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Globe

Artichokes
in Connecticut

BY DAVID E. HILL

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Globe Artichokes

in Connecticut

BY DAVID E. HILL

The production of globe artichokes for
American markets is largely confined to coastal
California where cool summers and mild winters
favor year-round supply from about 9,500 acres.
Although nearly 60% of California's artichokes
are sold locally in the Los Angeles-San Francisco
region, 30% of the crop is shipped to the New
York-Boston region (Anon. 1985).

As an alternate crop for Connecticut
farmers, artichoke culture captured my attention
4 years ago because the state lies in the center
of an important artichoke-consuming region and
an artichoke crop has a high cash value.

The globe artichoke, a biennial plant, grows
vegetatively the first year and matures the
second, sending forth the edible flower buds.
When artichokes are grown from seed, this two-
year cycle requires mild winters for survival; but
Connecticut's winters are severe and only heroic
measures of plant protection have allowed
artichokes to survive. The growth cycle of the
plant, however, can be shortened by vernalization
of seed (moist chilling) and application of
gibberellic acid (GA3) to young plants (Gerakis,
Markarian and Honma 1969). These treatments
initiate flower budding in 5 to 6-month-old
plants and permit production of artichokes in a
single year. Thus, the globe artichoke may be
grown as an annual plant.

In this Bulletin, I report experiments with
management requirements, yield and quality
trials, and winter protection in Connecticut.

MATERIALS AND METHODS

Vernalization of seeds and seedlings. Vernal-
ization, or moist chilling of seeds, was begun

between January 25 and February 5 for harvest
of artichokes beginning in late July. Seeds were
soaked in water for 2 days at room
temperature; packed in moist, unshredded
sphagnum moss in an unsealed plastic bag; and
refrigerated 4 weeks at 35 to 40 F. The seeds
were examined periodically and moistened when
necessary to prevent drying. After 2 to 4
weeks, the germinated seeds were ready to be
planted if the root emerged 1/2 to 1 inch.

Greenhouse management. About March 5 to
10, germinated seedlings were transferred to 1-
quart plastic containers filled with Promix BX
and placed in a greenhouse. The peaty potting
mixture contained enough fertilizer to maintain
early growth. Because warm days may
devernalize the seedlings (Harwood and Markarian
1968), the greenhouse was heated or ventilated
to maintain temperatures between 50 F at night
and 65 F during the day. No supplementary
light was used to extend daylength. About 20%
more seeds must be germinated to allow culling
of stunted plants. About April 10 to 25,
seedlings were transferred to a cold frame to
harden before transplanting in the field.

Transplanting. Trials were conducted at the
Valley Laboratory, Windsor, on Merrimac fine
sandy loam, a sandy terrace soil with somewhat
low moisture holding capacity; at Lockwood
Farm, Mt. Carmel, on Cheshire fine sandy loam,
a loamy upland soil with moderate moisture
holding capacity; and at Comstock-Ferre Farm,
Wethersfield, on Hadley silt loam, a silty flood
plain soil with high moisture holding capacity.
The soils were fertilized with 1300 lb/A of
10-10-10 and limed to attain a pH of 6.5.
Plants were set in the field May 5 to 10. The

Connecticut Agricultural Experiment Station

Bulletin 846

container-grown plants had prominent tap roots
curled at the bottom of each pot. After the
root ball was removed from the pot, the tap
root was straightened, and the plant was set in
a hole deep enough to accommodate its length.
Plants were set 3 feet apart in rows 4 feet
apart, a density of 3,630 plants/A.

Plot design and the cultivars ' used varied
according to the objective of the experiment.
In 1984, Green Globe and Grande Buerre were
planted at Mt. Car m el in 4 rows of 15 plants
each. Treatments were vernalization and GA3,
GA3 without vernalization, vernalization without
GA3, and no vernalization and no GA3. In
1985, 50 plants each of Green Globe, Grande
Buerre, Green Globe Improved, and Purple Globe
were planted at Windsor and Mt. Carmel. To
determine the most effective time of GA3
treatment, 10 vernalized plants of each cultivar
were treated on June 30, July 10, July 20, and
July 30. Ten vernalized plants remained
untreated. In 1986, this experiment was
repeated at Windsor and Mt. Carmel, except
that Purple Globe was not grown at Windsor.
In addition, 20 vernalized plants of each cultivar
were planted at Wethersfield. Fifteen of twenty
plants were selected for treatment with GA3 on
July 17; five were untreated. Plants with
visible flower buds on the treatment date were
not treated.

