Last revised February 15, 2010
Tomatoes, tree tomatoes (also called tamarillos), tomatillos, husk tomatoes (also called ground cherries) and the Japanese Lantern plant are all in the Solanaceae family. The tomatillo and related husk tomato belong to a different genus (Physalis) and differ from tomatoes in that their fruit is encased in a thin husk. Tomatillos produce large branched plants. The fruit are picked when they have reached full size and are still green. After the husk is removed, the fruit is often mixed with hot peppers and other ingredients to make green salsa. Varieties of tomatillo are: Tomatillo Green, Tomatillo Purple (purple fruit), and Rendidor (commonly used in Mexico).
The husk tomato or ground cherry fruit is much smaller than the tomatillo, is very sweet and used mainly for jam and preserves after the fruit has ripened and turned yellow. Varieties of husk tomato are: Husk Tomato Goldie, Husk Tomato Strawberry.
The Japanese Lantern plant is used as a cut ornamental and is most often marketed in the fall. The ornamental portion is an expanded calyx enclosing a pea-sized, globose berry.
The tree tomato belongs to still another genus, Cyphomandra betacea, and is a tropical plant not suited for outdoor production in the Pacific Northwest. Its fruit, promoted by New Zealand, is marketed in the U.S.A. under the trade name Tamarillo. The fruit is egg-shaped, may be red or yellow, and is bland or semi-sweet. Tree tomato plants are a small perennial bush or shrub 6 to 10 feet tall, frost sensitive, and bear after the second year.
Tomato varieties mature over a wide range, commonly from 75 days for early cherry types to 85 days for early full size fruit types, 100 days for medium, and 110 days for later, full season varieties from direct seeded plantings. Transplanted plantings would be about 25 days less.
Anti-oxidant and anti-cancer compounds found in tomatoes and other vegetables have become important considerations in the choice of varieties. Tomatoes with high levels of Vitamins A and C are being developed.
See the Vegetable Variety Selection Resources page to find varieties that have been shown to perform well in the Pacific NW.
VARIETY SELECTION FOR DISEASE AVOIDANCE
Varieties are listed below by their resistance to Verticillium and Fusarium wilts and root-knot nematode.
|`Better Boy F.'||Early||VFN|
|`Pik Red F.'||Early||VFN|
|`Pik Rite F.'||Early||VFN|
|`Small Fry' (cherry)||Early||VFN|
|`Toy Boy' (cherry)||Early||VFN|
* V = Resistant to Verticillium wilt
F = Resistant to Fusarium wilt
N = Resistant to root-knot nematode
T = Resistant to Tobacco Mosaic Virus
SEED AND SEED TREATMENT
Tomato seed numbers approximately 11,500 per ounce. Most of the new hybrids are sold by seed number. Use only treated seed from a reliable seed source. Some seed companies now can furnish tomato seed that has been "vigorized" or "conditioned" to allow germination under adverse (cool) temperature conditions.
Research in Indiana has demonstrated a benefit from starter or "pop-up" fertilizers. In direct seeded plantings, spray directly on the seed a solution of 2-6-0 (made up of 1 part 10-34-0 : 4 part water) at 1 pint per 100 lineal feet of row (use 1/2 this rate on sandy soils).
To reduce risk from Verticillium wilt and other diseases avoid using fields in your rotation plans in which eggplant, tomato, pepper, potato, strawberry, or caneberries have been planted.
Use one or more ounces of seed per acre, depending on the variety and required plant population. Sow them in the greenhouse 6 to 8 weeks before field transplanting. Seedlings are transplanted to other flats when the first true leaf has formed. Veneer bands or jiffy pots may be used to advantage. Space between the plants should be 2 to 2.5 inches. Provide adequate ventilation during the heat of the day, particularly after watering, which should be completed before l p.m. Water plants before signs of wilting appear.
Tomato is a warm-temperature vegetable and requires a long growing season. Transplants should be kept close to the following temperatures: 64 to 70 F during the day, 55 to 61 F at night until the seedlings are thinned out.
