Cultivation of Finnochio Fennel

Finnochio or Florence fennel (Foeniculum vulgare Mill. subsp. vulgare var. azoricum (Mill.) Thell.), a type of fennel that develops a bulb (a thickened base of leaves), is now being marketed as 'anise' in supermarkets throughout the United States. While many cultivars of fennel are grown for the aromatic seed and foliage, finnochio fennel is produced for the enlarged bulb. The plant, increasingly popular as a specialty vegetable (Simon, 1990) where the bulbs are prepared primarily by baking, blanching, or boiling, is sold commercially as "anise" because consumers and buyers associate the 'licorice' or 'anise' aroma and flavor with that of the anise plant (Pimpinella anisum L.). Regardless of the market name, however, the increased consumption and demand for the fresh product offers expanded opportunites for American growers in the marketplace.

The finnochio fennel plant is easy to grow in the garden, but difficult to produce commercially. As a cool-season crop, the plant has a tendency to bolt (flower prematurely) in warm summer weather. The plants should be grown on raised beds with either overhead or trickle irrigation. Ample space between plants (8-10inches or more) is needed to obtain the best bulb size and shape. Fennel is highly responsive to nitrogen and early field establishment and growth needs to be encouraged. Producing high quality fennel for the fresh market is not an easy task and should only be attempted if the grower is committed to marketing a superior product.

While fennel can be produced from seed or transplants, most growers in northern temperate zones use transplants to assure a mature crop within a short growing season. Transplants also allow for greater control of stand establishment and plant density. While higher total yields can be achieved with higher plant populations, the quality of bulbs may decline if plants are too close together. Because market demand and price are based on bulb size, shape, and visual appearance, the production system should be geared to obtain the most attractive bulbs.

Commercially, the plant is harvested after bulb enlargement. Just prior to flowering, the top of the foliage is removed by cutting or "topping." The remainder of the plant (foliage, bulbs, and roots) is transferred from the field to the storage location where the roots are removed. The bulb, with some of the foliage, is retained, cleaned of soil and debris, washed, and stored under refrigerated conditions to prolong the shelf-life. Selecting a cultivar that will grow for a long period of time before bolting gives growers a greater advantage in producing well developed bulbs prior to harvest.

Plant cultivars sold as finnochio fennel vary in time to maturity, shape, size, and compactness (firmness) of bulb. Many varieties have been developed for different locations and can only be produced successfully during certain times of the year or under specific climatic conditions. Distinct varieties have been designed for early spring, summer, and fall/winter production. Some cultivars are adapted for late winter/early spring production in the field using plastic tunnels. This assortment of finnochio fennel cultivars has resulted in confusion to farmers as to which ones to grow. Few studies have directly compared the relative differences in growth, vigor, quality, and susceptibility to bolting.

In order to provide a comparison for vigor, yield, and quality, we conducted field trials of 16 fennel cultivars in 1990. Plants were started in a greenhouse at Purdue University (West Lafayette, Indiana) on April 4, and transplanted into the field at the Purdue University O'Neall Vegetable Memorial Research Farm (Lafayette, Indiana) in late spring (May 11). A preplant application of nitrogen (100 lb/acre) was broadcast before planting. The soil, an Oakley loam with a neutral soil pH, was prepared in raised beds (6 inches in height). Overhead irrigation was used as needed to maintain plant growth, but little additional water was necessary as the 1990 growing season was marked by several heavy rains and above average rainfall.

A randomized block experimental design with three replications was used in the planting arrangement to allow for statistical evaluations of the fennel cultivars. Each replicate planting was a single row (9 feet long) and the rows were 3 feet apart. Plants were spaced 4 inches apart within the row. As the flowering dates for the cultivars varied, a single harvest July 17) was taken after all cultivars had begun to flower. Fresh weights of each cultivar were recorded to indicate potential market yield and the essential oils were extracted by hydrodistillation (Simon and Quinn, 1988), for a comparison of oil contents.

Significant differences in leaf yield, bulb yield and bulb size were observed among the selected cultivars. The highest yielding line was `Zefa fino' (from both Johnny's Selected Seeds and Royal Sluis seed sources). Bulb circumference appeared to be a good indicator of yield and increased bulb yields were reflective of the larger bulb size obtained with the `Zefa fino' cultivar as compared with all other cultivars. No consistent differences in leaf yield among the cultivars were noted, except between Waldenromen and Sicilia Grosso (the highest and lowest leaf yielding varieties, respectively). The content of essential oil extracted from all the cultivars averaged 0.05 percent (v/wt) and no differences among cultivars were observed. All plants were highly aromatic.

Significant differences were observed in the length of time the cultivars remained vegetative. By six weeks after transplanting into the field (June 27), flowering was observed in a total of nine cultivars. Among the fennel cultivars tested, the highest rates of flowering were observed in the cultivars Florence (31%), Parma sel. Fucino (15%) and Grosso dolce di Firenze (7%). Plants within all cultivars, except the two `Zefa fino' test entries, had flowered by July 6. The `Zefa fino' plants began to flower by July 17, but even at this late date only a small percentage (3%) of the plants were in flower as contrasted to the more than 60 percent of plants flowering in each of the other cultivars.

The cultivars did differ in the shape of the bulb and the tendency to have splits or additional shoots arising from the top of the leaf base. Some of the cultivars included in this study may have performed better if grown at a different time of the year and this possibility needs to be further examined. The `Zefa fino' cultivar proved to be the most promising in vigor, bulb size and yield, and in remaining vegetative much longer than any of the other cultivars.

References

Simon, J.E. and J. Quinn. 1988. Characterization of essential oil of parsley. J. Agric. Food and Chemistry 36:467-472.

Simon, J.E. 1990. Essential oils and culinary herbs, pp. 472-483. In: Janick, J. and J.E. Simon (eds). Advances in New Crops. Timber Press, Portland, OR.

The Herb, Spice, and Medicinal Plant Digest.

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By Mario Morales; Denys Charles and James Simon

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