One hundred parts per million GA3 was
applied to foliage on each treatment date. By
June 30, all plants had reached the 10-leaf
stage required for treatment (Gerakis, Markarian
and Honma 1969).

Pest control was not needed. Minor
infestations of aphids in the greenhouse were
controlled by indigenous lady beetles after
transplanting in the field.

Weeds were controlled by grass mulch in
1984 and by cultivation in 1985 and 1986.

Artichokes were harvested and weighed
before the lowest bracts on the bud began to
unfurl. Artichokes smaller than 70 grams
(2.5 oz) were culled.

The yields reported for each cultivar are
averages for the four treatment dates. Since
some treatment dates did not produce optimum
response of the plants to GA3, I report the
yields as "potentials", taking into account only
those plants that set buds and eliminating those

that were barren because of poor timing of
treatment. Actual yields can be calculated by
multiplying the buds/acre x % plants producing in
Table 3.

Winter protection. A dry mulching technique
used to protect roses in winter (Rose, Pellett,
and Aleong 1982), was applied to barren
artichoke plants in the fall. In mid-December
1984, the tops of barren plants were severed
1 inch above ground after they had partially
withered from earlier frosts. Plastic bags were
filled with vermiculite, perlite, or styrofoam
chips, inserted into 2-gal black plastic pots, and
inverted over the plant stump. The inverted
pots were pinned with stakes to resist wind.
Leaves were piled around the inverted pot, with
drain holes open for ventilation. For
comparison, other plants were simply mulched
with 8 inches of leaves. Ten plants received
each treatment. In addition, six plants of Green
Globe and Grande Buerre were dug November 1,
placed in 2-gal pots, transferred to a cool
greenhouse (50 to 65 F) over winter, and on
May 1, 1985, replanted in the field.

RESULTS

Vernalization and GA3 treatment. In initial
experiments in 1984, I determined the response
of Green Globe and Grande Buerre artichoke
plants to vernalization and GA3 treatment,
(Table 1). Flowering of both cultivars was
greatest with vernalization of seed and seedlings
and treatment with GA3. GA3 treatment alone
was clearly more effective than vernalization
alone. In 1985, however, up to 100% of
vernalized Green Globe, Green Globe Improved
and Grande Buerre plants not treated with GA3
flowered (Table 2). I speculate that the poorer

TABLE 1 —PERCENT OF ARTICHOKE PLANTS
FLOWERING IN RESPONSE TO VERNALIZATION
AND GA3 TREATMENT IN 1984

+Vern +Vern -Vera
+GA3 -GA3 +GA3

% % %

Green Globe
Grande Buerre

80
HO

10
5

35
25

-Vera
-GA3
%

0
0

Globe Artichokes

response of plants to vernalization alone in 1984
was probably due to devernalization by high
temperatures during hardening in a poorly
ventilated cold frame. In 1986, delayed
vernalization in late February caused some
cultivars to produce buds late in October when
damaging frosts occurred.

The percentage of plants producing buds was
not consistently affected by GA3 treatment
among years (Table 2). In 1985, treatment with
GA3 increased buds of Green Globe, Green
Globe Improved, and Purple Globe by 15 to 83%
at Mt. Carmel, and -9 to 300% at Windsor. At
Mt. Carmel, all plants of Grande Buerre

TABLE 2--RESP0NSE OF VERNALIZED PLANTS TO GA3 TREATMENT ON DIFFERENT
DATES IN 1985-1986 (10 PLANTS/TREATMENT)

Mt. i

Carmel

Wind

sor

% Plants

Budding

Buds/Plant*

Budding

Buds/Plant»

1985

1986

1985

1986

1985

1986

1985

1986

Green Globe

June 30

2.2

1.2

100

1.8

2.2

July 10

100

2.5

2.6

1.5

1.9

July 20

100

2.7

1.1

100

2.3

2.6

July 30

100

2.6

1.3

100

2.9

1.1

Average (treated)

2.5

1.5

2.1

2.0

Untreated

2.4

0.9

100

2.4

2.2

Grande Buerre

June 30

100

2.5

1.8

1.1

1.6

July 10

100

2.9

0.6

100

1.0

1.9

July 20

100

2.4

1.5

1.2

2.0

July 30

100

2.9

1.2

3.1

2.3

Average (treated)

100

2.7

1.3

1.6

2.0

Untreated

100

2.7

1.5

2.1

0.9

Green Globe Impr.

