From New Crops, Proceedings of the Second
National Symposium NEW
CROPS: Exploration, Research,
Commercialization
by Richard McCain
Goldenberry,
Passionfruit, & White Sapote: Potential Fruits for
Cool Subtropical Areas
1. GOLDENBERRY
1. Botany
2. Horticulture
2. PASSIONFRUIT
1. Botany
2. Horticulture
1. Passifloras
2. Hybrids
1. Conclusion
3. WHITE SAPOTE
1. Botany
2. Horticulture
4. REFERENCES
5. Table 1
In the West, as in other agricultural regions of the United States,
many farmers, especially small growers, have recently been looking at
new and unusual crops to diversify their operations. Factors leading to
diversification include water limitations, pressures from the
development sector, overproduction of many traditional local crops,
competition (i.e., lower prices) from out-of-state or foreign growers,
and increasing labor costs.
The central coast region of
California has a variety of soils and climates conducive to the growing
of a large assortment of crops. While this region is well known for its
production of strawberries, lettuce, and artichokes, its unique
conditions have encouraged farmers to experiment with many unusual
crops as well.
For example, since it was founded in 1979, the
author, a partner in Quail Mountain Herbs, has grown herbs, salad
crops, edible flowers, subtropical fruits, and other specialty produce
in the Monterey Bay region of the central coast. Since its inception,
Quail Mountain has successfully marketed over 100 different crops
nationwide. Quail Mountain's growing grounds are located in several
different microclimates. Due to this region's unique geography, at
least 25 different microclimates have been reported.
The author
has conducted research on a wide variety of herbs, flowers, vegetables,
and fruits over the years. Most of the research has focused on finding
or creating plants with superior taste, appearance or cultural
requirements. This is done through selection and hybridizing to achieve
desirable traits. The following fruits are among those crops that show
the most potential.
GOLDENBERRY
Botany
First described by Linnaeus in 1753, the cape
gooseberry or goldenberry, Physalis
peruviana
L., Solanaceae, has been cultivated for many decades along the Andes
Mountains of South America. Goldenberry, the proposed name (Legge 1974)
now being used to avoid any confusion with the common gooseberry (Ribes
ssp.), has been spread by explorers and travelers worldwide, but is
still considered a backyard fruit in most areas. Small industries are
developing around the goldenberry in countries in central and south
Africa, Australia, New Zealand, and India but nowhere has it really
achieved large commercial success (Morton 1987). The plant's
productivity in poor soils, its ease of cultivation, and low
requirement for water and fertilizer has made it an attractive
potential crop.
The goldenberry is an herbaceous, erect,
alternate-branched shrub with pubescent slightly toothed heart-shaped
leaves that appear irregularly along the stems (Moriconi et al. 1990).
Yellow, pendulous flowers have campanulate corollas with purple to
purplish brown spots. The genus, Physalis,
with 100 or so species of annual and perennial herbs, is characterized
by the fruit being enclosed in a papery husk or calyx. The goldenberry
has a particularly delicious fruit with a tangy pineapple-like flavor.
Several members of the genus are exploited for their berries. Among
them are the ground cherry, P.
pruinosa L. and the tomatillo of Mexico, P. ixocarpa Brat.
Horticulture
Dried
ripe fruits from selected clones of the previous seasons are fermented
in water for up to 5 days. After the seeds are separated from the pulp,
they are planted in flats of sterile peat-lite mix. The flats are kept
continually moist. Seeds germinate in 8 to 14 days in an unheated
greenhouse. The seedlings are field planted when they are 15 to 20 cm
tall with at least 1.0 m between each plant. The plants are watered by
either drip irrigation or overhead sprinklers, although drip irrigation
provides more control of water consumption and weeds. The plants appear
to need little or no fertilizer. Fruit production decreased
significantly when fertilizer was applied. When fish emulsion or
12-5-10 (NPK) fertilizer were applied at rates approximately 45 lb.
N/acre (50 kg/ha), the plants exhibited a great deal of vegetative
growth but produced few flowers or fruit. Plants planted in sandy soil
without any amendment or fertilizer produced 150 to 300 flowers per
plant with a corresponding number of fruit. Plants typically have a
sprawling habit similar in size and growth pattern to their relative,
the tomato. The plants should be trellised or staked.
