at this late date could 

 not be made to produce a crop of good 

 blooms before the end of the season. 

 This disease, if taken in hand in its 

 early^atages, can be checked and stamped 

 out readily enough, but when a plant 

 is thoroughly permeated with it, it wi^^ 

 never recover its normal vigor and health. 



After pulling up all the badly affected 

 plants, pick off the diseased leaves from 

 the plants left standing and burn jthem 

 up. Then mix up a batch of Bordeaux 

 mixture and apply it once each week. 

 You can wash it off each time just 

 prior to applying the next batch if you 

 like, say, the day before. 



Next season, keep a sharp lookout 

 for all such diseases and, as soon as 

 you discover any signs of them, begin 

 your work to check and eradicate them 

 at once. Don't wait until the plants 

 are doomed. A. r. J. B. 





SOIL AND 

 THE FLORIST 



i* 



Soil Sterilization. 



In those portions of the United States 

 where the soil does not freeze during the 

 winter months, or freezes only slightly, 

 low organisms, called nematodes, are able 

 ' to maintain themselves in the soil 

 throughout the winter. Under such en- 

 vironments these organisms have become 

 parasites upon a great variety of plants, 

 and interfere seriously with the commer- 

 cial cultivation of many crops through- 

 out the southern portion of the United 

 States, and in other sections where win- 

 ter conditions of the character above de- 

 scribed prevail. These little eel worms, 

 by attacking the tissue of the roots of 

 the plants, cause galls or enlargements 

 to appear upon the roots, and as these 

 are of a chalky nature, the normal func- 

 tion of the root is interfered with, and 

 the plant languishes and in many in- 

 stances dies. In practically all serious 

 infections from nematodes the possibility 

 of a profitable crop is defeated. In the 

 open there is no satisfactory way of com- 

 bating these organisms except in the de- 

 velopment of resistant strains of plants. 

 In many instances perennials have been 

 able to develop characters which make 

 them immune or able to contend with 

 these injuries, but in the case of most 

 annual plants conditions are quite differ- 

 ent, and few of them, or comparatively 

 few of them, are able to resist severe 

 attacks of nematodes. On small areas 

 it is possible to add materials which are- 

 more or less effective in the control of 

 these organisms, and in some instances it 



A paper by L. C. Corbett, of the United 

 States Department of Agriculture, read beton 

 the New York Florists' Club, March 9, 1908, 

 and continued from the Review of March 12 

 and March 19. 



is possible to sterilize the soil ^ means 

 of heat, but on large commercial* areas 

 this is a different question. 



In greenhouses, however, the problem 

 is quite different. As has been noted, 

 the soil is prepared artificially and the 

 question of keeping it free from nema- 

 todes is much more easily handled than 

 in fi^ld practice. While root galls upon 

 certain of our greenhouse plants have 

 been known for a number of years, par- 

 ticularly upon tomatoes, cucumbers and 

 roses, it was not until about 1892 that 

 any definite information was to be had 

 upon the subject. It had been deter- 

 mined that by freezing the soil in which 

 nematodes were abundant they could be 

 destroyed, and a clean crop then grown 

 in the same soil, but as not all the soil 

 which is used in the greenhouse can be 

 annually frozen, the idea of sterilizing 

 the soil by heat took hold upon the grow- 

 ers and has been practiced with good 

 results. 



Methods of Sterilizing. 



The first idea was to sterilize the soil 

 by heating it over an open fire in a shal- 

 low pan. This is effective for sand to 

 be used in propagating buds, and for 

 sand to be scattered upon the surface of 

 seed pans and flats where germinating 

 seeds or spores are to tfe handled. When 

 heating in an open fire in a pan is re- 

 sorted to, in soils containing a large pro- 

 portion of organic matter the physical 

 condition of the soil is very perceptibly 

 changed and is less practicable than when 

 not so heated. In fact, its water-holding 

 capacity is modified; its physical condi- 

 tions are also altered by the destruction 

 of a portion of the humus in the soil, and 

 then, too, chemical changes are decidedly 



interfered with. This practice, there- 

 fore, is almost entirely abandoned for ^''. 

 the apparently better one of sterilizing . 

 the soil by the use of live steafn. This - 

 worK can bb done either upon the 

 benches, when proper provision for doing 

 so has been provided, or it can be ac- 

 complished by means of a specially con- 

 structed sterilizing box. If the' work is 

 to be done upon the benches, il can be 

 accomplished by the use o£ drain tile laid 

 at intervals lengthwise or crosswise of 

 the benches and provided with an open- 

 ing through which a pressure hose carry- 

 ing live steam can be inserted. The 

 steam passes through the tile and out 

 into the soil, heating it to a sitfficiently 

 high degree to destroy these organisms. 

 One difficulty with this method is that 

 it requires a large amount of steam, and 

 it is not easy to cover the bed so as to -j- 

 hold the temperature in the surface soil 

 at the same point that it is in the deeper 

 layers. It has this advantage, that it 

 does not necessitate the removal of the 

 soil, but in ordinary greenhouse practice, 

 where raised beds are used and the soil 

 is annually removed, this advantage ia 

 of little consequence. 



The Sterilizing Box. 



The specially constructed sterilizing 

 box ia undoubtedly the most satisfactory 

 system of soil sterilization. The boxes, 

 of which there should be two, can be 

 constructed of such size as to enable 

 the operation of filling and emptying to 

 go on simultaneously; that is, while one 

 is being sterilized, the other can be emp- 

 tied and refilled, so that while the soil 

 in one box is becoming thoroughly cooked 

 the other will be ready for the admission 

 of the steam. In the construction of 

 boxes different plans have been fol- 

 lowed, and those best suited to the par- 

 ticular conditions will, of course, be 

 adopted by the grower. In general, how- 

 ^ever, a box two and one-half feet deep, 

 six feet wide and twelve to sixteen feet 

 in length will be found satisfactory. The 

 steam can be admitted either through 

 drain tiles laid in the bottom of the box, 

 or, perhaps better, through li^-inch pipes 

 perforated six inches apart with ^-inch 

 holes. The holes in the pipes should all 

 be made along one side and in line, and 

 when the pipes are placed in the mani- 

 fold from which the steam is to be drawn 

 the orifices should all look down, the 

 pipes being arranged at intervals suffi- 

 ciently wide apart to admit of the use 

 of a standard size shovel or spade be- 

 tween, and the rows about an inch or an 

 inch and a half from the bottom of the 

 box. The object in placing the holes 

 downward is to prevent them becoming 

 clogged by earth packed about the pipes. 

 The customary method of determining 

 the point to which sterilization should be 

 carried is to place a medium-sized potato 

 in the surface two inches of the sou, and 

 when it has become cooked by rtlre heat- 

 ing the soil is considered to be (sufficient- 

 ly sterilized. It is found that high-pres- 

 sure steam is more effective than low- 

 pressure steam for this work, and the 

 conditions usually recommended are forty 

 to sixty pounds' pressure, which gives a 

 drier steam and does the cooking more 

 rapidly than does low pressure. 



Necessary Precautions. 



In order that the work of sterilization 

 may be thoroughly effective, it is neces- 

 sary to observe certain precautions. These 

 organisms are of a low order, and, like 

 all low forms of life, multiply very rap- 



