794 
THE NATIONAL NURSERYMAN 
THE APPLICATION OF COLD TO THE RETARDING OF 
PLANTS AND THE PRESERVATION OF FLOWERS 
Professor L. C. CORBETT, Washington, D. C. 
The modern commercial nursery handles such an im¬ 
mense volume of stock, of such a varied nature, and possesses 
a patronage scattered through so wide a territory that in 
order to successfully handle and pack the product and 
deliver it for spring planting, the old practice of heeling in 
the stock has been abandoned to give place to the modern 
system of storing in retarding houses. The season for 
handling the stock is so short because 
the plants start so quickly in the 
spring, even when dug in the fall and 
heeled in according to the old practice, 
that it is practically impossible to 
operate extensive nurseries on such a 
basis. Small nurseries and plant gar¬ 
dens, "designed to 'meet the require¬ 
ments of local purchasers only, can be 
successfully operated without retarding 
buildings or the intervention of cold 
storage. In extensive enterprises, how¬ 
ever, where the sales lists reach thous¬ 
ands of people, and where the 
distribution is made through a number 
of states possessing a variety of soil 
and climatic conditions, the distribu¬ 
tion must extend over a very consider¬ 
able period of time, a'' period of time 
much greater than is allowed by the 
normal behavior of the plant; there¬ 
fore, artificial means must be resorted 
to in order to hold the nursery stock in suitable condition 
for shipment, to provide for this wide distribution. 
TYPES OF STRUCTURE USED FOR RETARDING 
PURPOSES 
The type of structure best suited for the work of storing 
nursery stock is determined by the amount of stock to be 
handled and the location of the nursery. In those sections 
where long, uniformly cold winters prevail, the cellar or half 
underground structure is very satisfactory. Further 
south, where conditions are less severe, and where there is 
greater variation in temperature within short periods of 
time, the aboveground type of structure, insulated by pro¬ 
viding multiple partitions of boards and paper in the outside 
walls, gives better satisfaction than any other type of 
structure. In those southern territories cellars become too 
damp and are influenced by soil temperature during the late 
spring months to such an extent as to greatly lessen their 
usefulness as retarding houses. The aboveground struc¬ 
ture, with walls packed with sawdust, is not satisfactory 
because the"’humid conditions which must be maintained 
within the structure, in order to successfully preserve the 
nursery stock, greatly lessens the life of the structure. At 
the same time a moist wall packing is a less efficient insulator 
than a dry one. Air spaces are, therefore, most satisfactory, 
particularly if the spaces are made horizontally, rather than 
perpendicular, so as to prevent rapid circulation of air. It j 
is necessary that these buildings be frost-proof, as well as 
capable of holding or retaining cold temperatures for a long 
period. Large structures, designed for this purpose, are 
built on a unit scheme. There are 
different storage rooms provided, each 
room being stored with material for a 
given goeographical area. Those con¬ 
taining stock to be planted first are 
emptied quickest, and those which con¬ 
tain stock to vo to most northern 
o 
localities are not opened after the 
temperature has been once reduced, 
more than is absolutely necessary, until 
time for packing out arrives. 
Besides being built on the unit 
or room plan, these buildings are 
provided with ventilating apparatus 
which can be controlled to regulate the 
circulation of air in the rooms as 
much as possible. While circulation 
of air is desirable, great "caution is 
necessary in ventilating the rooms to so 
manipulate it as to allow the entrance 
of air only at times when the tempera¬ 
ture of the room will not be raised 
above the desired point, or lowered beyond the safe limit 
for the stock in storage. Deterioration in stored stock is 
largely due to changes in humidity within the storage house, 
brought about by fluctuations in temperature. Uniformity 
of temperature is of greater importance than low tempera¬ 
ture. Besides the value of the retarding house as a means 
of facilitating the work of the nursery during the digging 
and packing season, the retarding house is a great safeguard 
to the nurseryman. Little stock is injured from storage in 
buildings with a uniform temperature, as compared with 
the loss of stock which is dug and “heeled in.” Much stock 
was lost under the old system from severe winter conditions, 
but because the temperature is never allowed to reach the 
danger point in the retarding houses this is not possible. 
Storage houses are, therefore, a great safeguard to the 
business. 
In addition to the storage house or retarding house, a 
number of American nurserymen have provided an addi¬ 
tional precaution for the purpose of maintaining a low 
temperature in the storage rooms much later in the season 
than would be possible under ordinary warehouse conditions 
by the installation of artificial refrigeration, consisting 
usually of a brine circulating system with ice or ammonia 
Professor L. C. Corbett 