The first
yellow, bell-shaped flowers appear 4 to 5 weeks after transplanting
during the onset of warm spring days in April and continue flowering
through November unless damaged by an early frost. The plants are
pollinated by wind and local insects including bees. While pollination
is not a problem, inconsistency in fruit size is a problem.
Goldenberry
plants typically are heavy fruit producers. Fruit production begins in
August and continues until the plants are killed by frost (usually
early December in this area). Yields of 150 to 300 fruits per plant are
not unusual. The fruits are ripe when they turn yellow-gold. Unripe
fruits are green. The fruits are 1.25 to 2.5 cm in diameter and are
encased in a papery, tan husk. When fully ripe, the fruits and husk
will naturally dehisce or fall when given a good shake. Harvesting can
be accomplished by allowing the fruit to fall on fabric or plastic
placed under the plants. Collection is either done by hand picking, or
by gathering up the plastic and pouring the fruit into containers.
Vacuum harvesting the fruit should be explored. Hand collection is
preferable if the fruit is to be sold on the fresh market, to avoid
bruising. The fruit is quite durable when left in the husk.
Goldenberries are generally sold with the husk left on as many chefs
use the husk for decorative purposes. After harvest, the ripe fruit may
last several months without refrigeration, if kept dry. They also may
be picked partially green and allowed to ripen, but these fruit never
become as sweet as vine-ripened fruit.
Fruits seen on the market
vary in taste and size. The fruits grown at Quail Mountain have a
sweet, tangy taste while some cultivars are mealy and tasteless. There
is great genetic variability. The fruit is eaten fresh or cooked. The
fruit makes excellent pies and jellies and is very high in pectin. The
fresh fruit may be served with husk pulled back for fondue. Goldenberry
sauce is a nice accompaniment to a meat dish. While not well known by
the retail consumer, the fruit has a strong following among chefs and
the market is likely to grow for good quality, vine-ripened fruit.
The
plant has been primarily pest and disease free at Quail Mountain.
Botyritis mold has been found on ripe fruit. This may be caused by the
frequent fog in this area.
PASSIONFRUIT
Botany
The
Passifloraceae contains nearly 600 species in 12 genera, four of which
are found in the New World. Of the 500 species of the genus Passiflora,
only 10 to 12 have been exploited for their fruits (Menzel 1990; Howell
1989). Most commercial production around the world is based on
cultivars of P. edulis
Sims, its yellow form P.e.f.
flavicarpa or their hybrids, which are species of the
subgenus Granadilla.
There are more than 60 other Passiflora
species with edible fruits, many that should excite consumer interest.
The subgenus Tacsonia
contains over 40 species with edible fruit (Escobar 1980). Originating
from the cool, middle to high altitude regions of the Andes, most of
the Tacsonia
are suited to
the ocean-influenced microclimates of Western North America. The arid
inter-Andean valleys are veritable biogeographic islands, each with
many endemic species that are isolated from other such valleys by wet
tropical forests below and cold Andean tundras above, a situation
favoring speciation (Iltis 1988). Although there is much genetic
variation in the Tacsonias,
a few natural hybridizations do occur (Killip 1938; Escobar 1980), and
members of Tacsonia
hybridize readily under cultivation. The feasibility of cross-breeding Passifloras to
improve their fruits has been demonstrated by Rupert-Torres and Martin
(1974) and Escobar (1980).
At Quail Mountain, the author started collecting Passifloras in 1979
and began hybridizing them in 1984. Hybridizing for fruit production
has focused primarily on the subgenus Tacsonia. At the
present time there are over 100 species of Passifloras in this
collection, 15 of which are Tacsonias.
Through numerous generations of hybrids and a continuous process of
selecting superior plants from hundreds of hybrids, several very
promising cultivars have been developed.
The very diverse genus Passifloras
is characterized by woody or herbaceous vines furnished with tendrils
in the leaf axils. The polymorphic, alternate leaves can be extremely
variable in size and shape. Some species produce egg mimics to avoid
predation by members of the Lepidoptera
family or other pests (Gilbert 1975; K.W. Williams and L.E. Gilbert
unpub.). The angular leaf stalks usually contain excrescences called
glands along the petioles. The flowers located in the leaf axils are
extremely colorful and elaborate in most species. The floral parts
consist of a calyx with 5 lobes or sepals and 5 petals. Inside the
petals are one to several series or rings of filaments forming the
corona, the center of which is filled with nectar. The outer rings
compose a perfect target for hummingbirds, bats, bees, moths, and other
pollinators.