When the first true leaf has formed, early flowering can be increased by a one-week cold treatment at 54 F. Caution: Do not subject transplants with 4-5 true leaves to cold temperatures (around 50 F nights and 60-65 F days) for more than a week since this will increase catfaced fruit.
Condition transplants for 1-2 days before transplanting to the field by slightly reducing the moisture and maintaining approximate outdoor temperatures. Do not over-harden (see note on catfacing above). Thoroughly water plants l2 to l4 hours before transplanting to the field. Plants should be dug or cut loose from the soil when being transplanted; ensure the roots are not exposed to sun or drying wind.
Apply a starter fertilizer solution to the transplants when transplanting to the field. Select starter fertilizers that have the highest level of phosphorus available, such as 10-52-17, 11-48-0, 11-55-0 dry fertilizers or 10-34-0 liquid fertilizer. Make up a stock solution of 3 lbs of the dry, such as 10-52-17, or 2 pints of liquid 10-34-0 per 50 gallons of water. Use 1/2 pint of this stock solution per plant, applying the solution directly to the plant roots when setting in the field.
Use rows 4-5 feet apart and space transplants 12 to 48 inches apart in the row, depending on variety.
Direct seeding should be done with early varieties only. Drop 1-3 seeds per hill and space 9-12 inches apart in rows spaced 48-60 inches.
Tomatillos are usually grown from transplants planted in rows 5 feet apart with a 2.5-foot spacing in the row.
Recent research indicates that a temperature of 68-78 F is ideal for optimal growth.
Use windbreaks as necessary especially in eastern Oregon. Grain windbreaks have been found effective when grain rows are used for each tomato row. Winter wheat varieties, rye, or oats can be used. Spring barley may be used for February plantings. Seed grain thickly, 2-3 seeds per inch. This requires about 10 lb of barley, 9 lb of wheat, or 8 lb of rye to seed grain rows 12 feet apart. Windbreaks may be cultivated out after the tomato plants are well established. If they are not, windbreaks should not be allowed to touch the tomato plants because abrasion of the enlarging fruit can cause that fruit to be misshapen.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
A soil test is the most accurate guide to fertilizer requirements. As a general guideline before transplanting, broadcast and disc in the following:
Nitrogen: 75-100 (N) lb/acre
Phosphate: 100-150 (P2O5) lb/acre
Potash: 100-150 (K2O) lb/acre
Sulfur: 25-30 (S) lb/acre
Side dress with 25-50 lb N/ acre when first fruits appear.
Where mulching and trickle irrigation are practiced, additional nitrogen can be fed through the trickle irrigation system at 15 lb/acre when the first fruit begins to set and an additional 15 lb/acre four weeks after. To prevent clogging or plugging from occurring use soluble forms of N (urea or ammonium nitrate), and chlorinate the system once a month with a l0 to 50 ppm. chlorine solution. Chlorinate more frequently if the flow rate decreases.
Avoid excessive nitrogen applications, which can cause excessive vine growth and delay maturity.
PLASTIC GROUND MULCHES AND ROW COVERS
The use of black plastic ground mulch is recommended, especially in Western Oregon, to enhance earliness and yield. Plastic mulch controls weeds, conserves moisture, may increase soil temperature, and protects fruit from ground rots. For black plastic mulch to increase soil temperature, it is critical that the soil surface be smooth and that the plastic be in close contact with the soil. This can only be achieved by laying the plastic with a machine designed and properly adjusted for this task. Clear plastic much is superior for heat transfer to the soil but does not control weeds.
A new generation of plastic mulch films allows for good weed control together with soil warming that is intermediate between black plastic and clear film. These films are called IRT (infrared-transmitting) or wavelength-selective films. They are more expensive than black or clear films, but may be cost-effective where soil warming is important. (See also section on spacing).
Plastic, spunbonded, and non-woven materials have been developed as crop covers for use as windbreaks, for frost protection, and to enhance yield and earliness. They complement the use of plastic mulch and drip irrigation in many crops.
