Maataloustieteellinen Aikakauskirja
Vol. 62: 237—244, 1990

The effect of planting date on growth, seed stalk development and yield
of sweet fennel

IRMA SUHONEN and LEENA KOKKONEN

Department of horticulture, University of Helsinki, SF-00710 Helsinki, Finland

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 greatestwidth of ‘ZEFA-Fino’ bulbs were
on average60 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 de-
pending on planting date. Plant and bulb weights, bulb width and thickness, stem height in-
side 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 16h) of the seedlings
retarded but did not inhibit bolting of ‘ZEFA-Tardo’.

Index words: sweet fennel, planting date, growth, seedstalk development

Introduction

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 Ita-

ly, but also 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

237

JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND

https://www.c-info.fi/en/info/?token=EcclF0V5heDC_H5W.bqEOHzhKO4etX8sfVmZKHw.7XN4Bg5NSz9b9pMSrKAimT_4o8E9bvtV9zYCIwh4gyZuRInDZ-aqYXz7NFgaHYfOkA-EENpn959evnDXlK8ChrR33aohQ4rFLFygcQJN5Hos4dzF9URcDyhQqNOq3nb5Lc2UE1W-TE83XakLNHZrgyZRGVAX1EZJ5c9XepkK9Gx1jBtCoAAW1diOhB7-


in many Middle and North European coun-
tries where efforts have been made to find
new varieties for outdoor vegetable produc-
tion. Several sweet fennel cultivars have been
in field tests also in Southern Finland, where
the outdoor season lasts from May to Septem-
ber/October, the results, however, were not
encouraging enough (Suhonen 1970) to be-
gin 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. As a consequence
of this process the “bulb” (the tight bundle
of swollen petiole bases) looses its tightness,
crispness and commercial value too. Breeding
of sweet fennel to diminish the sensitivity
to bolting has been done especially in Swit-
zerland, and a year around cultivar ZEFA-
Fino 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 then there can
be many bolters (Vogel 1987) resulting in
heavy loss of commercial sales.

To avoid the bolting losses during the cul-
tivation of sweet fennel, exact information of
seed stalk development would be useful, but
the information in literature on this subject
is limited. Thus experiments were designed to

study the growth pattern, seed stalk develop-
ment and yield of sweet fennel in early, middle
and late season. In early season the effects of
a covering mulch and a short day treatment
of seedlings were also examined. The experi-
ments were carried out on the test field at our
Department in 1987.

Materials and methods

The cultivars in a series of five experiments
were ZEFA-Fino and/or ZEFA-Tardo, a late
season cultivar (Table 1). Growing recommen-
dations given by Keller et al. (1977) and by
Buishand and Jonge (1984) were adapted as
follows. The young plants were raised in a
greenhouse with night temperature between
16—18°C. Seeds were sown in seedbeds on
April 10th, May sth, June 6th and June26th.
The seedlings at cotyledon stage were pricked
into peat pots (FP 622) which were filled with
fertilized peat. In experiment B two weeks
short day treatment (dark period 16 h from
4 p.m. to 8 a.m.) after 6 days from pricking
was given. The control plants were grown un-
der natural long day.

Sweet fennels were planted out when they
had 3—4 true leaves. Before planting (Table 1)
plants were hardend outdoors for 3—4 days.
The planting density was 45 cm X 20 cm. The
soil of experimental plots was humous coarse
silt with pH 6.8. As basic fertilization of
10 kg/100 m 2 a compound fertilizer (N 7 %,

P 5 %, K 15 %) was given just before plant-
ing. Additional nitrogen fertilization with cal-

Table 1. Cultivars, sowing and planting dates, length of plant raising period and growing time on field until first
harvest in experiments A, B, Cl, C 2 and C3.