The main characteristics that set the Tacsonia
apart from other subgenera in the family are that the filaments are
reduced to nubs or tubercles in the corona and the calyx tube is much
longer than the sepals. The male and female parts are raised aloft by
the narrow columnar gynophore. At the top of the gynophore is the ovary
with 5 stamens below and 3 stigmas above.
Many species of Passifloras
are self-infertile, but if pollinated, the ovary swells into a fruit
that is botanically classed as a berry. Hand pollination greatly
increases fruit size. In over 60 species, fruits, that vary in size
from that of a marble to a small melon, are filled with a deliciously
sweet or tangy acidic pulp. The juice is widely used in many countries
as a flavoring for juices, confections, ice cream, and other products.
Demand in the United States has been growing steadily in the last few
years for fruit which can be sold fresh or juiced for use in other
products.
Horticulture
While the cultivation of the many Passifloras may be
similar, the following is derived from the author's experimentation
with selected Tacsonia
species. Each year, passionfruit vines are selected from a growing area
of about 1 ha based on overall vigor, consistent flowering and
fruiting, fruit size and flavor, time of ripening, and disease
resistance. Cuttings from these selected clones are rooted in a
propagation house in the fall and over-wintered. Selections are
propagated by dipping cuttings with 5 to 10 nodes from vigorous growing
shoots in rooting hormone (IBA/IAA combination at a concentration of
1,500 ppm) and placed into flats containing a fast draining mix of
perlite and sand on a bench with bottom heat and intermittent mist.
Rooting takes three to five weeks. During the winter, well-rooted
cuttings are transplanted into containers with a peat-lite mix and
receive organic fertilizer once in late January.
The vines are
set out in fields at the beginning of February (3 x 1.8 m spacing) and
are drip irrigated weekly. The soil is amended with bone meal, blood
meal, and seaweed meal prior to planting. The vines are trellised as
they perform poorly when sprawling along the ground. The vines commence
flowering in May and continue nearly year-round unless killed by a hard
freeze. At Quail Mountain, nearly every flower sets a fruit.
Pollination is by bees, hummingbirds, and wind. Hand pollination can
increase fruit size. Vines produce 50 to 120 fruits each. With 740
vines/ha, estimates of harvest yield are 16,800 to 22,400 kg/ha.
Passifloras
The following Passifloras have
commercial possibilities but require further breeding efforts. Most of
the author's selections are Tacsonia
or other cool growing Passifloras
which have not had widespread commercial use in the United States.
Passiflora
ampullacea
is one of the only white flowered Tacsonias. This Passiflora has not
flowered yet in Northern California, but flowered in San Diego, in
1988. Fruits are reported to be larger and with a thicker rind than P. mollissima (NRC
1989). Hardiness is unknown. It is found in the mountains of Southern
Ecuador at elevations of 2,600 to 2,800 m.
P.
antioquiensis
thrives in shade, and must have large amounts of water. Flowers are
brickred, 15 cm across and hang down on peduncles up to 32 cm long. It
has flowered and fruited at Quail Mountain and as far north as San
Francisco. The fruit (to 12 cm) is similar in taste to the sweet
granadilla, (P. ligularis),
which is one of the sweetest passionfruits. Originally from the
mountains of Colombia up to 3,000 m, it cannot survive more than a
light frost.
P.
cumbalensis fruits have long been used in South America
for flavoring. Escobar (1987) reports at least seven distinct varieties
of P. cumbalensis
with variety goudatiana the best tasting. Flowers are rose to purple
and fruits are red and banana shaped. It has flowered in San Francisco
but not at Quail Mountain. P.
cumbalensis can be found in the Andes from western
Venezuela to northern Peru at elevations of 1,800 to 4,100 m.
P. manicata
flowers and fruits nearly year round at Quail Mountain. The flowers are
bright reddish-orange and attract hummingbirds. The fruits are small,
(2.5 x 5 cm) with good flavor. Widely distributed in the Andes from
1,500 to 2,500 m in elevation.
