Bloom Date Nurseries
NICK. Perhaps no four letters in the hybrid sunflower seed business carry more weight than N-I-C-K. The term “nick” refers to the synchronization of bloom periods of male and female parents within a foundation seed or hybrid production field. A “good nick” means the two parents overlap well, resulting in adequate pollination and, eventually, a high seed yield. A “bad nick” means the male and female plants do not bloom “in sync,” resulting in mediocre or poor pollination and an unsatisfactory seed yield.
Commercial sunflower seed suppliers and the California companies that produce their hybrids cannot afford bad nicks. That’s why the California seed producers operate an insurance policy — bloom date nurseries.
The bloom date nursery contains all the inbred lines a company currently works with, as well as many that they expect to be dealing with in the future. The males and females are planted simultaneously, with readings later taken on exactly when each starts to bloom, is at 50% bloom, at 95% bloom — and also, how long they remain in bloom.
Sunfield Seeds operates two bloom date nurseries — one that’s 9.5 acres in size and another about 2.5 acres. More than 100 inbred lines are evaluated annually for both bloom date timing and bloom period length. “The idea is to check the timing of the male pollen and the timing of the female pollen,” notes Bob Megli, the company’s general manager. By knowing how many days after planting an inbred blooms, their actual planting dates out in the hybrid seed production field can be adjusted in order to facilitate optimum pollination.
Sunfield employs two technicians whose main responsibility in the summer is to walk the thousands of nursery rows and count how many flowers have opened up and are throwing pollen. If, for example, the number in a given row is five out of 100, they note that it was 5% as of that date. When it hits 50 out of 100, they’ll note 50% as of that date; and so forth.
It’s not all black and white, of course. Days to bloom will vary, depending upon the time of year when an inbred is planted. Sunfield normally does three plantings of every inbred: March, April and May. “With the early plantings, since it’s cooler in the spring, it may take 85 to 90 days for an inbred to bloom,” Megli notes. “But if you plant in May, that goes down to 60 to 70 days, depending on the maturity of the inbred.” The gap between inbreds from “quickest to bloom” to “slowest to bloom” can be as much as 20-21 days.
Knowing an inbred’s bloom period length is critical, too. The better males will last up to three weeks, i.e., the point from when the main head starts to bloom until the last auxiliary head finishes blooming. “In most [male] inbreds, the main head is finishing bloom when most of the auxiliaries ‘kick in,’ ” observes Sunfield nursery technician Carl Lebrum. “There’s roughly a two- to three-day overcross.” Some male inbreds have significantly more auxiliary heads than others, he adds. The fewer auxiliary heads, the more likely that particular male’s planting will be spread out over two and even three dates in order to ensure plenty of pollen while the female is blooming.
Pioneer likewise conducts bloom date growouts every year to help figure out the optimum planting date(s) for the various male and female inbred lines. “We also use the information to determine ‘time isolation’ planting,” says Ann Walker. Being able to accurately predict flowering dates is hugely important to seed producers.
“But the problem we have,” Walker adds, “is that some of the inbreds are day length-sensitive and others are heat unit-sensitive. So we try to split plant.” In a split plant, the grower will be asked to plant perhaps one row of males on a given date, and a second row a few days later, just to spread out the pollen period. Depending how much pollen a given male tends to produce, the seed company may even request three different planting dates. — Don Lilleboe
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