Effects of Bark Mulches on Greenhouse Rose Production 



Cow manure is widely used as mulch for greenhouse roses. It is not too 

 readily available at times and waste bark seemed to offer some possibilities 

 as a substitute. Two ground-beds of soil, 14 feet by 4 feet, were each divided 

 in half, and each block prepared as follows: (a) received five 14-quart pails 

 full of old hardwood bark, (b) 5 pails of peat, (c) nothing, (d) 5 pails 

 old softwood bark. These additions were each mixed thoroughly with the 

 soil and the beds steam sterilized. Eight hundred grams of superphosphate 

 were then mixed with the contents of each block. Later, an equal number of 

 two varieties of budded rose plants, Hildegarde and Better Times, were 

 planted in the four blocks, 28 per block. Six hundred and eight grams of 

 ground limestone were worked into the soil of each block. Three weeks later 

 the following mulches were applied: block (a) a 3-4 inch layer of old 

 hardwood bark, block (b) 3-4 inches of new hardwood bark, block (c) 

 3-4 inches of fresh cow manure, and block (d) 3-4 inches of old softw^ood 

 bark. 



During the course of the growth of these plants some trouble was ex- 

 perienced with black spot and insects but application of Fermate sprays and 

 appropriate insecticides adequately controlled these troubles. 



On May 6, about two and one-half months after setting out the plants, 

 bloom started to appear. Two additional fertilizer applications were made 

 during the summer. Late in August additional manure had to be added 

 to block (c) because of the rapid breakdown of the mulch. 



Careful records were taken of the yields of blooms, a summary of Avhich 

 appears in Table 9. These results show that both new or old bark makes an 



Table 9. Yield of Roses with Bark and Manure Mulches 



Mulch Treatment 



Old Hard- New Hard- Old Soft- 

 wood Bark wood Bark wood Bark Manure 



Total no. of blooms 676 673 610 558 



Ave. length of stems in inches 16.5 18.7 18.0 17.1 



excellent mulch for roses. There is no significant difference between the 

 total yields of 676 marketable roses for the old hardwood bark and 673 

 for the new hardwood bark, but the differences between these and 558 roses 

 for the manure is probably significant. 



The various mulch treatments caused no appreciable differences in stem 

 lengths of the roses. All bark-mulched blocks produced stem lengths that 

 would be regarded as adequate in the rose trade. 



From the standpoint of working with the mulch in the greenhouse, the 

 bark treatments, especially the new and old hardwood, are much easier 

 to keep free of weeds. Also they do not decompose as rapidly as manure 

 and thus do not need replacement as often. 



There is a definite place for bark as a mulch in the rose industry. Corn 

 cobs (ground up), tobacco stalks, and manure are some of the mulches now 



10 



