6 CIRCULAR NO. 122, BUREAU OF PLANT INDUSTRY. 



of rotted u])l;iii(l peat, cither eliopped or riiblKHl throiij>h a sieve, and 

 three i)arts of clean broken crocks. No loam, and especially no lime, 

 should be used. Manure is not necessary, and in the present state 

 of our knowledge may be regarded as dangerous, although in small 

 amounts it serves to stimulate the plants, at least temporarily. The 

 danger from manure apparently lies in its tendency to produce an 

 alkaline condition in the soil. 



The use of broken crocks in the potting mixture is based on the fact 

 that the rootlets seek them and form around them the same kind of 

 mats that they form at the wall of the pot, thus increasing the 

 effective root surface and the vigor of growth. 



The peat most successfully used for potting blueberry plants is an 

 upland peat procured in kalmia, or laurel, thickets. In a sandy soil 

 in which the leaves of these bushes and of the oak trees with which 

 they usually grow have accumulated and rotted for many years un- 

 touched by fire, a mass of rich leaf peat is formed, interlaced by the 

 superficial rootlets of the oak and laurel into tough mats or turfs, 

 commonly 2 to 4 inches in thickness. These turfs, ripped from the 

 soil and rotted from two to six months in a moist but well-aerated 

 stack, make an ideal blueberry peat. A good substitute is found in 

 similar turfs formed in sandy oak woods having an underbrush of 

 ericaceous plants other than laurel. Oak leaves raked, stacked, and 

 rotted for about 18 months without lime or manure are also good. 

 The leaves of some trees, such as maples, rot so rapidly that within a 

 year they may have passed from the acid condition necessary for the 

 formation of good peat to the alkaline stage of decomposition, which 

 is fatal to blueberry plants. Even oak leaves rotted for several years 

 become alkaline if they are protected from the addition of new leaves 

 bearing fresh charges of acidity. 



TUBERING. 



By ordinary methods, cuttings of the swamp blueberry have been 

 rooted only in occasional instances. Two successful methods, how- 

 ever, have been especially devised for these plants. The most novel 

 of these but the one easiest of operation is that of " tubering." This 

 method involves the same principle as that employed in stumping, 

 namely the forcing of new shoots in such a manner that their basal 

 portions are morphologically scaly rootstocks, with a strong rooting 

 tendency. The directions for tubering as applied to the swamp blue- 

 berrv are as follows: 



1. Make stem cuttings from ontdoor plants between midwinter and early 

 spring, before the Ituds have begun to make their spring growth, and prefer- 

 ably on a warm day wlien the twigs are not frozen. A still better i)lan is to 

 make Ihe cultings in autuuni after tho leaves have fallen, and store them for 

 [Cir. 12LM 



