New Crops News, Spring 1993, vol. 3 no. 1
Increased consumption and demand for this fresh product in the U.S. may offer expanded opportunities for American growers, yet very little information is available for potential producers on production or varietal selection. Jim Simon, Denys Charles, and Mario Morales, of Purdue's Horticulture Department, have been searching for specialty vegetables that are popular abroad, yet relatively unknown in this country. As part of the mandate of the New Crops Center, they have been scouring international marketplaces for new types of vegetables that are in demand by consumers in other countries and could be imported and popularized here. Fennel was one of the specialty vegetables that appeared to have a promising future in this country.
Fennel, a perennial herb of the carrot family, is grown as an annual and has a tendency to bolt, a periodic problem with the splitting of the bulb and formation of excessive side shoots within the bulb. High quality bulbs should be firm, white, sweet, and whole, with a minimum diameter of 5 cm. The objective of this project was to evaluate fennel varieties for yield and quality. Using mostly commercial seed from European seed companies, 16 fennel accessions were evaluated in raised beds over a two year period in Lafayette, Indiana.
Significant variation among varieties in bulb yield, bulb dimensions, days to 50% bolting, plant height, and number of side shoots was observed. 'Zefa fino', from Royal Sluis (RS) and Johnny's Seed Company (JS), was the highest in bulb weight, the lowest in foliage yield, and the second lowest in plant height. This 'Zefa fino' had significantly greater bulb circumference than the other cultivars. Because the width and thickness of finnochio fennel bulbs continue to increase over time, the determination of the optimum harvest period was difficult. 'Zefa fino' also showed significant differences from the other varieties in days to 50% bolting. The later maturity of this variety is highly desirable because a longer vegetative period permits the plant to produce larger and heavier bulbs. 'Zefa fino' had the lowest number of side shoots on the bulbs, an undesirable genetic trait among some cultivars, and had the most attractive appearance, with bulbs that were white, firm, highly aromatic and has no visual discolorations.
The aroma and flavor components of the essential oils were extracted from all 16 lines and chemically analyzed via Gas Chromatography/Mass Spectrometry. Eight major constituents were found in both the foliage and the 'bulbs'. The major oil constituents (comprising >80% of the total oil) in the bulbs included anethole (thus, the strong licorice aroma) and limonene. Additional compounds in the oil included alpha-pinene, myrcene, gamma-terpinene, fenchone, methyl chavicol, and fenchyl acetate. The oil from the foliage was similar, but in contrast with the bulbs, the foliage oil always contained higher limonene than anethole. Finnochio fennel oil contains less anethole and higher limonene than sweet or bitter fennel oils which are grown commercially for the seeds (technically the fruit), yet higher anethole levels than traditional sweet fennel foliage.
This plant can be raised in many areas of the U.S., including the Midwest, if planted early in the season and managed properly. The time from sowing in the greenhouse to harvest ranged from 104 to 120 days over two growing seasons; time from field transplanting to harvest ranged from 67 to 80 days. Average growing season of direct seeded fennel in California ranges from 110 to 125 days. The challenge for producers will be to produce high quality bulbs with the size and shape of those found in the European marketplace. The challenge for the marketer will be to encourage greater awareness of this new vegetable/culinary herb. One challenge for researchers will be to develop a way to market both the aromatic fresh-cut foliage and the freshly harvested bulb from the same plant, which remains an intriguing yet unexplored possibility.