Mike, from the 2 courses I took, one can grow a tree from seed and it
will bear fruit. One has to wait till the fruit is evaluated to see if
the seed was true. Different species have different characteristics.
Grafting can combine good characteristics from different plants. A lot
of citrus is grown on "trifoliate rootstock" which is grafted on for its
cold tolerance.
Cold Hardy Citrus
As citrus trees are basically subtropical or tropical I am often asked
for information regarding their cold hardiness. Most citrus will not
tolerate temperatures below -2 C. For those of you who live in regions
where the winter chill regularly falls below this temperature there are
many preventative measures and cultural practices you can follow to grow
citrus successfully.
Cold Hardy Variety Selections
Trifoliate orange is an inedible citrus used as a rootstock. It
withstands the lowest temperatures of all citrus followed by kumquat,
satsuma mandarin, calamondin, mandarin, orange, grapefruit, lemon, lime
and citron. Considered cold hardy to about -15=B0F, its range of
cultivation can be extended into zone 5 if it is planted in a sheltered
location and perhaps given some extra protection. Grapefruit, lemon,
lime and citron being cold sensitive. Satsuma and kumquats are the most
prominent of the cold hardy citrus.
Cold Hardy Sweet Oranges
Hamlin and Navel Oranges are the most cold tolerant of the oranges. If
on trifoliate rootstock they exhibit the maximum cold-hardiness, with
swingle and sour orange following.
Cold Hardy Mandarins
The Sunburst Mandarin is one of the most cold hardy again with maximum
cold hardiness being achieved when budded onto trifoliata or sour orange
rootstock.
Satsuma Mandarins are the most cold-tolerant of commercial citrus, with
mature dormant trees having survived temperatures as low as -9C with
serious injury. The Satsuma is adapted to regions that are too cold for
most other citrus. The Satsuma tree is vigorous, of medium size and very
productive. Maximum cold hardiness is achieved when budded onto
trifoliate rootstock.
Cold Hardy Kumquats
Kumquats exceed even satsuma in terms of cold-hardiness being able to
sustain temperatures as low as -12C when dormant. Trifolate is the
recommended rootstock when growing kumquats in cold areas.
Planting site
When planting in cooler climates give some thought to the planting site.
Cold air drains downhill so higher elevations are somewhat warmer than
sites at the bottom of a slope. Planting citrus near a house or other
building will also offer protection. The building will act as a
windbreak, forcing cold air up and over it and therefore over the citrus
also. The house itself radiates considerable heat some of which will be
absorbed by the plants.
Cultural Practices
The soil under and around cold sensitive trees should be free of weeds
and mulch. These act as insulators preventing warmth from the sun from
entering the soil during the day. This warmth is stores in the soil for
release during the night. A clear surface allows maximum heat absorption
during the day and maximum heat radiation at night. It is also
recommended that soil be kept moist as it will absorb more heat than a
dry soil. Keeping your trees strong and healthy through good care will
also help them to withstand cold temperatures.
Cold Protection
For more information on how to protect your trees during winter visit
the July 2001 newsletter. =
Fahrenheit to Celsius Conversion Chart
For those of you in cooler climates you may find this chart interesting
when referring to text printed in the USA. It is a simple
http://www.crh.noaa.gov/pub/temp2.htm
Kumquats - The cold hardy Jewels of the Citrus Family
Many people think of kumquats as a tart fruit that is only used in
preserves. However their are two varieties, the Nagami and Meiwa that
are bite-size fruit eaten skin and all. They have a wonderful
combination of tangy and sweet flavours. They are becoming more and more
common on the supermarket shelves and are an ideal snack for school
lunches. They are delicious eaten straight from the tree but if there
are any left over they can be used in salads and marinades or as an
attractive garnish in desserts.
Meiwa is the sweetest kumquat and has round, sweet tender skin and a
sweet tangy centre. Marumi has tiny round, very tart kumquats and nagami
has oblong fruits that have a delicious sweet and tart taste. =
The plant itself is highly ornamental as it is almost always covered in
either delightfully scented blossoms or bright orange fruit. It is an
evergreen shrub with glossy green foliage that make fantastic additions
to wreaths and floral arrangements. They are great for planting in
containers and can be shaped into topiary forms.
