may use and so render unavailable some of the nitrogen of the soil
thus hindering the growth of the plants. This may be corrected by
seeing that abundant nitrogen is present in the soil either when
made up or by later application of nitrate sowed upon the soil while
plants are dry or applied in solution in watering.
Dirt bands of veneer are used and are very satisfactory. Blocking as
practiced by many growers is a cheap and effective way of attaining
much the same results.
The Blocking System
When the cold frame is prepared for the last transplanting, two
inches of fairly well-rotted manure is laid down and two or three
inches of prepared soil is placed on top. Plants are set about four
inches apart each way. About a week before field setting, a butcher
knife, or a hoe which has been straightened and sharpened, is run
between rows both ways. This cuts the roots whereupon the plant at
once begins to form new feeders within the block thus reducing, to
some extent at least, the damage which might be caused by
transplanting. The method is also used with flats.
Soil
Soil for plant growing should be free of disease and nematodes,
friable, not readily forming a crust, receiving and retaining
moisture well, but drying off quickly on the surface after watering
and well supplied with nutrients. A sandy loam base with good humus
content is desirable. It may be prepared, beginning a year or two
ahead by growing and plowing under well fertilized green manure
crops. Or a compost heap may be prepared with successive layers of
soil and manure or other humus making material. In either case, it
is usually mixed a time or two by shoveling over or by passing
through a shredding machine or a coarse screen.
If trouble is likely to be experienced from damping-off fungi, the
soil may be heated to 200 deg. F. and held there for an hour, using oven
or electric or steam sterilizer. Seed may also be treated with red
copper oxid or semesan.
Seed and Seed Sowing
Tomato seed runs about 125,000 to 150,000 per pound. An ounce of
seed is usually depended upon for plants for an acre. For growing
seedlings, seed may be sowed up to 100 or more per foot of row. For
a maximum number of strong seedlings from a small amount of seed,
thinner sowing is desirable. Rows are usually about two inches
apart, and a quarter of an inch is sufficient cover. The seedlings
break ground in a week or ten days.
[Illustration: FIGURE 13.--Tin can prepared for sowing tomato seed.]
Uniformity of depth of rows and of covering is important. Otherwise,
seedlings will come up unevenly and there will be considerable
waste.
Care of Seedlings
Water and heat should be provided to permit a steady and moderate
rate of growth in plants. Over-watering and high temperature yield
soft and spindling plants and also plants that are overgrown and
that are liable to severe checking before field setting.
Under-watering and low temperature give stunted plants. The
thermometer at the earlier stages of growth may well stand around 70
to 75 degrees by day and 10 degrees lower at night. A reasonable
range of temperature and moisture gives opportunity for the skillful
grower to forward or retard his plants as seems best. Great care
should be exercised to water evenly. It is necessary to watch the
plants constantly to detect the slightest variations in growth. The
watering may then be modified and even progress insured.
Ventilation finds its chief significance as a means of controlling
temperature and humidity, though actual change of air may be a
factor.
High soil moisture, high humidity, high temperature, and faulty
ventilation, all favor the ravages of the various damping-off fungi
mentioned above which cause little plants to rot off near the
ground.
Transplanting
The main advantage of transplanting plants before they are set in
the field is to give them increased space, or, in other words, to
conserve space in greenhouses and frames. Other advantages have been
claimed, but in many instances the gains have resulted from more
space rather than from the actual shift. Transplanting checks growth
through breakage and disturbance of the root system. Loomis[14]
finds that "the immediate effect of transplanting is a reduction in
the water supply, and the immediate and long-time results are
dependent upon the severity and duration of such reduction."
Transplanting has little effect upon very young plants and a shift
at the age of six or eight weeks checks the plant about as much as
two earlier transplantings. The tomato falls in the group of plants
that stand transplanting well, roots being rapidly replaced.
Transplanting breaks roots and so results in the growth of branches
which are shorter than the members of the old system. The new system
is accordingly less severely damaged in later transplantings.
