44
FLORIDA STATE HORTICULTURAL SOCIETY
was deaerated under 28 indies vacuum and
flash pasteurized at 190 to 200 degrees F.,
cooled and filled into cans at a temperature
of 185 degrees F . C-enamel cans were used
at first but later plain cans were used because
the high acidity and high amounts of peel oil
in the* juice caused the enamel to peel off.
One lot of grapefruit was tested just prior
to canning and the following results were
obtained: Brix 12 degrees, acidity 3.8 per
cent, ratio 3.16 to 1; when sweetened with
sugar to a Brix of 15.5 degrees it had a ratio
of 4.5 to 1 and it was too bitter to drink. An
analysis was made of some Washington Navel
oranges September 15, 1943, which is the lat
ter part of the season, with the following
results: Brix 12.59 degrees, acidity 1.14 per
cent, ratio 10.85 to 1, pulp of juice 12 percent
and 75 gallons of juice per 2000 pounds of
fruit.
Oranges analyzed from 30 to 50 mg.
of ascorbic acid per 100 ml. of juice
Refuse or waste from citrus canning plants
was usually thrown away, except in a few
plants which converted orange waste into
marmalades. A few plants had equipment for
recovery of peel oil.
By-products such as
feeds, alcohol, molasses, etc. were not in
cluded in the canning program.
In conclusion it can be said that unfortu
nately Australia is in an unfavorable position
for her citrus industry due to the following
reasons: (1) lack of efficient rail transporta
tion within her borders, (2) her home con
sumption limited by the 6^ million popula
tion in an area almost as large as the U. S.
with little prospect of increased population
from heavy immigration, (3) restricted ex
port trade as Australia is a long distance from
world markets and transportation to these
would make the price to the consumer too
high for competition, and (4) the high cost
of production per unit, with the attitude of
the trade unions there making competitive
selling almost impractical. It can also be said
that some of the leaders of the industry and
research workers are united in a movement
to better educate the grower to the applica
tion of scientific work in an attempt to raise
production and lower cost per unit through
more efficient methods.
This I hope succeeds.
ROOT SYSTEMS OF VARIOUS CITRUS
ROOTSTOCKS
E. M. SAVAGE, WILLIAM C. COOPER and R. B. PIPER
Division of Fruit and Vegetable Crops and Diseases, Bureau of
Plant Industry, Soils and Agricultural Engineering,
U. S. Dept. of Agriculture, Orlando
INTRODUCTION
Fifteen species and varieties of citrus are
now being tested by this station for their value
as rootstocks for oranges, grapefruit, and
tangerines. These rootstocks include seedlings
of the common sour orange, bittersweet
orange,
Pineapple
sweet
orange,
Parson
Brown sweet orange, rough lemon, Duncan
grapefruit, Bowen grapefruit, trifoliate or
ange, Cleopatra mandarin, Suen Kat man
darin, Morton citrange, Rusk citrange, sweet
lime, calamondin, and yuzu (kansu).
This
paper presents results of a study of the root
systems of these various stocks.
The rootstocks were grown in the nursery
at the experimental farm near Orlando. The
soil in this nursery is classed as Norfolk fine
sand. The seed were planted in January
1939, and transplanted to the rootstock nur
sery in November of the same year.
The
FLORIDA STATE
HORTICULTURAL SOCIETY
plants were spaced 1 foot apart in rows 3 feet
apart. They were budded with orange, grape
fruit, and tangerine varieties in May 1941.
The main rootstock plantings were planted
out at field spacing in 1942 and 1943. There
were, however, a number of the budded rootstocks left undisturbed in the original nur
sery, and it was with these that the present
investigation on root systems was made.
The root systems of the stocks were ex
cavated and photographed in January 1945,
six years after planting the seed and nearly
four years after budding.
Inasmuch as this
investigation is concerned primarily with the
comparative
character
of
the
root
systems
of the various stocks rather than with pos
sible effects of the scion variety on the roots,
tflie trees selected for study were all budded
to one scion variety, namely, Parson Brown
orange.
However, with one rootstock, the
Morton citrange, root systems of trees budded
to Duncan grapefruit and to Dancy tangerine
were also excavated and photographed in
order to determine with this one stock if there
were any striking scion effects on the char
acter of the roots.
The stocks, having grown at close spacing
for six years, had ttieir root systems fairly
well mingled with the adjoining plants, and
it was a slow, tedious task to extract the roots
intact.
It was frequently necessary to uproot
several adjoining trees
in
order
the
of
a
entire root
system
to remove
desired
plant.
