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Article 4-2 Home Grown Tomatoes

by Cindy Rae, Compliments of Homegrown Hydroponics

Imagine that first bite of a sweet, succulent, ripe tomato picked fresh from your garden. The warm juice runs down your chin as a delightful explosion of flavour awakens dormant tastebuds. In our harsh climate, fresh tomatoes can usually be enjoyed for only a few short weeks of the year. Then it's back to artificially ripened, flavourless imports your grocer charges a small fortune for. Take heart, you can savour the homegrown tomato experience year round.

Tomatoes grown hydroponically, indoors under lights, are equal to, or superior in flavour and nutrition than their outdoor, soil grown counter-parts. A tomato's sweetness and flavour is largely dependent on light and temperature. The nutritional value of a tomato is dependent on the nutrition the plant receives while growing and producing fruit. In the controlled environment of an indoor garden, the plants exact requirements can be met with artificial lighting, temperature control and supplemental nutrition. This enables the grower to enjoy a continuous harvest all year long without sacrificing taste and goodness.

Hydroponics is a pure, clean method of cultivation. For this reason it is recommended you start your tomatoes directly from seed. Bringing plants in from outside creates a potential for pest and disease contamination. Start seeds in one inch rockwool starter cubes in a standard nursery tray with dome. Rockwool cubes should be pre-soaked in water adjusted to a pH of 4.5 prior to planting. Keep covered tray in a moist, warm (20°-25°C) environment until seedlings begin to sprout. Once vegetation appears, immediately move the seedling into a light source, metal halide or flourescent lights, for at least 12 hours per day and remove domes. Failure to provide light soon enough will cause seedlings to bolt in search of a light source. Ensure roots are never exposed to the light as this will cause damage and death to the roots and delay plant growth.

Once true leaves appear and roots are showing through the bottom of the starter cubes, usually around 10 - 14 days, seedlings are ready to be transplanted to their hydroponic garden. There are several different hydroponic methods used for cultivating tomatoes indoors. Space restrictions, type of tomato and plant size all have to be considered when choosing a system.

The most common method employed for large plants is the drip irrigation system. In this fully automated, re-circulating system nutrient solution is pumped from a reservoir, fed to the plants through drip emitters and allowed to drain back to the reservoir by gravity. In order to create gravity flow the grow unit must be placed higher than the nutrient reservoir. The nutrient is continuously circulated during light-on hours. For the home hobbyist we recommend using the expando system. This consists of an individual pot for each plant, linked to the nutrient reservoir by 1/2" tubing. Heydite, small, reusable porous rocks are used as the growing medium providing excellent aeration to the roots. The one inch cube containing the seedling is transplanted directly into the pot and covered with heydite. The constant feeding allows the root system to develop in minimum space resulting in higher yields.

Drip irrigation can also be done with rockwool, a technique favoured by commercial growers. The starter cube and seedling are placed in the premade hole of a three or four inch rockwool cube which is placed on slabs of rockwool in a trough. The roots will grow down through the cubes and into the slabs. The troughs should be slightly wider than the slabs to allow room for the nutrient solution to drain back to the reservoir. Tomato plants should be spaced about 10 to 12 inches apart or four plants per slab.

With both techniques the size of reservoir and pump will be determined by the number of plants. Irrigation will need adjusting as the plants grow, allow for four liters of nutrient solution per day for mature plants, smaller seedlings will consume less. The nutrient reservoir should be changed once a week. Choose a pump with a high enough gallons per hour rating to adequately reach the plants farthest from the reservoir. Emitters can become clogged with salts from the nutrient solution and should be watched closely and cleaned when necessary.

Ebb and flow or "flood and drain" tables are another excellent method used for cultivating tomatoes. Tables range in size from 1' X 2' to 4' X 8' and can accommodate many plants in a small area. For cherry tomatoes or smaller determinate varieties, deep water culture may be used. Complete hydroponic gardens sold as kits are usually deep water culture and available in many shapes and sizes and are excellent for the novice hydroponic gardener.