Experiment Cultivars Sowing Plant raising Planting Growing time
date (days) date until first

harvest (days)

A ZEFA-Fino Apr 10 41 May 21 44
B ZEFA-Tardo » 41 » 44
Cl ZEFA-Fino May 5 35 Jun 10 43

and
ZEFA-Tardo

C 2 » Jun 6 31 Jul 7 45
C 3 » Jun 26 31 Jul 27 56

238



cium nitrate (2 kg/100 m 2) was performed
when the petiole bases began to swell. Dur-
ing dry periods the experimental plots were ir-
rigated. Weeds were controlledmechanically.
During the growth period the plants were
healthy and no treatments with pesticides or
fungicides were needed.

In experiment A Agryl P-17 sheet was used
to study the effects of a covering mulch early
in the season. The plants were covered just af-
ter planting out and sheet was taken off at the
first harvest. The control plants remained un-
covered.

First harvest (Table 1) was performed, when
the test measurements from the field showed
that the greatest width of ‘ZEFA-Fino’ bulbs
were on average 60 mm. The following three
harvests were undertaken at one week inter-
vals. At harvest the stem of sweet fennel was
cut just beneath the bulb. The height and
weight of rosettes were measured and the
number of leaves were counted. The plants
were then trimmed: sideshoots and loose outer
leaves were removed, and the petioles of
opened leaves were cut 5 cm over the swollen
leaf base, only the innermost leaves which
were shorter than 7 cm were left uncut.
Trimmed bulbs were weighed individually and
the greatest bulb width, height and thickness
were recorded. The bulb was then split and
the height of the stem inside the bulb was
measured. If the seed stalk had already grown
out of bulb, the plant was classified as a
bolter. In estimating salable yield healthy
proper bulbs weighing 100—450 g were in-
cluded.

All experiments were arranged according to
split plot design in quadruplicates. The aver-
ages presented in Tables 2—6 are means of 24
individual specimens, if no bolters were
found. If bolting percentage was 50 % or
more, no averages were calculated.

Results

Covering mulch on the vegetation from end
of May to beginning of July increased the

growth of ‘ZEFA-Fino’ (Table 2). When the
average bulb width in covering treatment was
60 mm, the width of control bulbs was only
49 mm. Also the bulb thickness and height
were greater in the covering treatment. The
average plant and bulb weights at first and sec-
ond harvests in the covering treatment were
53—56 % greater than the weights of control
plants, but the relationship between bulb and
plant weights were the same. The cover also
accelerated the growth of stem inside the bulb,
as well as the stem growth in relation to bulb
height, however, only 0.5 °7o of plants bolted.
In the control there were no bolters. The cover
especially increased the salable yield of first
and second harvests.

‘ZEFA-Tardo’ plants grown under short
day regime were less green after treatment and
shorter (24 cm) at the end of plant raising peri-
od than the control plants (30 cm), but both
had 4 opened true leaves on average. At the
first harvest the short day treated plants were
higher (47 cm) and heavier (104 g), and they
had less true leaves (8.1) than the control
plants (42 cm, 94 g, 9.9 true leaves). The treat-
ment retarded the number of bolters and the
growth of stem inside the bulb (Table 3), but
it was not effective enough to ensure a proper
yield. When the average bulb weight of the
short day treated plants was 100 g, there were
already 17 % bolters in the stand and a week
later the bolting percentage was 70 %.

The bulb width of ‘ZEFA-Fino’ planted on
June 10th and on July 7th reached 60 mm af-
ter 1.5 months growth in the field, but the last
planting lot needed about 10 days more to
reach the same stage (Table 4). The growth
of bulb width of ‘ZEFA-Tardo’ was slightly
slower (Table 5).

The bolting percentage of ‘ZEFA-Tardo’
was very high in lots planted out on June 10th
and July 7th (Table 5), and even in the last
group there were nearly 50 % bolters at the
time of the fourth harvest. Bolters in ‘ZEFA-
Fino’ were found only at the fourth harvest
in the lots planted out on June 10th (8 %) and
on July 7th (4 %), where the effective tem-

239



240

Table 2. The effect of covering mulch and harvesting time on the growth of ‘ZEFA-Fino’ planted May 21st
(experiment A). First harvest 44 days (July 34rd) after planting out, subsequent harvests at one week intervals.

