DIRECTIONS FOR BLUEBERRY CULTURE. _ 9 
(10) After the new twigs have stopped growing and their wood becomes 
hard new root growth takes place. Then secondary twig growth follows, either 
from the apex of the new twigs or from another bud lower down on the old 
wood of the original rooted shoot. Until this secondary twig growth takes place 
the life of the plant is not assured. 
SOIL MIXTURES FOR BLUEBERRIES. 
A very successful potting mixture or nursery-bed mixture for blue- 
berry plants consists of one part, by measure, of clean or washed sand, 
nine parts of rotted upland peat, either chopped or rubbed through 
a sieve, and three parts of clean, broken crocks—that is, pieces of 
ordinary unglazed, porous, earthenware flower pots. 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 quantities it serves to stimulate the plants, at least 
temporarily. The danger from manure apparently lies in its ten- 
dency to injure the beneficial root fungus of the blueberry plant. 
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. If crocks are not 
available, the soil mixture should consist of two to four parts of peat 
to one part of sand. 
The peat most successfully used for potting blueberry plants is an 
upland peat procured in kalmia, or laurel, thickets. Ina 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, untouched 
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 ground 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. The turfs of lowbush blueberries serve 
the same purpose admirably. 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. The much decomposed peat 
6 For a fuller discussion of the conditions under which leaves decompose into leaf peat 
as distinguished from leaf mold, and the fundamentally different effect of the two on the 
growth of plants, consult “ The Formation of Leafmold,”’ Smithsonian Report for 1913, 
pp. 333 to 343 (also separately printed). 