No matter what technique you choose, there are several growth influencing factors (GIFs) to consider. The most important GIF is light. Artificial metal halide light can simulate full summer sunlight when daylight is at it longest. At maturity, tomato plants require a 16-18 hour photo-period to ensure maximum fruit production and an eight hour respiration period of total darkness. Gradually introduce your plants to higher light levels by moving the bulb closer to the plants by an inch or two every few days.

pH is the measure of alkalinity or acidity of the nutrient solution and is another very important GIF. If pH levels are not maintained at the appropriate level (pH 5.8 - 6.3 for tomatoes) nutrient deficiencies and toxicity will occur. Even seemingly small fluctuations in pH levels can result in inferior nutrient uptake by the plant. pH will need to be adjusted up or down based on the original reading of your water source. Potassium hydroxide will raise pH while phosphoric acid will decrease pH levels. Both products are available at your local hydroponic retail store. pH can be influenced by other factors and must be monitored regularly and adjusted as necessary.

Electrical conductivity (EC), measured in milliMhos, is the measure of electrical conductance of the total dissolved solutes (minerals) in the solution. The optimum EC range for tomatoes is 2.0 to 3.5 milliMhos. While EC measures the total dissolved minerals in a solution it does not identify the amounts of specific elements present. Therefore, it is easier to achieve the ideal EC using premixed 2-part hydroponic nutrient formulations than attempting to create your own formula using individual components.

Temperature is also an important GIF however, it is quite easily controlled. Tomatoes, like most plants grow best with a day/night temperature differential based on light or daytime perception. When there is light the plant considers it daytime and the temperature should be adjusted accordingly. The ideal daytime temperature for mature tomato plants bearing fruit is 18° - 25°C and nighttime is 12° - 18°C. An independent thermostat should be placed among your plants to ensure temperature regulation. An exhaust fan will help control temperature and provide air exchange.

Plant nutrition is the basis for hydroponics and holds the key to the nutritional quality of your tomatoes. There are a wealth of pre-mixed nutrients available, however when determining which nutrient to use, look for a product that is especially formulated for hydroponic use. A 2-part formula will eliminate binding, solidification and waste of mineral elements, which occurs with ordinary 1-part plant foods.

Close observation of any changes are critical when growing hydroponic tomatoes. Early diagnosis and adjustment of nutritional disorders is crucial as they rapidly increase in severity and spread quickly.

• Check the colour of the leaves; yellow leaves may indicate that the nutrient solution isn't strong enough or pH is too high, locking out nitrogen - leach and change the solution.
• Leaf tips curl up or red stem may indicate a magnesium deficiency caused by too low a pH - leach and change solution
• Leaf tips curling under may mean the nutrient level is too high - add pH 6.0 water
• A potassium deficiency my cause flowers to fall off before setting fruit - leach and change solution.

Blossom-end-rot caused by too much water puddling in the root zone will create a calcium deficiency - leach and foliar spray with a calcium nitrate solution.

Leaching should be done at every reservoir change to avoid encountering problems. This will rid the growing medium and root zone of toxic salt build up. To leach, rince the root zone with straight pH balanced water. Use twice as much liquid as the hydroponic container would have held when empty.

These are some basic nutritional disorders however, they are easily avoided by using a good 2-part fertilizer, maintaining a correct pH and changing your solution regularly.

Tomatoes are pollinated outdoors by the wind, bees and other insects which carry the male pollen to the female part of the flower (stigma.) Indoors pollination must be performed manually by the grower. This can easily be accomplished using a small paint brush or Q-tip to transfer the pollen. Simply dab the brush or Q-tip on the stigma of each flower. This is best done daily over a period of several days when the flowers indicate their readiness to receive fertilization by bending their petals back and exposing the stigma.

Tomato plants are quite brittle and require gentle handling when pruning and staking. Use plastic twine or a plant yo-yo to encourage and support vertical growth and bear the weight of the fruit. Removing side shoots and suckers that grow between the main stem and leaf stems will further help train with vertical growth and eliminate unnecessary distribution of nutrients. Suckers should be gently broken off at their base by hand. Avoid the use of knives or scissors which can transfer diseases from plant to plant. As plants begin to produce fruit, the bottom leaves will start to yellow and dry out. Remove these leaves at the main stem of the plant to allow air flow and to prevent disease and infection.