Non-woven or spunbonded polyester or propylene, and perforated polyethylene row covers, may be used for 4 to 8 weeks immediately after transplanting or direct seeding. Covers should be removed when plants begin to flower or if temperatures become excessive under the covers. Do not allow temperatures to exceed 90 F for more than two or three consecutive days. Row covers increase heat unit accumulation by 2 to 3 times over ambient. Two to four degrees of frost protection may also be obtained at night. Soil temperatures and root growth are also increased under row covers as are early yields, and in some cases total yields.
Apply water uniformly to reduce incidence of blossom end rot. Irrigate carefully after fruit ripens to reduce fruit decay and cracking. A total of 12-15 inches may be needed in western Oregon. Approximate summer irrigation needs for the Hermiston area have been found to be: 3.5 inches in May, 5.0 in June, 7.5 in July, and 7.0 in August. Research has shown that the use of drip irrigation under black plastic mulch is superior to sprinkler irrigation with black plastic mulch. Yields usually increase dramatically.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
CHEMICAL FRUIT RIPENING
Ethephon (Ethrel) may be used for uniform ripening for once-over harvest and to enhance ripening in late varieties, or during late seasons, or when ripening is delayed. The proper use of Ethrel can advance harvest about 5-7 days. Fruit do not increase appreciably in size after ethephon treatment
Several factors must be considered for effective use of Ethrel:
- Because Ethrel can cause some defoliation and increase incidence of sunburned fruit, do not treat fields where growth is poor or the plants are stressed.
- Do not apply Ethrel if temperatures are expected to exceed 90 F.
- Apply when fruit is at 5 to 10% red/pink/breaker stage. Ethrel is effective only on fruit that is at least mature-green (fruit has gel inside). The key to good results is good coverage.
- Apply 1.25 to 1.75 pints Ethrel (2 lb/gal formulation) in 40-80 gal water/acre. Use higher rates when day temperatures are less than 64 F and tomato growth is dense. Ideal temperature range is 75-85 F.
- Avoid spraying more than can be harvested in one day as sprayed fields do not "store" as well as unsprayed.
- Varietal differences in foliage vigor and leaf characteristics affect Ethrel uptake and potential for fruit injury and ripening response. Experiment carefully and know how your variety responds.
- Do not exceed 6.5 pints/acre total, or excess residues may develop. Consult product label for full instructions and cautions.
- Harvest fruit at proper maturity, generally l4 to 2l days after treatment. Observe treated fruit frequently for condition of crop ripening. Cool temperatures can slow Ethrel absorption and color development and extend the period between treatment and harvest.
HARVESTING, HANDLING, AND STORAGE
Tomato yields vary with area and number of harvests. Yields may range from 230 to 270 cwt/acre, or about 1200 20-lb boxes/acre. With appropriate plasticulture techniques, yields of as high as 3200 20-lb boxes/acre have been reported.
Tomatoes may be harvested at the mature green stage (when the fruit cavity is filled by gel), semi-ripe (with different amounts of red pigmentation) or fully ripe, depending or marketing requirement. They are very perishable and subject to surface and internal damage, and must be handled accordingly. Tomatoes are sensitive to chilling injury, which differs with maturity of the fruit. Proper temperature management for ripening and storage are critical to maintain quality.
(Quoted or modified from USDA Ag. Handbook 66 (pdf) and other sources)
Store mature-green tomatoes at 55 to 70 F; ripe fruit at 45 to 50 F and a relative humidity of 90 to 95%.
Mature-green tomatoes cannot be successfully stored at temperatures that greatly delay ripening. Tomatoes held for 2 weeks or longer at 55 F may develop abnormal amount of decay and may fail to develop a deep red color. The optimum temperatures for ripening mature-green tomatoes range from 65 to 70 F. Tomatoes will not ripen normally at temperatures above 80 F. A temperature range of 57 to 61 F is probably most desirable for slowing ripening without increasing decay problems. At these temperatures the more mature fruit within the mature-green range will ripen enough to be packaged for retailing in 7 to 14 days.