Taxonomy, cultivars. =
The genus Citrus belongs to the Rutaceae family, sub-family
Aurantoideae. This family contains many edible species, some distantly
related such as White Sapote (Casimiroa edulis Llave & Lex.) and Wampee
(Clausena lansium Skeels.). While Citrus is by far the most important
genus, two other genera contain commercially important species: =
1. Fortunella spp. (Kumquats). Originally classified with citrus, then
moved to its own genus, named after Robert Fortune, who introduced
kumquats to Europe. Evergreen shrubs or small trees (8-15 ft), these
plants are native to southern China, but can be grown around the world
into subtropical areas. Unlike citrus fruits, the peel of the fruit is
edible, although tart/spicy. Fruit are eaten-out-of-hand, and often used
as a decoration in gift packs of citrus fruits for holiday trade.
Kumquats are grown commercially in China and Japan. They are
exceptionally high in calcium, potassium, Vitamins A and C, like most
citrus fruits. They are unusual fruits in that the peel is sweeter than
the pulp. Four major cultivars are given species status by some
taxonomists: =
a. F. margarita Swing. - 'Nagami'. Also called Oval Kumquat. =
b. F. hindsiiSwing. - 'Hong Kong', or 'Hong Kong Wild'. =
c. F. japonica Swing. - 'Marumi'. Also called round kumquat. =
d. F. crassifolia Swing. - 'Meiwa', or Large Round Kumquat.
2. Poncirus trifoliata L. Raf. (monotypic; the trifoliate orange).
Important as a rootstock for citrus, especially in Japan; also used as a
parent in production of citrange rootstocks. It has a deciduous habit in
cooler areas, and can tolerate more freezing than any other citrus or
related species; grown as far north as Philadelphia. Used as an
ornamental in some areas of Europe, Eastern US. =
There is considerable debate over the number of species within Citrus.
Some "lumpers" argue that all citrus fruits belong to one large species
as they are freely graft and cross-compatible for the most part. On the
other extreme, there are taxonomists that give almost each cultivar a
species name, which is clearly in error. Biochemical evidence (R.W.
Scora, 1988. Proc. 6th Int'l. Citrus Congress) suggests that there are
probably four "basic" species of citrus fruits: =
1. C. halimii Stone - Native to southern Thialand and west Malaysia,
this may have been the possible progenitor species for Poncirus and
Fortunella. =
2. C. medica L. (the citron). The citron is used mainly for its peel,
which is candied. It can also be used in place of lemons in cooking, and
may be the progenitor species for all acid citrus (lemons and lime-like
fruits). =
3. C. reticulata Blanco. The mandarin; This may be the ancestral form of
all oranges and tangerines, or may be the progeny of a now extinct
ancestor. It is more fully described below. =
4. C. maxima (Burm.) Merril (syn. C. grandis) - the pummelo or shaddock.
This is probably the progenitor of the pummelo and grapefruit.
The literature on citrus usually recognizes each economically important
type as a species, yielding the following: =
A. C. limon (lemons). Includes the lemons of commerce, such as 'Lisbon'
(oval to round, less pronounced stylar end) and 'Eureka' (oval,
pronounced stylar end bulge). The 'Meyer' is considered to be a lemon
hybrid of unknown parentage. The rough lemon C. jambhiri Tanaka, is used
as rootstock, as is C. limonia or the 'Rangpur' lime. =
=
B.C. aurantifolia (limes). The two main cultivars include the 'Key'
(syn. =91Mexican'), and 'Tahiti' (syn. =91Persian'). The latter is someti=
mes
given species status as C. latifolia (Tanaka) or Citrus x tahiti (C.