A little bit of knowledge and patience will produce infinite rewards in hydroponic gardening. That first bite of juicy August tomato in the middle of January will be your stepping stone to a culinary adventure. Harvest all of summer's pleasure's indoors year round hydroponically, the homegrown way.

Hydroponics University

Hydro-U is a service of Simply Hydroponics and Organics On-line as part of our consumer education program. We welcome your feedback. Your input is what makes this site work. Please contact us with any questions or ideas.

Greenhouse Tomato Culture

There are several methods used to produce greenhouse tomatoes.  However, the basic cultural requirements of the plant are similar.  The following describes some of the factors to be considered.

Environmental Conditions

Temperature plays a key role in the production of quality fruit.  In general, optimum right time temperatures should be maintained between 60 degrees - 65 degrees F.  This provides for good fruit ripening with no reduction in growth or fruit set.  Optimum daytime temperatures should be maintained between 70 degrees to 80 degrees F, but do not artificially heat the greenhouse above the desired night temperature during daylight hours.  Employ maximum cooling when temperatures within the greenhouse exceed 80 degrees F.

Air movement is also important in tomato production.  Air in the greenhouse should be circulated when the exhaust fans are not operating.  Circulation maintains a constant level of humidity and helps reduce potential problems from plant diseases.

Row and Plant Spacing

Work aisles between pairs of tomato rows are normally 36 inches.  The rows in the pairs should be no closer than 28 to 30 inches.  This allows light to penetrate to the lower leaves of plants in the close rows.

Plant spacing in the row should be 3.1 to 3.4 square feet per plant and narrower rows may sometimes result in greater yields, the value of the increased yield often does not offset the cost of the increased labor required to care for the additional number of plants.

Planting Schedules

1. Single crop rotation-seeded in July or by early August.  Transplants set in greenhouse  within 10 to 30 days of seeding.  Harvest begins from 85 to 100 days following date of  seeding and continues into June or early July.  Cessation of pollination is six weeks before  termination of the crop.  Growing point is allowed to grow for at least five to seven leaves  above last fruit truss to help prevent sunburned fruit.  Remove flower buds above last fruit  truss to assure no additional fruit set.

2. Two crop rotation-Fall crop seeded and transplanted same as for a single crop.  Normally  fall crop terminated from late December to mid-January with cessation of pollination from  55 to 60 days earlier.  Spring crop seeded 30 to 35 days before transplanting into the  greenhouse which is the day following termination of the fall crop.  Harvest begins in late   March to early April and usually continues through June.

Pruning and Training

Greenhouse tomatoes are trained to a single stem by removing all side shoots as they develop in the axils of the leaves.  These side shoots or ìsuckersî should be removed weekly by breaking them off or rubbing them out when quite small.

Transplants are set in most media so that the stem is covered about one-half inch above the line of the previous media.  Before the plants grow more than about a foot in height when they generally start falling over, support the plant by tying plastic twine (1,000 to 1,200 feet per pound), with one end secured to the stem near the base of the plant [with a loose fitting non-slip loop] and the other end attached to a No. 9 to 10 gauge wire supported 7 to 8 feet above the row.  As the plant grows, the twine is wrapped around the plant with one complete spiral between consecutive fruit trusses.  Always wrap the twine in the same direction, clockwise or counter clockwise.

When the plants grow to the overhead wire, they are lowered about 2 to 2 ½ feet.  When the plants again grow to wire, they are lowered with the same procedure repeated until the time when fruit setting is stopped.  The lowering or dropping of the plant is accomplished by loosening the twine at the wire. If the original twine length did not allow a three foot pigtail after tying, a new five foot piece of twine is tied to the end of the other twine, and then the plant is lowered.  The twine is again attached to the wire about 2 to 2 ½ feet down the wire from when it was originally tied so that about 2 to 2 ½ feet of stem rests on the ground.  At the end of the cropping season, for one long, single crop, the top of a plant in a row may be more than 10 feet down the wire from where it originally started.  The leaves on that part of the stem laying on the ground should be removed to prevent the creation of a disease hazard.

