---

DATE
Phoenix dactylifera L., family Palmaceae

Dates are grown on about 4,600 acres in southern California and about 300 acres in southwestern Arizona. The value of the crop is about $4 million (Henderson and Swedberg 1970, Nixon 1959). The plants prosper in hot, arid climate with ample subsurface moisture.

Plant:

The date palm may reach 50 feet in height but has only a single bud or growing point, the leaf-crowned tip. The leaf may be 10 to 20 feet long, and it has a normal lifespan of 3 to 7 years. Leaves do not shed but are removed under cultivation after drooping in death. Palms are grown entirely under cultivation and irrigation. The trees are usually spaced 60 feet apart in the grove.

Inflorescence:

The date is normally dioecious, although occasional trees may be bisexual at times. The 2- to 4-foot staminate inflo rescence is a branching ax illary sp ad ix with numerous racemes and hundreds of flowers, each flower having three petals and usually six stamens, all in a protecting sheath or spathe (Nixon 1959). The less numerous pistillate flowers have three petals and also three ovaries but only one ovary develops into a seed. They occur on a slightly smaller branching spadix in a protecting spathe, that opens upon maturity of the flowers.

Pollen is produced in abundance on the staminate trees and is eagerly sought after by bees. If nectar is produced by date flowers it is not mentioned in the literature.

Pollination Requirements:

Pollen must be transferred from staminate trees to pistillate ones if fruit is produced. Leding (1928) showed that delay in placement of pollen on pistillate flowers reduced production to 89 percent by the second day, to 70 percent by the fourth day, to 54 percent by the sixth day, to 46 percent by the eighth day, and to 23 percent by the eleventh day. Nixon (1928) showed that the source of pollen affected the date of ripening (as much as 10 days), the shape of seed, and the size of the seed. Later, he (1935a, b, 1956) showed that pollen not only affects the seed but also the fruit pulp, which he termed "metaxenia." Nixon (1959) stated that pollination of 50 to 80 percent of the pistillate flowers is sufficient for a full crop.

Pollinators:

If sufficient staminate or "male" trees are near the pistillate or "female" ones, wind and sometimes insects will transfer sufficient pollen for adequate fruit set (Knuth 1908*, p. 487). However, the grower keeps male trees to a minimum inasmuch as they yield no fruit and he distributes the pollen manually. Meeuse ( 1961 *) stated that man was hand-pollinating dates before 800 B.C.; it is the oldest known means of controlled pollination of crops.

Pollination Recommendations and Practices:

For best set of fruit, the most common method of pollination is to cut strands of the staminate flowers from a freshly opened inflorescence and invert two or three pieces, 3 to 6 inches long, between the strands of pistillate flowers during the first three days after opening. Twine should be tied around the cluster to hold the flowers in place during the pollination process. Also the dried pollen taken from mature anthers may be dusted onto a 1- to 2-inch ball of cotton, which is then tied into the pistillate strands, or the pollen may be placed into a clean insecticide dust gun and dusted into the flowers. Aircraft have also been tried for distributing pollen (Brown 1966), but such use is economically questionable.

LITERATURE CITED:

BROWN, G. K.
1966. POLLINATION RESEARCH DISCUSSIONS. Date Growers Inst. Rpt. 43: 29.

HENDERSON, W. W., and SWEDBERG, J. H.
1970. CALIFORNIA FRUIT AND NUT STATISTICS 1968-69. Calif. Crop and Livestock Rptg. Serv., 11 pp.

LEDING, A. R.
1928. DETERMINATION OF LENGTH OF TIME DURING WHICH THE FLOWERS OF THE DATE PALM REMAIN RECEPTIVE TO FERTILIZATION. Jour. Agr. Res. 36: 129-134.

____ 1928. THE DIRECT EFFECT OF POLLEN ON THE FRUIT OF THE DATE PALM. Jour. Agr. Res. 36: 97 - 128.

____ 1935a. METAXENIA IN DATES. Amer. Soc. Hort. Sci. Proc. 32: 221 - 226.

____ 1935b. METAXENIA AND INTERSPECIFIC POLLINATIONS IN PHOENIX. Amer. Soc. Hort. Sci. Proc. 33: 21 - 26.

____ 1956. EFFECT OF METAXENIA AND FRUIT THINNING ON SIZE AND CHECKING OF DEGLET NOOR DATES. Amer. Soc. Hort. Sci. Proc. 67: 258-264.

____ 1959. GROWING DATES IN THE UNITED STATES. U.S. Dept. Agr., Agr. Inform. Bul. 207, 50 pp.

---