Campbell). C. macrophylla is a lime-like fruit used as a rootstock for
lemons in California. =
C. C. aurantium (the sour orange). This is allied with limes by some,
but is a very important rootstock and ornamental. Cultivars and variants
include: Bittersweet, Oklawaha, Vermillion Globe, Paraguay, Trabut, var.
myrtifolia (Myrtle), Bergamot, daidai (Japanese), Leaf of Chinnoto, and
C. taiwanica Tanaka. =
D. C. sinensis (the sweet oranges). This is a widely accepted name for
this group, containing 4 groups of cultivars: =
a. Common or round oranges. Mostly used for juice or fresh market.
Cultivars include =91Valencia', =91Hamlin', =91Parson Brown', =91Pineappl=
e', and
=91Washington Navel'. =
b. Blood oranges. Increasing in importance in the US, these red-juiced
variants contain anthocyanin in the peel and juice. =91Torocco' and =91Mo=
ro'
are the major cultivars. =
c. Navel oranges. This group is unique in that cultivars have a
secondary ovary embedded within the usual ovary, giving a small fruitlet
at the stylar end of the fruit at maturity; a fruit-within-a-fruit.
=91Washington' is a major cultivar, but there are dozens. =
d. Acidless oranges. Insipidly sweet flavor; used mostly in the
Mediterranean region.
The term "orange" is used rather loosely, sometimes for fruits that look
like oranges but are not C. sinensis. Examples include: 'Temple' and
=91Page' oranges ( tangerine hybrids), Satsuma orange (a cold hardy
variant of tangerine), and Trifoliate orange (Poncirus trifoliata). =
E. C. reticulata (mandarin, satsuma, or tangerine). As stated above,
this is probably a "real" species. Due to the success of breeding with
these types, many cultivars and hybrids have been produced or formed
naturally, some erroneously given species status. Common cultivars
include: 'Dancy', Clementine' or 'Algerian', 'Owari' (a satsuma),
=91Cleopatra' (common mandarin rootstock). I prefer to use C. reticulata
for all tangerines, but other species names sometimes given in the
literature a X Citrofortunella mitis (Calamondin), C. unshiu
(Satsuma), and C. deliciosa (Willowleaf mandarin). =
Tangerine hybrids may be more important economically than pure
tangerines. The most important hybrids are tangelos (tangerine x
grapefruit), tangors (tangerine x orange), and tangtangelos (tangerine x
tangelo). Popular cultivars include: 'Orlando' tangelo, 'Minneola'
tangelo, 'Page' orange (actually a tangtangelo), 'Robinson' tangerine (a
tangtangelo). "Ugli" fruit from Jamaica is probably a chance seedling
from a natural cross between reticulata and paradisi; it is now marketed
under the more politically correct name "Unique" fruit. =
F. C. grandis or C. maxima (the pummelo or shaddock). This species
originates from southeast Asia where it is used as grapefruit is in the
US. It is much larger and thicker-peeled than grapefruit. =
=
G. C. paradisi (the grapefruit). This is a relatively recent species
(since 1700's) of unknown origin. It probably derives from Caribbean
'Forbidden Fruit', and was introduced to Florida from there. Cultivars
include: 'Duncan', 'Marsh', 'Red-blush', and 'Thompson' (syn. 'Pink
Marsh'). Hybrids include the tangelos and citrumelos; the latter are
used as rootstocks.
Origin, history of cultivation. =
The center of diversity for Citrus ranges from northeastern India
eastward through the Malay archipelago and south to Australia. Sweet
oranges probably arose in India, the trifoliate orange and mandarin in
China, and acid citrus types from Malaysia. Oranges and pummelos were
mentioned in Chinese literature in 2400 BC, and later in Sanskrit
writings (800 BC) lemons were mentioned. Theophrastus, the Father of
Botany, gave a taxonomic description of the citron in 310 BC,
classifying it with apple as Malus medica or Malus persicum. At the time
of Christ and shortly thereafter, the term "citrus" arose as a
mispronounciation of the Greek word for cedar cones, "Kedros".
