>^:.-7"^'*,7' ikTT;-'^*'- ■•^f^t^'w^, >.. -v-. 6,^ j- 



JUNK 9, 1904. 



The Weekly Horists' Review. 



J07 



time on throughout the season, but is 

 most noticeable at two periods, the set- 

 ting of the plants and the time of 

 blooming. Complaints of this trouble 

 are most abundant from the latter part 

 of July to the middle of August, as it is 

 during this period that most of it ap- 

 pears. 



Those who examine closely find that 

 the stem of the plant just at the surface 

 of the ground is badly rotted and evi- 

 dently the seat of the dificulty, the hard 

 inner woody portion only remaining. 

 This, however, is the final stage of the 

 disease, which may be recognized much 

 earlier. Its effects are always seen first 

 upon one side of the plant, usually in 

 one of the lower leaves and almost al- 

 ways in one-half of the leaf. Here the 

 normal color begins to turn to a dull 

 yellowish green. Soon this is apparent 

 up and down the whole length of the 

 plant, but still on one side, a wilting, 

 fading, "blighting" effect. At the top 

 of the plant the leaves on the affected 

 side are somewhat smaller than the 

 others, while further down they gradu- 

 ally droop and die away. The whole ap- 

 pearance is very characteristic, one side 

 of the plant having the dull-green, wilted, 

 blighted appearance with only one- 

 half of many of the leaves affected at 

 first. When the disease is prevalent 

 many plants take on this appearance 

 and die soon after being set out in the 

 bed. Often a large lot will be a total 

 loss before developing a bloom. In other 

 cases plants in which the symptoms are 

 apparent, but not so strongly marked, 

 will throw out branches, form buds and 

 develop a few feeble flowers before en- 

 tirely perishing. Again it is very com- 

 mon for plants which appear healthy up 

 to the time of blooming to throw out 

 a normal crop of flowers, then suddenly 

 show the characteristic blight, wilt and 

 dry up in a very short time. In all 

 these cases the disease is the same. 



If affected plants in the earlier 

 stages of the disease are pulled up and 

 examined no indication of injury can be 

 seen except in the wilted, dying lower 

 leaves. The roots and stem appear per- 

 fectly sound and healthy. It is only on 

 cutting open the stem, just at the surface 

 of the ground, that the seat of the 

 trouble is found. Here will be found a 

 dark discoloration in the outer edge of 

 the harder, woody portion of the stem, 

 where it joins the soft "bark" which 

 covers it. At first this is only a small 

 spot on the affected side, but may al- 

 ways be found when the exterior symp- 

 toms have begun to appear. This dis- 

 coloration spreads around and up the 

 stem, always in the woody portion at 

 first, but finally the soft outer part is 

 affected and rots away, leaving the 

 wood intact, though it was the first 

 portion to be attacked.' By this time 

 the plant is dead so that if first exam- 

 ined at this stage the stem is found in 

 the condition described. 



The cause of this trouble may readily 

 be found with the microscope. This is 

 soon to the best advantage in a plant in 

 the earlier stages of the disease where 

 the outer green cortex of the stem is still 

 sound. By examining a thin section of 

 the discolored woody portion it will be 

 sw^n that the discoloration is confined 

 mostly to the large vessels or pores 

 through which the water passes up from 

 the roots. These are still intact and 

 "nin.iured, but in the interior of most of 

 those which are already"" affected as 

 Shown by the darker color, there wilj be 



Greenhouse at Plant of W. H« Evans, Colora<lo Springs, Colo. 



seen a mass of fungous growth which 

 completely plugs up the opening and 

 evidently prevents the free passage of 

 water or sap through the vessel. 



The important question now arises, 

 where does this fungus come from and 

 how does it attack tae plant f The so- 

 lution of this point underlies the whole 

 problem of preventing or treating the 

 disease. A particular case may be de- 

 scribed. In the spring of 1900 we 

 planted a large amount of aster seed 

 in flats in a greenhouse. The seed was 

 planted quite thickly, so that the plants 

 after coming up stood very close to- 

 gether in the rows. A long period of 

 wet, cloudy weather followed and soon 

 the trouble known as ' * damping off ' ' 

 set in quite abundantly. As soon as 

 possible the plants were pricked out, sav- 

 ing only the best. Many more rotted 

 off after this, so that when the perma- 

 nent beds were set out on June 8 many 

 varieties were very poorly represented. 

 It was noticeable in the flats that many 

 plants showed a 'trouble, evidently a 

 continuation of the^ damping off in the 

 seed bed. In many cases, however, an 

 apparent recovery took place. In some 

 lots of badly affected seedlings almost 

 every plant showed at the time of prick- 

 ing out a small dark spot on the stem, 

 from which the rotting proceeded. In 

 those which appeared to recover a cal- 

 lus tissue grew over this spot, becom- 

 ing a sort of scab and appearing to 

 check the decay of the stem. By care- 

 fully following the individual plants it 

 was found that these were the plants 

 which showed the wilt disease after be- 

 ing set out. The fungus in all these 

 cases was the same. This is an import- 

 ant point, namely, that the disease was 

 contracted in the seed bed as a result of 

 conditions which favor damping off. 



Acting upon this idea comparisons 

 were constantly made oetween plants 

 started in the greenhouse which damped 

 off more or less and those which were 

 started in the open ground and kept in 

 vigorous gjpowth from the first. The de- 

 velopment of individual plants and typi- 

 cal lota 'Of plants, affi^tea and unaf- 

 fected, Was carefully followed up, witli 

 the result that in every case where 



plants died from stem rot after being set 

 out in the bed, even though in many in« 

 stances no trouble showed itself until 

 the time of blossoming, the disease came 

 from the seed bed and was not con- 

 tracted by healthy plants after being 

 set out in the field. 



Our own plants have been started 

 each year in the same house, the same 

 flats and possibly to some extent in the 

 same soil. It 'seemis almost certain that 

 the germs of this fungus are thoroughly 

 established here; at any rate the trouble 

 lias steadily increased from none in 1899 

 to almost every plant in 1901, whue 

 each year plants started out of doors, 

 set out in the same beds and often in 

 ground occupied by diseased plants the 

 previous year have shown no trouble oil 

 this sort whatever. The past season 

 when the greenhouse-started plants were 

 almost all killed sooner or later by the 

 stem rot, our large bed presented a most 

 instructive appearance. At one end was 

 a large block of plants started out of 

 doors. Here and there through the bed 

 were a few other rows of similar plants. 

 The rest of the field had been set with 

 greenhouse plants. By the time that 

 blooming was well under way scarcely a 

 plant remained alive in the whole bed 

 except in the portions set with outdoor 

 plants, and here not a single plant 

 showed this blight. 



Plainly the avoidance of this disease 

 lies in starting with healthy plants, 

 grown out of doors or in cold frames, 

 rather than in the greenhouse where the 

 conditions are more favorable to damp- 

 ing off. Of course many good plants 

 are started in greenhouses, but the dis- 

 ease is rapidly increasing in prevalence 

 and appears to start almost invariably 

 from such conditions. Plants started out 

 of doors are insured against this 

 trouble, and, though perhaps a little 

 later, may easily be brought to full de- 

 velopment at the normal season. 



As regards time of blooming there is 

 no marked advantage in obtaining very 

 early plants, with the possible exception 

 of Queen of the Market and similar ex- 

 tra early varieties. Plant the seed in 

 good soil out of doors as early as the 

 ground can be thoroughly worked, in a 