Harvest

Treatment' 1 2 3 4 Mean>

Bulb width mm M 60 80 82 102 81**
C 49 64 79 84 69

Number of true M 8.1 9.0 9.3 10.8 9.3 n.s.
leaves C 7.3 8.0 9.3 10.1 8.7
Plant height cm M 61 65 64 61 63*

C 48 56 59 54 54
Plant weight g (A) M 176 313 355 504 337*

C 113 205 307 368 248
Bulb weight g (B) M 84 153 185 276 175**

C 54 98 159 196 127
Relation B/A M 0.48 0.49 0.52 0.55 0.51

C 0.48 0.48 0.52 0.53 0.50
Bulb thickness mm M 31 43 45 51 43**

C 27 35 44 47 38
Bulb height mm (C) M 82 93 100 120 99**

C 73 84 92 105 89
Stem height inside M 35 53 62 99 62*
bulb mm (D) C 31 43 55 78 52
Relation D/C M 0.44 0.57 0.63 0.81 0.61

C 0.43 0.51 0.60 0.74 0.57
Salable yield M 32 165 199 280 169**
kg/100m 2 C 0 69 166 216 113

' M - mulch, C = control
> and significance of differences between means of M and C, Tukey’s test.

Table 3. Effect of short day treatment during plant raising and of harvesting time on bolting and on properties
of non-bolted bulbs of ‘ZEFA-Tardo’ planted out May 21st (experiment B), First harvest 44 days (July 3rd) after
planting out, subsequent harvests at one week intervals.

Treatment Harvest Non-bolted bulbs

Bolting Width Weight Height Stem height Relation
% mm g mm (A) mm (B) B/A

Natural 1 4 45 45 76 47 0.61
long day 2 46 55 70 91 64 0.71

3 78
4 100

Short day I 0 45 50 78 33 0.42
2 0 58 77 89 52 0.58
3 17 63 107 102 73 0.71
4 70

perature sums were 595°C and 546°C respec-
tively (Figure 1).

In the last planting, ‘ZEFA-Fino’ plants
had less true leaves than in the earlier lots, but
they were above average in height (Table 4).

The width and the stem height inside the bulb,
and also the thickness of ‘ZEFA-Fino’ bulbs
increased with a longer growing period, but
the increase in bulb height was significant only
for the lot planted out in June(Table 4). The



Table 4. The effect of planting date and harvesting time on number of true leaves, plant height and on properties
of bulbs of ‘ZEFA-Fino’. First harvest 43 days (planted June 10th, experiment Cl), 45 days (planted July 7th, ex-
periment C2) and 56 days (planted July 27th, experiment C3) after planting out, subsequent harvests at one week
intervals.

Harvest Planting date

June 10th x July 7th x July 27th x

Bulb width mm 1 62a 71a 69a
2 75b 80ab 75ab
3 93c 87c 79b
4 98c 96cd 77b

Number of true leaves 1 B.la 8.4 a 7.7 a
2 8.9 b 8.6 a 7.5 a
3 11.0 c 9.0 a 7.3 a
4 11.4 c 9.1 a 7.7 a

Plant height cm 1 57a 68a 70a
2 64a 69a 72a
3 65a 69a 71a
4 64a 68a 70a

Bulb thickness mm 1 36a 42a 42a
2 41a 52b 44a
3 52b 55b 45a
4 55b 59b 48a

Bulb height mm (A) 1 84a 104 a 95a
2 95ab 100 a 102 a
3 107bc 107 a 107 a
4 126 c 103 a 101 a

Stem height inside 1 36a 42a 43a
bulb mm (B) 2 53b 52b 47b

3 73c 64c 46b
4 98d 79d 52c

Relation B/A 1 0.42 0.40 0.45
2 0.55 0.52 0.46
3 0.68 0.59 0.42
4 0.77 0.76 0.51

x Values followed by same letter are not significantly different at P = 0.05 by Tukey’s test.

increases in average plant and bulb weights be-
tween harvests were notable especially in the
lot planted out on June 10th (Figure 1). The
relationship between bulb weight and plant
weight varied from 0.47 to 0.62. This ratio was
lowest at the time of the first harvests. The
highest ratio was obtained for the lot planted
on June 10th at the last harvest. The growth
of bulbs in the last planting lot was very slow
after the first harvest, but there still was sig-
nificant increase in bulb weight (73 g) between
first and fourth harvest. The increase in ef-
fective temperature sum between those har-
vests was only 46°C.