Fruit held below 50 F become susceptible to alternaria decay during subsequent ripening. Increased decay during ripening occurs after 6 days of exposure at 32 or 9 days at 40 F. Mature-green tomatoes may also be damaged by low temperatures in the field. A high percentage of tomatoes exposed to temperatures below 50 F for a week before harvest would probably develop alternaria rot even at recommended storage temperatures. Some loss due to chilling can be expected in fall-grown tomatoes exposed for over 95 hours to temperatures below 60 F during the week before harvest. Severity of chilling increases with increases in exposure time, so 135 hours exposure to below 60 F may result in heavy losses.
Chilling periods for fruit while in the field, during transit, and in storage have a cumulative effect. Thus, fruit chilled for only a short period in the field can become very susceptible to decay when held for only a short period at chilling temperature during transit or storage. Tomatoes should be kept out of cold, wet rooms because in addition to potential development of chilling injury, extended refrigeration damages the ability of fruit to develop desirable fresh tomato flavor.
Ripening of tomatoes is initiated by the ethylene they produce. However, in commercial practice, mature-green tomatoes are commonly treated with supplemental ethylene to hasten ripening within a lot. For treatment, tomatoes are exposed to 100 to 150 ppm ethylene for 24 to 48 hours at 68 to 77 F and 85 to 95% relative humidity. Ethylene is applied in a fairly airtight room by a shot method, a generator, or a flow-through system. Immature tomatoes may ripen with supplemental ethylene, but the ripened fruit will lack quality. Fruit beyond the breaker stage do not benefit from supplemental ethylene because their ripening processes already have been initiated by their own ethylene.
Semi-ripe tomatoes with 60 to 90% color can be held up to a week at 50 F. If held longer, they will probably not have a normal shelf life during retailing. Riper tomatoes will tolerate lower temperatures. For example, "firm-rip" tomatoes can be held a few days at 45 to 50. Long holding of ripened tomatoes at low temperatures (40 and below) results in loss of color, shelf life, and firmness.
Fully ripe: When it is necessary to hold fully ripe tomatoes for the longest possible time before their immediate consumption upon removal from storage, as for example, for ship-board or overseas use, they can be held at 32 to 35 F for up to 3 weeks. Such tomatoes, although acceptable, would not be of high quality and would have little if any shelf life remaining. Mature-green, turning, or pink tomatoes should be ripened before storing at such low temperatures.
A storage temperature of 50 to 55 F is recommended for semi-ripe to fully ripe greenhouse-grown tomatoes. Ripening of less mature tomatoes at 70 F is recommended before storage at 50 to 55 F.
Research showed that an atmosphere with 3% oxygen and 97% nitrogen extended the life of mature-green tomatoes up to 6 weeks at 55 F and that the flavor of the ripened fruit had no off-flavor and was acceptable to the taste panel. A 1% or lower oxygen level can cause off-flavor. Increased carbon dioxide levels provide no benefit; in fact, levels of 3 to 5% have been reported to cause injury at 55 F.
Cherry tomatoes are commonly packaged in 8-lb baskets.
Mature green tomatoes are commonly packaged in 30-lb cartons and wirebound crates, volume-fill pack.
Pink and ripe tomatoes are commonly packaged in 20-lb two-layer flats and cartons, tray pack; or 28-lb three-layer lugs and cartons, tray pack; or 30-lb cartons, loose pack.
NON-PATHOGENIC FRUIT DISORDERS
Blossom end rot
Calcium deficiency aggravated by widely fluctuating soil moisture conditions-nonpathogenic. Calcium in the fruit may be deficient because (1) insufficient calcium in the soil, (2) excess N, Mg, K or Na has been applied as fertilizer, (3) very wet or very dry soils interfere with uptake of calcium, (4) combinations of (1) to (3).
Symptoms: Black leathery lesions form on blossom end of fruit. The affected area shrinks and causes misshapen fruits. Only some fruits on a plant may be affected. Green as well as ripe fruits may be affected.
- Add lime to adjust pH of soil to 6.8 to 7.2. Mix lime thoroughly in top 8 to 12 inches of soil. Lime is best applied in fall.
- Use only moderate amounts of additional fertilizers to keep plants normally green and vigorous but not luxuriant.
- Do not plant tomatoes where drainage is poor, surface water accumulates, or soil is droughty.
