THE SWEET POTATO IX HAWAII. 9 
station. If the yield is estimated on a small basis, 100 plants, 
spaced 4 by 2 feet apart, should produce at least 150 pounds of 
merchantable and 50 pounds of cull roots. 
In varietal tests covering a period of five years at the central station 
at Honolulu an average yield of 4 tons per acre was obtained from 
all the varieties tested. In these tests the early maturing varieties 
were less productive than either the medium or late varieties. The 
following table gives the comparative yield of a number of these 
varieties : 
Comparative yield of sweet potatoes tested at the central station. 
Variety. 
Yicld Variety 
per acre. ' ane • ■ 
Yield 
per acre. 
Delicious 
Tens. 
3.7 Native Red 
4.1 ' " Yellow Yam''' 
Tons. 
6.0 
6.6 
3. - New Era 
3. 1 Tantalus 
5. i 
6.7 
No. 111-A 
6.2 
The yield of sweet potatoes may be increased by proper culture 
and the application of fertilizers, or by the selection through several 
generations of individual hills producing heavy crops of desirable 
and well-shaped roots. The most opportune time to select for 
improvement is when the crop is being harvested. Hills are then 
dug individually, showing numbers of roots of varying shape and 
size. Vine cuttings should be taken from the hills which contain 
the largest number of roots of good size and uniform shape (PL III, 
fig. 2). These should be carefully labeled and notes made concerning 
their individual parents. 
Many hills should be selected for foundation work, because some 
of them will fail to transmit their prolific characteristics. Improve- 
ment should then be continued by eliminating the unproductive 
vines and retaining those bearing heavy crops of roots. (PI. IV, 
fig. 1.) Within a period of five or six years, representing 10 or 
more generations, the grower will be able to establish a prolific strain 
of fine quality which he is entitled to call his own and to give a special 
name if its characters are sufficiently distinct. 
GRADING. 
Although sweet-potato grading has been advocated in Hawaii for 
many years, wholesalers continue to purchase solely on the basis 
of exchange of so much money for so much weight, regardless of 
kind of material weighed. The local farmers raising diversified 
crops recognize the importance of standardizing agricultural produce 
as a means of building up their business, but the local growers, who 
supply the markets with sweet potatoes for culinary purposes, are 
indifferent to suggestions regarding grading, either because the planting 
of this crop is incidental to their specialized crops and the area is so 
small that it does not justify the extra labor expended in grading, 
or they have learned that quotations are the same for graded and 
ungraded sweet potatoes. Standardization of the crop will not 
become a reality until uniformity of size, shape, and color enters into 