To insure efficiency, the work of transplanting merits careful
attention. Carelessness as to details means loss through unevenness
of plants. For example, if soil is not carefully packed at the edges
and corners of the flats, irregular water supply and irregular
growth result. If much transplanting is to be done, it pays to
divide up the work, as is done in a factory. Have a good place for
doing the work--a warm, light, and comfortable room. Tired workers
are not efficient. Spotting boards are of service if properly made
and correctly used. Soil should always contain just the right degree
of moisture to allow holes to stand open. Care must be taken that
the workers in setting plants do not double the roots or close the
holes at the top leaving the roots dangling in an open space below.
It is said that a good worker will prick out 10,000 plants per day,
though everything must be convenient to accomplish this and many
growers regard 6,000 plants as a good day's work.
Pruning Young Plants
Pruning of tops injures rather than helps the plant, for it destroys
leaves which are the machines that make carbohydrates, the principal
material for growth. Pruning to cure legginess is bad. Proper
management of time, temperature and water will provide adequate
control and if plants should become leggy, it is better to plant
them by laying them down in a trench with a few inches of top above
ground than it is to prune them.
Nipping out the growing point with the first cluster of flower buds
is sometimes practiced to encourage branching and a heavier yield of
early fruit. If this is done, ample space and nutrients must
accompany careful management. Otherwise, the plant finds itself with
inadequate resources to do a big job.
Hardening
Tomato plants cannot be made frost proof, but low temperature,
reduced moisture supply, partial starvation, and crowding all tend
to make plants more resistant to cold, to drying winds, to heat, to
mechanical injury such as breakage of leaves and stems, and even to
cut-worm attacks. Plants can be hardened appreciably in a short
time--say a week. It is now generally accepted that moisture control
is more useful than reduced temperature as a means of hardening.
Starving and crowding are not desirable methods. Plants can be kept
on the dry side if glass or other water-shedding cover is
available.
Great care must be exercised to avoid over-hardening of tomato
plants, for in this way a check in growth is incurred from which
they recover slowly, and perhaps never fully.
Much study has been given to the changes in plants which underlie
the hardening process, and papers by Harvey, Rosa, Loomis, and
others should be consulted in this connection.
[Illustration: FIGURE 14.--Plants that have been crowded and
overgrown, probably undernourished and over-hardened. Plants like
this are very often set in the field. They are definitely slow in
starting growth.]
Watts[15] has shown that adverse conditions, especially low
temperature and water deficiency prevailing at the time when fruit
clusters are barely beginning to form, commonly occasion the
development of misshapen fruits.
Faithful spraying or dusting with Bordeaux in the plant bed has
proved a useful means of forestalling destructive leaf blights which
often devastate whole fields.
V
GOOD CULTURE FAVORS GOOD RETURNS
The tomato is not especially exacting as to care after it has been
set out-of-doors. It will do business if given half a chance. At the
same time, much can be done to favor earliness, good yield and high
quality.
Time of Planting
In general, tomatoes are set in field or garden as soon as danger of
frost is reasonably past. Suppose May 1st is average date of last
killing frost. Growers would make general plantings from May 18th to
25th though, in rare instances, frost might occur as late as May
28th or 30th. The last week of May is planting time over a vast area
of the North. Venturesome souls will set home garden plants as early
as May 10th, standing ready to replant if necessary. There is little
gain in rushing the season too much, however, for the tomato is not
only sensitive to frost but it does not thrive under what people
call "raw, mean, chilly weather." Such conditions may also be
responsible for misshapen fruits. A grower for local market not
infrequently risks a share of his plants before safe setting time in
the hope that warm weather may give the crop a good start toward
early ripe fruit to sell at high prices.
Delayed planting and use of plants that do not start quickly into
vigorous growth is the cause of heavy losses in the north,
especially among cannery growers. Better quality and heavier yields
are attained if the bulk of the crop matures before cool weather in
the fall. In the south, it is necessary to get good plant
development and a full set of fruit before hot weather which often
destroys the blossoms.