Alternatively, "citrus" may have arose through a condensation of
"Callistris", the name for the sandalwood tree. =
At this time, citrus fruits were spread throughout Asia, North
Africa, and Europe along trade routes. The dissemination was carried out
by many cultures, indicating widespread appeal of the fruits at this
time. From the first centuries BC to medievil times, orangeries and
citrus "groves" were established in Europe, and cultivation became more
sophisticated. Columbus, Ponce de Leon, and Juan de Grijavla carried
various citrus fruits to the new world in the late 1400's early 1500's.
Citrus culture proliferated in Florida in the late 1700's, when the
first commercial shipments were made. Right about this time, citrus was
introduced to California, although it was much later that commercial
production began in the west. With the advent of large-scale irrigation
projects in the 1940's, citrus culture increased greatly in western
states. In Florida, citrus acreage peaked in the 1970's at about 1
million acres, but has declined since then due to freezes and Foreign
competition. Today, Citrus is grown in Florida, California, Arizona, and
to a limited extent in Texas and Louisiana. =
Folklore, medicinal and non-food uses. =
In addition to various food products from pulp, citrus peels
are candied, fed to livestock, used to scent perfumes and soap products,
and limonene oils from the peel have an insecticidal property recently
discovered. Seeds are used to derive a cooking oil, and oils for
plastics and soaps. Flowers and foliage are used in perfume manufacture.
Nectar is converted to honey by bees, and is a profitable industry
itself. =
A. Limonene oils - in peel and leaves may cause contact dermatitis.
These are also "photosensitizing compounds", meaning that one may get a
sunburn rash if juice gets on skin while exposed to UV light. (agent =3D
furocoumarin?). =
B. Citromellal - volatile oil, has mutagenic properties. =
C. Chewing and sucking "quids" - of various tribal peoples; contain lime
juice and other alkaloids. May actually cause cancer. Lime juice causes
release of alkaloids from other materials. =
D. Cancer therapy - Two citrus relatives being studied for cancer
therapy drugs: =
Acronychia baueri (Australia) - Acronycine =
Fagara macrophylla (Nigeria) - 8-methoxy-dihydronitidine. =
=
E. Hesperidin (syn. citrin, vitamin P) - a bioflavonoid, up to 8% in
dried peel. Strong vasopressor agent (reduces blood pressure). Also in
rose hips and black currants, which oddly enough, are used for vitamin C
sources like citrus. =
F. Sweeteners - =
1. Naringin (flavonoid) - in grapefruit, has 1000x the sweetness of
sugar. Said to be a long-lasting sweetness that is slow to develop -
aftertaste like licorice or menthol. =
2. Neohesperidin (dihydrochalcone) - flavonoid in C. grandis. =
=
G. Volatile oils - in Clausena anisata, anise-scented leaves are used to
repel mosquitos in tropical Africa. In many species these oils are used
to scent creams, shampoos, etc. =
H. Oral - =
1. Aegle marmelos - twigs used as chew sticks in Africa. =
2. Sweet orange - peel used in Panama for toothache relief. Also, leaf
decoctions of sour orange used as mouthwash or gargle for sore throat. =
=
3. Toothache tree - (Zanthoxylum hirsuta). Native to Texas, leaves can
be crushed and applied to gums for relief. =
=
I. General medical - =
=
1. Sour orange - Said to be good for headache, fever, dysentery,
ophthalmia, oral infections, vermifuge, vomiting. =
2. Clausena anisata - Stems used in Africa for evacuant, headache,
liniment, respiration, ailments. =
3. Anti-diarrheal agent - rind of Aegle marmelos and other edible citrus
may control diarrhea. =
4. Citrus pectin reduced cholesterol 30%, aortal plaque 85%, and
narrowing of coronary arteries by 88% in animals feeding studies. =
=
J. Myth/folklore - Because the orange tree bears flowers and fruits at
the same time, it was used in fertility rituals and weddings - the white
flower symbolized virginity, and the fruits symbolized fertility. The
citron is used in certain religious ceremonies by Hebrews. The word
"orange" is said to have derived from the spanish word naranja;
english-speaking folks applied the indefinite article to the spanish
word to give "a naranja" which was corrupted to "an orange". =
The term "golden apples" arose from the myth of Hercules and the
golden apples. The Hesperides were Mediterranean islands, where the
giant Atlas lived, and were a haven for the golden apples (probably
quinces, not citron). This is because the Gods were fearful of the
golden apples being stolen. Hercules managed to obtain some of the
golden apples as one of his 12 tasks, despite Atlas' attempt to trick
him into holding up the sky. Later Perseus visited the Hesperides to
obtain some golden apples, and succeeded by turning Atlas to stone using
the head of Medusa; the Atlas Mountains of northern Africa now hold up
the sky, fortunately. =
There is also the myth of the Grecian Maiden Atlanta, "who was as
fleet of foot as she was beautiful". To obtain her hand in marriage, her
suitor had to beat her in a foot race; if he lost, he was beheaded.