P. mollissima
is a widespread and variable species found from Venezuela down the
central cordillera of Columbia to southeastern Peru and western Bolivia
at 2,000 to 3,200 m in altitude. It is grown commercially in many areas
and is reputed to be one of the best for juice. P. mollissima
flowers from May to the first freeze (December-January). The yellow
oblong fruits are approximately 10 to 15 cm long and have overtones of
citrus. Some clones can be sweet. The species grows vigorously and
shoots develop from the roots after frost injury.
P. mixta
is a very diverse species found at higher elevations than P. mollissima
(2,500 to 3,600 m) but with a similar range in the Andes. P. mixta
has survived -7°C. Flowers are light pink to rosy-peach and bloom in
successive flushes throughout the year in a cool coastal climate. The
fruits are 2 to 3 cm wide and 8 to 12 cm long and are usually
yellow-green when ripe. Fruits have a hint of raspberry flavor.
P. trisecta
is found from southern Peru to Bolivia within a very limited range of
elevation (2,400 to 2,800 m). It has broad white flowers with a short
calyx tube. The anthers and stigmas are all located on one side of the
flower. P. trisecta
has
flowered and fruited at Quail Mountain. The fruits are green and
egg-shaped, 3 to 4 x 7 to 8 cm. Plant hardiness is unknown.
P. trifoliata
is found in the Andes of central and southeastern Peru at 3500 to over
4000 m. The plant is very pubescent, appears to be hardy, but is
susceptible to spider mites. Flowers are pink and similar to P. mixta although
miniature in size (2 to 3 x 7 to 8 cm). Fruit is egg-shaped (3 to 4 x 5
cm) with three indentations longitudinally.
P. tripartita
may be a variant of P.
mollissima, but is limited to Columbia. The flowers are
similar in color to P.
mollissima but the petals and sepals flare open more.
Fruit is similar in size, shape, and color to P. mollissima but
tastes tarter.
Hybrids
P.
antioquiensis (P.
mollissima x P.
exoniensis) is an extremely vigorous plant. The flowers
are larger than P.
antioquiensis and darker pink than P. mollissima. The
fruit reported to be delicious (Vanderplank 1991).
P. manicata
x P. mollissima
flowers all year round on the coast of California. It must be hand
pollinated to produce fruit. Fruit is larger than P. manicata, but
smaller than P.
mollissima.
P. mixta
x P. mollissima
is a vigorous grower but not as floriferous as P. mixta, nor as
self-fertile as P.
mollissima.
P. mollissima x P. mixta
is fast growing and hardier than either parent with showier, vibrant
pink flowers. Fruit is much larger and juicier than either parent with
a different, but delicious flavor.
P.
tripartita x P.
mollissima is a weak grower with bright green leaves. The
flowers are similar to the P.
tripartita parent. The fruit retains the sour flavor
of P.
tripartita .
P. trisecta
x P. mixta
is fast growing, but has not flowered or fruited yet.
(P. manicata
x P. mollissima)
x P. mollissima is vigorous and hardier than either original parent.
The fruit is delicious and as large as P. mollissima but
pointed at the end.
Conclusions
Passionfruit
vines are easy to bring to fruit if their basic cultural needs are met.
Mixed-cropping or perennial cropping systems hold the most promise. At
Quail Mountain, vines grow between rows of white sapotes in an
orchard-like fashion. Between these rows, are rows of goldenberry and
Yacon (Polymnia
sonchifolia).
At the ground level, a variety of herbs flourish. All of these crops
seem to be very compatible with minimal disease or pest problems. Herbs
in the Lamiaceae and Apiaceae are advantageous as they attract bees and
other pollinating insects when they flower. Many Passifloras
are self-infertile, so a sister seedling or closely related species
must be in the vicinity to benefit pollination. Hand pollination is
very labor intensive and expensive. Combinations of compatible species
or clones need to be examined further to improve pollination in larger
plantings. Fruits of many Tacsonias
are soft and may bruise with mechanical harvesting, so clones must be
selected for thicker skins. Selection of superior clones with larger
sizes and improved fruit flavor will be continued. Processing and
storage of fruit pulp needs to be investigated further. Passiflora
fruits produce ethylene gas and need to be packed, stored, and shipped
in such a way that this is not a hindrance to fruit quality. There is
every reason to believe that with more research a greater variety of
passionfruit flavors could be made available to the American consumer.