Because of these difficulties and because it
had been observed in digging the large num
ber of trees for field planting that the various
trees on any -one stock had remarkably uni
form root systems,
only two trees
of
each
stock were carefully excavated for detailed
study.
It is believed
that the
photographs
shown are typical for these rootstocks under
the conditions -of these experiments.
RESULTS AND DISCUSSION
In studying the results presented in figures
1 to 17, inclusive, it should be kept in mind
that the trees under observation are young,
and the depth of penetration and spread of
the root system are considerably less than
that which undoubtedly occurs in mature
45
bearing trees.
Al&o, as is obvious from the
photographs, the ends of many of the roots
were clipped on excavation of the tree from
the soil. It was almost impossible to obtain
every root of the plant intact.
Accordingly,
when a depth of 4 feet and a spread of 5 feet
are observed in the photograph it is quite
possible that the actual depth and spread
were slightly greater. The photographs show
clearly whenever the roots were clipped and
the results can be interpreted accordingly.
When taking the photographs, all plants
were placed the same distance from 1Sie
camera.
A measuring stick marked in one
foot intervals was placed at the side and top
of each plant.
Sour Orange (Citrus aurantium L.), Figs.
A 1 and A 2.
This stock, which is widely used in Florida,
is frequently characterized as possessing
abundant and deeply penetrating roots. The
photographs of this variety show three or
more well-developed central tap roots pene
trating 3 to 4 feet deep in tihe soil. There
were numerous relatively small and delicate
lateral roots, particularly in the upper foot
of soil.
Some of these had a horizontal
spread of 5 feet from the trunk to end of
root. These laterals were well supplied with
many fine, fibrous roots.
Bittersweet Orange (possibly sour orange
hybrid, Swingle), Figs. B 1 and B 2.
The root system of the bittersweet differed
mainly from that of the regular sour orange
in having fewer laterals and very few fine
fibrous roots. The central or tap roots were
more vigorous and penetrated slightly deeper
than the regular sour orange.
Sweet Orange
(Citrus sinensis
Figs. C 1, C2, Dl and D 2.
Osbeck
The root systems of both Pineapple and
Parson Brown sweet orange seedlings, which
were very similar in character, showed well
developed central roots, usually two, which
penetrated the soil to about the same depth
(3 to 4 feet), as the sour orange. There were
numerous small lateral roots over the full
length of the tap roots.
The laterals in the
upper foot .were not so long as those of the
sour orange.
There was an abundance
of
FLORIDA STATE
46
HORTICULTURAL SOCIETY
fibrous roots, particularly in the upper foot
of soil.
dwarfs the top of most varieties worked upon
it. Its root system, with Parson Brown sweet
These observations are not in agreement
orange worked on it, was of fair vigor even
with Mills' (1) observations that in California
the sweet orange has a shallow root system.
The results are more in agreement with
though- the growth of the top was dwarfed.
It had deeply penetrating central roots and
numerous laterals with abundant fibrous roots
in the upper 1% feet of the soil. The root
system was similar to that of the sour orange
except it had a smaller spread of the laterals.
Cleopatra or Ponki Mandarin (Citrus reticu-
Hume's (2) statement that the roots of sweet
stock are equal in development to the deeprooted sour orange stock.
likewise,
reports that
the
Oppenheimer (3),
sweet
orange
is
deep-rooted in the sandy soils of Palestine.
Rough Lemon
(possibly lemon-citron hy
brid, Webber), Figs. E 1 and E 2.
This stock, which grows so well on the light
sandy soils of central Florida, had the most
vigorous root system of all fifteen stocks un
der test and appeared to be well adapted, by
virtue of its root spread, for securing water
and nutrients from such soils.
The stock was
characterized by its exceptionally large lateral
roots which had a horizontal spread of 5 or
more feet from tree trunk to end of root.
The central tap roots penetrated vertically
into the soil as deeply as did the sour orange
tap roots.
The lateral roots of the rough
lemon had many fine fibrous roots, but they
were not so abundant around the crown of
the plant as were those of the sour and sweet
oranges.
Grapefruit (Citrus paradisi Macf.), Figs. F
1, F 2, G 1, and G 2.
The root systems of both the Duncan and
the Bowen grapefruit seedlings were char
acterized by their abundance of fibrous roots
and paucity of vigorous laterals.
They had
two or more large, moderately penetrating
(approximately 3 feet) tap roots which were
practically hidden from view by a thick mass
of fine fibrous roots for a full three-foot depth.
lata Blanco), Figs. I 1 and 2.
The Cleopatra mandarin has received some
attention as a possible substitute for rough
lemon rootstock, on tiie assumption that it
is more cold-resistant and produces betterquality fruit.