Hippomenes, an apparently slow but sly individual, obtained some golden
apples, and during the race rolled them at her feet as she passed. She
stopped to pick them up and Hippomenes scooted to the finish line the
victor. =
K. Bael Fruit (Aegle marmelos Correa) - Hard-shelled fruit, used for
medicinal purposes ranging from laxative, diuretic, treatment of
hemorrhoids, diarrhea and dysentery (unripe fruit), purgative. Has
antibiotic activity in fruits, leaves, and roots. =
L. Wampee (Clausena lansium Skeels). - Small, peel-able fruit of
southeast Asia; eaten out-of-hand or made into jams, desserts, pies,
etc. Vietnamese remedy for bronchitis.
Botanical description =
A. Plant: Small, spreading, evergreen trees or tall shrubs. Stems often
armed with long thorns, particularly in limes or in all types when
young. Current season's shoots are angular, green like the leaves. Older
wood has thin, dark grey bark. Leaves are unifoliate (sometimes termed
compound unifoliate to indicate the loss of lateral leaflets over time),
relatively thick, ovate with acute to obtuse tips, having entire margins
and a petiole wing of various width, depending on species (grapefruit =3D=
large, tangerine =3D small). Leaves contain characteristic citrus oils in=
glands ("pellucid dots") which makes them fragrant when crushed. =
B. Flowers: Fragrant flowers are solitary or in short cymes, borne
axillary on current flush of growth (then termed "leafy bloom"), and
also without leaves from the previous flush of growth (then termed
"bouquet bloom). Usually perfect, rarely staminate by pistil abortion.
Normally 5 petals and sepals; petals linear, sometimes curved
lengthwise, white, waxy, and thick; sepals fused at base to form a small
cup. A globular, green ovary subtends a thin straight style which
terminates in a pronounced, donut-shaped stigma. Ovary with 10-14
locules in most commercial cultivars, each with potentially 4-8 seeds;
axile placentation. Ovary, superior, subtended by raised nectary disc. =
C. Pollination: Most cultivars are self-fruitful through
self-pollination, and some are parthenocarpic, setting and maturing
commercial crops of seedless fruit without fertilization (but not
necessarily without pollination). Examples of parthenocarpic cultivars
are 'Marsh' grapefruit, 'Tahiti' or Persian lime, 'Hamlin' sweet orange.
'Marsh' and 'Hamlin' also develop seeds. Fruit size is related to seed #
in all cultivars. Pollinizers are necessary for some tangerine (hybrid)
cultivars. 'Robinson', 'Nova', and 'Page' (all tangtangelos) require
pollination for adequate fruit set. =
D. Fruit: A hesperidium. The endocarp (edible portion) is divided into
10-14 sections, separated by thin septa, each containing up to 8 seeds,
but usually only one seed/segment. Placentation is axile. Each segment
is composed of juice vesicles ("pulp"), with long stalks attached to the
outer wall, containing juice. The mesocarp is the white tissue usually
adherent to the outer surface of the endocarp, except for mandarins; it
is also called the albedo. The exocarp, or flavedo, is the thin,
pigmented outer portion of the rind, with numerous oil glands. The seeds
contain both nucellar (maternal) and multiple embryos, except in some
tangerines where only 1 zygotic embryo forms. Nucellar embryony and
polyembryony are characteristics exploited by nurserymen, but impede
breeding efforts, since germination often exceeds 100% in seed lots, yet
variation in seedling progeny is non-existent since most seedlings are
clones of the maternal parent. =
General Culture =
A. Soils and Climate: =
Soils: Citrus is adapted to a wide variety of soil types and conditions.