WHITE SAPOTE
Botany
The white sapote, Casimiroa
edulis Llave & Lex, Rutaceae, has attracted
interest among rare fruit growers and orchardists in California. The
genus Casimiroa
contains 5 or 6 species (Thompson 1972; Morton 1987). Among these are
three little-known shrubs or small trees from Mexico, C. pubescens
Ramirez, C. pringlei
Engl., and C. watsonii
Engl. Another species, C.
emarginata Standley & Steyerin, was described in
1944 from a single specimen found in Guatemala (Morton 1987). The C. sapota Oerst,
matasano, is very similar to and often confused with C. edulis, along
with C. tetrameria
Millsp., the wooly-leaved white sapote. Although these last two species
sometimes hybridize with C.
edulis, their flavor is considered inferior (Thompson
1972). C. edulis, C.
sapota, and C.
tetrameria are found in central Mexico. Their range is
broad, extending down into Central America as far as Costa Rica. The
white sapote, C. edulis,
remains the preferred fruit of the genus due to its delicious flavor
and wide appeal.
In
its native habitat, trees are found at altitudes of 750 to 2,700 m.
They do not flourish in the hot, tropical lowlands (Morton 1987), but
are cultivated around the world in subtropical areas and regions with a
mild Mediterranean climate. The trees have been planted in the northern
part of South America, the Caribbean region, Spain, Portugal, Southern
France, and Italy. They are grown commercially on a small scale in New
Zealand, Australia, and South Africa. White sapote have not been
successfully grown in the Philippines, but have been cultivated in
other islands of the East Indies (Morton 1987). There are small
plantings in Florida, Hawaii, and experimental plantings in three
different regions in Israel (Nerd et al. 1990). The white sapote has
grown well in California since the early 1800s (Schneider 1986). It is
thought to be first introduced by Franciscan monks along with figs,
olives, and grapes (Thompson 1972). Some cultivars have fruited well as
far north as San Francisco (Thompson 1972).
White sapotes are
medium to large-sized, fast growing trees with aggressive spreading
roots that help them withstand periods of drought. Mature trees can
reach 15 to 18 m in height and produce 900 kg (2,000 lb.) of fruit per
year. Thompson, (1972) reported a tree of 'Chestnut' produced nearly
2,700 kg (6,000 lb.) of fruit in 1971 in Vista, California. Grafted
trees remain smaller and develop a better canopy than seedlings.
Horticulture
The
author first planted a few white sapote trees at Quail Mountain in
1983. In 1986, 190 two-year-old grafted trees, representing 18
cultivars, were planted approximately 6 m apart (346/ha). The trees
were drip fertigated weekly, for the first two years, and bi-monthly
thereafter. After the trees were two years old, yearly top dressings of
goat manure were added to the base of each tree and the trees were
foliar fed with seaweed solution in the summer and fall. Very light
skirt pruning is practiced annually.
The first cultivars to
fruit were 'Suebelle' in 1988 followed by 'Lemon Gold' in 1989. The
first frost of the decade occurred in the winter of 1988 (29° to 30°F;
-1.7° to -1.1°C), followed by another series of frosts in 1989 (lows to
28°F; -2.2°C). These frosts injured the young growing shoots and caused
fruit to drop, but there was otherwise no severe damage and the trees
recovered rapidly in the spring. In December of 1990, a devastating
"freeze of the century" struck California. Low temperatures in the
sapote orchard were 20°F (-6.7°C) followed by 21°F (-6.1°C) and then
two weeks of 25 to 28°F (-3.9° to -2.2°C) nights. The cultivars most
susceptible to freeze damage were killed below the graft, although most
survived to come back from the roots (Table 1).
In California,
the trees do well on well drained sandy loam or clay soils. They grow
and fruit well on the deep sands of Florida, but may become chlorotic
on oolitic limestone (Morton 1987). The young branches are bright green
but turn gray and become very strong with age. Trunks of older trees
can become buttressed. Leaves are shiny above, glabrous below, and
palmately compound with 3 to 5 pointed leaflets.
