Abstract
To study the growth and development of sweet fennel (‘ZEFA-Fino’ and ‘ZEFA-Tardo’) seedlings were raised under greenhouse conditions (night temperature 16—18°C) and planted out at 3—4 true leaf stage on May 21st, June 10th, July 7th and July 27th. The effects of covering mulch and short day treatment of seedlings were studied also. First harvests were performed when field measurements showed that the greatest width of ‘ZEFA-Fino’ bulbs were on average 60 mm. Three harvests were then performed at one week intervals. Plant and bulb weights, bulb greatest width and thickness and, the heights of plant, bulb and stem inside the bulb was measured. The number of bolters were recorded. The bulb width of ‘ZEFA-Fino’ reached 60 mm in 1.5—2 months after planting out depending on planting date. Plant and bulb weights, bulb width and thickness, stem height inside the bulb and the bulb height in the earliest plantings increased as the growth period lengthened. The bulb width of ‘ZEFA-Fino’ was in higher correlation with bulb weight than bulb thickness or height. The ratio between the height of stem inside the bulb and bulb height increased fastest in the lot planted under cover in May and in the lot planted out in June; at the fourth harvest the relationship was 0.8. The largest number of bolters (8 %) was found in the latter lot. The yield estimate for ‘ZEFA-Fino’ at the third and fourth harvest was 170—360 kg/are depending on planting date and length of the growing season. All lots of ‘ZEFA-Tardo’ except that planted in July bolted quickly after the bulb width had grown to 60—70 mm. The yield quality of ‘ZEFA-Tardo’ was low because of elongated bulbs and great variation in bulb height. Short day treatment (dark period 16 h) of the seedlings retarded but did not inhibit bolting of ‘ZEFA-Tardo’.
Highlights
Sweet fennel {Foeniculum vulgare L. var. azoricum), an old vegetable in Mediterranean countries (Mansfeld 1986), is cultivated for late season and winter crop especially in Italy, and in other South European and some North African countries (Buishand & Jonge 1984, Vogel 1986)
Several sweet fennel cultivars have been in field tests in Southern Finland, where the outdoor season lasts from May to September/October, the results, were not encouraging enough (Suhonen 1970) to begin commercial production, but the Swiss cultivar Wadenswil was accepted by home gardeners
Our results with ‘ZEFA-Tardo’ are in agreement with the Danish results (Henriksen 1982), but differ from the Dutch results, which showed no bolters in late season cultivation (Buishand & Jonge 1984)
Summary
Sweet fennel {Foeniculum vulgare L. var. azoricum), an old vegetable in Mediterranean countries (Mansfeld 1986), is cultivated for late season and winter crop especially in Italy, and in other South European and some North African countries (Buishand & Jonge 1984, Vogel 1986). During the last few years an interest in growing sweet fennel has arisen in many Middle and North European countries where efforts have been made to find new varieties for outdoor vegetable production. Several sweet fennel cultivars have been in field tests in Southern Finland, where the outdoor season lasts from May to September/October, the results, were not encouraging enough (Suhonen 1970) to begin commercial production, but the Swiss cultivar Wadenswil was accepted by home gardeners. In growing sweet fennel during spring and summer the main problem has been the quick development of seed stalk. Breeding of sweet fennel to diminish the sensitivity to bolting has been done especially in Switzerland, and a year around cultivar ZEFAFino was introduced in 1977 (Keller et al 1977). According to field tests in Switzerland (Keller et al 1977), in FRG (Andresen & Frenz 1981), in Denmark (Henriksen 1982), in Norway (Rygg & Roed 1986), in GDR (Vogel 1987) and in Finland (Anon. 1985) ‘ZEFA-Fino’ yields proper bulbs during spring and summer, but even there can be many bolters (Vogel 1987) resulting in heavy loss of commercial sales
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