Horticulture Principles and Practices

Mature fruit color is usually red, but also green and yellow cultivars and other colors
exist. Red cultivars are more expensive than green cultivars because color development
takes a long time and the yields are lower. Fruit size can be very small in some cultivars and
very large in bell peppers, the latter used in food preparations such as stuffed peppers.
The leading production states for fresh market peppers include California, Florida,
North Carolina, New Jersey, and Texas, in that order of decreasing production. Bell
peppers make up over 2/3 of the total pepper production.
Pepper is frost sensitive. The soil should be well drained and have a pH of about
6.5–7.0. Commercial production is usually done on raised beds. Establishment of the
field is by transplanting. Double rows spaced 18–24 inches within rows are commonly
used. Plasticulture is practiced in the eastern United States. Just like tomato, pepper
responds to nitrogen fertilization.
Pepper is not a climacteric fruit and must be harvested vine-ripened. Bell peppers
are hand harvested to avoid damaging the fragile branches. Fruits should be stored at
temperatures above 50°F to avoid damage. For powdered pepper production, growers
usually cut entire plants and dry them in the field.
640 Chapter 20 Growing Vegetables Outdoors
20.13 POTATO (SOLANUM TUBEROSUM)
White or Irish potato is Solanum tuberosum. It is a tetraploid that grows in the wild as
perennial but is commercially cultivated as an annual. Most cultivars have a white flesh, but
yellow potato (e.g.,Yukon Gold) is increasing in acreage. Over 50 percent white potato crop
is produced using a few cultivars—Russet Burbank, Kennebec, Katadin, and Sebago.
Potato cultivars are distinguished by traits that determine their food use. High
starch content cultivars are used for baking in salads, while low starch tuber content is
preferred for cooking by boiling. Low sugar content is required for processing (fries),
while low sugar is preferred for boiling or cooking. Cultivars for boiling also have large
cells. Tubers differ in size, shape, length, width, and end shape (blunt or round). Skin or
periderm characteristics are also widely variable. Skin color may be red, tan, or brown,
and be netted (russet) or smooth. White tuber flesh is most popular in the United States
while yellow is most popular in Europe.
Potato is best cultivated in cool climates. Top-producing states are Idaho, North
Dakota, Washington, Minnesota, and Wisconsin. Early summer potatoes are produced in
Virginia, Maine, and North Carolina, while production for late summer and fall harvests
occur in Idaho, North Dakota, Washington, Oregon, Wisconsin, New York, and
Colorado. Winter and late spring potatoes are harvested in Florida, California, and Texas,
while late spring harvests occur in California, Alabama, Arkansas, and North Carolina.
The potato crop is established by seed potatoes (whole tomatoes) or seed pieces
(large tubers cut into pieces so that each piece has at least one “eye”). Potatoes grow best
under daily temperatures of 60–65°F. To control soilborne diseases like fungal scab, the
crop performs best on acidic soils with a pH of 4.5–5.5. The soil should be free from
stones and loose for proper tuber formation. Seed potato is spaced at 6–12 inches within
rows and 34–36 inches between rows, the wider spacing being used when whole seed is
used for crop establishment. Cut pieces should be treated against rot by applying a
fungicide (e.g., Captan).
Tubers form best under short days, low temperatures, and high sunlight intensity.
Excessive nitrogen fertilization delays tuberization, tuber maturity, and tuber solids.
Irrigation is critical during the tuber formation. If moisture is not uniformly applied
during that period, the tuber becomes knobby. On the other hand, if moisture is excessive,
the lenticels (pores in the periderm) increase in size. Irrigation is by sprinkler or drip and
never flood irrigation, since it is a tuber crop.
It is important for the tubers to be completely burring in the soil during production.
Exposure to sunlight causes greening, a condition that causes the chlorophyll and solanine
to form in the skin. Mechanical injury to the tuber can also cause solanine to form.