Trees are grown on almost pure sand in central Florida, to organic muck
in south Florida, to loamy, heavy soils in the San Joaquin valley of
California. =
Climate: Citrus fruit obtains highest internal quality in subtropical
humid climates. However, with irrigation, it also grows well in
Mediterranean climates, like California, achieving the best external
quality. In the tropics, citrus accumulates less sugar and acid, and the
peel usually remains green; also, bloom is not synchronized, so several
stages of maturity are present on the tree at any given time, causing
some immature fruit to be harvested. =
Cold hardiness is the major limiting factor for citrus production in
subtropical areas. Fruit are killed by 30 minutes @ 26-28 F; larger
fruit are more cold tolerant due to greater thermal mass. Fruit freeze
from the stem end to the button, and mildly frozen fruit can be salvaged
for juice. Leaves and stems are killed by a few minutes at 20-28=B0 F,
depending on stage of acclimation, species, and age of tissue. =
Hardiness increases in the following order: Citron limes & lemons
grapefruit & pummelo sweet oranges tangerines & hybrids sour
orange satsuma kumquats citranges trifoliate orange. =
Citrus has no chilling requirement, and does not attain a truly dormant
state, but becomes quiescent at temperatures below 55=B0F (13=B0C). =
Flowering is induced following emergence from quiescence, and sometimes
by drought in tropical species like limes. =
Fruit quality and climate: Internal and external quality of citrus
differs in humid subtropical and Mediterranean climates. Heat and
humidity are the main environmental factors controlling quality. =
=
1. Peel thickness, texture - Peels become thicker and have more "pebbly"
or rough texture in Mediterranean climates than more humid climates. =
2. Peel color - is higher in Mediterranean climates than warmer areas
due to cool winters and greater day/night temperature fluctuations. =
3. Juice content - is higher in humid climates. =
4. Sugar and acid content - Acid content is higher and sugar content
generally lower in Mediterranean climates than areas with warm temps
during ripening. Acids do not accumulate as much in areas with warm
nights, like Florida; hence the solids:acid ratio is higher in Florida,
and fruit is said to be richer in flavor, because flavor results from a
balance of sugar and acids. =
5. Fruit size - may be larger in humid climates, although this parameter
is more strongly influenced by fruit set and seed #/fruit. =
6. Rate of maturation - is faster in hot, desert areas of California and
Arizona than in cool, coastal areas.
B. Propagation: Although citrus seedlings will produce fruit identical
to the parent tree, due to nucellar embryony, trees are generally
T-budded onto various rootstocks to avoid the long juvenile period for
seedlings. Budding can be performed during most of the year, when
pencil-sized, round budsticks are available, and bark slips on
rootstocks. =
C. Rootstocks: Citrus was grown from seed until the mid-1800s, due to
ease of propagation from seed and trueness of type. Phytophthora foot
rot appeared in the Azores in 1842 and later in other parts of the
world, which stimulated a search for resistant stocks. =
Common stocks: =
1. Sour orange (C. aurantium L.). Highly used worldwide, except in areas
with tristeza. Produces a tree with moderate to high vigor, size, and
yield. Imparts excellent fruit quality characteristics to both sweet
orange and grapefruit, although harvest may be delayed due to higher
acid content. Complete resistance to phytophthora and high quality make
this stock useful for grapefruit on the Indian River. Imparts cold
hardiness to the scion. =
2. Rough Lemon (C. jambhiri Lush.). This stock enabled the movement of
the Florida industry onto the deep, excessively drained sands of the
"Ridge" after the 1890's freezes. Hence, it imparts drought tolerance,
high vigor and yield, even though the tree itself is low in vigor, but
poor internal quality. Fruit size is generally higher than for other
stocks. Intolerant of Phytophthora and nematodes, and imparts poor cold
hardiness to scions. Used for grapefruit, oranges, and lemons where
yield and not quality are important; a good stock for juice oranges. =
3. Rangpur lime (C. limonia Osb.). Actually not a lime but probably
descended from rough lemon and sour orange parentage. Very similar to
rough lemon in many characteristics, but generally better fruit quality
and more tolerant of high pH and salt. Mostly used in Sao Paulo, Brazil
for juice orange production. =
4. Citranges (P. trifoliata x C. sinensis). 'Carrizo', and 'Troyer', are
the most common. Excellent stocks in general; good cold hardiness and
vigor, good fruit quality and yield. Susceptible to blight, exocortis,
poor tolerance of salt and high pH. Excellent nursery characteristics.