June 30

1.7

0.5

1.6

0.6

July 10

1.9

1.3

2.3

0.9

July 20

100

2.3

1.8

July 30

2.4

0.1

1.6

Average (treated)

2.1

0.5

2.2

0.4

Untreated

1.8

1.4

Purple Globe

June 30

0.8

0.2

0.3

July 10

1.8

0.6

July 20

1.0

0.4

0.8

July 30

1.1

0.4

Average (treated)

1.2

0.2

0.5

Untreated

0.7

0.2

•Barren plants were excluded from calculations.

Connecticut Agricultural Experiment Station

Bulletin 846

produced artichokes, and at Windsor, treated
plants with buds increased 7% compared to
untreated.

In 1986 at Mt. Carmel, most cultivars had
28-72% fewer plants respond to GA3 treatment
compared to treated plants in 1985. There was
a similar response among untreated vernalized
plants. In 1986 at Windsor, however, Green
Globe and Grande Buerre had 3-1796 more plants
respond to GA3 treatment compared to 1985.
In 1986, untreated Green Globe Improved was
barren at both sites. At Mt. Carmel and
Windsor, GA3 treatments on June 30 or July 10
caused 30-40% of Green Globe Improved to form
buds. At Mt. Carmel, Purple Globe responded
poorly to GA3 treatment.

Although GA3 treatment accelerates bud
development and earliness (Snyder, Welch, and
Rubatzley, 1971), it is important to determine
its effect on yield. There was no clear effect

of GA3 treatment on yield of Green Globe and
Grande Buerre for 1985 and 1986 (Table 2). I
averaged the buds/plant for the four treatment
dates and compared them to buds produced by
untreated plants for each cultivar. It is evident
that GA3 treatment does not consistently
increase the number of buds/plant for Green
Globe and Grande Buerre. These cultivars are
easily vernalized and can form productive
laterals without GA3 treatment.

By comparison, Green Globe Improved and
Purple Globe responded to GA3 treatments.
Seeds and seedlings of these cultivars are more
difficult to vernalize and GA3 treatment in 1985
and 1986 at both sites increased production by
0.3 to 0.8 buds/plant. Despite the increased
production caused by GA3 treatment, however,
neither Green Globe Improved nor Purple Globe
matched the yield of Green Globe or Grande
Buerre.

TABLE 3— YIELD OF ARTICHOKES FROM VERNALIZED PLANTS TREATED WITH GA3

Windsor

Mt . Carmel

Wethersfield

Plants

Producing

Buds/

Plant

No»

Buds/
Acre
No"

Plants

Producing

Buds/

Plant

No«

Buds/
Acre
No"

Plants
Producing

Buds/ Buds/
Plant Acre

No» No"

1984

Green Globe

Grande Buerre

1985

Green Globe

814

Grande Buerre

Green Globe Imp.

Purple Globe

1986

Green Globe

Grande Buerre

Green Globe Imp.

Purple Globe

2.6

9438

2.5

9075

100

2.3

8348

1.8

6534

2.3

8348

2.0

7260

2.1

•Barren plants were excluded from calculations.
"Potential yields are calculated from average buds/plant x 3630 plants/A
yields are about 11,000 buds/A.

4.4

15972

1.7

6171

—

2.7

9801

„

—

2.7

9801

2.3

8348

2.2

7986

2.1

7623

3.9

14157

1.9

6897

3.8

13794

3.0

3.5

1.6

—

x 36:

30 plant

;s/A. California

Globe Artichokes

Neither percentage of plants producing
artichokes nor buds/plant offer a clear indication
of the best date of GA3 treatment. In 1985 at
Mt. Car m el, percentage of plants with buds was
greatest with July 10 treatment, but at Windsor,
with June 30 or July 30 treatment. In 1986,
the highest percentage of plants with buds
occurred with June 30 treatment at both sites.
In 1985, the greatest number of buds/plant
followed July 30 treatment, but in 1986,
followed July 10 treatment.

Yield. In frost-free California, larger plants
are grown at wider spacing than in Connecticut.
With 1,100 plants/A (Ryder, DeVos, and Bari
1983) and an average of 10 buds/plant, about
11,000 buds/A in each crop in California.