When lowering the plants, one row of a pair is dropped in one direction and the other in the opposite direction.  At the end of the row, the plants are dropped across to its paired row rather than allowing them to ìbunch up.

Pollination

Vibrating the flower clusters is the means of transferring the pollen from the anthers to the stigma of the blooms and is necessary for fruit set.  The wind is normally responsible for this transfer in the garden and field.

In the greenhouse, pollination is accomplished by electric vibrators (battery or 110 volt), electric toothbrushes, mist blowers, striking the overhead wires with a broom handle while walking down the rows or automatic systems which shake the overhead wires either longitudinally or across the wires.

The electric vibrators manufactured for the purpose are normally more effective than the lower vibrating frequency of the electric toothbrushes.  Both are time consuming.

To be highly effective, the air stream of the mist blowers must be directed at the individual flower clusters.  The broom handle technique as well as the automatic vibrators are not too effective until the plants are about 2 feet or more in height when the weight of the plants keep the twine taut.

Experiments in a Midwest greenhouse showed that vibrating the flower clusters with a 110-volt vibrator every day versus every other day between the hours of 10 a.m. and 2 p.m. resulted in no difference in number or size of fruit.  However, pollinating before 10 a.m. or after 2 p.m.  reduced the number and size of fruit.  An advantage of an automatic pollinator other than labor saving is that it could be adjusted to operate every day for a few seconds as various times between 10 a.m. and 2 p.m.

Harvesting

Normally tomatoes must be harvested 3 times a week except during the winter when yields are usually low and twice weekly is sufficient.  When possible, the fruit should be harvested as they approach full-red color.  The nearer tomatoes approach full ripens on the vines, the heavier and more flavorful they become.  When left on the vine to ripen, an average of 20 percent increase in weight of the fruit which occurs between the time that the first trace of color is apparent on the fruit and the time the fruit is fully colored.

Some Problems and Causes

Blossom-end-rot - Calcium deficiency as a result of too little calcium, too much potassium and magnesium and possibly ammonium nitrogen in relation to calcium or lack of aeration in growth medium.
Square and puffy fruit - carbohydrate deficiency as a result of too little sunshine or shade on greenhouse covering.
Blossom drop - same as puffy fruit above or also can result from a manganese deficiency.  Sometimes, plants set about 30 fruit each before fruit truss begin to ripen.  This is about maximum load for a plant with a result that blossoms drop until stress is relieved by harvest.
Thin stems near growing point - low nitrogen, too little moisture in growing media, low total nutrients, or excessive total salts or nutrients.
Bun at edges of lower leaves, thin stems at top of plant, and dark green shoulders on fruit - excessive total salts or nutrients.  Leach growing media and water to remove salts.
Deformed leaves and leaflets at growing point occurring during the heating season, leaflets more serrated than normal, leaflets blotchy, leaflets appear somewhat like they had been sprayed with 2.4-D herbicide, and if above systems severe, than bloom buds fail to develop but turn yellow and may drop - combustion products from heaters usually ethylene.  Check heat exchangers for cracks, and allow sufficient outside air to enter greenhouse so that combustion products can be exhausted out the vents.
Failure of flower buds to develop into blooms - deficiency of manganese especially during December and January.  Also can be manganese toxicity in which case new leaves usually show interveinal chlorosis somewhat like magnesium deficiency rather than iron deficiency chlorosis.
Interveinal chlorosis in newer leaves at time of plant - iron, manganese or zinc deficiency.  With zinc deficiency, the leaves will be much shorter than normal.  With manganese deficiency, the bloom buds will also fail to develop into blooms.
New leaves twist and curl downward into a ball-like growth, stems and internodes between leaves very short - nitrogen too high with low boron.  Increasing boron to roots may not help but boron sprays at top of plant helpful.  Decrease nitrogen or restrict water which in effect decreases nitrogen availability.
Hydroponics Index

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