It had a. cone-shaped root
system with well developed central roots pene
trating vertically 4 feet or more into the soil.
The long, fine-textured lateral roots in the
upper 2 feet of soil were well supplied with
fibrous roots.
In general it did not differ
greatly from the root system of the sour
orange except that its tap root was straight,
slightly longer, and less divided.
Another variety of mandarin, called Suen
Kat (Citrus reticulata var. austera Swing.)
has'also been studied and its root system ap
peared to be identical with that of the Cleo
patra.
Citrange
(Poncirus trifoliataxCitrus sinen-
sis hybrid), Figs. J 1, J 2, K 1, K 2, L 1 and
L 2.
The citranges appear to be worthy of more
attention as rootstocks than they have received
in the past.
From their Poncirus trifoliata
parent they have inherited a marked degree
of cold hardiness and induce in scion varieties
budded -on them at least some degree of this
resistance. Unlike trifoliata, which is a dwarf
There were numerous small delicate lateral
grower, the
roots in this mass of fibrous roots, and they
tended to descend obliquely through the soil.
This abundance of fibrous roots in grape
fruit confirms both Mills' (1) and Oppenheimer's (3) observations on grapefruit in
California and in Palestine* respectively.
Trifoliate
Orange
(Poncirus
trifoliata
and produce vigorous budded trees.
The root systems of the Morton citrange
with Parson Brown orange, Duncan grape
fruit, and Dancy tangerine scions are illus
Raf.), Figs. H. 1 and 2.
The trifoliate orange is the most cold-hardy
of all stocks commonly used for citrus.
It
citranges
exhibit unusual vigor
trated in figures J to L.
There appeared to
be no marked difference in tita character of
the roots with the three scion varieties. The,
tap root, in most instances, was divided into
several roots which, instead of penetrating
the soil vertically, as was the case with most
FLORIDA
STATE
HORTICULTURAL
of the other stocks, tended to fan out and
descend obliquely. They penetrated ttie soil
for about 3 feet. The lateral roots were sim
ilar to those of the sour orange.
In general
they showed a tendency to descend obliquely
in the soil rather than horizontally and were
well supplied with fine fibrous roots.
The root system of the Rusk citrange was
tested.
Sweet Lime (possible lime x lemon hybrid,
used for citrus in Palestine. The vigor of the
growth of Parson Brown tops obtained on
this stock exceeded that on rough lemon. The
root system is composed of many slender
laterals covered witii a mass «of fine fibrous
roots. This stock developed no tap root. The
even
expressed in Okie
horizontal direction and turned downward.
Yuzu
(possibly Citrus ichangensis x Citrus
reticulata var. austera hybrid, Swingle), Figs.
0 1 and 0 2.
The yuzu, sometimes called kansu, has been
satsuma, and it is also the stock on which, in
The
trated three or more feet deep and had a
spread of about 2 feet from the trunk. This
root system resembled the grapefruit some
what in its abundance of fibrous roots. The
a pronounced tap
root
system
was
fifteen stocks tested.
the
smallest
of
the
It penetrated the soil
deeply but there was a scarcity
of laterals
and, what few there were appeared to grow
mainly in a vertical rather than horizontal
direction.
It produced less top growth- of the
iParson Brown scion than
any -of the
other
stocks tested.
abundant fibrous root system, however, pene
had
was
lateral roots which sometimes changed their
Japan, Thompson navel orange succeeds best.
and M 2.
The sweet lime, sometimes referred to as
the sweet lemon, is the principal rootstock
however,
The marked tendency of the roots to
grow downward
used widely in Japan as a hardy stock for the
except that it had fewer fibrous roots.
grapefruit,
47
penetrating tap root system of the varieties
found to be similar to that of the Morton
Webber), Figs. M 1
SOCIET^
Sweet Orange Cuttings, Fig. Q.
All
of the
root
systems
described
above
were derived from seedlings of the rootstock
varieties.
This
propagating
is
the
common
citrus rootstocks.
method
of
Many varie
ties of citrus, however, can be readily propa
gated from cuttings with the aid of growth
root, while the sweet lime had none.
Cuban Shaddock (possibly lime x lemon hy
substances (Cooper 4).
The roots on cuttings
This variety is highly recommended in Cuba
of tflie Pineapple sweet orange after six years'
growth in the nursery are shown in figure Q
as a stock for the Washington Navel orange
and may be compared to roots of seedlings,
and reputedly grows well on saline soils.
figures C 1 and C 2.
brid, Webber), Fig. P.