Plant Protectors
Many forms of plant protectors are on the market--of paper and of
other materials. These act as little greenhouses for the individual
plant, protecting against frost and promoting growth. Plants may be
set out-of-doors a couple of weeks earlier by their use. The most
common forms are of translucent paper reinforced by pasted strips
of paper or by wire. The trick is to devise one that is cheap, that
will admit maximum light and that will withstand the weather. For
tomatoes, they need to be tall, which makes the problem of wind
resistance more serious.
For emergencies, opaque cover, baskets upside down or even newspaper
may be used. Many a field has been saved by burying the plants when
frost threatened, carefully uncovering when danger is past.
Spacing
Untrained tomatoes are set at distances from 3-1/2 feet each way to
7 x 7 feet or even more. The extreme width is found on rich
irrigated lands in California where plants make tremendous growth.
The closer spacings are found on lighter soils where humus, plant
food, and moisture are not too abundant. The variety should also be
considered. Sixteen square feet per plant is about average.
Check row planting is common, though it is not feasible where
transplanters are used. Wider spacing between the rows than between
plants is desirable as it permits later cultivation one way and
leaves a better passage for pickers with less damage to plants and
fruits. Thus, 3-1/2 x 4-1/2 feet might be preferred to 4 x 4 feet.
Rows for single stem, staked and pruned plants may be as close as
three feet and plants may be as close as eighteen or even twelve
inches, though some growers contend that two feet is close enough.
Methods of Planting
The essential point in field setting is to pack the soil firmly
about the roots, thus establishing maximum contact for moisture
absorption. Whatever the method of planting, the aim should be to
get the plants from the old home to the new with as little delay and
check in growth as possible. For the first-early crop, they should
be moved so that "they never know it." With bands, pots or blocking
in flats or beds, it is feasible to avoid practically all
disturbance of roots.
The tomato will, under ordinary favorable conditions, take hold and
grow even if shaken quite free of earth. Plants, however, should be
dug loose rather than pulled, to prevent undue breakage of roots.
Plants ought to be watered well some hours before transplanting.
Transplanting machines and hand planters of the Masters type give a
little shot of water at the root, thus helping to establish contact
with the soil. Starter solutions are discussed on page 35. These
machines are commonly used for cannery setting and, to some extent,
for market tomatoes. Blocked plants can be set pretty fast by hand
with much less disturbance of roots. Some manage to set potted or
blocked plants by machine, keeping a ball of earth about the roots.
The rows are usually marked out fairly deeply, plants are dropped in
fours between rows and it is a very short job to pack soil about the
clod of earth in which the plant is growing. Another method is for
one worker to make an opening with a spade. A second places the
plant in the wedge-like opening and the first steps on the soil to
firm it solidly about the roots.
Plants are generally set a little deeper than in the plant bed.
Cultivation
The old idea about cultivation was "the more, the better." More
recent experiments notably those by Thompson have shown that little
need be done beyond controlling weeds. He found that stirring the
soil gave no significant increase in yield over mere scraping
sufficient to destroy weeds. It is pretty hard to convince many old
time gardeners of this. The value of dust mulch for conservation of
moisture has been pretty well discredited by experimental
comparisons.
Irrigation
Irrigation is not essential for tomato production in humid climates
and is seldom provided except under market garden conditions. Water
is occasionally an asset in a dry season and, of course, the grower
who waters at such times reaps a harvest in higher prices as well as
in increased yield. The advantage of irrigation is especially marked
if dry weather retards plant growth and delays maturity of the first
of the crop, for the high prices of the early market are involved.
Judicious irrigation will sometimes continue production for late
fall market. Yet gardeners seldom plan permanent overhead equipment
for tomatoes. The movable lines that are now used to a considerable
extent serve well for the tomato crop.
The furrow method of irrigating tomatoes is the most common in the
West. This plan allows the water to make its way down the rows,
slowly soaking in all along the line. The tomato stands drouth
better than many of our crops, especially if the soil holds moisture
fairly well, either naturally or through a liberal humus content.