The salableyield of ‘ZEFA-Fino’ increased

with a lengthening of the growing period, and
the greatest salable yields were achieved from
stands planted out on June 10th and on July
7th (Figure 1). The yield of ‘ZEFA-Tardo’ was
low because of bolters, and the yield quality
was also poor, because of elongated bulbs and
great variation in bulb heights especially for
the last planting lot (Table 5).

In bulbs of ‘ZEFA-Fino’ there were signifi-
cant correlations between bulb weight vs bulb
greatest width, greatest thickness and height
in all experiments (Table 6). The best corre-
lation coefficients were between weight vs
width. Using the average values of bulb width
and bulb weight presented in Tables 2 and 4

241



242

Table 5. The effect of planting date and harvesting time on bolting and on properties of non-bolted bulbs of
‘ZEFA-Tardo’. First harvests 43 days (planted June 10th), 45 days (planted July 7th) and 56 days (planted July 27th)
after planting out, subsequent harvests at one week intervals.

Harvest Planting date

June 10th July 7th July 27th'

mean variation

Bolting % 1 21 29 0
2 46 42 4
3 92 54 17
4 92 67 44

Bulb width mm 1 59 66 63a
2 (67) (76) 74b
3 —73 b
4 - - (72)

Bulb weight g 1 78 127 116 a
2 (128) (197) 161 b
3 —174 b
4 (181)

Bulb height* 1 101 119 118 a 95—180
mm (A) 2 (138) (151) 130 a 90—190

3 —131 a
4 (148)

Stem height* inside 1 74 72 71a 38—115
bulb mm (B) 2 (115) (113) 83a 40—180

3 —88 a
4 - - (113)

Relation B/A 1 0.73 0.60 0.60
2 (0.83) (0.74) 0.71
3 0.67
4 (0.76)

* Values followed by same letter are not significantly different at P = 0.05 by Tukey’s test.
> Great variation between individuals specially in the last planting lot, limits are given in the table.

Fig. I. Plant and bulb weights and estimated salable yield of ‘ZEFA-Fino’ at harvests 1 to 4 in experiment A
(planted May 21st) and in experiments Cl, C 2 and C 3 (planted June 10th, July 7th and July 27th).
Temp, sum = the sum of effective day degrees over 5°C



Table 6. Correlations between bulb weight and bulb
width, thickness and height of ‘ZEFA-Fino’ in experi-
ments A, Cl, C 2 and C3.

Weight vsExperiment

width thickness height

A (cover) o.94*** o.B4*** 0.62»**
A (control) o.9s*** o.9l*** o.64***
C 1 o.9l*** o.Bs*** o.6s***o.9l*** o.Bs*** o.6s***
C 2 o.93*** o.Bl*** 0.24*
C 3 0.87*»* o.Bl*** 0.33**
• Pc0.05, �* P<o.ol, �••PcO.OOl

and in Figure 1, it can be estimated that the
bulb size of 100 g was reached when the bulb
widthwas about 64 mm and 200 g whenbulb
width was about 82 mm.

Discussion

The test cultivars behaved themselves very
differently under the prevailing circumstances.
‘ZEFA-Tardo’ proved to be a quick bolter
in spring and in summer as was to be expect-
ed, but there was also plenty of bolters in au-
tumn, when it should have yielded proper
bulbs. Our results with ‘ZEFA-Tardo’ are in
agreement with the Danish results (Henrik-
sen 1982), but differ from the Dutch results,
which showed no bolters in late season culti-
vation (Buishand & Jonge 1984). Short day
treatment during seedling phase retarded, but
did not inhibit the development of seed stalk
of ‘ZEFA-Tardo’, which agrees with a similar
experiment in Denmark (Henriksen 1982).
The non-bolted individuals of ‘ZEFA-Tardo’
gave small bulbs weighing under 200 g, which
had relatively long stem inside the bulb.