Used as a replacement for Rough Lemon in Florida, for oranges in
California, unpopular but increasing in use outside the US. =
5. Cleopatra mandarin (C. reshni Hort. ex Tan.). The major rootstock for
tangerines and hybrids, due to excellent fruit quality. Also tolerant of
tristeza, exocortis, xyloporosis, Phytophthora, salt, cold, and high pH.
Two major faults preclude use for grapefruit and processing oranges: 1)
trees are slow to come into bearing, and Cleo is very slow in the
nursery, 2) fruit size is small. =
6. Trifoliate orange (P. trifoliata (L.) Raf.). More important as a
parent of hybrid stocks, it is used in Japan for satsumas due to cold
hardiness, and to a limited extent in Argentina. Two misconceptions
prevail about this stock: trees are very cold hardy with proper
acclimation, but cold tender in areas with warm winters; dwarfing was a
result mostly of exocortis infection, and drought stress on sandy soils
since trees are relatively shallow rooted. 'Flying Dragon' is a
trifoliate mutant with serpentine stems, curved thorns, small leaves,
and contorted habit; can be useful in pot culture since it truly dwarfs
trees. Fruit yield and quality are very good. Trees are intolerant of
high pH. =
7. Citrumelos (P. trifoliata x C. paradisi). 'Swingle' is the only
important selection. Tolerance includes citrus nematode, Phytophthora,
and viruses including tristeza. High pH is a problem as for all
trifoliate hybrids. Production declined in Florida in the early 1980s
due to supposed susceptibility to citrus canker; however, this was
probably over-rated and more a function of vigor than species.
Performance with oranges, grapefruit and lemons has been very good to
date.
D. Orchard design, pruning, training: =
1. Design. Citrus has been traditionally grown in rectangular
arrangements which eventaully become tall hedgerows. Spacings are
typically 20 x 25 for grapefruit and vigorous trees, 15 x 20 for oranges
and tangerines, and 12-15 x 18-20 for limes and smaller cultivars. =
2. Pruning and Training. Citrus has a naturally sympodial growth habit,
forming a large bush (18-20 ft tall) if left unpruned. Very little
training is done; young trees are headed at 30 inches to induce
branching, and stripped of trunk sprouts and suckers and de-fruited for
the first 2-3 yr. At maturity, trees are hedged and topped to form
hedges about 12 ft tall and wide with automated equipment. Almost no
hand pruning is done. Equipment is expensive, but growers can contract
this service by specialists. Typically, hedging and topping is done
every other year. =
E. Backyard considerations. Citrus trees make excellent containerized
plants for the patio or deck; kumquats, =91Meyer' lemon, and calamondin
are ornamental and do very well in large pots. They must be brought
indoors or covered if temperatures drop below 25=B0F. Of course,
trifoliate orange is hardy throughout the southeast, and the =91Flying
Dragon' cultivar makes a good rock garden or specimen tree with its
striking serpentine stems. In coastal Georgia, I have successfully
fruited =91Owari' satsuma, =91Changsha' tangerine, =91Sinton' and
=91Thomasville' citrangequat, and a few others outdoors with temperatures=
as low as 17=B0F! =
Harvest, post-harvest. =
A. Maturity. The best indices of maturity for citrus are Brix, acid
content, and the Brix/acid ratio. External color is a function of
climate more than ripeness, and is a poor indicator of maturity. Legal
maturity standards are enforced in major citrus regions. For limes,
juice content must be at least 42% to market; diameter must be at least