The small
flowers are 5-petaled, creamy white with a greenish tinge, and occur in
panicles of 5 to 100 in number. In California, many cultivars bloom in
spring, summer, and fall. Blooming time varies among the cultivars
which prolongs fruit harvest. Most trees have two successive blooming
flushes, separated by several months. The panicles are usually held
terminally or in bases of the branch shoots or axils of mature leaves.
The flowers sometimes are cauliflorous (Batten 1984). If bees are in
the area, pollination is no problem, but many flowers and immature
fruits abort naturally. For maximum fruit size, the fruit should be
thinned. Fruits ripen gradually about 4 to 5 months after pollination
occurs. On most cultivars, the fruit remains green when ripe. The fruit
is ripe when the skin yields to slight pressure. Fruits are spherical
to slightly oval in shape and are 6 to 11 x 6 to 12 cm in size. Fruits
have a cream to yellowish custard-like pulp with a melting flavor of
banana, peach, and pear. Each fruit has one to four seeds which
resemble those of a large orange or grapefruit and are reportedly
fatally toxic if eaten (Morton 1987). The fruit quality is quite good
in coastal areas of California (Chandler 1950).
Fruit should be
hand harvested as many varieties bruise easily. The fruit may be
harvested early, which may be an advantage if the fruit is to be
shipped for the fresh market. The fruit is high in ethylene so
postharvest handling procedures should avoid prolonged storage.
Separation of fruit or wrapping individually may retard ripening. The
fruit lasts up to two weeks when ripe, under refrigeration. Fruit
should be packaged in a manner that avoids bruising. Many new packaging
methods are being used for other crops, such as Asian pears, that may
be easily adapted to the sapote. Cultivars with thicker skin are
needed. The fruit is liked by most all who try it, so it may "market
itself" once it becomes more readily available to the general public
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• Roecklein, J.C. and P.S. Leung. 1987. A profile of economic plants.
Transaction Books, New Brunswick, NJ.
• Schneider, E. 1986. Uncommon fruits and vegetables. A common sense
guide. Harper & Row, New York.
Table 1 Performance
of white sapote cultivars planted as 2-year-old trees in 1986 in
central California (Monterey Bay region).
|
Tree response to 1990 freezez |
|
| No. surviving |
|
| Cultivar |
above graft |
below graft |
No. dead |
Fruit |
Comments |
Tree type |
| Chestnut |
6 |
2 |
2 |
Large, round, good flavor |
Commercial cv. in California |
Vigorous, upright |
| Denzler |
|
2 |
3 |
|
Hawaiian cv. |
|
| Fred |
9 |
|
1 |
|
Hardy |
Vigorous |
| Guinn |
3 |
5 |
2 |
|
Performs poorly |
|
| Lemon Gold |
1 |
5 |
|
Medium, round, good flavor |
Good producer in Southern California |
Small to medium |
| Malibu |
1 |
2 |
3 |
|
Not vigorous |
|
| Miller |
5 |
1 |
|
|
Flowers early |
Strong grower |
| McDill |
7 |
2 |
1 |
Lg., round, yellowish |
|
Vigorous |
| Ortega |
1 |
2 |
3 |
|
Weak grower |
|
| Pike |
4 |
2 |
|
Lg., pointed, execellent flavor |
Prolific |
Small tree |
| Rainbow |
2 |
7 |
1 |
|
Fast grower |
Bushy growth |
| Suebelle |
10 |
|
|
Small, green |
Attracts pests |
Very bushy |
| T.S. Suebelle |
3 |
3 |
|
Small, yellow |
Medium vigor |
Bushy growth |
| Sunrise |
|
6 |
|
Small, green |
|
Mostly dead |
| White |
|
3 |
3 |
|
Poor |
Mostly dead |
| Wilson |
5 |
1 |
|
Excellent flavor, green |
Vigorous |
Bears year-round |
| Vernon |
6 |
|
|
Medium to large |
Fast grower |
Rounded |
| Vista |
6 |
|
|
Small, oval, good flavor |
Alternate bearing |
|
z December 1990 freeze; low
temperatures of -6.7°C followed by -6.1°C and 2 weeks of -3.9° to
-2.2°C nights.
Last update April 24, 1997 aw
|
|