Excessive moisture is doubtless a factor in causing the plants to
run to vine and drop their blossoms. Hence, in western sections, it
is customary to water thoroughly just before or just after setting
the plants and then to avoid applications until the setting of fruit
is well advanced.
Thorough soaking is better than frequent light waterings, as it
encourages a better development of root system. An Idaho bulletin
suggests three irrigations. Late irrigations tend to delay ripening
of fruit, but this object is sought in the late fall shipping
districts of California which find their best markets after eastern
crops have been nipped by frost.
Irrigation must be handled with care to avoid cracking of fruit,
which occurs when soil becomes rather dry and then is heavily
watered. Watering late in the season is said to make fruit watery
and of poor quality.
Mulching
R. A. Emerson[16] in 1903 reported results of careful comparisons
between vegetables that were cultivated and others that were mulched
with straw. These results indicate that mulching gives good results
with tomatoes, both as to yield and quality. However, frost injury
was more severe on mulched plats, and Emerson points out that the
mulch should not be applied until the plants are well established.
Mulching is recommended by a good many writers and growers and it
seems to be practiced to some extent in Missouri. The advantages
claimed are conservation of moisture and clean, fine quality fruit.
L. W. Purdum and Sons of Virginia use 4-5 tons per acre of wheat
straw, staking their plants and irrigating. They report unusually
heavy returns per acre under these methods. The Missouri people
apply as much as sixteen tons per acre, making the cover five or six
inches thick. The practice of mulching, however, is not common, and
the cost will likely prevent its general use.
VI
TO TRAIN THEM UP OR LET THEM SPREAD
Growers attending conventions will often stay up half the night to
argue about training and pruning tomatoes and to debate the details
of their favorite procedures.
For home garden, the method is strongly commended. Many market
gardeners follow the practice and it has gained materially of recent
years in New England. Some market reports quote staked tomatoes
separately and at a materially higher level than fruit from unpruned
plants.
Most of the southern shipping sections follow the practice and it is
practically universal in greenhouses.
One way is to drive a stake by each plant tying at several points
along the stem with cheap twine. The other plan, recently gaining in
favor, is to set posts every 25 feet or so, string a heavy wire on
top, and another a foot from the ground. Cheap jute twine is strung
between wires and the tomato plants are merely twisted around the
string. Tying is not required. Some omit the lower wire, tying a
non-slipping bowline loop around the plant near the ground. In
either case, plants are kept trimmed to a single stem though
occasionally an extra branch is allowed to grow. In southern
Illinois, plants are tied to a short stake without pruning.
[Illustration: FIGURE 15.--Tomatoes pruned and trained with post,
wire and twine. This is the trellis system of New England.]
[Illustration: FIGURE 16.--Fine clusters on trained plants.]
Pro and Con
The advantages claimed for pruning and training are:
Earliness.
High yield per acre.
Ease of cultivating and spraying.
Ease of picking.
No injury from snails and wire worms.
Quality of fruit:--size, color, smoothness and cleanliness.
Crop finished earlier.
Less sunscald.
The disadvantages claimed are:
Many plants required.
Reduced yield.
More blossom-end rot.
Higher cost of labor.
Cost and care of stakes and wire.
The validity of each of these points varies greatly with conditions;
in fact, the answer to the whole question depends largely upon the
location and the ideas of the grower. In trying to reach a
conclusion, it is well to realize that training makes certain
radical changes in the plant. It loses leaves through pruning, it is
supported from the ground, and it is spaced differently. Since the
leaves manufacture the basic substance for themselves, and for the
rest of the plant, removal of leaves reduces the resources of the
plant. H. C. Thompson[17] has found that the root system is reduced
about in proportion to leaf reduction. It is fairly clear that
single-stem training greatly reduces the yield per plant, and other
methods result similarly in proportion to the severity of pruning.
When plants are spaced closely enough together the yield may be
brought up to that of areas unpruned and unstaked. Idaho experiments
indicate that staking alone does not affect the total yield, but
that it does favor early maturity under the different pruning
systems. The disadvantages of training are largely economic. Will
the marketing conditions justify the extra cost of staking and
pruning?
