The seed should not be harvested until fully ripe. When gathered in wholesale lots without the careful selection which has been described, the plants are cut, hung in the dry for a few days and then threshed. The chaff is next removed and the berries soaked in water for a day or two when the skin and the pulp may be readily removed by the use of a wooden block, followed by successive washings. Carefully selected seeds are stripped from the plants by hand, soaked for a day or two and the pulp removed by rubbing the berries between the hands or by the gentle use of a wooden block, after which they are washed, thoroughly dried and stored as other dry seeds. In the process of washing, the heavy seeds sink, while the light ones float and are poured off with the shells and the pulp. Further selection of large, plump seed may be made by screening with a mesh of proper size.
It is universally conceded that a strong one-year-old crown is superior to older crowns. The roots of two-year plants are seriously mutilated when dug, and the younger plant becomes established more quickly and grows more rapidly. The best cultural conditions must be provided to grow strong crowns in a single season.
The richest garden soils should be selected for this purpose, and the seed sown in the spring as soon as the ground can be prepared. As the seed germinates very slowly, an early start is important to have the benefit of a long season. If hand wheel hoes are to be used, the rows should be not less than 15 inches apart; while for horse tillage 30 inches is not too much space. A pound of plump, fresh seed should produce at least 3,000 plants. The propagator should aim to have a strong plant every 2 inches, though 3 inches apart in the row is better spacing to produce the most vigorous crowns.
Thinning is often necessary to prevent crowding and the production of weak plants. As the small plants are very delicate, the depth of covering over the seed should not be more than 1« inches to insure germination. Since asparagus seeds germinate very slowly, a few radish seeds should be sown with them to mark the rows, so that tillage may begin as soon as the radish plants appear. The button-shaped radishes should be used because they will be ready to pull in four weeks or less and may be removed without any detriment to the asparagus plants. The most thorough tillage should be given the nursery plat throughout the season. Nitrate of soda can generally be employed very effectively, by applying as a top dressing at frequent intervals during the summer. One hundred pounds an acre may be applied each time, sowing broadcast or along the rows.
The Missouri Experiment Station recommends sowing the seeds in hotbed or greenhouse during February or early March, transplanting the best when 3 inches high into small pots. Later the plants are shifted into larger pots, so they may make a good start before being set in the field. By this method very strong plants are secured the first season, and a larger percentage of marketable shoots become available during the early life of the plantation.
Asparagus may also be propagated by dividing the crowns. This method, however, is not satisfactory and it is seldom, if ever, practiced by commercial growers.
In seed production, the importance of selecting proper plants, then the best berries on the chosen plants, and, finally, the large, plump seeds, has been emphasized. Selection again plays an important part when seedlings are chosen for the new plantation. The possibility of rigid selection is one of the main arguments advanced by the Missouri Station for the pot method of propagation. Professor Whitten urges liberal sowing, because seven-eighths of the seedlings should be discarded. In regard to selection he recommends that as asparagus plants vary more than almost any other vegetable, only those plants which have the thickest, fleshiest and most numerous stems be chosen for potting. "Many that appear large and vigorous will have broad, flat, twisted or corrugated stems. Discard them. Beware, also, of those that put out leaves close to the soil. These will all make tough, stringy, undesirable plants. The best plants are those which are cylindrical, smooth and free from ridges. They shoot up rapidly, and attain a height of 2 inches before leaves are put out. They look like smooth needles. This matter of selecting the best plants for potting and subsequent planting out, is of the greatest importance in asparagus culture."
The principles of selection have been discussed. One-year plants are better than two. Whatever the age, it pays to select plants with four to eight large stems. Several times as many seedlings should be grown as will be actually needed for the new plantation. When propagated in the field, the selection should be made in the fall before the stems break down. The plants may be tied together in bundles of 50 and stored under proper conditions until spring. Very satisfactory conditions are furnished by packing in barrels with slightly moist sand or sawdust and burying the barrels late in the fall, first covering with straw or leaves and then adding a few inches of soil. If proper methods of seed selection have been practiced, it should not be difficult to sell the surplus plants at good prices.
The consensus of opinion is that male plants are more productive than female. Experiments made at the Ohio Station (Ohio Station Bul. 9, Vol. III) gave results as expressed in the table which follows.
Product from Fifty Plants Each, Male and Female
Product from 50 male plants
50 female plants oz.
First Period. 10 days ...............
Second period. 10 days ...................
Third period, 10 days ..................
Fourth period, 10 days ................
Total of the season ............................
"This shows a gain of the male over the female plants of 76 per cent for the first period and a fraction less than 50 per cent for the whole season. Reversing the standard of comparison, it will be seen that the female plants fall below the male 43 per cent for the first period and a little more than 33 per cent in the total. In no case did the female plants produce equally with the male."