The top growth produced by the
Parson
It is seen that while the
seedling roots penetrated deeply into the soil,
Brown scion grafted on this stock, as on the
the cuttings had a shallow root system with
sweet lime, greatly exceeded that on tfae rough
lemon. The root system, however, was almost
ting
identical in character with that of the rough
lemon, except that it was supplied with more
out a tap root.
consisted
The root system of the cut
of
about
10
long,
vigorous
lateral roots wtoch did not penetrate the soil
any more deeply than about 2 to 3 feet.
a matter
austera x Fortunella hybrid, Swingle), Figs.
adapted for foraging f«or water in the deeper
system
layers
N 1 and N 2.
The calamondin is reputedly cold-resistant
of
speculation,
would,
of
light
the
As
fine fibrous roots.
Calamondin (possibly Citrus retioulata var.
therefore,
sandy
roots from cuttings.
soil
seedling root
appear
than
better
would
the
The vigorous, shallow
and has been mentioned as a promising stock
root system of the cuttings might be adapted
for tfoe lime in Texas.
to
The outstanding char
acteristic of the root system of the calamon
din was the group of vigorous central roots,
usually 4 or more, which grew vertically down
to considerable depth.
the
moist hammock or
shallow flatwood
soils.
Summary
The root systems of 15 different citrus root-
Under the conditions
stocks budded to Parson Brown sweet orange
of these experiments it had the most deeply
have been excavated, photographed, and de-
FLORIDA STATE HORTICULTURAL SOCIETY
48
scribed.
Many
striking
differences
in
the
spread as the root system of the sour orange.
character of the r-oot systems of the various
varieties were observed.
The rough lemon
and Cuban shaddock had the most extensive
Literature Cited
1. Mills, J. M. Citrus fruit culture.
root systems, the calamondin the deepest, and
2. Hume,
the sweet lime and grapefruit the greatest
fruits.
abundance of fine fibrous roots.
All stocks
had more or less deeply penetrating tap roots
except the sweet lime.
The root systems of
the bittersweet orange, sweet orange, man
darin, and citrange penetrated approximately
as deeply and had nearly the same lateral
Calif.
Agr. Expt. Sta. Bull. 138, 1902.
H.
H. The cultivation of citrus
The Macmillan Co., New York.
1926.
3. Oppenheimer, H. R. A citrus rootstock
trial on light soil. Hadar 9(2): 3-8, 1936.
4. Co-oper, William C. Rooting citrus cuttings
with synthetic growth substances.
Proc.
Fla. State Hort. Soc. 53: 174-177, 1940.
THE FREEZING PRESERVATION OF
CITRUS HEARTS
A. L. STAHL
Florida Agricultural Experiment Station, Gainesville
The characteristics and nutritional values
of fresh foods are more nearly preserved by
freezing than by any other method of preser
vation. The bright natural colors are retained
that are destroyed under high temperatures
necessary for canning. In texture and flavor,
also, the frozen foods are very similar to the
fresh, for freezing preserves the crisp, firm
served by freezing.
of these tests.
texture, the mild, pleasing flavors and most
of the nutritive value of the fresh products.
Citrus fruits when heated lose their flavor,
ature, storage temperature and packaging.
texture and nutritive value,
most «other fruits. Cooking
the taste of most fruits as
citrus.
Most cooked fruits
more so than do
does not change
much as it does
have a pleasant
taste and the taste of some are even improved
by cooking but any heat used on citrus fruits
detracts from the appearance and flavor ma
terially. We have therefore looked for other
means of preserving citrus hearts than can
ning and have found freezing to be ideal for
the preservation of flavor, texture, appearance
and quality of all types and varieties of citrus.
For the past several years we have been
investigating methods and procedures by
which citrus hearts could be successfully pre
This paper is a report
Freezing Grapefruit Hearts
The work on grapefruit freezing was started
several years ago and the effects of various
things were determined, namely, variety,
method of preparation, syrup concentration,
deaeration, inert gases, anti-oxidants, temper
Various varieties of mature grapefruit were
tried and comparisons made as to their suit
ability for frozen hearts. Taste, color, tex
ture, quality, acidity, appearance and Vita
min C were determined at intervals over a
period of 12 months, the test being made di
rectly upon thawing.
Silver Cluster, Duncan, Excelsior, Florida
Common, Marsh (Seedless) and Thompson
(Pink) were tried, and their value for freez
ing as hearts was found to be in the order
named above. All .of the seedy varieties were
far superior to the seedless varieties, the only
disadvantage being the labor of removing the
seeds.
Several methods of preparation of the
hearts were compared as to the effect on the