1 7/8" also. =
Brix sugar content (measured with hydrometer or hand refractometer);
increases during maturation: =
Oranges - 7-14% =
Grapefruit - 10-12% =
Tangerines - 16-17% =
Lemons/limes - 10% (Brix not a factor for these fruits) =
Acid; (measured by titration with NaOH (Phenolphthalein) indicator);
decreases with maturation: =
Oranges - 1.5 - 0.5% =
Grapefruit - 2.0 - 1.0 % =
Tangerines - 2.3 - 0.6% =
Lemons/limes - 6.0% =
=
Brix:acid ratio; "sliding scale"; ratio can be lower for early season
fruit; increases as season progresses. Minimum ratio is 8:1. =
External quality: Blemishes caused by 1) wind scar, 2) melanose, 3) rust
mites. An example: =
US Fancy #1 =3D 10% blemishes, any cause. =
US # 1 =3D 20% blemishes. =
US # 1 bronze =3D 33% blemished by rust mite. [Florida only] =
US # 1 russet =3D 33% blemished by any cause. =
US # 2 =3D 33% blemished; culls in Florida.
B. Harvest Method. Citrus is hand harvested, whether processed or
marketed fresh. Mechanical harvesters have been attempted but have not
been successful to date. Tangerines and some fresh oranges must be
clipped, not pulled from the tree, to prevent plugging the peel. =
C. Handling and Packing. Citrus can be handled fairly roughly from tree
to packinghouse since fruit are tough and resilient, with the exception
of tangerines. Fruit are dumped from picking bags into 900 lb bulk bins,
which are moved by forklift onto trucks. For fresh fruit, packing line
operations include (in order) dumping, culling, washing, brushing,
waxing, drying, grading (human), sizing, and boxing. For processed
fruit, growers are paid for lbs-solids or sugar, based on analysis.
Fruits are culled for rots and splits, then fruit is washed prior to
crushing. Juice is separated from pulp, and pooled into lots of various
colors and sugar levels; some mixing is done to produce uniform product.
Juice is then evaporated to 44-48 Brix for frozen concentrate, or canned
as single-strength juice. The peels and rag are sold as livestock feed
supplement. =
D. Storage. Citrus is a non-climacteric fruit, and may be stored for
fairly long periods at low temperatures. Chilling injury is common in
grapefruit and other acid citrus when stored at 10-15 C, and rare in
oranges and mandarins at this temp. Brown pitting and staining of the
rind occur, sometimes with a watery breakdown of peel and pulp. Several
pathogenic rots, including the common green mold (Penicillium spp.) can
occur post-harvest. A unique aspect of citrus is the ability to store
fruit on the tree; since fruit are nonclimacteric, they ripen slowly,
will not soften or abscise for periods up to several months, as with
grapefruit in California. This allows growers to pick over an extended
period of time, choosing prices at their highest. The danger of course
is potential freeze damage, or loss due to diseases. =
J
Michael P Gabriel wrote:
=
"chaz" wrote in message news:r42Lb.32473$IM3.24658=
@newsread3.news.atl.earthlink.net...
I have some lemon and lime seeds. What kind of advice can you give me=
on
starting them?
chaz-
=
Hi! I read the responses to your post and am I baffled! I would
swear that I was taught that you CAN grow the seeds but the plant/tree
won't bear, and that it had to be grafted to a base tree in order to
have the graft bear. Tell me I'm wrong? Tell me I'm right?
=
Mike
Picture Rocks, AZ
-- =
Celestial Habitats by J. Kolenovsky
2003 Honorable Mention Award, Keep Houston Beautiful
=F4=BF=F4 -
http://www.celestialhabitats.com - business
=F4=BF=F4 -
http://www.hal-pc.org/~garden/personal.html - personal