In contrast to ‘ZEFA-Tardo’ bolters were
only found with ‘ZEFA-Fino’ when the har-
vest was 2 months after planting out. In sow-
ing and planting time experiments carried out
in Switzerland, the bolting of ‘ZEFA-Fino’ af-
ter about 2 months growing time under field
conditions was under 1 %, except in one lot
planted out in beginning of July (Keller
et al. 1977). In the Danish experiments there
were I—ls % bolters after two months grow-
ing time under field conditions, and after

70 days the percentage of bolters was 37 %

in a lot planted out at the end of June (Hen-
riksen 1982). In field tests made in GDR the
numberof bolters in ‘ZEFA-Fino’ after about
two months growing time was usually high,
often over 20 %. It was stated that the speed
of bolting depends on weather, and in stands
planted out during June or during the two first
weeks of July a high percentage of bolting can
be expected (Vogel 1987). In our tests with
‘ZEFA-Fino’ the tendency was the same; dur-
ing warmest periods of weather, and under
cover the growth of stem inside the bulb was
fastest, and some individuals bolted.

The field measurements of bulb width of
‘ZEFA-Fino’ to forecast the average bulb
width in yield gave good correlations in ex-
periments A and Cl, but not as good in ex-
periments C 2 and C3, where the first harvests
were delayed. Obviously there were too long
intervals between field measurements. Ac-
cording to our results, the bulb width of
‘ZEFA-Fino’ is highly correlated to bulb
weight, and it is better forecaster for yield than
bulb height or thickness. In foretelling the de-
velopment of seed stalk the measurement of
stem length inside the bulb seems to be a good
parameter. Our observations indicate, that the
relation 0.7 between stem height inside the
bulb and bulb height will predict that in warm
weather ‘ZEFA-Tardo’ is likely to bolt. In
‘ZEFA-Fino’ the same stem/bulb height re-
lation did not give a high number of bolters
under the test conditions. A warmer period at
this stage could alter the behavior of this cul-
tivar, thus further tests are required.

In our experiments the number of individu-
als was insufficient for giving an exact prog-
nosis of salable yields. The estimates, howev-
er, indicate, that a yield level of 200—300 kg/
are for ‘ZEFA-Fino’ can be reached in 2—2.5
months growing time under field conditions,
if young plants are raised beforehand in a hot
house and the weight of 100 g per bulb is ap-
proved as the lower limit. The leaf yield will
be nearly the same as the bulb yield, or slightly
smaller with the swelling of bulbs.

243



According to our observations ‘ZEFA-
Fino’ benefits from a covering sheet early
in the season. If 200 kg/are is the target for
yield, the covered stand was about a week
earlier than the uncovered one. In tests of
Andresen and Frenz (1981) the growing time

of ‘ZEFA-Fino’ was reduced by nine days,
when a perforated plastic cover was kept on
a stand planted out in April for five weeks.
If the cover is kept on sweet fennel for too
long a time, then the bulb weight can be
reduced (Buishand & Jonge 1984).

References

Andresen, F. & Frenz, F.W. 1981. Der Einfluss des
Saattermins auf das Schossen und den Ertrag von
Knollenfenchel-Sorten. Gemiise 17; 162—168.

Anon. 1985. Kirjallinen tieto. Finska Flushällningssäll-
skapet. Turku.

Buishand, T. & de Jonoe, P. 1984. Teelt van knolvenkel.
Teelthandleiding nr. 16. 39 p. Lelystad.

Henriksen, K. 1982. Dyrking af knoldfennikel. Stat.
Planteavlforsog. Medd. 1677. 4 p.

Keller, F., Stenoel, E., Toot, W. Wixinoer, K. 1977.
Anbau und Vermarktung von Knollenfenchel in der
Schweiz. 55 p. Schweizerische Gemiise-Union. Zurich.