Experiments have shown pretty clearly that sunscald, blossom-end rot
and cracking are worse on trained plants. Using varieties of good
foliage will help the first trouble while uniform and adequate water
supply achieved by selection of suitable land, by building humus
content of the soil and by irrigation will solve the latter two
problems. Thompson found increased yield of early fruit. Other
evidence is somewhat conflicting but, in general, it supports
Thompson. It is generally agreed that pruned plants yield larger,
cleaner and more perfectly formed and colored fruits. Ease of
spraying or dusting and of picking is important.
For pruned plants, 3-1/2 feet between rows and 1-1/2-2 feet between
plants is about right.
To train or not to train is a question that one must answer for
himself as the controlling factors vary too widely--costs of stakes,
wire and labor, prices of early tomatoes and possibility of
cultivating a more or less fancy trade.
VII
THE ETERNAL BATTLE WITH INSECTS AND DISEASES
The tomato, in most regions, is not one of our most "pestered"
crops. Although over thirty diseases of tomatoes are discussed in
books and bulletins, most of them are only occasionally serious or
are subject to definite control methods. Enemies are generally worse
in the warmer climates.
Most home garden tomatoes and many commercial crops are grown
without benefit of spray or dust. If trouble arises, county agent or
college specialist can usually advise, suggesting methods suitable
for local conditions.
Experience must, of necessity, be the guide in shaping a program and
costs must be carefully balanced against results.
The principal measures that are widely used are seed treatment
against damping off, use of resistant strains against fusarium wilt
and application of bordeaux mixture against leaf blights.
As with all plants, thoroughness must be the watchword in spraying
or dusting. Timeliness, choice of weather conditions so far as
possible, and covering all surface lightly rather than throwing on
heavy blotches of spray or dust all require careful attention.
_Fusarium Wilt_ (Fusarium lycopersici) is perhaps the most serious
of all the tomato diseases although it occasions little trouble in
the more northerly states. It is troublesome as far north as New
Jersey to Iowa.
The fungus winters in the soil, enters through the roots and blocks
the water passages of the plant causing wilting, yellowing, and
finally, death. Water vessels in the stem are discolored,--another
means of identifying the disease.
Spraying or dusting are of no service since the fungus is within.
Long time rotation and use of the many resistant strains are
effective means of control.
[Illustration: FIGURE 17.--Resistance to fusarium wilt. Row on left
center is planted to an ordinary variety, row on right with one of
F. J. Pritchard's wilt-resistant selections. Insert shows plant
attacked by wilt fungus.]
_Leaf Spot_, _Septoria Blight_ (Septoria lycopersici) causes heavy
loss by destroying the foliage and so the fruit-making power of the
plant. It also opens the fruits to sunscald. The spots appear as
small dark water soaked areas which enlarge but little though they
increase in number and turn brown. Tiny black dots, the fruiting
bodies of the fungus, appear. The spores germinate only on moist
leaves and the disease is spread by wind, rain, workers and the
like. It winters on refuse of the tomato and related plants.
Fall plowing helps to control. Bordeaux spraying beginning in the
seed bed and carried faithfully through the season will usually hold
the trouble in check.
_Late Blight_ (Phytophthora infestans) is the same fungus as the
late blight of potatoes, affecting both foliage and fruit. It is
often troublesome the first few weeks after plants are set
out-of-doors. Clean soil in seed bed and bordeaux spraying are
helpful.
_Western Blight_, _Yellows_, _Curly Top_,--cause unknown,--is
prevalent in California. Leaves roll and become thickened and
brittle, later turning a sulfury yellow. Veins become purplish. The
trouble prevails in hot weather. The cause is likely a virus,
similar to or identical with the curly top of beets. It is
apparently spread by leaf hoppers. No satisfactory control has been
devised though there is some promise in resistant strains.
[Illustration: FIGURE 18.--Diseases of the tomato. 1. Septoria or
leaf spot. 2. Mosaic. 3. Mosaic, filiform.]