Chapter 6: Common Vegetables for Seed and Fruit


Chapter 6: Common Vegetables for Seed and Fruit


ASPARAGUS
Asparagus officinalis L., family Liliaceae

In 1969, asparagus was grown on 123,830 acres in the United States. Almost half, 44,700 acres, was in California; 22,700, in New Jersey; 17,400, in Washington; and 13,900, in Michigan. The crop was valued at $57 million.

Plant:

The underground portion of the perennial, herbaceous asparagus plant is a massive collection of rhizomes and fleshy and fibrous roots. The rhizome sends up a shoot or spear that is harvested when a few inches above ground, otherwise it will continue to develop as an upright flowering stalk or "fern" 4 to 6 feet tall. The stalk develops either female or male flowers, rarely both. If the flower is female, it produces a small round, reddish, 3/8-inch berry that may have a total of two seeds in each of its three locules or six seeds per berry. Frost kills the upright portion of the plant, but the underground portion may live 10 years or more (Henna 1952).

Reproduction is by seeds or by rhizomes called "crowns."

Inflorescence:

The asparagus inflorescence has been variously referred to as pseudohermaphrodite male and pseudohermaphrodite female (Kerner 1897*, p. 299); dioecious, rarely hermaphrodite (Knuth 1909*, p. 464); dioecious, sometimes changing to monoecious (Hexamer 1908); normally dioecious (Jones and Rosa 1928*); and dioecious (Hawthorn and Pollard 1954 *). Intergrades from strongly pistillate to strongly staminate have been observed (Jones and Robbins 1928). In their early stages, the flowers are similar, with both sets of sexual organs present. Later, however, one set usually aborts, leaving a "male" flower with an outer and inner whorl of three stamens each, or a "female" flower with a three-lobed pistil and three-locule ovary, and the other parts rudimentary (fig. 45). Both kinds of flowers have nectaries at the base of the corolla. The individual, whitish-green flowers, from one to four in each axil, are pendulous, bell-shaped, about one-quarter inch long (the male is slightly larger than the female flower) with a characteristic odor (Knuth, 1909*, p. 464). They are freely visited by honey bees and other bees (Norton 1913, Jones and Robbins 1928, Eckert 1956, Pellett 1947*, Jones and Rosa 1928*).

The flowers produce nectar and pollen copiously (Norton 1 913), and beekeepers sometimes get good honey crops from asparagus when the plants are allowed to flower (Pellett 1947*).

[gfx] FIGURE 45. - Longitudinal section of asparagus flower, x 17. A, Female; B, male

Pollination Requirements:

If asparagus seed is to be produced, the pollen must be transferred from the male or staminate flowers to the female or pistillate ones. This transfer must be made between early morning, when the pollen first becomes available, and about noon, when it begins to dry. There should be at least one male plant within 5 feet of each female (Huyskes 1959), about one male for each six female plants.

Pollinators:

Wind is not a factor in asparagus pollination. Bees and primarily honey bees are responsible for the seed crop (Norton 1913, Jones and Robbins 1928, Jones and Rosa 1928*). Eckert (1956) caged one female and two male crowns to exclude all except tiny insects. He harvested only 6.2 g of seed, but an open plant near the cage produced 775 g of seed. He concluded that insect pollination was essential to commercial seed production and that growers should provide one to two colonies per acre to their seed fields for pollination purposes.

Pollination Recommendations and Practices:

There have been no specific recommendations for the use of bees in asparagus seed production except the previously mentioned work by Eckert (1956). Later, he (1959*) made a general recommendation of two colonies per acre for vegetable seed production. There are no reports to indicate that growers take steps to provide insect pollination.

LITERATURE CITED:

ECKERT, J. E.
1956. HONEY BEES INCREASE ASPARAGUS SEED. Amer. Bee Jour. 96: 153-154.

MANNA, G. C.
1952. ASPARAGUS PLANT BREEDING. Calif. Agr. 6(1): 6.

HEXAMER, E. M.
1908. ASPARAGUS, ITS CULTURE FOR HOME USE AND FOR MARKET. 168 pp. Orange-Judd Co., New York.

HUYSKES, J. A.
1959. THE VALUE OF COMPARATIVE TESTS OF PROGENIES FROM OPEN- POLLINATED FEMALE ASPARAGUS PLANTS. Euphytica 8: 141-144.

JONES, H. A., and ROBBINS, W. W.
1928. THE ASPARAGUS INDUSTRY IN CALIFORNIA. Calif. Agr. Expt. Sta. Bul. 446,105 pp.

NORTON, J. B.
1913. METHODS USED IN BREEDING ASPARAGUS FOR RUST RESISTANCE. U.S. Dept. Agr. Burl Plant Ind. Bul. 263,60 pp.


Capturé par MemoWeb ŕ partir de http://www.beeculture.com/content/pollination_handbook/asparagus.html  le 10/03/2006