Mansfeld, R. 1985. Verzeichnis landvvirtschaftlicher

und gärtnerischer Kulturpflanzen 2. p. 1014—1018.
Springer-Verlag. Berlin etc.

Ryog, M. & Roed, U. 1986. Semesteroppgave 1 GD 2
1986. Norges Landbrugshogskule, As, Norge.

Suhonen, I. 1970. Kylvöajan vaikutuksesta salaattiven-
kolin kehitykseen. Puutarha 73: 262—265.

Vogel, G. 1986. Knollenfenchel, eine schnellwachsende
Gemiiseart, die den Staffelanbau ermöglicht. Gartenb.
33: 116—119.
1987. Zum Einfluss gestaffelterPlanztermine und un-
terschiedlicher Standweiten auf die Ertragsleistung von
Knollenfenchel. Arch. Gartenb. 35(1): 1—ll,

Ms received September 25, 1989

SELOSTUS

Istutusajan vaikutus salaattifenkolin
kasvuun ja kehittymiseen

Irma Suhonen ja Leena Kokkonen
Helsingin yliopiston puutarhatieteen laitos,
Viikki, 00710 Helsinki

Kasvihuoneessa esikasvatetun ja kolmi-nelilehtiasteella
avomaalle istutetun salaattifenkolin (‘ZEFA-Fino’ ja
‘ZEFA-Tardo’)kasvua jakehittymistä tutkittiin v. 1987
viiden kokeen koesarjassa. Ensimmäiset erät istutettiin
21.5. ja viimeinen 27.7. Aikaisten erien viljelyssä selvi-
tettiin myös harsokatteen ja taimien lyhytpäiväkäsittelyn
(pimeäjakso 16 h) merkitystä.

Kokeissa sato korjattiin ensimmäisen kerran, kun
‘ZEFA-Finon’ lehtikantakimpun, “mukulan”, suurin le-
veys oli kenttämittausten mukaan 60 mm. Seuraavat 3
korjuuta tapahtuivat viikon välein. Kasvin korkeus japai-
no, mukulan paino, korkeus, suurin leveys japaksuus,
mukulan sisässä olevan varren pituus sekä kukkavarren
esiinkasvu määritettiin yksilömittauksin.

‘ZEFA-Finon’ mukulat saavuttivat 60 mmm leveyden
1,5—2 kuukaudessa istutuksesta lukien, Kasvuajan pide-
tessä yksilöpaino ja mukulan paino, leveys, paksuus se-
kä korkeus kasvoivat, ja mukulan sisässä oleva varsi pi-
teni. ‘ZEFA-Finon’ mukuloiden suurimman leveyden ja

painon välinen korrelaatiokerroin oli0,87 —0,95 kokeesta
riippuen. Suurimman leveyden ollessa n. 64 mm muku-
lat painoivat keskimäärin 100 g, ja keskimäärin 200 g,
kun suurin leveys oli n. 82 mm. Toukokuun loppupuo-
lella istutetun ‘ZEFA-Finon’ sato aikaistui noin viikon
harsokatteen ansiosta.

Molemmissa lajikkeissa mukulan sisässä olevan varren
pituuden suhde mukulan korkeuteen suureni kasvuajan
pidetessä. Kesäkuun 10. päivänä istutetulla ‘ZEFA-Finol-
la’ tämä suhde kasvoi neljänteen korjuukertaan mennessä
o,B:aan, ja tällöin esiintyi eniten (8 %) yksilöitä, joiden
kukkavarsi oli kasvamassa tai kasvanut esiin mukulasta.
Muutoin tällä lajikkeella kukkavarren esiinkasvua oli vä-
hän. ‘ZEFA-Tardolla’ kukkavarren kasvu oli yleensä niin
nopeaa, ettei kauppakelpoista satoa juuri saatu. Fleinä-
kuun lopussa istutettu erä kehitti kukkavarsia muita hi-
taammin, mutta siinäkin sato oli heikkolaatuista. Lyhyt-
päiväkäsittely taimivaiheessa hidasti, mutta ei estänyt
‘ZEFA-Tardon’ kukkavarren kasvua.

244