In 1984 at Mt. Carmel, Green Globe
averaged 4.4 buds/flowering plant, the highest
yield among all cultivars (Table 3). With 3,630
plants/ A, Green Globe could produce nearly
16,000 buds/A. Grande Buerre yielded only 40%
as many.

In 1985, the average potential yield of four
cultivars at Mt. Carmel was 8,984 buds/A and
at Windsor, 8,349 buds/A, a difference of 8%.
At both sites, Green Globe and Grande Buerre
had the highest potential yields, which would
approximate California's production. "Potential"
yield is the yield calculated for (buds/flowering
plant) x (number of all plants). Mt. Carmel had

the highest percentage of budding plants.

In 1986, the average potential yield of Green
Globe and Grande Buerre at Windsor was 7,804
buds/A, at Mt. Carmel, 7,260 buds/A, and at
Wethersfield nearly twice as many, 13,976
buds/A. Although fewer plants produced
artichokes at Wethersfield, higher yields were
borne on larger plants. Green Globe Improved
and Purple Globe were excluded from the
averages because of the low percentage of
budding plants.

At Mt. Carmel and Windsor, the percentage
of budding plants and yield/plant were less in
1986 compared to 1985. Among sites, Windsor
had the highest percentage of budding plants and
Wethersfield the lowest.

Maturity. Table 4 lists the harvest dates of
all cultivars at all sites for 1984-1986. The
first date represents the harvest of the first
artichoke of commercial quality. Early
production of small artichokes was not included.
The concluding date was usually when the
temperature fell below 25 F.

In 1984, the harvest began in late August
and concluded in early October, a 6-7 week
harvest. A killing frost ended the harvest.

In 1985, harvest of most cultivars began July
16 to 17 at Mt. Carmel and Windsor and
concluded with killing frosts on October 24 at
Windsor and November 11 at Mt. Carmel.

TABLE 4-- HARVEST DATES OF ARTICHOKES IN 1984-1986

1984
Green Globe
Grande Buerre

Mt. Carmel

Aug 22-0ct 9
Aug 27-0ct 9

Windsor

Wethersfield

1985
Green Globe
Grande Buerre
Green Globe Impr.
Purple Globe

Jul 17-Nov 11
Jul 17-Nov 11
Jul 17-Nov 11
Jul 30-Nov 11

Jul 16-Oct 24

Jul 16-Oct 10

Jul 30-0ct 24

1986
Green Globe
Grande Buerre
Green Globe Impr.
Purple Globe

Jul 21-0ct 10
Jul 17-Oct 10
Jul 27-Oct 16
Jul 27-Sep 12

Jul 10-Sep 25
Jul 10-Sep 25
Aug 12-0et 9

Jul 17-Oct 16
Aug 12-0ct 16
Aug 26-Oct 16

Connecticut Agricultural Experiment Station

Bulletin 846

Harvest lasted 17 weeks at Mt. Carmel and 14
weeks at Windsor for most cultivars.

In 1986, harvest at Mt. Carmel began July
17 and concluded October 16, a 13-week period.
At Windsor, harvest of three cultivars began on
July 10 and concluded on October 9, a 13-week
period. At Wethersfield, harvest of Green Globe
lasted 13 weeks, but harvest of Grande Buerre
and Green Globe Improved started late and
concluded after 7-9 weeks. Despite the early
conclusion of harvest of the four cultivars on
October 9 to 16, the harvest of other cultivars
not included in this study began in late August
and concluded November 5 with a killing frost
at all sites.

Finally, the harvest period of 1985 was
extended by formation of a second crop on some
plants. Plants that had produced artichokes by
mid-August withered and sent forth new shoots
from the root crown. Artichokes were produced
on about 5% of these resprouted plants.

Winter protection. Artichoke plants that are
unproductive the first year despite vernalization
or GA3 treatments require winter protection.
Three methods can be considered: 1) outdoor
mulching, 2) repotting the whole plant for indoor
maintenance, and 3) root storage.

Periodic examination of the soil surrounding
the root crown of mulched plants revealed that
the soil remained unfrozen except when
temperatures fell below 15 F. At this time
frost penetration was about one inch.