- Mulch plants with black plastic or loose organic materials.
- Fertilize with nitrogen side-dressing only if it is required to maintain green color and moderate-growth. Use calcium nitrate or ammonium sulfate at rate of 0.25 lb to 100 sq ft (100 lb/A).
- Maintain uniform soil moisture. Apply water to wet all soil in root zone every 7 to 10 days. About 24 hours after watering, dig a small hole with a trowel to a depth of 1 foot to be certain water has penetrated to that level.
- If symptoms of blossom end rot are detected, spray the leaves and fruit with calcium chloride at the rate of 2 Tbs in 1 gal water (4 lb in 200 gal water/A). Apply two or more sprays at 1-week intervals. The spray may cause some injury to the margins of the leaves.
Gray-wall or blotchy ripening
This disorder appears as gray or brown blotchy areas in the fruit wall tissue, beginning when the fruit is green. It can occur on more than half of the fruit of a particular field. Cross-sections of fruit show blackened tissue. This causes the external fruit color to look somewhat gray. When the fruit ripens, the area remains firm and turns from green to yellow, rather than red. Fruit thus ripens unevenly. The affected area appears woody when cut. White wall tissue has been considered to be an early stage of gray wall, but may also be related to other disorders (see "internal white tissue" section below). A definite cause for gray wall has not been defined but a number of factors play a role in predisposing fruit to gray wall, these are listed in their considered lessening degree of importance:
- Low light or prolonged cloudy periods.
- Excess nitrogen causing excessive plant vigor.
- High soil moisture from excess rain or irrigation.
- Potassium deficiency.
- Soil compaction.
- Temperature fluctuations, particularly unusually cool nights and warm days.
Tobacco mosaic virus is also reported to be involved in gray wall. In those cases the disorder is also called internal browning. That tobacco mosaic virus is involved in a disorder called internal browning is not in dispute. What is in dispute is whether the two disorders are the same or separate. In a few other cases certain bacteria and fungi are thought to also be implicated. Another confusion is that gray wall is also sometimes called blotchy ripening!
Information from Florida indicates that the varieties Merced and Floridade may have tolerance to the conditions that predispose tomatoes to gray wall
Internal white tissue
The expression of white tissue varies widely, and is considered dependent on cultivar and environmental conditions. It is sometimes attributed to gray wall. Potassium deficiency and high temperatures are believed to aggravate the problem.
Solar yellowing (also called yellow shoulder, yellow top and persistent green shoulder)
This problem occurs most commonly on fruit ripening in late May and June when days are longest, sunlight is most intense, and temperatures exceed 85 F. Under such conditions, lycopene (the red pigment in tomato) fails to develop normally in some varieties, leaving only the carotene (yellow) pigment to show at the shoulder or, with green-shoulder type tomatoes, where the dark green portion was. Even with temperatures under 85 F the surface temperature of exposed fruit, especially those with dark green shoulders can become high enough to inhibit normal red color development. In other parts of the day or night, when temperatures do not exceed 85 F some red color may develop, resulting in an orange rather than a yellow abnormality. To reduce this problem, choose uniform-ripening varieties and protect fruit surfaces from short-wave solar radiation by choosing varieties having good fruit cover or, by the use of non-phytotoxic white wash applied when fruit are at the mature-green stage. The white wash will have to be removed before the fruit is marketed.
Mature green and tomatoes just turning red are most susceptible. Fruit develops white necrotic tissue surrounded by a yellow halo. The area may be sunken and wrinkled. Damage is confined mainly to the upper portion of the fruit, and is seen where fruit that has been covered by leaves is suddenly exposed to light. The area can later be covered by a black fungus when the rest of the fruit turns red.
Roughness and scars
Varieties differ in susceptibility. associated with large fruit. Particularly severe when young plants are exposed to cool temperatures, and night temperatures below 50 F when flower clusters are differentiating.
Varieties differ in susceptibility. Promoted by fluctuations in soil moisture and temperature. Often seen when varieties developed for hot, arid climates are subjected to humid, wet conditions. Cracks may be radial or concentric.