Vermiculite pillows offered the best
protection for both Green Globe and Grande
Buerre. Perlite and styrofoam were less
effective protectors for both varieties. Plants
that were merely covered with leaves did not
survive. In the spring, surviving plants had
viable shoot buds on the root crown just below

TABLE 5--PERCENT SURVIVAL OF ARTICHOKE
PLANTS PROTECTED BY DRY MULCHES OR LEAVES
IN THE FIELD

Green Globe Grande Buerre

i %

Vermiculite

Perlite

Styrofoam

Leaves

ground level. If buds were numerous, the roots
were dug and cut into two or three "stump
pieces" and replanted. If the buds were few,
the root was replanted intact. Only a third of
the plants from stump pieces had buds, and they
averaged 1.4 buds/plant. About 55% of the
roots planted intact yielded 2.1 buds/plant.

Plants dug and placed in 2-gal plastic pots
in a cool greenhouse survived well. The plants
did not enlarge and maintained a relatively
constant number of leaves. As old leaves died
at the base, new leaves emerged from the
crown. After replanting in the field on May 1,
the plants grew. Harvest began July 30.
Nearly 85% of Green Globe had buds and
averaged 3.2 buds/plant. Only 3396 of Grande
Buerre had buds and produced an average of 3.0
buds/plant.

Attempts to store dug artichoke roots over
winter were largely unsuccessful. Only 5% of
roots stored at 40 F survived.

CONCLUSIONS

1. Artichokes of commercial quality can be
grown in Connecticut. Three years of testing
have shown that the harvest period ranges from
6-17 weeks and is highly dependent upon local
climate. Artichokes seem best suited for
Connecticut's roadside and farmers markets for
retail sales because the harvest generally occurs
in the summer and early fall when wholesale
prices are low. November harvests are
preferable because the California crop is
insufficient to meet consumer demand and prices
rise. November harvest, however, requires
careful control of the growth cycle of the plant
and cooperative weather.

2. Gibberellic acid to promote early budding
is necessary only if the crop shows no bud
formation. Only barren plants need to be
treated between July 10-20.

3. Winter protection is expensive, labor
intensive, and likely has no place in commercial
production. For the home gardener with a few
plants, winter protection by moving barren plants
to a cool, sunny area indoors may suffice.
Artichokes normally appear on replanted plants
as they complete their biennial cycle.

4. Among the four cultivars tested, only
Green Globe and Grande Buerre approached

Globe Artichokes

California yields. About 30 cultivars from
Mediterranean countries will be tested in 1987.

REFERENCES

1. Anon. 1985. Agricultural Statistics 1985.
USDA. 551p.

2. Gerakis, P.A., D. Markarian, and S. Honma.
1969. Vernalization of globe artichoke, Cynara
scolymus L. J. Amer. Soc. Hort. Sci. 94:254-8.

3. Harwood, R.R. and D. Markarian. 1968.
Annual culture of globe artichoke (Cynara
scolymus L.). I. Preliminary Report. Proc.
Amer. Soc. Hort. Sci. 92:400-9.

4. Rose, A.E., N.E. Pellett, and J. Aleong.
1982. Effect of protective covers on cold
acclimation and survival of Hybrid Tea roses.

J. Amer. Soc. Hort. Sci. 107:1173-7.

5. Ryder, E.J., N.E. DeVos, and M.A. Bori.
1983. The globe artichoke (Cynara scolymus L.).
HortSci. 18:646-53.

6. Snyder, M.J., N.C. Welch, and V.E.
Rubatsky. 1971. Influence of gibberellin on
time of bud development in globe artichoke.
HortSci. 6:484-5.

ACKNOWLEDGMENTS

I thank Abigail A. Maynard for her faithful
and capable assistance in the field, and in
compilation of data. I also thank the Williards
of Comstock-Ferre Seed Company, Wethersfield,
for generously allowing me to use a portion of
their All American Seed Trial garden for my
trials in 1986.

I*
The Connecticut Agricultural Experiment Station,

founded in 1875, is the first experiment station in America. It is chartered
by the General Assembly to make scientific inquiries and experiments
regarding plants and their pests, insects, soil and water, and to perform analyses for State
agencies. The laboratories of the Station are in New Haven and Windsor; its Lockwood
Farm is in Hamden. Single copies of bulletins are available free upon request to Pub-
lications; Box 1 106; New Haven, Connecticut 06504. ISSN 0097-0905

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Full text of "Globe artichokes in Connecticut"

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